draft-ietf-ccamp-gmpls-architecture-07.txt   rfc3945.txt 
Network Working Group Eric Mannie - Editor Network Working Group E. Mannie, Ed.
Internet Draft Request for Comments: 3945 October 2004
Category: Standard Track Category: Standards Track
Expiration date: November 2003 May 2003
Generalized Multi-Protocol Label Switching Architecture
draft-ietf-ccamp-gmpls-architecture-07.txt Generalized Multi-Protocol Label Switching (GMPLS) Architecture
Status of this Memo Status of this Memo
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Abstract Abstract
Future data and transmission networks will consist of elements such Future data and transmission networks will consist of elements such
as routers, switches, Dense Wavelength Division Multiplexing (DWDM) as routers, switches, Dense Wavelength Division Multiplexing (DWDM)
systems, Add-Drop Multiplexors (ADMs), photonic cross-connects systems, Add-Drop Multiplexors (ADMs), photonic cross-connects
(PXCs), optical cross-connects (OXCs), etc. that will use (PXCs), optical cross-connects (OXCs), etc. that will use Generalized
Generalized Multi-Protocol Label Switching (GMPLS) to dynamically Multi-Protocol Label Switching (GMPLS) to dynamically provision
provision resources and to provide network survivability using resources and to provide network survivability using protection and
protection and restoration techniques. restoration techniques.
This document describes the architecture of GMPLS. GMPLS extends This document describes the architecture of GMPLS. GMPLS extends
MPLS to encompass time-division (e.g. SONET/SDH, PDH, G.709), MPLS to encompass time-division (e.g., SONET/SDH, PDH, G.709),
wavelength (lambdas), and spatial switching (e.g. incoming port or wavelength (lambdas), and spatial switching (e.g., incoming port or
fiber to outgoing port or fiber). The focus of GMPLS is on the fiber to outgoing port or fiber). The focus of GMPLS is on the
control plane of these various layers since each of them can use control plane of these various layers since each of them can use
physically diverse data or forwarding planes. The intention is to physically diverse data or forwarding planes. The intention is to
cover both the signaling and the routing part of that control plane. cover both the signaling and the routing part of that control plane.
E. Mannie (Editor) et al. Standard Track 1 Table of Contents
1. Table of Contents
Status of this Memo .............................................. 1
Abstract ......................................................... 1
1. Table of Contents ............................................. 2
2. Conventions used in this document ............................. 3
3. Introduction .................................................. 3
3.1. Acronyms & Abbreviations .................................... 4
3.2. Multiple Types of Switching and Forwarding Hierarchies ...... 4
3.3. Extension of the MPLS Control Plane ......................... 6
3.4. GMPLS Key Extensions to MPLS-TE ............................. 9
4. Routing and Addressing Mode .................................. 10
4.1. Addressing of PSC and non-PSC layers ....................... 11
4.2. GMPLS Scalability Enhancements ............................. 11
4.3. TE Extensions to IP Routing Protocols ...................... 12
5. Unnumbered Links ............................................. 13
5.1. Unnumbered Forwarding Adjacencies .......................... 14
6. Link Bundling ................................................ 14
6.1. Restrictions on Bundling ................................... 15
6.2. Routing Considerations for Bundling ........................ 15
6.3. Signaling Considerations ................................... 16
6.3.1 Mechanism 1: Implicit Indication .......................... 16
6.3.2 Mechanism 2: Explicit Indication by Numbered Interface ID . 16
6.3.3 Mechanism 3: Explicit Indication by Unnumbered Interface ID 16
6.4. Unnumbered Bundled Link .................................... 17
6.5. Forming Bundled Links ...................................... 17
7. Relationship with the UNI .................................... 18
7.1. Relationship with the OIF UNI .............................. 18
7.2. Reachability across the UNI ................................ 19
8. Link Management .............................................. 19
8.1. Control Channel and Control Channel Management ............. 20
8.2. Link Property Correlation .................................. 21
8.3. Link Connectivity Verification ............................. 21
8.4. Fault Management ........................................... 22
8.5. LMP for DWDM Optical Line Systems (OLSs) ................... 23
9. Generalized Signaling ........................................ 24
9.1. Overview: How to Request an LSP ............................ 25
9.2. Generalized Label Request .................................. 26
9.3. SONET/SDH Traffic Parameters ............................... 27
9.4. G.709 Traffic Parameters ................................... 28
9.5. Bandwidth Encoding ......................................... 29
9.6. Generalized Label .......................................... 29
9.7. Waveband Switching ......................................... 30
9.8. Label Suggestion by the Upstream ........................... 30
9.9. Label Restriction by the Upstream .......................... 31
9.10. Bi-directional LSP ........................................ 31
9.11. Bi-directional LSP Contention Resolution .................. 32
9.12. Rapid Notification of Failure ............................. 33
9.13. Link Protection ........................................... 33
9.14. Explicit Routing and Explicit Label Control ............... 34
9.15. Route Recording ........................................... 35
9.16. LSP Modification and LSP Re-routing ....................... 35
9.17. LSP Administrative Status Handling ........................ 36
9.18. Control Channel Separation ................................ 36
E. Mannie (Editor) et al. Standard Track 2
10. Forwarding Adjacencies (FA) ................................. 37
10.1. Routing and Forwarding Adjacencies ........................ 38
10.2. Signaling Aspects ......................................... 39
10.3. Cascading of Forwarding Adjacencies ....................... 39
11. Routing and Signaling Adjacencies ........................... 39
12. Control Plane Fault Handling ................................ 40
13. LSP Protection and Restoration .............................. 41
13.1. Protection Escalation across Domains and Layers ........... 42
13.2. Mapping of Services to P&R Resources ...................... 43
13.3. Classification of P&R Mechanism Characteristics ........... 43
13.4. Different Stages in P&R ................................... 44
13.5. Recovery Strategies ....................................... 44
13.6. Recovery mechanisms: Protection schemes ................... 45
13.7. Recovery mechanisms: Restoration schemes .................. 45
13.8. Schema Selection Criteria ................................. 46
14. Network Management .......................................... 48
14.1. Network Management Systems (NMS) .......................... 48
14.2. Management Information Base (MIB) ......................... 48
14.3. Tools ..................................................... 49
14.4. Fault Correlation Between Multiple Layers ................. 49
15. Security Considerations ..................................... 50
16. Acknowledgements ............................................ 51
17. Intellectual Property Considerations ........................ 51
18. References .................................................. 51
18.1 Normative References ....................................... 51
18.2 Information References ..................................... 54
19. Author's Address ............................................ 55
20. Contributors ................................................ 55
Full Copyright Statement ........................................ 58
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 4
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in 1.1. Acronyms & Abbreviations. . . . . . . . . . . . . . . . 4
this document are to be interpreted as described in [RFC2119]. 1.2. Multiple Types of Switching and Forwarding Hierarchies. 5
1.3. Extension of the MPLS Control Plane . . . . . . . . . . 7
1.4. GMPLS Key Extensions to MPLS-TE . . . . . . . . . . . . 10
2. Routing and Addressing Model. . . . . . . . . . . . . . . . . 11
2.1. Addressing of PSC and non-PSC layers. . . . . . . . . . 13
2.2. GMPLS Scalability Enhancements. . . . . . . . . . . . . 13
2.3. TE Extensions to IP Routing Protocols . . . . . . . . . 14
3. Unnumbered Links. . . . . . . . . . . . . . . . . . . . . . . 15
3.1. Unnumbered Forwarding Adjacencies . . . . . . . . . . . 16
4. Link Bundling . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1. Restrictions on Bundling. . . . . . . . . . . . . . . . 17
4.2. Routing Considerations for Bundling . . . . . . . . . . 17
4.3. Signaling Considerations. . . . . . . . . . . . . . . . 18
4.3.1. Mechanism 1: Implicit Indication. . . . . . . . 18
4.3.2. Mechanism 2: Explicit Indication by Numbered
Interface ID. . . . . . . . . . . . . . . . . . 19
4.3.3. Mechanism 3: Explicit Indication by Unnumbered
Interface ID. . . . . . . . . . . . . . . . . . 19
4.4. Unnumbered Bundled Link . . . . . . . . . . . . . . . . 19
4.5. Forming Bundled Links . . . . . . . . . . . . . . . . . 20
5. Relationship with the UNI . . . . . . . . . . . . . . . . . . 20
5.1. Relationship with the OIF UNI . . . . . . . . . . . . . 21
5.2. Reachability across the UNI . . . . . . . . . . . . . . 21
6. Link Management . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. Control Channel and Control Channel Management. . . . . 23
6.2. Link Property Correlation . . . . . . . . . . . . . . . 24
6.3. Link Connectivity Verification. . . . . . . . . . . . . 24
6.4. Fault Management. . . . . . . . . . . . . . . . . . . . 25
6.5. LMP for DWDM Optical Line Systems (OLSs). . . . . . . . 26
7. Generalized Signaling . . . . . . . . . . . . . . . . . . . . 27
7.1. Overview: How to Request an LSP . . . . . . . . . . . . 29
7.2. Generalized Label Request . . . . . . . . . . . . . . . 30
7.3. SONET/SDH Traffic Parameters. . . . . . . . . . . . . . 31
7.4. G.709 Traffic Parameters. . . . . . . . . . . . . . . . 32
7.5. Bandwidth Encoding. . . . . . . . . . . . . . . . . . . 33
7.6. Generalized Label . . . . . . . . . . . . . . . . . . . 34
7.7. Waveband Switching. . . . . . . . . . . . . . . . . . . 34
7.8. Label Suggestion by the Upstream. . . . . . . . . . . . 35
7.9. Label Restriction by the Upstream . . . . . . . . . . . 35
7.10. Bi-directional LSP. . . . . . . . . . . . . . . . . . . 36
7.11. Bi-directional LSP Contention Resolution. . . . . . . . 37
7.12. Rapid Notification of Failure . . . . . . . . . . . . . 37
7.13. Link Protection . . . . . . . . . . . . . . . . . . . . 38
7.14. Explicit Routing and Explicit Label Control . . . . . . 39
7.15. Route Recording . . . . . . . . . . . . . . . . . . . . 40
7.16. LSP Modification and LSP Re-routing . . . . . . . . . . 40
7.17. LSP Administrative Status Handling. . . . . . . . . . . 41
7.18. Control Channel Separation. . . . . . . . . . . . . . . 42
8. Forwarding Adjacencies (FA) . . . . . . . . . . . . . . . . . 43
8.1. Routing and Forwarding Adjacencies. . . . . . . . . . . 43
8.2. Signaling Aspects . . . . . . . . . . . . . . . . . . . 44
8.3. Cascading of Forwarding Adjacencies . . . . . . . . . . 44
9. Routing and Signaling Adjacencies . . . . . . . . . . . . . . 45
10. Control Plane Fault Handling. . . . . . . . . . . . . . . . . 46
11. LSP Protection and Restoration. . . . . . . . . . . . . . . . 47
11.1. Protection Escalation across Domains and Layers . . . . 48
11.2. Mapping of Services to P&R Resources. . . . . . . . . . 49
11.3. Classification of P&R Mechanism Characteristics . . . . 49
11.4. Different Stages in P&R . . . . . . . . . . . . . . . . 50
11.5. Recovery Strategies . . . . . . . . . . . . . . . . . . 50
11.6. Recovery mechanisms: Protection schemes . . . . . . . . 51
11.7. Recovery mechanisms: Restoration schemes. . . . . . . . 52
11.8. Schema Selection Criteria . . . . . . . . . . . . . . . 53
12. Network Management. . . . . . . . . . . . . . . . . . . . . . 54
12.1. Network Management Systems (NMS). . . . . . . . . . . . 55
12.2. Management Information Base (MIB) . . . . . . . . . . . 55
12.3. Tools . . . . . . . . . . . . . . . . . . . . . . . . . 56
12.4. Fault Correlation Between Multiple Layers . . . . . . . 56
13. Security Considerations . . . . . . . . . . . . . . . . . . . 57
14. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . 58
15. References. . . . . . . . . . . . . . . . . . . . . . . . . . 58
15.1. Normative References. . . . . . . . . . . . . . . . . . 58
15.2. Informative References. . . . . . . . . . . . . . . . . 59
16. Contributors. . . . . . . . . . . . . . . . . . . . . . . . . 63
17. Author's Address. . . . . . . . . . . . . . . . . . . . . . . 68
Full Copyright Statement. . . . . . . . . . . . . . . . . . . 69
3. Introduction 1. Introduction
The architecture described in this document covers the main building The architecture described in this document covers the main building
blocks needed to build a consistent control plane for multiple blocks needed to build a consistent control plane for multiple
switching layers. It does not restrict the way that these layers switching layers. It does not restrict the way that these layers
work together. Different models can be applied: e.g. overlay, work together. Different models can be applied, e.g., overlay,
augmented or integrated. Moreover, each pair of contiguous layers augmented or integrated. Moreover, each pair of contiguous layers
may collaborate in different ways, resulting in a number of possible may collaborate in different ways, resulting in a number of possible
combinations, at the discretion of manufacturers and operators. combinations, at the discretion of manufacturers and operators.
This architecture clearly separates the control plane and the This architecture clearly separates the control plane and the
forwarding plane. In addition, it also clearly separates the control forwarding plane. In addition, it also clearly separates the control
plane in two parts, the signaling plane containing the signaling plane in two parts, the signaling plane containing the signaling
protocols and the routing plane containing the routing protocols. protocols and the routing plane containing the routing protocols.
This document is a generalization of the Multi-Protocol Label This document is a generalization of the Multi-Protocol Label
Switching (MPLS) architecture [RFC3031], and in some cases may Switching (MPLS) architecture [RFC3031], and in some cases may differ
differ slightly from that architecture since non packet-based slightly from that architecture since non packet-based forwarding
planes are now considered. It is not the intention of this document
E. Mannie (Editor) et al. Standard Track 3 to describe concepts already described in the current MPLS
forwarding planes are now considered. It is not the intention of architecture. The goal is to describe specific concepts of
this document to describe concepts already described in the current
MPLS architecture. The goal is to describe specific concepts of
Generalized MPLS (GMPLS). Generalized MPLS (GMPLS).
However, some of the concepts explained hereafter are not part of However, some of the concepts explained hereafter are not part of the
the current MPLS architecture and are applicable to both MPLS and current MPLS architecture and are applicable to both MPLS and GMPLS
GMPLS (i.e. link bundling, unnumbered links, and LSP hierarchy). (i.e., link bundling, unnumbered links, and LSP hierarchy). Since
Since these concepts were introduced together with GMPLS and since these concepts were introduced together with GMPLS and since they are
they are of paramount importance for an operational GMPLS network, of paramount importance for an operational GMPLS network, they will
they will be discussed here. be discussed here.
The organization of the remainder of this document is as follows. We The organization of the remainder of this document is as follows. We
begin with an introduction of GMPLS. We then present the specific begin with an introduction of GMPLS. We then present the specific
GMPLS building blocks and explain how they can be combined together GMPLS building blocks and explain how they can be combined together
to build an operational GMPLS network. Specific details of the to build an operational GMPLS network. Specific details of the
separate building blocks can be found in the corresponding separate building blocks can be found in the corresponding documents.
documents.
3.1. Acronyms & Abbreviations 1.1. Acronyms & Abbreviations
AS Autonomous System AS Autonomous System
BGP Border Gateway Protocol BGP Border Gateway Protocol
CR-LDP Constraint-based Routing LDP CR-LDP Constraint-based Routing LDP
CSPF Constraint-based Shortest Path First CSPF Constraint-based Shortest Path First
DWDM Dense Wavelength Division Multiplexing DWDM Dense Wavelength Division Multiplexing
FA Forwarding Adjacency FA Forwarding Adjacency
GMPLS Generalized Multi-Protocol Label Switching GMPLS Generalized Multi-Protocol Label Switching
IGP Interior Gateway Protocol IGP Interior Gateway Protocol
LDP Label Distribution Protocol LDP Label Distribution Protocol
skipping to change at line 211 skipping to change at page 5, line 20
OXC Optical Cross-Connect OXC Optical Cross-Connect
PXC Photonic Cross-Connect PXC Photonic Cross-Connect
RSVP ReSource reserVation Protocol RSVP ReSource reserVation Protocol
SDH Synchronous Digital Hierarchy SDH Synchronous Digital Hierarchy
SONET Synchronous Optical Networks SONET Synchronous Optical Networks
STM(-N) Synchronous Transport Module (-N) STM(-N) Synchronous Transport Module (-N)
STS(-N) Synchronous Transport Signal-Level N (SONET) STS(-N) Synchronous Transport Signal-Level N (SONET)
TDM Time Division Multiplexing TDM Time Division Multiplexing
TE Traffic Engineering TE Traffic Engineering
3.2. Multiple Types of Switching and Forwarding Hierarchies 1.2. Multiple Types of Switching and Forwarding Hierarchies
Generalized MPLS (GMPLS) differs from traditional MPLS in that it Generalized MPLS (GMPLS) differs from traditional MPLS in that it
supports multiple types of switching, i.e. the addition of support supports multiple types of switching, i.e., the addition of support
for TDM, lambda, and fiber (port) switching. The support for the for TDM, lambda, and fiber (port) switching. The support for the
additional types of switching has driven GMPLS to extend certain additional types of switching has driven GMPLS to extend certain base
base functions of traditional MPLS and, in some cases, to add functions of traditional MPLS and, in some cases, to add
functionality. These changes and additions impact basic LSP
E. Mannie (Editor) et al. Standard Track 4
functionality. These changes and additions impact basic LSP
properties: how labels are requested and communicated, the properties: how labels are requested and communicated, the
unidirectional nature of LSPs, how errors are propagated, and unidirectional nature of LSPs, how errors are propagated, and
information provided for synchronizing the ingress and egress LSRs. information provided for synchronizing the ingress and egress LSRs.
The MPLS architecture [RFC3031] was defined to support the The MPLS architecture [RFC3031] was defined to support the forwarding
forwarding of data based on a label. In this architecture, Label of data based on a label. In this architecture, Label Switching
Switching Routers (LSRs) were assumed to have a forwarding plane Routers (LSRs) were assumed to have a forwarding plane that is
that is capable of (a) recognizing either packet or cell boundaries, capable of (a) recognizing either packet or cell boundaries, and (b)
and (b) being able to process either packet headers (for LSRs being able to process either packet headers (for LSRs capable of
capable of recognizing packet boundaries) or cell headers (for LSRs recognizing packet boundaries) or cell headers (for LSRs capable of
capable of recognizing cell boundaries). recognizing cell boundaries).
The original MPLS architecture is here being extended to include The original MPLS architecture is here being extended to include LSRs
LSRs whose forwarding plane recognizes neither packet, nor cell whose forwarding plane recognizes neither packet, nor cell
boundaries, and therefore, can't forward data based on the boundaries, and therefore, cannot forward data based on the
information carried in either packet or cell headers. Specifically, information carried in either packet or cell headers. Specifically,
such LSRs include devices where the switching decision is based on such LSRs include devices where the switching decision is based on
time slots, wavelengths, or physical ports. So, the new set of LSRs, time slots, wavelengths, or physical ports. So, the new set of LSRs,
or more precisely interfaces on these LSRs, can be subdivided into or more precisely interfaces on these LSRs, can be subdivided into
the following classes: the following classes:
1. Packet Switch Capable (PSC) interfaces: 1. Packet Switch Capable (PSC) interfaces:
Interfaces that recognize packet boundaries and can forward data Interfaces that recognize packet boundaries and can forward data
based on the content of the packet header. Examples include based on the content of the packet header. Examples include
interfaces on routers that forward data based on the content of the interfaces on routers that forward data based on the content of
IP header and interfaces on routers that switch data based on the the IP header and interfaces on routers that switch data based on
content of the MPLS "shim" header. the content of the MPLS "shim" header.
2. Layer-2 Switch Capable (L2SC) interfaces: 2. Layer-2 Switch Capable (L2SC) interfaces:
Interfaces that recognize frame/cell boundaries and can switch data Interfaces that recognize frame/cell boundaries and can switch
based on the content of the frame/cell header. Examples include data based on the content of the frame/cell header. Examples
interfaces on Ethernet bridges that switch data based on the content include interfaces on Ethernet bridges that switch data based on
of the MAC header and interfaces on ATM-LSRs that forward data based the content of the MAC header and interfaces on ATM-LSRs that
on the ATM VPI/VCI. forward data based on the ATM VPI/VCI.
3. Time-Division Multiplex Capable (TDM) interfaces: 3. Time-Division Multiplex Capable (TDM) interfaces:
Interfaces that switch data based on the data's time slot in a Interfaces that switch data based on the data's time slot in a
repeating cycle. An example of such an interface is that of a repeating cycle. An example of such an interface is that of a
SONET/SDH Cross-Connect (XC), Terminal Multiplexer (TM), or Add-Drop SONET/SDH Cross-Connect (XC), Terminal Multiplexer (TM), or Add-
Multiplexer (ADM). Other examples include interfaces providing G.709 Drop Multiplexer (ADM). Other examples include interfaces
TDM capabilities (the "digital wrapper") and PDH interfaces. providing G.709 TDM capabilities (the "digital wrapper") and PDH
interfaces.
4. Lambda Switch Capable (LSC) interfaces: 4. Lambda Switch Capable (LSC) interfaces:
Interfaces that switch data based on the wavelength on which the Interfaces that switch data based on the wavelength on which the
data is received. An example of such an interface is that of a data is received. An example of such an interface is that of a
Photonic Cross-Connect (PXC) or Optical Cross-Connect (OXC) that can Photonic Cross-Connect (PXC) or Optical Cross-Connect (OXC) that
operate at the level of an individual wavelength. Additional can operate at the level of an individual wavelength. Additional
examples include PXC interfaces that can operate at the level of a examples include PXC interfaces that can operate at the level of a
group of wavelengths, i.e., a waveband and G.709 interfaces
E. Mannie (Editor) et al. Standard Track 5 providing optical capabilities.
group of wavelengths, i.e. a waveband and G.709 interfaces providing
optical capabilities.
5. Fiber-Switch Capable (FSC) interfaces: 5. Fiber-Switch Capable (FSC) interfaces:
Interfaces that switch data based on a position of the data in the Interfaces that switch data based on a position of the data in the
(real world) physical spaces. An example of such an interface is (real world) physical spaces. An example of such an interface is
that of a PXC or OXC that can operate at the level of a single or that of a PXC or OXC that can operate at the level of a single or
multiple fibers. multiple fibers.
A circuit can be established only between, or through, interfaces of A circuit can be established only between, or through, interfaces of
the same type. Depending on the particular technology being used for the same type. Depending on the particular technology being used for
each interface, different circuit names can be used, e.g. SDH each interface, different circuit names can be used, e.g., SDH
circuit, optical trail, light-path, etc. In the context of GMPLS, circuit, optical trail, light-path, etc. In the context of GMPLS,
all these circuits are referenced by a common name: Label Switched all these circuits are referenced by a common name: Label Switched
Path (LSP). Path (LSP).
The concept of nested LSP (LSP within LSP), already available in the The concept of nested LSP (LSP within LSP), already available in the
traditional MPLS, facilitates building a forwarding hierarchy, i.e. traditional MPLS, facilitates building a forwarding hierarchy, i.e.,
a hierarchy of LSPs. This hierarchy of LSPs can occur on the same a hierarchy of LSPs. This hierarchy of LSPs can occur on the same
interface, or between different interfaces. interface, or between different interfaces.
For example, a hierarchy can be built if an interface is capable of For example, a hierarchy can be built if an interface is capable of
multiplexing several LSPs from the same technology (layer), e.g. a multiplexing several LSPs from the same technology (layer), e.g., a
lower order SONET/SDH LSP (e.g. VT2/VC-12) nested in a higher order lower order SONET/SDH LSP (e.g., VT2/VC-12) nested in a higher order
SONET/SDH LSP (e.g. STS-3c/VC-4). Several levels of signal (LSP) SONET/SDH LSP (e.g., STS-3c/VC-4). Several levels of signal (LSP)
nesting are defined in the SONET/SDH multiplexing hierarchy. nesting are defined in the SONET/SDH multiplexing hierarchy.
The nesting can also occur between interface types. At the top of The nesting can also occur between interface types. At the top of
the hierarchy are FSC interfaces, followed by LSC interfaces, the hierarchy are FSC interfaces, followed by LSC interfaces,
followed by TDM interfaces, followed by L2SC, and followed by PSC followed by TDM interfaces, followed by L2SC, and followed by PSC
interfaces. This way, an LSP that starts and ends on a PSC interface interfaces. This way, an LSP that starts and ends on a PSC interface
can be nested (together with other LSPs) into an LSP that starts and can be nested (together with other LSPs) into an LSP that starts and
ends on a L2SC interface. This LSP, in turn, can be nested (together ends on a L2SC interface. This LSP, in turn, can be nested (together
with other LSPs) into an LSP that starts and ends on a TDM with other LSPs) into an LSP that starts and ends on a TDM interface.
interface. In turn, this LSP can be nested (together with other In turn, this LSP can be nested (together with other LSPs) into an
LSPs) into an LSP that starts and ends on a LSC interface, which in LSP that starts and ends on a LSC interface, which in turn can be
turn can be nested (together with other LSPs) into an LSP that nested (together with other LSPs) into an LSP that starts and ends on
starts and ends on a FSC interface. a FSC interface.
3.3. Extension of the MPLS Control Plane 1.3. Extension of the MPLS Control Plane
The establishment of LSPs that span only Packet Switch Capable (PSC) The establishment of LSPs that span only Packet Switch Capable (PSC)
or Layer-2 Switch Capable (L2SC) interfaces is defined for the or Layer-2 Switch Capable (L2SC) interfaces is defined for the
original MPLS and/or MPLS-TE control planes. GMPLS extends these original MPLS and/or MPLS-TE control planes. GMPLS extends these
control planes to support each of the five classes of interfaces control planes to support each of the five classes of interfaces
(i.e. layers) defined in the previous section. (i.e., layers) defined in the previous section.
Note that the GMPLS control plane supports an overlay model, an Note that the GMPLS control plane supports an overlay model, an
augmented model, and a peer (integrated) model. In the near term, augmented model, and a peer (integrated) model. In the near term,
GMPLS appears to be very suitable for controlling each layer GMPLS appears to be very suitable for controlling each layer
independently. This elegant approach will facilitate the future independently. This elegant approach will facilitate the future
deployment of other models. deployment of other models.
E. Mannie (Editor) et al. Standard Track 6 The GMPLS control plane is made of several building blocks as
The GMPLS control plane is made of several building blocks are described in more details in the following sections. These building
described in more detail in the following sections. These building
blocks are based on well-known signaling and routing protocols that blocks are based on well-known signaling and routing protocols that
have been extended and/or modified to support GMPLS. They use IPv4 have been extended and/or modified to support GMPLS. They use IPv4
and/or IPv6 addresses. Only one new specialized protocol is required and/or IPv6 addresses. Only one new specialized protocol is required
to support the operations of GMPLS, a signaling protocol for link to support the operations of GMPLS, a signaling protocol for link
management [LMP]. management [LMP].
GMPLS is indeed based on the Traffic Engineering (TE) extensions to GMPLS is indeed based on the Traffic Engineering (TE) extensions to
MPLS, a.k.a. MPLS-TE [RFC2702]. This, because most of the MPLS, a.k.a. MPLS-TE [RFC2702]. This, because most of the
technologies that can be used below the PSC level requires some technologies that can be used below the PSC level requires some
traffic engineering. The placement of LSPs at these levels needs in traffic engineering. The placement of LSPs at these levels needs in
general to consider several constraints (such as framing, bandwidth, general to consider several constraints (such as framing, bandwidth,
protection capability, etc) and to bypass the legacy Shortest-Path protection capability, etc) and to bypass the legacy Shortest-Path
First (SPF) algorithm. Note, however, that this is not mandatory and First (SPF) algorithm. Note, however, that this is not mandatory and
that in some cases SPF routing can be applied. that in some cases SPF routing can be applied.
In order to facilitate constrained-based SPF routing of LSPs, nodes In order to facilitate constrained-based SPF routing of LSPs, nodes
that perform LSP establishment need more information about the links that perform LSP establishment need more information about the links
in the network than standard intra-domain routing protocols provide. in the network than standard intra-domain routing protocols provide.
These TE attributes are distributed using the transport mechanisms These TE attributes are distributed using the transport mechanisms
already available in IGPs (e.g. flooding) and taken into already available in IGPs (e.g., flooding) and taken into
consideration by the LSP routing algorithm. Optimization of the LSP consideration by the LSP routing algorithm. Optimization of the LSP
routes may also require some external simulations using heuristics routes may also require some external simulations using heuristics
that serve as input for the actual path calculation and LSP that serve as input for the actual path calculation and LSP
establishment process. establishment process.
By definition, a TE link is a representation in the IS-IS/OSPF Link By definition, a TE link is a representation in the IS-IS/OSPF Link
State advertisements and in the link state database of certain State advertisements and in the link state database of certain
physical resources, and their properties, between two GMPLS nodes. physical resources, and their properties, between two GMPLS nodes.
TE Links are used by the GMPLS control plane (routing and signaling) TE Links are used by the GMPLS control plane (routing and signaling)
for establishing LSPs. for establishing LSPs.
Extensions to traditional routing protocols and algorithms are Extensions to traditional routing protocols and algorithms are needed
needed to uniformly encode and carry TE link information, and to uniformly encode and carry TE link information, and explicit
explicit routes (e.g. source routes) are required in the signaling. routes (e.g., source routes) are required in the signaling. In
In addition, the signaling must now be capable of transporting the addition, the signaling must now be capable of transporting the
required circuit (LSP) parameters such as the bandwidth, the type of required circuit (LSP) parameters such as the bandwidth, the type of
signal, the desired protection and/or restoration, the position in a signal, the desired protection and/or restoration, the position in a
particular multiplex, etc. Most of these extensions have already particular multiplex, etc. Most of these extensions have already
been defined for PSC and L2SC traffic engineering with MPLS. GMPLS been defined for PSC and L2SC traffic engineering with MPLS. GMPLS
primarily defines additional extensions for TDM, LSC, and FSC primarily defines additional extensions for TDM, LSC, and FSC traffic
traffic engineering. A very few elements are technology specific. engineering. A very few elements are technology specific.
Thus, GMPLS extends the two signaling protocols defined for MPLS-TE Thus, GMPLS extends the two signaling protocols defined for MPLS-TE
signaling, i.e. RSVP-TE [RFC3209] and CR-LDP [RFC3212]. However, signaling, i.e., RSVP-TE [RFC3209] and CR-LDP [RFC3212]. However,
GMPLS does not specify which one of these two signaling protocols GMPLS does not specify which one of these two signaling protocols
must be used. It is the role of manufacturers and operators to must be used. It is the role of manufacturers and operators to
evaluate the two possible solutions for their own interest. evaluate the two possible solutions for their own interest.
Since GMPLS signalling is based on RSVP-TE and CR-LDP, it mandates a Since GMPLS signaling is based on RSVP-TE and CR-LDP, it mandates a
downstream-on-demand label allocation and distribution, with ingress downstream-on-demand label allocation and distribution, with ingress
initiated ordered control. Liberal label retention is normally used, initiated ordered control. Liberal label retention is normally used,
but conservative label retention mode could also be used. but conservative label retention mode could also be used.
E. Mannie (Editor) et al. Standard Track 7
Furthermore, there is no restriction on the label allocation Furthermore, there is no restriction on the label allocation
strategy, it can be request/signaling driven (obvious for circuit strategy, it can be request/signaling driven (obvious for circuit
switching technologies), traffic/data driven, or even topology switching technologies), traffic/data driven, or even topology
driven. There is also no restriction on the route selection; driven. There is also no restriction on the route selection;
explicit routing is normally used (strict or loose) but hop-by-hop explicit routing is normally used (strict or loose) but hop-by-hop
routing could be used as well. routing could be used as well.
GMPLS also extends two traditional intra-domain link-state routing GMPLS also extends two traditional intra-domain link-state routing
protocols already extended for TE purposes, i.e. OSPF-TE [OSPF-TE] protocols already extended for TE purposes, i.e., OSPF-TE [OSPF-TE]
and IS-IS-TE [ISIS-TE]. However, if explicit (source) routing is and IS-IS-TE [ISIS-TE]. However, if explicit (source) routing is
used, the routing algorithms used by these protocols no longer need used, the routing algorithms used by these protocols no longer need
to be standardized. Extensions for inter-domain routing (e.g. BGP) to be standardized. Extensions for inter-domain routing (e.g., BGP)
are for further study. are for further study.
The use of technologies like DWDM (Dense Wavelength Division The use of technologies like DWDM (Dense Wavelength Division
Multiplexing) implies that we can now have a very large number of Multiplexing) implies that we can now have a very large number of
parallel links between two directly adjacent nodes (hundreds of parallel links between two directly adjacent nodes (hundreds of
wavelengths, or even thousands of wavelengths if multiple fibers are wavelengths, or even thousands of wavelengths if multiple fibers are
used). Such a large number of links was not originally considered used). Such a large number of links was not originally considered
for an IP or MPLS control plane, although it could be done. Some for an IP or MPLS control plane, although it could be done. Some
slight adaptations of that control plane are thus required if we slight adaptations of that control plane are thus required if we want
want to better reuse it in the GMPLS context. to better reuse it in the GMPLS context.
For instance, the traditional IP routing model assumes the For instance, the traditional IP routing model assumes the
establishment of a routing adjacency over each link connecting two establishment of a routing adjacency over each link connecting two
adjacent nodes. Having such a large number of adjacencies does not adjacent nodes. Having such a large number of adjacencies does not
scale well. Each node needs to maintain each of its adjacencies one scale well. Each node needs to maintain each of its adjacencies one
by one, and link state routing information must be flooded by one, and link state routing information must be flooded throughout
throughout the network. the network.
To solve this issue the concept of link bundling was introduced. To solve this issue the concept of link bundling was introduced.
Moreover, the manual configuration and control of these links, even Moreover, the manual configuration and control of these links, even
if they are unnumbered, becomes impractical. The Link Management if they are unnumbered, becomes impractical. The Link Management
Protocol (LMP) was specified to solve these issues. Protocol (LMP) was specified to solve these issues.
LMP runs between data plane adjacent nodes and is used to manage TE LMP runs between data plane adjacent nodes and is used to manage TE
links. Specifically, LMP provides mechanisms to maintain control links. Specifically, LMP provides mechanisms to maintain control
channel connectivity (IP Control Channel Maintenance), verify the channel connectivity (IP Control Channel Maintenance), verify the
physical connectivity of the data-bearing links (Link Verification), physical connectivity of the data-bearing links (Link Verification),
correlate the link property information (Link Property Correlation), correlate the link property information (Link Property Correlation),
and manage link failures (Fault Localization and Fault and manage link failures (Fault Localization and Fault Notification).
Notification). A unique feature of LMP is that it is able to A unique feature of LMP is that it is able to localize faults in both
localize faults in both opaque and transparent networks (i.e. opaque and transparent networks (i.e., independent of the encoding
independent of the encoding scheme and bit rate used for the data). scheme and bit rate used for the data).
LMP is defined in the context of GMPLS, but is specified LMP is defined in the context of GMPLS, but is specified
independently of the GMPLS signaling specification since it is a independently of the GMPLS signaling specification since it is a
local protocol running between data-plane adjacent nodes. local protocol running between data-plane adjacent nodes.
Consequently, LMP can be used in other contexts with non-GMPLS Consequently, LMP can be used in other contexts with non-GMPLS
signaling protocols. signaling protocols.
MPLS signaling and routing protocols require at least one bi- MPLS signaling and routing protocols require at least one bi-
directional control channel to communicate even if two adjacent directional control channel to communicate even if two adjacent nodes
nodes are connected by unidirectional links. Several control are connected by unidirectional links. Several control channels can
be used. LMP can be used to establish, maintain and manage these
E. Mannie (Editor) et al. Standard Track 8 control channels.
channels can be used. LMP can be used to establish, maintain and
manage these control channels.
GMPLS does not specify how these control channels must be GMPLS does not specify how these control channels must be
implemented, but GMPLS requires IP to transport the signaling and implemented, but GMPLS requires IP to transport the signaling and
routing protocols over them. Control channels can be either in-band routing protocols over them. Control channels can be either in-band
or out-of-band, and several solutions can be used to carry IP. Note or out-of-band, and several solutions can be used to carry IP. Note
also that one type of LMP message (the Test message) is used in-band also that one type of LMP message (the Test message) is used in-band
in the data plane and may not be transported over IP, but this is a in the data plane and may not be transported over IP, but this is a
particular case, needed to verify connectivity in the data plane. particular case, needed to verify connectivity in the data plane.
3.4. GMPLS Key Extensions to MPLS-TE 1.4. GMPLS Key Extensions to MPLS-TE
Some key extensions brought by GMPLS to MPLS-TE are highlighted in Some key extensions brought by GMPLS to MPLS-TE are highlighted in
the following. Some of them are key advantages of GMPLS to control the following. Some of them are key advantages of GMPLS to control
TDM, LSC and FSC layers. TDM, LSC and FSC layers.
- In MPLS-TE, links traversed by an LSP can include an intermix of - In MPLS-TE, links traversed by an LSP can include an intermix of
links with heterogeneous label encoding (e.g. links between routers, links with heterogeneous label encoding (e.g., links between
links between routers and ATM-LSRs, and links between ATM-LSRs. routers, links between routers and ATM-LSRs, and links between
GMPLS extends this by including links where the label is encoded as ATM-LSRs. GMPLS extends this by including links where the label is
a time slot, or a wavelength, or a position in the (real world) encoded as a time slot, or a wavelength, or a position in the
physical space. (real world) physical space.
- In MPLS-TE, an LSP that carries IP has to start and end on a - In MPLS-TE, an LSP that carries IP has to start and end on a
router. GMPLS extends this by requiring an LSP to start and end on router. GMPLS extends this by requiring an LSP to start and end
similar type of interfaces. on similar type of interfaces.
- The type of a payload that can be carried in GMPLS by an LSP is - The type of a payload that can be carried in GMPLS by an LSP is
extended to allow such payloads as SONET/SDH, G.709, 1Gb or 10Gb extended to allow such payloads as SONET/SDH, G.709, 1Gb or 10Gb
Ethernet, etc. Ethernet, etc.
- The use of Forwarding Adjacencies (FA) provides a mechanism that - The use of Forwarding Adjacencies (FA) provides a mechanism that
can improve bandwidth utilization, when bandwidth allocation can be can improve bandwidth utilization, when bandwidth allocation can
performed only in discrete units. It offers also a mechanism to be performed only in discrete units. It offers also a mechanism
aggregate forwarding state, thus allowing the number of required to aggregate forwarding state, thus allowing the number of
labels to be reduced. required labels to be reduced.
- GMPLS allows suggesting a label by an upstream node to reduce the - GMPLS allows suggesting a label by an upstream node to reduce the
setup latency. This suggestion may be overridden by a downstream setup latency. This suggestion may be overridden by a downstream
node but in some cases, at the cost of higher LSP setup time. node but in some cases, at the cost of higher LSP setup time.
- GMPLS extends on the notion of restricting the range of labels - GMPLS extends on the notion of restricting the range of labels
that may be selected by a downstream node. In GMPLS, an upstream that may be selected by a downstream node. In GMPLS, an upstream
node may restrict the labels for an LSP along either a single hop or node may restrict the labels for an LSP along either a single hop
the entire LSP path. This feature is useful in photonic networks or the entire LSP path. This feature is useful in photonic
where wavelength conversion may not be available. networks where wavelength conversion may not be available.
- While traditional TE-based (and even LDP-based) LSPs are - While traditional TE-based (and even LDP-based) LSPs are
unidirectional, GMPLS supports the establishment of bi-directional unidirectional, GMPLS supports the establishment of bi-directional
LSPs. LSPs.
- GMPLS supports the termination of an LSP on a specific egress - GMPLS supports the termination of an LSP on a specific egress
port, i.e. the port selection at the destination side. port, i.e., the port selection at the destination side.
E. Mannie (Editor) et al. Standard Track 9 - GMPLS with RSVP-TE supports an RSVP specific mechanism for rapid
- GMPLS with RSVP-TE supports an RSVP specific mechanism for rapid failure notification.
failure notification.
Note also some other key differences between MPLS-TE and GMPLS: Note also some other key differences between MPLS-TE and GMPLS:
- For TDM, LSC and FSC interfaces, bandwidth allocation for an LSP - For TDM, LSC and FSC interfaces, bandwidth allocation for an LSP
can be performed only in discrete units. can be performed only in discrete units.
- It is expected to have (much) fewer labels on TDM, LSC or FSC - It is expected to have (much) fewer labels on TDM, LSC or FSC
links than on PSC or L2SC links, because the former are physical links than on PSC or L2SC links, because the former are physical
labels instead of logical labels. labels instead of logical labels.
4. Routing and Addressing Model 2. Routing and Addressing Model
GMPLS is based on the IP routing and addressing models. This assumes GMPLS is based on the IP routing and addressing models. This assumes
that IPv4 and/or IPv6 addresses are used to identify interfaces but that IPv4 and/or IPv6 addresses are used to identify interfaces but
also that traditional (distributed) IP routing protocols are reused. also that traditional (distributed) IP routing protocols are reused.
Indeed, the discovery of the topology and the resource state of all Indeed, the discovery of the topology and the resource state of all
links in a routing domain is achieved via these routing protocols. links in a routing domain is achieved via these routing protocols.
Since control and data planes are de-coupled in GMPLS, control-plane Since control and data planes are de-coupled in GMPLS, control-plane
neighbors (i.e. IGP-learnt neighbors) may not be data-plane neighbors (i.e., IGP-learnt neighbors) may not be data-plane
neighbors. Hence, mechanisms like LMP are needed to associate TE neighbors. Hence, mechanisms like LMP are needed to associate TE
links with neighboring nodes. links with neighboring nodes.
IP addresses are not used only to identify interfaces of IP hosts IP addresses are not used only to identify interfaces of IP hosts and
and routers, but more generally to identify any PSC and non-PSC routers, but more generally to identify any PSC and non-PSC
interfaces. Similarly, IP routing protocols are used to find routes interfaces. Similarly, IP routing protocols are used to find routes
for IP datagrams with a SPF algorithm; they are also used to find for IP datagrams with a SPF algorithm; they are also used to find
routes for non-PSC circuits by using a CSPF algorithm. routes for non-PSC circuits by using a CSPF algorithm.
However, some additional mechanisms are needed to increase the However, some additional mechanisms are needed to increase the
scalability of these models and to deal with specific traffic scalability of these models and to deal with specific traffic
engineering requirements of non-PSC layers. These mechanisms will be engineering requirements of non-PSC layers. These mechanisms will be
introduced in the following. introduced in the following.
Re-using existing IP routing protocols allows for non-PSC layers Re-using existing IP routing protocols allows for non-PSC layers
taking advantage of all the valuable developments that took place taking advantage of all the valuable developments that took place
since years for IP routing, in particular, in the context of intra- since years for IP routing, in particular, in the context of intra-
domain routing (link-state routing) and inter-domain routing (policy domain routing (link-state routing) and inter-domain routing (policy
routing). routing).
In an overlay model, each particular non-PSC layer can be seen as a In an overlay model, each particular non-PSC layer can be seen as a
set of Autonomous Systems (ASs) interconnected in an arbitrary way. set of Autonomous Systems (ASs) interconnected in an arbitrary way.
Similarly to the traditional IP routing, each AS is managed by a Similarly to the traditional IP routing, each AS is managed by a
single administrative authority. For instance, an AS can be an single administrative authority. For instance, an AS can be an
SONET/SDH network operated by a given carrier. The set of SONET/SDH network operated by a given carrier. The set of
interconnected ASs can be viewed as SONET/SDH internetworks. interconnected ASs can be viewed as SONET/SDH internetworks.
Exchange of routing information between ASs can be done via an Exchange of routing information between ASs can be done via an
inter-domain routing protocol like BGP-4. There is obviously a huge inter-domain routing protocol like BGP-4. There is obviously a huge
value of re-using well-known policy routing facilities provided by value of re-using well-known policy routing facilities provided by
BGP in a non-PSC context. Extensions for BGP traffic engineering BGP in a non-PSC context. Extensions for BGP traffic engineering
(BGP-TE) in the context of non-PSC layers are left for further study.
E. Mannie (Editor) et al. Standard Track 10
(BGP-TE) in the context of non-PSC layers are left for further
study.
Each AS can be sub-divided in different routing domains, and each Each AS can be sub-divided in different routing domains, and each can
can run a different intra-domain routing protocol. In turn, each run a different intra-domain routing protocol. In turn, each
routing-domain can be divided in areas. routing-domain can be divided in areas.
A routing domain is made of GMPLS enabled nodes (i.e. a network A routing domain is made of GMPLS enabled nodes (i.e., a network
device including a GMPLS entity). These nodes can be either edge device including a GMPLS entity). These nodes can be either edge
nodes (i.e. hosts, ingress LSRs or egress LSRs), or internal LSRs. nodes (i.e., hosts, ingress LSRs or egress LSRs), or internal LSRs.
An example of non-PSC host is an SONET/SDH Terminal Multiplexer An example of non-PSC host is an SONET/SDH Terminal Multiplexer (TM).
(TM). Another example is an SONET/SDH interface card within an IP Another example is an SONET/SDH interface card within an IP router or
router or ATM switch. ATM switch.
Note that traffic engineering in the intra-domain requires the use Note that traffic engineering in the intra-domain requires the use of
of link-state routing protocols like OSPF or IS-IS. link-state routing protocols like OSPF or IS-IS.
GMPLS defines extensions to these protocols. These extensions are GMPLS defines extensions to these protocols. These extensions are
needed to disseminate specific TDM, LSC and FSC static and dynamic needed to disseminate specific TDM, LSC and FSC static and dynamic
characteristics related to nodes and links. The current focus is on characteristics related to nodes and links. The current focus is on
intra-area traffic engineering. However, inter-area traffic intra-area traffic engineering. However, inter-area traffic
engineering is also under investigation. engineering is also under investigation.
4.1. Addressing of PSC and non-PSC Layers 2.1. Addressing of PSC and non-PSC Layers
The fact that IPv4 and/or IPv6 addresses are used doesn't imply at The fact that IPv4 and/or IPv6 addresses are used does not imply at
all that they should be allocated in the same addressing space than all that they should be allocated in the same addressing space than
public IPv4 and/or IPv6 addresses used for the Internet. Private IP public IPv4 and/or IPv6 addresses used for the Internet. Private IP
addresses can be used if they don't require to be exchanged with any addresses can be used if they do not require to be exchanged with any
other operator; public IP addresses are otherwise required. Of other operator; public IP addresses are otherwise required. Of
course, if an integrated model is used, two layers could share the course, if an integrated model is used, two layers could share the
same addressing space. Finally, TE links may be "unnumbered" i.e. same addressing space. Finally, TE links may be "unnumbered" i.e.,
not have any IP addresses, in case IP addresses are not available, not have any IP addresses, in case IP addresses are not available, or
or the overhead of managing them is considered too high. the overhead of managing them is considered too high.
Note that there is a benefit of using public IPv4 and/or IPv6 Note that there is a benefit of using public IPv4 and/or IPv6
Internet addresses for non-PSC layers if an integrated model with Internet addresses for non-PSC layers if an integrated model with the
the IP layer is foreseen. IP layer is foreseen.
If we consider the scalability enhancements proposed in the next If we consider the scalability enhancements proposed in the next
section, the IPv4 (32 bits) and the IPv6 (128 bits) addressing section, the IPv4 (32 bits) and the IPv6 (128 bits) addressing spaces
spaces are both more than sufficient to accommodate any non-PSC are both more than sufficient to accommodate any non-PSC layer. We
layer. We can reasonably expect to have much less non-PSC devices can reasonably expect to have much less non-PSC devices (e.g.,
(e.g. SONET/SDH nodes) than we have today IP hosts and routers. SONET/SDH nodes) than we have today IP hosts and routers.
4.2. GMPLS Scalability Enhancements 2.2. GMPLS Scalability Enhancements
TDM, LSC and FSC layers introduce new constraints on the IP TDM, LSC and FSC layers introduce new constraints on the IP
addressing and routing models since several hundreds of parallel addressing and routing models since several hundreds of parallel
physical links (e.g. wavelengths) can now connect two nodes. Most of physical links (e.g., wavelengths) can now connect two nodes. Most
the carriers already have today several tens of wavelengths per of the carriers already have today several tens of wavelengths per
fiber between two nodes. New generation of DWDM systems will allow fiber between two nodes. New generation of DWDM systems will allow
several hundreds of wavelengths per fiber. several hundreds of wavelengths per fiber.
E. Mannie (Editor) et al. Standard Track 11
It becomes rather impractical to associate an IP address with each It becomes rather impractical to associate an IP address with each
end of each physical link, to represent each link as a separate end of each physical link, to represent each link as a separate
routing adjacency, and to advertise and to maintain link states for routing adjacency, and to advertise and to maintain link states for
each of these links. For that purpose, GMPLS enhances the MPLS each of these links. For that purpose, GMPLS enhances the MPLS
routing and addressing models to increase their scalability. routing and addressing models to increase their scalability.
Two optional mechanisms can be used to increase the scalability of Two optional mechanisms can be used to increase the scalability of
the addressing and the routing: unnumbered links and link bundling. the addressing and the routing: unnumbered links and link bundling.
These two mechanisms can also be combined. They require extensions These two mechanisms can also be combined. They require extensions
to signaling (RSVP-TE and CR-LDP) and routing (OSPF-TE and IS-IS-TE) to signaling (RSVP-TE and CR-LDP) and routing (OSPF-TE and IS-IS-TE)
protocols. protocols.
4.3. TE Extensions to IP Routing Protocols 2.3. TE Extensions to IP Routing Protocols
Traditionally, a TE link is advertised as an adjunct to a "regular" Traditionally, a TE link is advertised as an adjunct to a "regular"
OSPF or IS-IS link, i.e., an adjacency is brought up on the link. OSPF or IS-IS link, i.e., an adjacency is brought up on the link.
When the link is up, both the regular IGP properties of the link When the link is up, both the regular IGP properties of the link
(basically, the SPF metric) and the TE properties of the link are (basically, the SPF metric) and the TE properties of the link are
then advertised. then advertised.
However, GMPLS challenges this notion in three ways: However, GMPLS challenges this notion in three ways:
- First, links that are non-PSC may yet have TE properties; however, - First, links that are non-PSC may yet have TE properties; however,
an OSPF adjacency could not be brought up directly on such links. an OSPF adjacency could not be brought up directly on such links.
- Second, an LSP can be advertised as a point-to-point TE link in - Second, an LSP can be advertised as a point-to-point TE link in
the routing protocol, i.e. as a Forwarding Adjacency (FA); thus, an the routing protocol, i.e., as a Forwarding Adjacency (FA); thus,
advertised TE link need no longer be between two OSPF direct an advertised TE link need no longer be between two OSPF direct
neighbors. Forwarding Adjacencies (FA) are further described in neighbors. Forwarding Adjacencies (FA) are further described in
Section 10. Section 8.
- Third, a number of links may be advertised as a single TE link - Third, a number of links may be advertised as a single TE link
(e.g. for improved scalability), so again, there is no longer a one- (e.g., for improved scalability), so again, there is no longer a
to-one association of a regular adjacency and a TE link. one-to-one association of a regular adjacency and a TE link.
Thus, we have a more general notion of a TE link. A TE link is a Thus, we have a more general notion of a TE link. A TE link is a
logical link that has TE properties. Some of these properties may be logical link that has TE properties. Some of these properties may be
configured on the advertising LSR, others may be obtained from other configured on the advertising LSR, others may be obtained from other
LSRs by means of some protocol, and yet others may be deduced from LSRs by means of some protocol, and yet others may be deduced from
the component(s) of the TE link. the component(s) of the TE link.
An important TE property of a TE link is related to the bandwidth An important TE property of a TE link is related to the bandwidth
accounting for that link. GMPLS will define different accounting accounting for that link. GMPLS will define different accounting
rules for different non-PSC layers. Generic bandwidth attributes are rules for different non-PSC layers. Generic bandwidth attributes are
however defined by the TE routing extensions and by GMPLS, such as however defined by the TE routing extensions and by GMPLS, such as
the unreserved bandwidth, the maximum reservable bandwidth and the the unreserved bandwidth, the maximum reservable bandwidth and the
maximum LSP bandwidth. maximum LSP bandwidth.
It is expected in a dynamic environment to have frequent changes of It is expected in a dynamic environment to have frequent changes of
bandwidth accounting information. A flexible policy for triggering bandwidth accounting information. A flexible policy for triggering
link state updates based on bandwidth thresholds and link-dampening link state updates based on bandwidth thresholds and link-dampening
mechanism can be implemented. mechanism can be implemented.
E. Mannie (Editor) et al. Standard Track 12
TE properties associated with a link should also capture protection TE properties associated with a link should also capture protection
and restoration related characteristics. For instance, shared and restoration related characteristics. For instance, shared
protection can be elegantly combined with bundling. Protection and protection can be elegantly combined with bundling. Protection and
restoration are mainly generic mechanisms also applicable to MPLS. restoration are mainly generic mechanisms also applicable to MPLS. It
It is expected that they will first be developed for MPLS and later is expected that they will first be developed for MPLS and later on
on generalized to GMPLS. generalized to GMPLS.
A TE link between a pair of LSRs doesn't imply the existence of an A TE link between a pair of LSRs does not imply the existence of an
IGP adjacency between these LSRs. A TE link must also have some IGP adjacency between these LSRs. A TE link must also have some
means by which the advertising LSR can know of its liveness (e.g. by means by which the advertising LSR can know of its liveness (e.g., by
using LMP hellos). When an LSR knows that a TE link is up, and can using LMP hellos). When an LSR knows that a TE link is up, and can
determine the TE link's TE properties, the LSR may then advertise determine the TE link's TE properties, the LSR may then advertise
that link to its GMPLS enhanced OSPF or IS-IS neighbors using the TE that link to its GMPLS enhanced OSPF or IS-IS neighbors using the TE
objects/TLVs. We call the interfaces over which GMPLS enhanced OSPF objects/TLVs. We call the interfaces over which GMPLS enhanced OSPF
or IS-IS adjacencies are established "control channels". or IS-IS adjacencies are established "control channels".
5. Unnumbered Links 3. Unnumbered Links
Unnumbered links (or interfaces) are links (or interfaces) that do Unnumbered links (or interfaces) are links (or interfaces) that do
not have IP addresses. Using such links involves two capabilities: not have IP addresses. Using such links involves two capabilities:
the ability to specify unnumbered links in MPLS TE signaling, and the ability to specify unnumbered links in MPLS TE signaling, and the
the ability to carry (TE) information about unnumbered links in IGP ability to carry (TE) information about unnumbered links in IGP TE
TE extensions of IS-IS-TE and OSPF-TE. extensions of IS-IS-TE and OSPF-TE.
A. The ability to specify unnumbered links in MPLS TE signaling A. The ability to specify unnumbered links in MPLS TE signaling
requires extensions to RSVP-TE [RFC3477] and CR-LDP [RFC3480]. The requires extensions to RSVP-TE [RFC3477] and CR-LDP [RFC3480].
MPLS-TE signaling doesn't provide support for unnumbered links, The MPLS-TE signaling does not provide support for unnumbered
because it doesn't provide a way to indicate an unnumbered link in links, because it does not provide a way to indicate an unnumbered
its Explicit Route Object/TLV and in its Record Route Object link in its Explicit Route Object/TLV and in its Record Route
(there is no such TLV for CR-LDP). GMPLS defines simple extensions Object (there is no such TLV for CR-LDP). GMPLS defines simple
to indicate an unnumbered link in these two Objects/TLVs, using a extensions to indicate an unnumbered link in these two
new Unnumbered Interface ID sub-object/sub-TLV. Objects/TLVs, using a new Unnumbered Interface ID sub-object/sub-
TLV.
Since unnumbered links are not identified by an IP address, then Since unnumbered links are not identified by an IP address, then
for the purpose of MPLS TE each end need some other identifier, for the purpose of MPLS TE each end need some other identifier,
local to the LSR to which the link belongs. LSRs at the two end- local to the LSR to which the link belongs. LSRs at the two end-
points of an unnumbered link exchange with each other the points of an unnumbered link exchange with each other the
identifiers they assign to the link. Exchanging the identifiers identifiers they assign to the link. Exchanging the identifiers
may be accomplished by configuration, by means of a protocol such may be accomplished by configuration, by means of a protocol such
as LMP ([LMP]), by means of RSVP-TE/CR-LDP (especially in the case as LMP ([LMP]), by means of RSVP-TE/CR-LDP (especially in the case
where a link is a Forwarding Adjacency, see below), or by means of where a link is a Forwarding Adjacency, see below), or by means of
IS-IS or OSPF extensions ([ISIS-TE-GMPLS], [OSPF-TE-GMPLS]). IS-IS or OSPF extensions ([ISIS-TE-GMPLS], [OSPF-TE-GMPLS]).
Consider an (unnumbered) link between LSRs A and B. LSR A chooses Consider an (unnumbered) link between LSRs A and B. LSR A chooses
an identifier for that link. So does LSR B. From A's perspective an identifier for that link. So does LSR B. From A's perspective
we refer to the identifier that A assigned to the link as the we refer to the identifier that A assigned to the link as the
"link local identifier" (or just "local identifier"), and to the "link local identifier" (or just "local identifier"), and to the
identifier that B assigned to the link as the "link remote identifier that B assigned to the link as the "link remote
identifier" (or just "remote identifier"). Likewise, from B's identifier" (or just "remote identifier"). Likewise, from B's
perspective the identifier that B assigned to the link is the perspective the identifier that B assigned to the link is the
local identifier, and the identifier that A assigned to the link local identifier, and the identifier that A assigned to the link
is the remote identifier. is the remote identifier.
E. Mannie (Editor) et al. Standard Track 13 The new Unnumbered Interface ID sub-object/sub-TLV for the ER
The new Unnumbered Interface ID sub-object/sub-TLV for the ER Object/TLV contains the Router ID of the LSR at the upstream end
Object/TLV contains the Router ID of the LSR at the upstream end of the unnumbered link and the link local identifier with respect
of the unnumbered link and the link local identifier with respect to that upstream LSR.
to that upstream LSR.
The new Unnumbered Interface ID sub-object for the RR Object The new Unnumbered Interface ID sub-object for the RR Object
contains the link local identifier with respect to the LSR that contains the link local identifier with respect to the LSR that
adds it in the RR Object. adds it in the RR Object.
B. The ability to carry (TE) information about unnumbered links in B. The ability to carry (TE) information about unnumbered links in
IGP TE extensions requires new sub-TLVs for the extended IS IGP TE extensions requires new sub-TLVs for the extended IS
reachability TLV defined in IS-IS-TE and for the TE LSA (which is reachability TLV defined in IS-IS-TE and for the TE LSA (which is
an opaque LSA) defined in OSPF-TE. A Link Local Identifier sub-TLV an opaque LSA) defined in OSPF-TE. A Link Local Identifier sub-
and a Link Remote Identifier sub-TLV are defined. TLV and a Link Remote Identifier sub-TLV are defined.
5.1. Unnumbered Forwarding Adjacencies 3.1. Unnumbered Forwarding Adjacencies
If an LSR that originates an LSP advertises this LSP as an If an LSR that originates an LSP advertises this LSP as an unnumbered
unnumbered FA in IS-IS or OSPF, or the LSR uses this FA as an FA in IS-IS or OSPF, or the LSR uses this FA as an unnumbered
unnumbered component link of a bundled link, the LSR must allocate component link of a bundled link, the LSR must allocate an Interface
an Interface ID to that FA. If the LSP is bi-directional, the tail ID to that FA. If the LSP is bi-directional, the tail end does the
end does the same and allocates an Interface ID to the reverse FA. same and allocates an Interface ID to the reverse FA.
Signaling has been enhanced to carry the Interface ID of a FA in the Signaling has been enhanced to carry the Interface ID of a FA in the
new LSP Tunnel Interface ID object/TLV. This object/TLV contains the new LSP Tunnel Interface ID object/TLV. This object/TLV contains the
Router ID (of the LSR that generates it) and the Interface ID. It is Router ID (of the LSR that generates it) and the Interface ID. It is
called the Forward Interface ID when it appears in a Path/REQUEST called the Forward Interface ID when it appears in a Path/REQUEST
message, and it is called the Reverse Interface ID when it appears message, and it is called the Reverse Interface ID when it appears in
in the Resv/MAPPING message. the Resv/MAPPING message.
6. Link Bundling 4. Link Bundling
The concept of link bundling is essential in certain networks The concept of link bundling is essential in certain networks
employing the GMPLS control plane as is defined in [BUNDLE]. A employing the GMPLS control plane as is defined in [BUNDLE]. A
typical example is an optical meshed network where adjacent optical typical example is an optical meshed network where adjacent optical
cross-connects (LSRs) are connected by several hundreds of parallel cross-connects (LSRs) are connected by several hundreds of parallel
wavelengths. In this network, consider the application of link state wavelengths. In this network, consider the application of link state
routing protocols, like OSPF or IS-IS, with suitable extensions for routing protocols, like OSPF or IS-IS, with suitable extensions for
resource discovery and dynamic route computation. Each wavelength resource discovery and dynamic route computation. Each wavelength
must be advertised separately to be used, except if link bundling is must be advertised separately to be used, except if link bundling is
used. used.
When a pair of LSRs is connected by multiple links, it is possible When a pair of LSRs is connected by multiple links, it is possible to
to advertise several (or all) of these links as a single link into advertise several (or all) of these links as a single link into OSPF
OSPF and/or IS-IS. This process is called link bundling, or just and/or IS-IS. This process is called link bundling, or just
bundling. The resulting logical link is called a bundled link as its bundling. The resulting logical link is called a bundled link as its
physical links are called component links (and are identified by physical links are called component links (and are identified by
interface indexes). interface indexes).
The result is that a combination of three identifiers ((bundled) The result is that a combination of three identifiers ((bundled) link
link identifier, component link identifier, label) is sufficient to identifier, component link identifier, label) is sufficient to
unambiguously identify the appropriate resources used by an LSP. unambiguously identify the appropriate resources used by an LSP.
E. Mannie (Editor) et al. Standard Track 14
The purpose of link bundling is to improve routing scalability by The purpose of link bundling is to improve routing scalability by
reducing the amount of information that has to be handled by OSPF reducing the amount of information that has to be handled by OSPF
and/or IS-IS. This reduction is accomplished by performing and/or IS-IS. This reduction is accomplished by performing
information aggregation/abstraction. As with any other information information aggregation/abstraction. As with any other information
aggregation/abstraction, this results in losing some of the aggregation/abstraction, this results in losing some of the
information. To limit the amount of losses one need to restrict the information. To limit the amount of losses one need to restrict the
type of the information that can be aggregated/abstracted. type of the information that can be aggregated/abstracted.
6.1. Restrictions on Bundling 4.1. Restrictions on Bundling
The following restrictions are required for bundling links. All The following restrictions are required for bundling links. All
component links in a bundle must begin and end on the same pair of component links in a bundle must begin and end on the same pair of
LSRs; and share some common characteristics or properties defined in LSRs; and share some common characteristics or properties defined in
[OSPF-TE] and [ISIS-TE], i.e. they must have the same: [OSPF-TE] and [ISIS-TE], i.e., they must have the same:
- Link Type (i.e. point-to-point or multi-access), - Link Type (i.e., point-to-point or multi-access),
- TE Metric (i.e. an administrative cost), - TE Metric (i.e., an administrative cost),
- Set of Resource Classes at each end of the links (i.e. colors). - Set of Resource Classes at each end of the links (i.e., colors).
Note that a FA may also be a component link. In fact, a bundle can Note that a FA may also be a component link. In fact, a bundle can
consist of a mix of point-to-point links and FAs, but all sharing consist of a mix of point-to-point links and FAs, but all sharing
some common properties. some common properties.
6.2. Routing Considerations for Bundling 4.2. Routing Considerations for Bundling
A bundled link is just another kind of TE link such as those defined A bundled link is just another kind of TE link such as those defined
by [GMPLS-ROUTING]. The liveness of the bundled link is determined by [GMPLS-ROUTING]. The liveness of the bundled link is determined
by the liveness of each its component links. A bundled link is alive by the liveness of each its component links. A bundled link is alive
when at least one of its component links is alive. The liveness of a when at least one of its component links is alive. The liveness of a
component link can be determined by any of several means: IS-IS or component link can be determined by any of several means: IS-IS or
OSPF hellos over the component link, or RSVP Hello (hop local), or OSPF hellos over the component link, or RSVP Hello (hop local), or
LMP hellos (link local), or from layer 1 or layer 2 indications. LMP hellos (link local), or from layer 1 or layer 2 indications.
Note that (according to the RSVP-TE specification [RFC3209]) the Note that (according to the RSVP-TE specification [RFC3209]) the RSVP
RSVP Hello mechanism is intended to be used when notification of Hello mechanism is intended to be used when notification of link
link layer failures is not available and unnumbered links are not layer failures is not available and unnumbered links are not used, or
used, or when the failure detection mechanisms provided by the link when the failure detection mechanisms provided by the link layer are
layer are not sufficient for timely node failure detection. not sufficient for timely node failure detection.
Once a bundled link is determined to be alive, it can be advertised Once a bundled link is determined to be alive, it can be advertised
as a TE link and the TE information can be flooded. If IS-IS/OSPF as a TE link and the TE information can be flooded. If IS-IS/OSPF
hellos are run over the component links, IS-IS/OSPF flooding can be hellos are run over the component links, IS-IS/OSPF flooding can be
restricted to just one of the component links. restricted to just one of the component links.
Note that advertising a (bundled) TE link between a pair of LSRs Note that advertising a (bundled) TE link between a pair of LSRs does
doesn't imply that there is an IGP adjacency between these LSRs that not imply that there is an IGP adjacency between these LSRs that is
is associated with just that link. In fact, in certain cases a TE associated with just that link. In fact, in certain cases a TE link
link between a pair of LSRs could be advertised even if there is no between a pair of LSRs could be advertised even if there is no IGP
IGP adjacency at all between the LSR (e.g. when the TE link is an adjacency at all between the LSR (e.g., when the TE link is an FA).
FA).
Forming a bundled link consist in aggregating the identical TE Forming a bundled link consist in aggregating the identical TE
parameters of each individual component link to produce aggregated parameters of each individual component link to produce aggregated TE
parameters. A TE link as defined by [GMPLS-ROUTING] has many
E. Mannie (Editor) et al. Standard Track 15
TE parameters. A TE link as defined by [GMPLS-ROUTING] has many
parameters; adequate aggregation rules must be defined for each one. parameters; adequate aggregation rules must be defined for each one.
Some parameters can be sums of component characteristics such as the Some parameters can be sums of component characteristics such as the
unreserved bandwidth and the maximum reservable bandwidth. Bandwidth unreserved bandwidth and the maximum reservable bandwidth. Bandwidth
information is an important part of a bundle advertisement and it information is an important part of a bundle advertisement and it
must be clearly defined since an abstraction is done. must be clearly defined since an abstraction is done.
A GMPLS node with bundled links must apply admission control on a A GMPLS node with bundled links must apply admission control on a
per-component link basis. per-component link basis.
6.3. Signaling Considerations 4.3. Signaling Considerations
Typically, an LSP's explicit route (e.g. contained in an explicit Typically, an LSP's explicit route (e.g., contained in an explicit
route Object/TLV) will choose the bundled link to be used for the route Object/TLV) will choose the bundled link to be used for the
LSP, but not the component link(s). This because information about LSP, but not the component link(s). This because information about
the bundled link is flooded but information about the component the bundled link is flooded but information about the component links
links is not. is not.
The choice of the component link to use is always made by an The choice of the component link to use is always made by an upstream
upstream node. If the LSP is bi-directional, the upstream node node. If the LSP is bi-directional, the upstream node chooses a
chooses a component link in each direction. component link in each direction.
Three mechanisms for indicating this choice to the downstream node Three mechanisms for indicating this choice to the downstream node
are possible. are possible.
6.3.1. Mechanism 1: Implicit Indication 4.3.1. Mechanism 1: Implicit Indication
This mechanism requires that each component link has a dedicated This mechanism requires that each component link has a dedicated
signaling channel (e.g., the link is a Sonet/SDH link using the DCC signaling channel (e.g., the link is a Sonet/SDH link using the DCC
for in-band signaling). The upstream node tells the receiver which for in-band signaling). The upstream node tells the receiver which
component link to use by sending the message over the chosen component link to use by sending the message over the chosen
component link's dedicated signaling channel. Note that this component link's dedicated signaling channel. Note that this
signaling channel can be in-band or out-of-band. In this last case, signaling channel can be in-band or out-of-band. In this last case,
the association between the signaling channel and that component the association between the signaling channel and that component link
link need to be explicitly configured. need to be explicitly configured.
6.3.2. Mechanism 2: Explicit Indication by Numbered Interface ID 4.3.2. Mechanism 2: Explicit Indication by Numbered Interface ID
This mechanism requires that the component link has a unique remote This mechanism requires that the component link has a unique remote
IP address. The upstream node indicates the choice of the component IP address. The upstream node indicates the choice of the component
link by including a new IF_ID RSVP_HOP object/IF_ID TLV carrying link by including a new IF_ID RSVP_HOP object/IF_ID TLV carrying
either an IPv4 or an IPv6 address in the Path/Label Request message either an IPv4 or an IPv6 address in the Path/Label Request message
(see [RFC3473]/[RFC3472], respectively). For a bi-directional LSP, a (see [RFC3473]/[RFC3472], respectively). For a bi-directional LSP, a
component link is provided for each direction by the upstream node. component link is provided for each direction by the upstream node.
This mechanism does not require each component link to have its own This mechanism does not require each component link to have its own
control channel. In fact, it doesn't even require the whole control channel. In fact, it does not even require the whole
(bundled) link to have its own control channel. (bundled) link to have its own control channel.
6.3.3. Mechanism 3: Explicit Indication by Unnumbered Interface ID 4.3.3. Mechanism 3: Explicit Indication by Unnumbered Interface ID
With this mechanism, each component link that is unnumbered is With this mechanism, each component link that is unnumbered is
assigned a unique Interface Identifier (32 bits value). The upstream assigned a unique Interface Identifier (32 bits value). The upstream
E. Mannie (Editor) et al. Standard Track 16
node indicates the choice of the component link by including a new node indicates the choice of the component link by including a new
IF_ID RSVP_HOP object/IF_ID TLV in the Path/Label Request message IF_ID RSVP_HOP object/IF_ID TLV in the Path/Label Request message
(see [RFC3473]/[RFC3472], respectively). (see [RFC3473]/[RFC3472], respectively).
This object/TLV carries the component interface ID in the downstream This object/TLV carries the component interface ID in the downstream
direction for a unidirectional LSP, and in addition, the component direction for a unidirectional LSP, and in addition, the component
interface ID in the upstream direction for a bi-directional LSP. interface ID in the upstream direction for a bi-directional LSP.
The two LSRs at each end of the bundled link exchange these The two LSRs at each end of the bundled link exchange these
identifiers. Exchanging the identifiers may be accomplished by identifiers. Exchanging the identifiers may be accomplished by
configuration, by means of a protocol such as LMP (preferred configuration, by means of a protocol such as LMP (preferred
solution), by means of RSVP-TE/CR-LDP (especially in the case where solution), by means of RSVP-TE/CR-LDP (especially in the case where a
a component link is a Forwarding Adjacency), or by means of IS-IS or component link is a Forwarding Adjacency), or by means of IS-IS or
OSPF extensions. OSPF extensions.
This mechanism does not require each component link to have its own This mechanism does not require each component link to have its own
control channel. In fact, it doesn't even require the whole control channel. In fact, it does not even require the whole
(bundled) link to have its own control channel. (bundled) link to have its own control channel.
6.4. Unnumbered Bundled Link 4.4. Unnumbered Bundled Link
A bundled link may itself be numbered or unnumbered independent of A bundled link may itself be numbered or unnumbered independent of
whether the component links are numbered or not. This affects how whether the component links are numbered or not. This affects how
the bundled link is advertised in IS-IS/OSPF and the format of LSP the bundled link is advertised in IS-IS/OSPF and the format of LSP
EROs that traverse the bundled link. Furthermore, unnumbered EROs that traverse the bundled link. Furthermore, unnumbered
Interface Identifiers for all unnumbered outgoing links of a given Interface Identifiers for all unnumbered outgoing links of a given
LSR (whether component links, Forwarding Adjacencies or bundled LSR (whether component links, Forwarding Adjacencies or bundled
links) must be unique in the context of that LSR. links) must be unique in the context of that LSR.
6.5. Forming Bundled Links 4.5. Forming Bundled Links
The generic rule for bundling component links is to place those The generic rule for bundling component links is to place those links
links that are correlated in some manner in the same bundle. If that are correlated in some manner in the same bundle. If links may
links may be correlated based on multiple properties then the be correlated based on multiple properties then the bundling may be
bundling may be applied sequentially based on these properties. For applied sequentially based on these properties. For instance, links
instance, links may be first grouped based on the first property. may be first grouped based on the first property. Each of these
Each of these groups may be then divided into smaller groups based groups may be then divided into smaller groups based on the second
on the second property and so on. The main principle followed in property and so on. The main principle followed in this process is
this process is that the properties of the resulting bundles should that the properties of the resulting bundles should be concisely
be concisely summarizable. Link bundling may be done automatically summarizable. Link bundling may be done automatically or by
or by configuration. Automatic link bundling can apply bundling configuration. Automatic link bundling can apply bundling rules
rules sequentially to produce bundles. sequentially to produce bundles.
For instance, the first property on which component links may be For instance, the first property on which component links may be
correlated could be the Interface Switching Capability [GMPLS- correlated could be the Interface Switching Capability
ROUTING], the second property could be the Encoding [GMPLS-ROUTING], [GMPLS-ROUTING], the second property could be the Encoding
the third property could be the Administrative Weight (cost), the [GMPLS-ROUTING], the third property could be the Administrative
fourth property could be the Resource Classes and finally links may Weight (cost), the fourth property could be the Resource Classes and
be correlated based on other metrics such as SRLG (Shared Risk Link finally links may be correlated based on other metrics such as SRLG
Groups). (Shared Risk Link Groups).
When routing an alternate path for protection purposes, the general When routing an alternate path for protection purposes, the general
principle followed is that the alternate path is not routed over any principle followed is that the alternate path is not routed over any
link belonging to an SRLG that belongs to some link of the primary link belonging to an SRLG that belongs to some link of the primary
path. Thus, the rule to be followed is to group links belonging to
E. Mannie (Editor) et al. Standard Track 17
path. Thus, the rule to be followed is to group links belonging to
exactly the same set of SRLGs. exactly the same set of SRLGs.
This type of sequential sub-division may result in a number of This type of sequential sub-division may result in a number of
bundles between two adjacent nodes. In practice, however, the link bundles between two adjacent nodes. In practice, however, the link
properties may not be very heterogeneous among component links properties may not be very heterogeneous among component links
between two adjacent nodes. Thus, the number of bundles in practice between two adjacent nodes. Thus, the number of bundles in practice
may not be large. may not be large.
7. Relationship with the UNI 5. Relationship with the UNI
The interface between an edge GMPLS node and a GMPLS LSR on the The interface between an edge GMPLS node and a GMPLS LSR on the
network side may be referred to as a User to Network Interface network side may be referred to as a User to Network Interface (UNI),
(UNI), while the interface between two-network side LSRs may be while the interface between two-network side LSRs may be referred to
referred to as a Network to Network Interface (NNI). as a Network to Network Interface (NNI).
GMPLS does not specify separately a UNI and an NNI. Edge nodes are GMPLS does not specify separately a UNI and an NNI. Edge nodes are
connected to LSRs on the network side, and these LSRs are in turn connected to LSRs on the network side, and these LSRs are in turn
connected between them. Of course, the behavior of an edge node is connected between them. Of course, the behavior of an edge node is
not exactly the same as the behavior of an LSR on the network side. not exactly the same as the behavior of an LSR on the network side.
Note also, that an edge node may run a routing protocol, however it Note also, that an edge node may run a routing protocol, however it
is expected that in most of the cases it will not (see also section is expected that in most of the cases it will not (see also section
7.2 and the section about signaling with an explicit route). 5.2 and the section about signaling with an explicit route).
Conceptually, a difference between UNI and NNI make sense either if Conceptually, a difference between UNI and NNI make sense either if
both interface uses completely different protocols, or if they use both interface uses completely different protocols, or if they use
the same protocols but with some outstanding differences. In the the same protocols but with some outstanding differences. In the
first case, separate protocols are often defined successively, with first case, separate protocols are often defined successively, with
more or less success. more or less success.
The GMPLS approach consisted in building a consistent model from day The GMPLS approach consisted in building a consistent model from day
one, considering both the UNI and NNI interfaces at the same time one, considering both the UNI and NNI interfaces at the same time
[GMPLS-OVERLAY]. For that purpose, a very few specific UNI [GMPLS-OVERLAY]. For that purpose, a very few specific UNI
particularities have been ignored in a first time. GMPLS has been particularities have been ignored in a first time. GMPLS has been
enhanced to support such particularities at the UNI by some other enhanced to support such particularities at the UNI by some other
standardization bodies (see hereafter). standardization bodies (see hereafter).
7.1. Relationship with the OIF UNI 5.1. Relationship with the OIF UNI
This section is only given for reference to the OIF work related to This section is only given for reference to the OIF work related to
GMPLS. The current OIF UNI specification [OIF-UNI] defines an GMPLS. The current OIF UNI specification [OIF-UNI] defines an
interface between a client SONET/SDH equipment and an SONET/SDH interface between a client SONET/SDH equipment and an SONET/SDH
network, each belonging to a distinct administrative authority. It network, each belonging to a distinct administrative authority. It
is designed for an overlay model. The OIF UNI defines additional is designed for an overlay model. The OIF UNI defines additional
mechanisms on the top of GMPLS for the UNI. mechanisms on the top of GMPLS for the UNI.
For instance, the OIF service discovery procedure is a precursor to For instance, the OIF service discovery procedure is a precursor to
obtaining UNI services. Service discovery allows a client to obtaining UNI services. Service discovery allows a client to
determine the static parameters of the interconnection with the determine the static parameters of the interconnection with the
network, including the UNI signaling protocol, the type of network, including the UNI signaling protocol, the type of
concatenation, the transparency level as well as the type of concatenation, the transparency level as well as the type of
diversity (node, link, SRLG) supported by the network. diversity (node, link, SRLG) supported by the network.
E. Mannie (Editor) et al. Standard Track 18 Since the current OIF UNI interface does not cover photonic networks,
Since the current OIF UNI interface does not cover photonic G.709 Digital Wrapper, etc, it is from that perspective a subset of
networks, G.709 Digital Wrapper, etc, it is from that perspective a the GMPLS Architecture at the UNI.
subset of the GMPLS Architecture at the UNI.
7.2. Reachability across the UNI 5.2. Reachability across the UNI
This section discusses the selection of an explicit route by an edge This section discusses the selection of an explicit route by an edge
node. The selection of the first LSR by an edge node connected to node. The selection of the first LSR by an edge node connected to
multiple LSRs is part of that problem. multiple LSRs is part of that problem.
An edge node (host or LSR) can participate more or less deeply in An edge node (host or LSR) can participate more or less deeply in the
the GMPLS routing. Four different routing models can be supported at GMPLS routing. Four different routing models can be supported at the
the UNI: configuration based, partial peering, silent listening and UNI: configuration based, partial peering, silent listening and full
full peering. peering.
- Configuration based: this routing model requires the manual or - Configuration based: this routing model requires the manual or
automatic configuration of an edge node with a list of neighbor LSRs automatic configuration of an edge node with a list of neighbor
sorted by preference order. Automatic configuration can be achieved LSRs sorted by preference order. Automatic configuration can be
using DHCP for instance. No routing information is exchanged at the achieved using DHCP for instance. No routing information is
UNI, except maybe the ordered list of LSRs. The only routing exchanged at the UNI, except maybe the ordered list of LSRs. The
information used by the edge node is that list. The edge node sends only routing information used by the edge node is that list. The
by default an LSP request to the preferred LSR. ICMP redirects could edge node sends by default an LSP request to the preferred LSR.
be send by this LSR to redirect some LSP requests to another LSR ICMP redirects could be send by this LSR to redirect some LSP
connected to the edge node. GMPLS does not preclude that model. requests to another LSR connected to the edge node. GMPLS does
not preclude that model.
- Partial peering: limited routing information (mainly reachability) - Partial peering: limited routing information (mainly reachability)
can be exchanged across the UNI using some extensions in the can be exchanged across the UNI using some extensions in the
signaling plane. The reachability information exchanged at the UNI signaling plane. The reachability information exchanged at the
may be used to initiate edge node specific routing decision over the UNI may be used to initiate edge node specific routing decision
network. GMPLS does not have any capability to support this model over the network. GMPLS does not have any capability to support
today. this model today.
- Silent listening: the edge node can silently listen to routing - Silent listening: the edge node can silently listen to routing
protocols and take routing decisions based on the information protocols and take routing decisions based on the information
obtained. An edge node receives the full routing information, obtained. An edge node receives the full routing information,
including traffic engineering extensions. One LSR should forward including traffic engineering extensions. One LSR should forward
transparently all routing PDUs to the edge node. An edge node can transparently all routing PDUs to the edge node. An edge node can
now compute a complete explicit route taking into consideration all now compute a complete explicit route taking into consideration
the end-to-end routing information. GMPLS does not preclude this all the end-to-end routing information. GMPLS does not preclude
model. this model.
- Full peering: in addition to silent listening, the edge node - Full peering: in addition to silent listening, the edge node
participates within the routing, establish adjacencies with its participates within the routing, establish adjacencies with its
neighbors and advertises LSAs. This is useful only if there are neighbors and advertises LSAs. This is useful only if there are
benefits for edge nodes to advertise themselves traffic engineering benefits for edge nodes to advertise themselves traffic
information. GMPLS does not preclude this model. engineering information. GMPLS does not preclude this model.
8. Link Management 6. Link Management
In the context of GMPLS, a pair of nodes (e.g., a photonic switch) In the context of GMPLS, a pair of nodes (e.g., a photonic switch)
may be connected by tens of fibers, and each fiber may be used to may be connected by tens of fibers, and each fiber may be used to
transmit hundreds of wavelengths if DWDM is used. Multiple fibers transmit hundreds of wavelengths if DWDM is used. Multiple fibers
and/or multiple wavelengths may also be combined into one or more and/or multiple wavelengths may also be combined into one or more
bundled links for routing purposes. Furthermore, to enable bundled links for routing purposes. Furthermore, to enable
E. Mannie (Editor) et al. Standard Track 19
communication between nodes for routing, signaling, and link communication between nodes for routing, signaling, and link
management, control channels must be established between a node management, control channels must be established between a node pair.
pair.
Link management is a collection of useful procedures between Link management is a collection of useful procedures between adjacent
adjacent nodes that provide local services such as control channel nodes that provide local services such as control channel management,
management, link connectivity verification, link property link connectivity verification, link property correlation, and fault
correlation, and fault management. The Link Management Protocol management. The Link Management Protocol (LMP) [LMP] has been
(LMP) [LMP] has been defined to fulfill these operations. LMP has defined to fulfill these operations. LMP has been initiated in the
been initiated in the context of GMPLS but is a generic toolbox that context of GMPLS but is a generic toolbox that can be also used in
can be also used in other contexts. other contexts.
In GMPLS, the control channels between two adjacent nodes are no In GMPLS, the control channels between two adjacent nodes are no
longer required to use the same physical medium as the data links longer required to use the same physical medium as the data links
between those nodes. Moreover, the control channels that are used to between those nodes. Moreover, the control channels that are used to
exchange the GMPLS control-plane information exist independently of exchange the GMPLS control-plane information exist independently of
the links they manage. Hence, LMP was designed to manage the data the links they manage. Hence, LMP was designed to manage the data
links, independently of the termination capabilities of those data links, independently of the termination capabilities of those data
links. links.
Control channel management and link property correlation procedures Control channel management and link property correlation procedures
are mandatory per LMP. Link connectivity verification and fault are mandatory per LMP. Link connectivity verification and fault
management procedures are optional. management procedures are optional.
8.1. Control Channel and Control Channel Management 6.1. Control Channel and Control Channel Management
LMP control channel management is used to establish and maintain LMP control channel management is used to establish and maintain
control channels between nodes. Control channels exist independently control channels between nodes. Control channels exist independently
of TE links, and can be used to exchange MPLS control-plane of TE links, and can be used to exchange MPLS control-plane
information such as signaling, routing, and link management information such as signaling, routing, and link management
information. information.
An "LMP adjacency" is formed between two nodes that support the same An "LMP adjacency" is formed between two nodes that support the same
LMP capabilities. Multiple control channels may be active LMP capabilities. Multiple control channels may be active
simultaneously for each adjacency. A control channel can be either simultaneously for each adjacency. A control channel can be either
explicitly configured or automatically selected, however, LMP explicitly configured or automatically selected, however, LMP
currently assume that control channels are explicitly configured currently assume that control channels are explicitly configured
while the configuration of the control channel capabilities can be while the configuration of the control channel capabilities can be
dynamically negotiated. dynamically negotiated.
For the purposes of LMP, the exact implementation of the control For the purposes of LMP, the exact implementation of the control
channel is left unspecified. The control channel(s) between two channel is left unspecified. The control channel(s) between two
adjacent nodes is no longer required to use the same physical medium adjacent nodes is no longer required to use the same physical medium
as the data-bearing links between those nodes. For example, a as the data-bearing links between those nodes. For example, a
control channel could use a separate wavelength or fiber, an control channel could use a separate wavelength or fiber, an Ethernet
Ethernet link, or an IP tunnel through a separate management link, or an IP tunnel through a separate management network.
network.
A consequence of allowing the control channel(s) between two nodes A consequence of allowing the control channel(s) between two nodes to
to be physically diverse from the associated data-bearing links is be physically diverse from the associated data-bearing links is that
that the health of a control channel does not necessarily correlate the health of a control channel does not necessarily correlate to the
to the health of the data-bearing links, and vice-versa. Therefore, health of the data-bearing links, and vice-versa. Therefore, new
new mechanisms have been developed in LMP to manage links, both in mechanisms have been developed in LMP to manage links, both in terms
terms of link provisioning and fault isolation. of link provisioning and fault isolation.
E. Mannie (Editor) et al. Standard Track 20
LMP does not specify the signaling transport mechanism used in the LMP does not specify the signaling transport mechanism used in the
control channel, however it states that messages transported over a control channel, however it states that messages transported over a
control channel must be IP encoded. Furthermore, since the messages control channel must be IP encoded. Furthermore, since the messages
are IP encoded, the link level encoding is not part of LMP. A 32-bit are IP encoded, the link level encoding is not part of LMP. A 32-bit
non-zero integer Control Channel Identifier (CCId) is assigned to non-zero integer Control Channel Identifier (CCId) is assigned to
each direction of a control channel. each direction of a control channel.
Each control channel individually negotiates its control channel Each control channel individually negotiates its control channel
parameters and maintains connectivity using a fast Hello protocol. parameters and maintains connectivity using a fast Hello protocol.
The latter is required if lower-level mechanisms are not available The latter is required if lower-level mechanisms are not available to
to detect link failures. detect link failures.
The Hello protocol of LMP is intended to be a lightweight keep-alive The Hello protocol of LMP is intended to be a lightweight keep-alive
mechanism that will react to control channel failures rapidly so mechanism that will react to control channel failures rapidly so that
that IGP Hellos are not lost and the associated link-state IGP Hellos are not lost and the associated link-state adjacencies are
adjacencies are not removed uselessly. not removed uselessly.
The Hello protocol consists of two phases: a negotiation phase and a The Hello protocol consists of two phases: a negotiation phase and a
keep-alive phase. The negotiation phase allows negotiation of some keep-alive phase. The negotiation phase allows negotiation of some
basic Hello protocol parameters, like the Hello frequency. The keep- basic Hello protocol parameters, like the Hello frequency. The
alive phase consists of a fast lightweight bi-directional Hello keep-alive phase consists of a fast lightweight bi-directional Hello
message exchange. message exchange.
If a group of control channels share a common node pair and support If a group of control channels share a common node pair and support
the same LMP capabilities, then LMP control channel messages (except the same LMP capabilities, then LMP control channel messages (except
Configuration messages, and Hello's) may be transmitted over any of Configuration messages, and Hello's) may be transmitted over any of
the active control channels without coordination between the local the active control channels without coordination between the local
and remote nodes. and remote nodes.
For LMP, it is essential that at least one control channel is always For LMP, it is essential that at least one control channel is always
available. In case of control channel failure, it may be possible to available. In case of control channel failure, it may be possible to
use an alternate active control channel without coordination. use an alternate active control channel without coordination.
8.2. Link Property Correlation 6.2. Link Property Correlation
As part of LMP, a link property correlation exchange is defined. As part of LMP, a link property correlation exchange is defined. The
The exchange is used to aggregate multiple data-bearing links (i.e. exchange is used to aggregate multiple data-bearing links (i.e.,
component links) into a bundled link and exchange, correlate, or component links) into a bundled link and exchange, correlate, or
change TE link parameters. The link property correlation exchange change TE link parameters. The link property correlation exchange
may be done at any time a link is up and not in the Verification may be done at any time a link is up and not in the Verification
process (see next section). process (see next section).
It allows for instance to add component links to a link bundle, It allows, for instance, the addition of component links to a link
change link's minimum/maximum reservable bandwidth, change port bundle, change of a link's minimum/maximum reservable bandwidth,
identifiers, or change component identifiers in a bundle. This change of port identifiers, or change of component identifiers in a
mechanism is supported by an exchange of link summary messages. bundle. This mechanism is supported by an exchange of link summary
messages.
8.3. Link Connectivity Verification 6.3. Link Connectivity Verification
Link connectivity verification is an optional procedure that may be Link connectivity verification is an optional procedure that may be
used to verify the physical connectivity of data-bearing links as used to verify the physical connectivity of data-bearing links as
well as to exchange the link identifiers that are used in the GMPLS well as to exchange the link identifiers that are used in the GMPLS
signaling. signaling.
E. Mannie (Editor) et al. Standard Track 21 This procedure should be performed initially when a data-bearing link
This procedure should be performed initially when a data-bearing is first established, and subsequently, on a periodic basis for all
link is first established, and subsequently, on a periodic basis for unallocated (free) data-bearing links.
all unallocated (free) data-bearing links.
The verification procedure consists of sending Test messages in-band The verification procedure consists of sending Test messages in-band
over the data-bearing links. This requires that the unallocated over the data-bearing links. This requires that the unallocated
links must be opaque; however, multiple degrees of opaqueness (e.g., links must be opaque; however, multiple degrees of opaqueness (e.g.,
examining overhead bytes, terminating the payload, etc.), and hence examining overhead bytes, terminating the payload, etc.), and hence
different mechanisms to transport the Test messages, are specified. different mechanisms to transport the Test messages, are specified.
Note that the Test message is the only LMP message that is Note that the Test message is the only LMP message that is
transmitted over the data-bearing link, and that Hello messages transmitted over the data-bearing link, and that Hello messages
continue to be exchanged over the control channel during the link continue to be exchanged over the control channel during the link
verification process. Data-bearing links are tested in the transmit verification process. Data-bearing links are tested in the transmit
direction as they are unidirectional. As such, it is possible for direction as they are unidirectional. As such, it is possible for
LMP neighboring nodes to exchange the Test messages simultaneously LMP neighboring nodes to exchange the Test messages simultaneously in
in both directions. both directions.
To initiate the link verification procedure, a node must first To initiate the link verification procedure, a node must first notify
notify the adjacent node that it will begin sending Test messages the adjacent node that it will begin sending Test messages over a
over a particular data-bearing link, or over the component links of particular data-bearing link, or over the component links of a
a particular bundled link. The node must also indicate the number of particular bundled link. The node must also indicate the number of
data-bearing links that are to be verified; the interval at which data-bearing links that are to be verified; the interval at which the
the test messages will be sent; the encoding scheme, the transport test messages will be sent; the encoding scheme, the transport
mechanisms that are supported, the data rate for Test messages; and, mechanisms that are supported, the data rate for Test messages; and,
in the case where the data-bearing links correspond to fibers, the in the case where the data-bearing links correspond to fibers, the
wavelength over which the Test messages will be transmitted. wavelength over which the Test messages will be transmitted.
Furthermore, the local and remote bundled link identifiers are Furthermore, the local and remote bundled link identifiers are
transmitted at this time to perform the component link association transmitted at this time to perform the component link association
with the bundled link identifiers. with the bundled link identifiers.
8.4. Fault Management 6.4. Fault Management
Fault management is an important requirement from the operational Fault management is an important requirement from the operational
point of view. Fault management includes usually: fault detection, point of view. Fault management includes usually: fault detection,
fault localization and fault notification. When a failure occurs and fault localization and fault notification. When a failure occurs and
is detected (fault detection), an operator needs to know exactly is detected (fault detection), an operator needs to know exactly
where it happened (fault localization) and a source node may need to where it happened (fault localization) and a source node may need to
be notified in order to take some actions (fault notification). be notified in order to take some actions (fault notification).
Note that fault localization can also be used to support some Note that fault localization can also be used to support some
specific (local) protection/restoration mechanisms. specific (local) protection/restoration mechanisms.
In new technologies such as transparent photonic switching currently In new technologies such as transparent photonic switching currently
no method is defined to locate a fault, and the mechanism by which no method is defined to locate a fault, and the mechanism by which
the fault information is propagated must be sent "out of band" (via the fault information is propagated must be sent "out of band" (via
the control plane). the control plane).
LMP provides a fault localization procedure that can be used to LMP provides a fault localization procedure that can be used to
rapidly localize link failures, by notifying a fault up to the node rapidly localize link failures, by notifying a fault up to the node
upstream of that fault (i.e. through a fault notification upstream of that fault (i.e., through a fault notification
procedure). procedure).
E. Mannie (Editor) et al. Standard Track 22
A downstream LMP neighbor that detects data link failures will send A downstream LMP neighbor that detects data link failures will send
an LMP message to its upstream neighbor notifying it of the failure. an LMP message to its upstream neighbor notifying it of the failure.
When an upstream node receives a failure notification, it can When an upstream node receives a failure notification, it can
correlate the failure with the corresponding input ports to correlate the failure with the corresponding input ports to determine
determine if the failure is between the two nodes. Once the failure if the failure is between the two nodes. Once the failure has been
has been localized, the signaling protocols can be used to initiate localized, the signaling protocols can be used to initiate link or
link or path protection/restoration procedures. path protection/restoration procedures.
8.5 LMP for DWDM Optical Line Systems (OLSs) 6.5. LMP for DWDM Optical Line Systems (OLSs)
In an all-optical environment, LMP focuses on peer communications In an all-optical environment, LMP focuses on peer communications
(e.g. OXC-to-OXC). A great deal of information about a link between (e.g., OXC-to-OXC). A great deal of information about a link between
two OXCs is known by the OLS (Optical Line System or WDM Terminal two OXCs is known by the OLS (Optical Line System or WDM Terminal
multiplexer). Exposing this information to the control plane can multiplexer). Exposing this information to the control plane can
improve network usability by further reducing required manual improve network usability by further reducing required manual
configuration, and by greatly enhancing fault detection and configuration, and by greatly enhancing fault detection and recovery.
recovery.
LMP-WDM [LMP-WDM] defines extensions to LMP for use between an OXC LMP-WDM [LMP-WDM] defines extensions to LMP for use between an OXC
and an OLS. These extensions are intended to satisfy the Optical and an OLS. These extensions are intended to satisfy the Optical
Link Interface Requirements described in [OLI-REQ]. Link Interface Requirements described in [OLI-REQ].
Fault detection is particularly an issue when the network is using Fault detection is particularly an issue when the network is using
all-optical photonic switches (PXC). Once a connection is all-optical photonic switches (PXC). Once a connection is
established, PXCs have only limited visibility into the health of established, PXCs have only limited visibility into the health of the
the connection. Although the PXC is all-optical, long-haul OLSs connection. Although the PXC is all-optical, long-haul OLSs
typically terminate channels electrically and regenerate them typically terminate channels electrically and regenerate them
optically. This provides an opportunity to monitor the health of a optically. This provides an opportunity to monitor the health of a
channel between PXCs. LMP-WDM can then be used by the OLS to provide channel between PXCs. LMP-WDM can then be used by the OLS to provide
this information to the PXC. this information to the PXC.
In addition to the link information known to the OLS that is In addition to the link information known to the OLS that is
exchanged through LMP-WDM, some information known to the OXC may exchanged through LMP-WDM, some information known to the OXC may also
also be exchanged with the OLS through LMP-WDM. This information is be exchanged with the OLS through LMP-WDM. This information is
useful for alarm management and link monitoring (e.g. trace useful for alarm management and link monitoring (e.g., trace
monitoring). Alarm management is important because the monitoring). Alarm management is important because the
administrative state of a connection, known to the OXC (e.g. this administrative state of a connection, known to the OXC (e.g., this
information may be learned through the Admin Status object of GMPLS information may be learned through the Admin Status object of GMPLS
signaling [RFC3471]), can be used to suppress spurious alarms. For signaling [RFC3471]), can be used to suppress spurious alarms. For
example, the OXC may know that a connection is "up", "down", in a example, the OXC may know that a connection is "up", "down", in a
"testing" mode, or being deleted ("deletion-in-progress"). The OXC "testing" mode, or being deleted ("deletion-in-progress"). The OXC
can use this information to inhibit alarm reporting from the OLS can use this information to inhibit alarm reporting from the OLS when
when a connection is "down", "testing", or being deleted. a connection is "down", "testing", or being deleted.
It is important to note that an OXC may peer with one or more OLSs It is important to note that an OXC may peer with one or more OLSs
and an OLS may peer with one or more OXCs. Although there are many and an OLS may peer with one or more OXCs. Although there are many
similarities between an OXC-OXC LMP session and an OXC-OLS LMP similarities between an OXC-OXC LMP session and an OXC-OLS LMP
session, particularly for control management and link verification, session, particularly for control management and link verification,
there are some differences as well. These differences can primarily there are some differences as well. These differences can primarily
be attributed to the nature of an OXC-OLS link, and the purpose of be attributed to the nature of an OXC-OLS link, and the purpose of
OXC-OLS LMP sessions. The OXC-OXC links can be used to provide the OXC-OLS LMP sessions. The OXC-OXC links can be used to provide the
basis for GMPLS signaling and routing at the optical layer. The basis for GMPLS signaling and routing at the optical layer. The
information exchanged over LMP-WDM sessions is used to augment information exchanged over LMP-WDM sessions is used to augment
knowledge about the links between OXCs. knowledge about the links between OXCs.
E. Mannie (Editor) et al. Standard Track 23
In order for the information exchanged over the OXC-OLS LMP sessions In order for the information exchanged over the OXC-OLS LMP sessions
to be used by the OXC-OXC session, the information must be to be used by the OXC-OXC session, the information must be
coordinated by the OXC. However, the OXC-OXC and OXC-OLS LMP coordinated by the OXC. However, the OXC-OXC and OXC-OLS LMP
sessions are run independently and must be maintained separately. sessions are run independently and must be maintained separately. One
One critical requirement when running an OXC-OLS LMP session is the critical requirement when running an OXC-OLS LMP session is the
ability of the OLS to make a data link transparent when not doing ability of the OLS to make a data link transparent when not doing the
the verification procedure. This is because the same data link may verification procedure. This is because the same data link may be
be verified between OXC-OLS and between OXC-OXC. The verification verified between OXC-OLS and between OXC-OXC. The verification
procedure of LMP is used to coordinate the Test procedure (and hence procedure of LMP is used to coordinate the Test procedure (and hence
the transparency/opaqueness of the data links). To maintain the transparency/opaqueness of the data links). To maintain
independence between the sessions, it must be possible for the LMP independence between the sessions, it must be possible for the LMP
sessions to come up in any order. In particular, it must be possible sessions to come up in any order. In particular, it must be possible
for an OXC-OXC LMP session to come up without an OXC-OLS LMP session for an OXC-OXC LMP session to come up without an OXC-OLS LMP session
being brought up, and vice-versa. being brought up, and vice-versa.
9. Generalized Signaling 7. Generalized Signaling
The GMPLS signaling extends certain base functions of the RSVP-TE The GMPLS signaling extends certain base functions of the RSVP-TE and
and CR-LDP signaling and, in some cases, adds functionality. These CR-LDP signaling and, in some cases, adds functionality. These
changes and additions impact basic LSP properties: how labels are changes and additions impact basic LSP properties: how labels are
requested and communicated, the unidirectional nature of LSPs, how requested and communicated, the unidirectional nature of LSPs, how
errors are propagated, and information provided for synchronizing errors are propagated, and information provided for synchronizing the
the ingress and egress. ingress and egress.
The core GMPLS signaling specification is available in three parts: The core GMPLS signaling specification is available in three parts:
1. A signaling functional description [RFC3471]. 1. A signaling functional description [RFC3471].
2. RSVP-TE extensions [RFC3473]. 2. RSVP-TE extensions [RFC3473].
3. CR-LDP extensions [RFC3472]. 3. CR-LDP extensions [RFC3472].
In addition, independent parts are available per technology: In addition, independent parts are available per technology:
1. GMPLS extensions for SONET and SDH control [GMPLS-SONET-SDH]. 1. GMPLS extensions for SONET and SDH control [RFC3946].
2. GMPLS extensions for G.709 control [GMPLS-G709]. 2. GMPLS extensions for G.709 control [GMPLS-G709].
The following MPLS profile expressed in terms of MPLS features The following MPLS profile expressed in terms of MPLS features
[RFC3031] applies to GMPLS: [RFC3031] applies to GMPLS:
- Downstream-on-demand label allocation and distribution. - Downstream-on-demand label allocation and distribution.
- Ingress initiated ordered control.
- Liberal (typical), or conservative (could) label retention - Ingress initiated ordered control.
mode.
- Request, traffic/data, or topology driven label allocation - Liberal (typical), or conservative (could) label retention mode.
strategy.
- Explicit routing (typical), or hop-by-hop routing. - Request, traffic/data, or topology driven label allocation
strategy.
- Explicit routing (typical), or hop-by-hop routing.
The GMPLS signaling defines the following new building blocks on the The GMPLS signaling defines the following new building blocks on the
top of MPLS-TE: top of MPLS-TE:
1. A new generic label request format. 1. A new generic label request format.
2. Labels for TDM, LSC and FSC interfaces, generically known as 2. Labels for TDM, LSC and FSC interfaces, generically known as
Generalized Label. Generalized Label.
3. Waveband switching support. 3. Waveband switching support.
4. Label suggestion by the upstream for optimization purposes (e.g.,
E. Mannie (Editor) et al. Standard Track 24 latency).
4. Label suggestion by the upstream for optimization purposes 5. Label restriction by the upstream to support some optical
(e.g. latency). constraints.
5. Label restriction by the upstream to support some optical 6. Bi-directional LSP establishment with contention resolution.
constraints. 7. Rapid failure notification extensions.
6. Bi-directional LSP establishment with contention resolution. 8. Protection information currently focusing on link protection,
7. Rapid failure notification extensions. plus primary and secondary LSP indication.
8. Protection information currently focusing on link protection, 9. Explicit routing with explicit label control for a fine degree of
plus primary and secondary LSP indication. control.
9. Explicit routing with explicit label control for a fine 10. Specific traffic parameters per technology.
degree of control. 11. LSP administrative status handling.
10. Specific traffic parameters per technology. 12. Control channel separation.
11. LSP administrative status handling.
12. Control channel separation.
These building blocks will be described in more details in the These building blocks will be described in more details in the
following. A complete specification can be found in the following. A complete specification can be found in the
corresponding documents. corresponding documents.
Note that GMPLS is highly generic and has many options. Only Note that GMPLS is highly generic and has many options. Only
building blocks 1, 2 and 10 are mandatory, and only within the building blocks 1, 2 and 10 are mandatory, and only within the
specific format that is needed. Typically, building blocks 6 and 9 specific format that is needed. Typically, building blocks 6 and 9
should be implemented. Building blocks 3, 4, 5, 7, 8, 11 and 12 are should be implemented. Building blocks 3, 4, 5, 7, 8, 11 and 12 are
optional. optional.
A typical SONET/SDH switching network would implement building A typical SONET/SDH switching network would implement building
blocks: 1, 2 (the SONET/SDH label), 6, 9, 10 and 11. Building blocks blocks: 1, 2 (the SONET/SDH label), 6, 9, 10 and 11. Building blocks
7 and 8 are optional since protection can be achieved using SONET/ 7 and 8 are optional since the protection can be achieved using
SDH overhead bytes. SONET/SDH overhead bytes.
A typical wavelength switching network would implement building A typical wavelength switching network would implement building
blocks: 1, 2 (the generic format), 4, 5, 6, 7, 8, 9 and 11. Building blocks: 1, 2 (the generic format), 4, 5, 6, 7, 8, 9 and 11. Building
block 3 is only needed in the particular case of waveband switching. block 3 is only needed in the particular case of waveband switching.
A typical fiber switching network would implement building blocks: A typical fiber switching network would implement building blocks:
1, 2 (the generic format), 6, 7, 8, 9 and 11. 1, 2 (the generic format), 6, 7, 8, 9 and 11.
A typical MPLS-IP network would not implement any of these building A typical MPLS-IP network would not implement any of these building
blocks, since the absence of building block 1 would indicate regular blocks, since the absence of building block 1 would indicate regular
MPLS-IP. Note however that building block 1 and 8 can be used to MPLS-IP. Note however that building block 1 and 8 can be used to
signal MPLS-IP as well. In that case, the MPLS-IP network can signal MPLS-IP as well. In that case, the MPLS-IP network can
benefit from the link protection type (not available in CR-LDP, some benefit from the link protection type (not available in CR-LDP, some
very basic form being available in RSVP-TE). Building block 2 is very basic form being available in RSVP-TE). Building block 2 is
here a regular MPLS label and no new label format is required. here a regular MPLS label and no new label format is required.
GMPLS does not specify any profile for RSVP-TE and CR-LDP GMPLS does not specify any profile for RSVP-TE and CR-LDP
implementations that have to support GMPLS - except for what is implementations that have to support GMPLS - except for what is
directly related to GMPLS procedures. It is to the manufacturer to directly related to GMPLS procedures. It is to the manufacturer to
decide which are the optional elements and procedures of RSVP-TE and decide which are the optional elements and procedures of RSVP-TE and
CR-LDP that need to be implemented. Some optional MPLS-TE elements CR-LDP that need to be implemented. Some optional MPLS-TE elements
can be useful for TDM, LSC and FSC layers, for instance the setup can be useful for TDM, LSC and FSC layers, for instance the setup and
and holding priorities that are inherited from MPLS-TE. holding priorities that are inherited from MPLS-TE.
9.1. Overview: How to Request an LSP 7.1. Overview: How to Request an LSP
E. Mannie (Editor) et al. Standard Track 25
A TDM, LSC or FSC LSP is established by sending a PATH/Label Request A TDM, LSC or FSC LSP is established by sending a PATH/Label Request
message downstream to the destination. This message contains a message downstream to the destination. This message contains a
Generalized Label Request with the type of LSP (i.e. the layer Generalized Label Request with the type of LSP (i.e., the layer
concerned), and its payload type. An Explicit Route Object (ERO) is concerned), and its payload type. An Explicit Route Object (ERO) is
also normally added to the message, but this can be added and/or also normally added to the message, but this can be added and/or
completed by the first/default LSR. completed by the first/default LSR.
The requested bandwidth is encoded in the RSVP-TE SENDER_TSPEC The requested bandwidth is encoded in the RSVP-TE SENDER_TSPEC
object, or in the CR-LDP Traffic Parameters TLV. Specific parameters object, or in the CR-LDP Traffic Parameters TLV. Specific parameters
for a given technology are given in these traffic parameters, such for a given technology are given in these traffic parameters, such as
as the type of signal, concatenation and/or transparency for a the type of signal, concatenation and/or transparency for a SONET/SDH
SONET/SDH LSP. For some other technology there be could just one LSP. For some other technology there be could just one bandwidth
bandwidth parameter indicating the bandwidth as a floating-point parameter indicating the bandwidth as a floating-point value.
value.
The requested local protection per link may be requested using the The requested local protection per link may be requested using the
Protection Information Object/TLV. The end-to-end LSP protection is Protection Information Object/TLV. The end-to-end LSP protection is
for further study and is introduced LSP protection/restoration for further study and is introduced LSP protection/restoration
section (see after). section (see after).
If the LSP is a bi-directional LSP, an Upstream Label is also If the LSP is a bi-directional LSP, an Upstream Label is also
specified in the Path/Label Request message. This label will be the specified in the Path/Label Request message. This label will be the
one to use in the upstream direction. one to use in the upstream direction.
Additionally, a Suggested Label, a Label Set and a Waveband Label Additionally, a Suggested Label, a Label Set and a Waveband Label can
can also be included in the message. Other operations are defined in also be included in the message. Other operations are defined in
MPLS-TE. MPLS-TE.
The downstream node will send back a Resv/Label Mapping message The downstream node will send back a Resv/Label Mapping message
including one Generalized Label object/TLV that can contain several including one Generalized Label object/TLV that can contain several
Generalized Labels. For instance, if a concatenated SONET/SDH signal Generalized Labels. For instance, if a concatenated SONET/SDH signal
is requested, several labels can be returned. is requested, several labels can be returned.
In case of SONET/SDH virtual concatenation, a list of labels is In case of SONET/SDH virtual concatenation, a list of labels is
returned. Each label identifying one element of the virtual returned. Each label identifying one element of the virtual
concatenated signal. This limits virtual concatenation to remain concatenated signal. This limits virtual concatenation to remain
within a single (component) link. within a single (component) link.
In case of any type of SONET/SDH contiguous concatenation, only one In case of any type of SONET/SDH contiguous concatenation, only one
label is returned. That label is the lowest signal of the contiguous label is returned. That label is the lowest signal of the contiguous
concatenated signal (given an order specified in [GMPLS-SONET-SDH]). concatenated signal (given an order specified in [RFC3946]).
In case of SONET/SDH "multiplication", i.e. co-routing of circuits In case of SONET/SDH "multiplication", i.e., co-routing of circuits
of the same type but without concatenation but all belonging to the of the same type but without concatenation but all belonging to the
same LSP, the explicit ordered list of all signals that take part in same LSP, the explicit ordered list of all signals that take part in
the LSP is returned. the LSP is returned.
9.2. Generalized Label Request 7.2. Generalized Label Request
The Generalized Label Request is a new object/TLV to be added in an The Generalized Label Request is a new object/TLV to be added in an
RSVP-TE Path message instead of the regular Label Request, or in a RSVP-TE Path message instead of the regular Label Request, or in a
CR-LDP Request message in addition to the already existing TLVs. CR-LDP Request message in addition to the already existing TLVs. Only
Only one label request can be used per message, so a single LSP can one label request can be used per message, so a single LSP can be
be requested at a time per signaling message. requested at a time per signaling message.
E. Mannie (Editor) et al. Standard Track 26
The Generalized Label Request gives three major characteristics The Generalized Label Request gives three major characteristics
(parameters) required to support the LSP being requested: the LSP (parameters) required to support the LSP being requested: the LSP
Encoding Type, the Switching Type that must be used and the LSP Encoding Type, the Switching Type that must be used and the LSP
payload type called Generalized PID (G-PID). payload type called Generalized PID (G-PID).
The LSP Encoding Type indicates the encoding type that will be used The LSP Encoding Type indicates the encoding type that will be used
with the data associated with the LSP, i.e. the type of technology with the data associated with the LSP, i.e., the type of technology
being considered. For instance, it can be SDH, SONET, Ethernet, ANSI being considered. For instance, it can be SDH, SONET, Ethernet, ANSI
PDH, etc. It represents the nature of the LSP, and not the nature of PDH, etc. It represents the nature of the LSP, and not the nature of
the links that the LSP traverses. This is used hop-by-hop by each the links that the LSP traverses. This is used hop-by-hop by each
node. node.
A link may support a set of encoding formats, where support means A link may support a set of encoding formats, where support means
that a link is able to carry and switch a signal of one or more of that a link is able to carry and switch a signal of one or more of
these encoding formats. The Switching Type indicates then the type these encoding formats. The Switching Type indicates then the type
of switching that should be performed on a particular link for that of switching that should be performed on a particular link for that
LSP. This information is needed for links that advertise more than LSP. This information is needed for links that advertise more than
one type of switching capability. one type of switching capability.
Nodes must verify that the type indicated in the Switching Type is Nodes must verify that the type indicated in the Switching Type is
supported on the corresponding incoming interface; otherwise, the supported on the corresponding incoming interface; otherwise, the
node must generate a notification message with a "Routing node must generate a notification message with a "Routing
problem/Switching Type" indication. problem/Switching Type" indication.
The LSP payload type (G-PID) identifies the payload carried by the The LSP payload type (G-PID) identifies the payload carried by the
LSP, i.e. an identifier of the client layer of that LSP. For some LSP, i.e., an identifier of the client layer of that LSP. For some
technologies, it also indicates the mapping used by the client technologies, it also indicates the mapping used by the client layer,
layer, e.g. byte synchronous mapping of E1. This must be interpreted e.g., byte synchronous mapping of E1. This must be interpreted
according to the LSP encoding type and is used by the nodes at the according to the LSP encoding type and is used by the nodes at the
endpoints of the LSP to know to which client layer a request is endpoints of the LSP to know to which client layer a request is
destined, and in some cases by the penultimate hop. destined, and in some cases by the penultimate hop.
Other technology specific parameters are not transported in the Other technology specific parameters are not transported in the
Generalized Label Request but in technology specific traffic Generalized Label Request but in technology specific traffic
parameters as explained hereafter. Currently, two set of traffic parameters as explained hereafter. Currently, two set of traffic
parameters are defined, one for SONET/SDH and one for G.709. parameters are defined, one for SONET/SDH and one for G.709.
Note that it is expected than specific traffic parameters will be Note that it is expected than specific traffic parameters will be
defined in the future for photonic (all optical) switching. defined in the future for photonic (all optical) switching.
9.3. SONET/SDH Traffic Parameters 7.3. SONET/SDH Traffic Parameters
The GMPLS SONET/SDH traffic parameters [GMPLS-SONET-SDH] specify a The GMPLS SONET/SDH traffic parameters [RFC3946] specify a powerful
powerful set of capabilities for SONET [ANSI T1.105] and SDH [ITU-T set of capabilities for SONET [ANSI-T1.105] and SDH [ITUT-G.707].
G.707].
The first traffic parameter specifies the type of the elementary The first traffic parameter specifies the type of the elementary
SONET/SDH signal that comprises the requested LSP, e.g. VC-11, VT6, SONET/SDH signal that comprises the requested LSP, e.g., VC-11, VT6,
VC-4, STS-3c, etc. Several transforms can then be applied VC-4, STS-3c, etc. Several transforms can then be applied
successively on the elementary Signal to build the final signal successively on the elementary Signal to build the final signal being
being actually requested for the LSP. actually requested for the LSP.
E. Mannie (Editor) et al. Standard Track 27
These transforms are the contiguous concatenation, the virtual These transforms are the contiguous concatenation, the virtual
concatenation, the transparency and the multiplication. Each one is concatenation, the transparency and the multiplication. Each one is
optional. They must be applied strictly in the following order: optional. They must be applied strictly in the following order:
- First, contiguous concatenation can be optionally applied on the - First, contiguous concatenation can be optionally applied on the
Elementary Signal, resulting in a contiguously concatenated Elementary Signal, resulting in a contiguously concatenated
signal. signal.
- Second, virtual concatenation can be optionally applied either
directly on the elementary Signal, or on the contiguously - Second, virtual concatenation can be optionally applied either
concatenated signal obtained from the previous phase. directly on the elementary Signal, or on the contiguously
- Third, some transparency can be optionally specified when concatenated signal obtained from the previous phase.
requesting a frame as signal rather than a container. Several
transparency packages are defined. - Third, some transparency can be optionally specified when
- Fourth, a multiplication can be optionally applied either directly requesting a frame as signal rather than a container. Several
on the elementary Signal, or on the contiguously concatenated transparency packages are defined.
signal obtained from the first phase, or on the virtually
concatenated signal obtained from the second phase, or on these - Fourth, a multiplication can be optionally applied either directly
signals combined with some transparency. on the elementary Signal, or on the contiguously concatenated
signal obtained from the first phase, or on the virtually
concatenated signal obtained from the second phase, or on these
signals combined with some transparency.
For RSVP-TE, the SONET/SDH traffic parameters are carried in a new For RSVP-TE, the SONET/SDH traffic parameters are carried in a new
SENDER_TSPEC and FLOWSPEC. The same format is used for both. There SENDER_TSPEC and FLOWSPEC. The same format is used for both. There
is no Adspec associated with the SENDER_TSPEC, it is omitted or a is no Adspec associated with the SENDER_TSPEC, it is omitted or a
default value is used. The content of the FLOWSPEC object received default value is used. The content of the FLOWSPEC object received
in a Resv message should be identical to the content of the in a Resv message should be identical to the content of the
SENDER_TSPEC of the corresponding Path message. In other words, the SENDER_TSPEC of the corresponding Path message. In other words, the
receiver is normally not allowed to change the values of the traffic receiver is normally not allowed to change the values of the traffic
parameters. However, some level of negotiation may be achieved as parameters. However, some level of negotiation may be achieved as
explained in [GMPLS-SONET-SDH]. explained in [RFC3946].
For CR-LDP, the SONET/SDH traffic parameters are simply carried in a For CR-LDP, the SONET/SDH traffic parameters are simply carried in a
new TLV. new TLV.
Note that a general discussion on SONET/SDH and GMPLS can be found Note that a general discussion on SONET/SDH and GMPLS can be found in
in [SONET-SDH-GMPLS-FRM]. [SONET-SDH-GMPLS-FRM].
9.4. G.709 Traffic Parameters 7.4. G.709 Traffic Parameters
Simply said, an [ITU-T G.709] based network is decomposed in two Simply said, an [ITUT-G.709] based network is decomposed in two major
major layers: an optical layer (i.e. made of wavelengths) and a layers: an optical layer (i.e., made of wavelengths) and a digital
digital layer. These two layers are divided into sub-layers and layer. These two layers are divided into sub-layers and switching
switching occurs at two specific sub-layers: at the OCh (Optical occurs at two specific sub-layers: at the OCh (Optical Channel)
Channel) optical layer and at the ODU (Optical channel Data Unit) optical layer and at the ODU (Optical channel Data Unit) electrical
electrical layer. The ODUk notation is used to denote ODUs at layer. The ODUk notation is used to denote ODUs at different
different bandwidths. bandwidths.
The GMPLS G.709 traffic parameters [GMPLS-G709] specify a powerful The GMPLS G.709 traffic parameters [GMPLS-G709] specify a powerful
set of capabilities for ITU-T G.709 networks. set of capabilities for ITU-T G.709 networks.
The first traffic parameter specifies the type of the elementary The first traffic parameter specifies the type of the elementary
G.709 signal that comprises the requested LSP, e.g. ODU1, OCh at 40 G.709 signal that comprises the requested LSP, e.g., ODU1, OCh at 40
Gbps, etc. Several transforms can then be applied successively on Gbps, etc. Several transforms can then be applied successively on
the elementary Signal to build the final signal being actually the elementary Signal to build the final signal being actually
requested for the LSP. requested for the LSP.
E. Mannie (Editor) et al. Standard Track 28
These transforms are the virtual concatenation and the These transforms are the virtual concatenation and the
multiplication. Each one of these transforms is optional. They must multiplication. Each one of these transforms is optional. They must
be applied strictly in the following order: be applied strictly in the following order:
- First, virtual concatenation can be optionally applied directly on - First, virtual concatenation can be optionally applied directly on
the elementary Signal, the elementary Signal,
- Second, a multiplication can be optionally applied, either
directly on the elementary Signal, or on the virtually - Second, a multiplication can be optionally applied, either
concatenated signal obtained from the first phase. directly on the elementary Signal, or on the virtually
concatenated signal obtained from the first phase.
Additional ODUk Multiplexing traffic parameters allow indicating an Additional ODUk Multiplexing traffic parameters allow indicating an
ODUk mapping (ODUj into ODUk) for an ODUk multiplexing LSP request. ODUk mapping (ODUj into ODUk) for an ODUk multiplexing LSP request.
G.709 supports the following multiplexing capabilities: ODUj into G.709 supports the following multiplexing capabilities: ODUj into
ODUk (k > j) and ODU1 with ODU2 multiplexing into ODU3. ODUk (k > j) and ODU1 with ODU2 multiplexing into ODU3.
For RSVP-TE, the G.709 traffic parameters are carried in a new For RSVP-TE, the G.709 traffic parameters are carried in a new
SENDER-TSPEC and FLOWSPEC. The same format is used for both. There SENDER-TSPEC and FLOWSPEC. The same format is used for both. There
is no Adspec associated with the SENDER_TSPEC, it is omitted or a is no Adspec associated with the SENDER_TSPEC, it is omitted or a
default value is used. The content of the FLOWSPEC object received default value is used. The content of the FLOWSPEC object received
in a Resv message should be identical to the content of the in a Resv message should be identical to the content of the
SENDER_TSPEC of the corresponding Path message. SENDER_TSPEC of the corresponding Path message.
For CR-LDP, the G.709 traffic parameters are simply carried in a new For CR-LDP, the G.709 traffic parameters are simply carried in a new
TLV. TLV.
9.5. Bandwidth Encoding 7.5. Bandwidth Encoding
Some technologies that do not have (yet) specific traffic parameters Some technologies that do not have (yet) specific traffic parameters
just require a bandwidth encoding transported in a generic form. just require a bandwidth encoding transported in a generic form.
Bandwidth is carried in 32-bit number in IEEE floating-point format Bandwidth is carried in 32-bit number in IEEE floating-point format
(the unit is bytes per second). Values are carried in a per protocol (the unit is bytes per second). Values are carried in a per protocol
specific manner. For non-packet LSPs, it is useful to define specific manner. For non-packet LSPs, it is useful to define
discrete values to identify the bandwidth of the LSP. discrete values to identify the bandwidth of the LSP.
It should be noted that this bandwidth encoding do not apply to It should be noted that this bandwidth encoding do not apply to
SONET/SDH and G.709, for which the traffic parameters fully define SONET/SDH and G.709, for which the traffic parameters fully define
the requested SONET/SDH or G.709 signal. the requested SONET/SDH or G.709 signal.
The bandwidth is coded in the Peak Data Rate field of Int-Serv The bandwidth is coded in the Peak Data Rate field of Int-Serv
objects for RSVP-TE in the SENDER_TSPEC and FLOWSPEC objects and in objects for RSVP-TE in the SENDER_TSPEC and FLOWSPEC objects and in
the Peak and Committed Data Rate fields of the CR-LDP Traffic the Peak and Committed Data Rate fields of the CR-LDP Traffic
Parameters TLV. Parameters TLV.
9.6. Generalized Label 7.6. Generalized Label
The Generalized Label extends the traditional MPLS label by allowing The Generalized Label extends the traditional MPLS label by allowing
the representation of not only labels that travel in-band with the representation of not only labels that travel in-band with
associated data packets, but also (virtual) labels that identify associated data packets, but also (virtual) labels that identify
time-slots, wavelengths, or space division multiplexed positions. time-slots, wavelengths, or space division multiplexed positions.
For example, the Generalized Label may identify (a) a single fiber For example, the Generalized Label may identify (a) a single fiber in
in a bundle, (b) a single waveband within fiber, (c) a single a bundle, (b) a single waveband within fiber, (c) a single wavelength
wavelength within a waveband (or fiber), or (d) a set of time-slots within a waveband (or fiber), or (d) a set of time-slots within a
within a wavelength (or fiber). It may also be a generic MPLS label, wavelength (or fiber). It may also be a generic MPLS label, a Frame
Relay label, or an ATM label (VCI/VPI). The format of a label can be
E. Mannie (Editor) et al. Standard Track 29 as simple as an integer value such as a wavelength label or can be
a Frame Relay label, or an ATM label (VCI/VPI). The format of a more elaborated such as an SONET/SDH or a G.709 label.
label can be as simple as an integer value such as a wavelength
label or can be more elaborated such as an SONET/SDH or a G.709
label.
SDH and SONET define each a multiplexing structure. These SDH and SONET define each a multiplexing structure. These
multiplexing structures will be used as naming trees to create multiplexing structures will be used as naming trees to create unique
unique labels. Such a label will identify the exact position (times- labels. Such a label will identify the exact position (times-lot(s))
lot(s)) of a signal in a multiplexing structure. Since the SONET of a signal in a multiplexing structure. Since the SONET
multiplexing structure may be seen as a subset of the SDH multiplexing structure may be seen as a subset of the SDH
multiplexing structure, the same format of label is used for SDH and multiplexing structure, the same format of label is used for SDH and
SONET. A similar concept is applied to build a label at the G.709 SONET. A similar concept is applied to build a label at the G.709
ODU layer. ODU layer.
Since the nodes sending and receiving the Generalized Label know Since the nodes sending and receiving the Generalized Label know what
what kinds of link they are using, the Generalized Label does not kinds of link they are using, the Generalized Label does not identify
identify its type. Instead, the nodes are expected to know from the its type. Instead, the nodes are expected to know from the context
context what type of label to expect. what type of label to expect.
A Generalized Label only carries a single level of label i.e. it is A Generalized Label only carries a single level of label i.e., it is
non-hierarchical. When multiple levels of labels (LSPs within LSPs) non-hierarchical. When multiple levels of labels (LSPs within LSPs)
are required, each LSP must be established separately. are required, each LSP must be established separately.
9.7. Waveband Switching 7.7. Waveband Switching
A special case of wavelength switching is waveband switching. A A special case of wavelength switching is waveband switching. A
waveband represents a set of contiguous wavelengths, which can be waveband represents a set of contiguous wavelengths, which can be
switched together to a new waveband. For optimization reasons, it switched together to a new waveband. For optimization reasons, it
may be desirable for a photonic cross-connect to optically switch may be desirable for a photonic cross-connect to optically switch
multiple wavelengths as a unit. This may reduce the distortion on multiple wavelengths as a unit. This may reduce the distortion on
the individual wavelengths and may allow tighter separation of the the individual wavelengths and may allow tighter separation of the
individual wavelengths. A Waveband label is defined to support this individual wavelengths. A Waveband label is defined to support this
special case. special case.
Waveband switching naturally introduces another level of label Waveband switching naturally introduces another level of label
hierarchy and as such the waveband is treated the same way, all hierarchy and as such the waveband is treated the same way, all other
other upper layer labels are treated. As far as the MPLS protocols upper layer labels are treated. As far as the MPLS protocols are
are concerned, there is little difference between a waveband label concerned, there is little difference between a waveband label and a
and a wavelength label. Exception is that semantically the waveband wavelength label. Exception is that semantically the waveband can be
can be subdivided into wavelengths whereas the wavelength can only subdivided into wavelengths whereas the wavelength can only be
be subdivided into time or statistically multiplexed labels. subdivided into time or statistically multiplexed labels.
In the context of waveband switching, the generalized label used to In the context of waveband switching, the generalized label used to
indicate a waveband contains three fields, a waveband ID, a Start indicate a waveband contains three fields, a waveband ID, a Start
Label and an End Label. The Start and End Labels are channel Label and an End Label. The Start and End Labels are channel
identifiers from the sender perspective that identify respectively, identifiers from the sender perspective that identify respectively,
the lowest value wavelength and the highest value wavelength making the lowest value wavelength and the highest value wavelength making
up the waveband. up the waveband.
9.8. Label Suggestion by the Upstream 7.8. Label Suggestion by the Upstream
GMPLS allows for a label to be optionally suggested by an upstream GMPLS allows for a label to be optionally suggested by an upstream
node. This suggestion may be overridden by a downstream node but in node. This suggestion may be overridden by a downstream node but in
some cases, at the cost of higher LSP setup time. The suggested some cases, at the cost of higher LSP setup time. The suggested
E. Mannie (Editor) et al. Standard Track 30
label is valuable when establishing LSPs through certain kinds of label is valuable when establishing LSPs through certain kinds of
optical equipment where there may be a lengthy (in electrical terms) optical equipment where there may be a lengthy (in electrical terms)
delay in configuring the switching fabric. For example, micro delay in configuring the switching fabric. For example, micro
mirrors may have to be elevated or moved, and this physical motion mirrors may have to be elevated or moved, and this physical motion
and subsequent damping takes time. If the labels and hence switching and subsequent damping takes time. If the labels and hence switching
fabric are configured in the reverse direction (the norm), the Resv/ fabric are configured in the reverse direction (the norm), the
MAPPING message may need to be delayed by 10's of milliseconds per Resv/MAPPING message may need to be delayed by 10's of milliseconds
hop in order to establish a usable forwarding path. It can be per hop in order to establish a usable forwarding path. It can be
important for restoration purposes where alternate LSPs may need to important for restoration purposes where alternate LSPs may need to
be rapidly established as a result of network failures. be rapidly established as a result of network failures.
9.9. Label Restriction by the Upstream 7.9. Label Restriction by the Upstream
An upstream node can optionally restrict (limit) the choice of label An upstream node can optionally restrict (limit) the choice of label
of a downstream node to a set of acceptable labels. Giving lists of a downstream node to a set of acceptable labels. Giving lists
and/or ranges of inclusive (acceptable) or exclusive (unacceptable) and/or ranges of inclusive (acceptable) or exclusive (unacceptable)
labels in a Label Set provides this restriction. If not applied, all labels in a Label Set provides this restriction. If not applied, all
labels from the valid label range may be used. There are at least labels from the valid label range may be used. There are at least
four cases where a label restriction is useful in the "optical" four cases where a label restriction is useful in the "optical"
domain. domain.
Case 1: the end equipment is only capable of transmitting and Case 1: the end equipment is only capable of transmitting and
receiving on a small specific set of wavelengths/wavebands. receiving on a small specific set of wavelengths/wavebands.
Case 2: there is a sequence of interfaces, which cannot support Case 2: there is a sequence of interfaces, which cannot support
wavelength conversion and require the same wavelength be used end- wavelength conversion and require the same wavelength be used
to-end over a sequence of hops, or even an entire path. end-to-end over a sequence of hops, or even an entire path.
Case 3: it is desirable to limit the amount of wavelength conversion Case 3: it is desirable to limit the amount of wavelength conversion
being performed to reduce the distortion on the optical signals. being performed to reduce the distortion on the optical signals.
Case 4: two ends of a link support different sets of wavelengths. Case 4: two ends of a link support different sets of wavelengths.
The receiver of a Label Set must restrict its choice of labels to The receiver of a Label Set must restrict its choice of labels to one
one that is in the Label Set. A Label Set may be present across that is in the Label Set. A Label Set may be present across multiple
multiple hops. In this case, each node generates its own outgoing hops. In this case, each node generates its own outgoing Label Set,
Label Set, possibly based on the incoming Label Set and the node's possibly based on the incoming Label Set and the node's hardware
hardware capabilities. This case is expected to be the norm for capabilities. This case is expected to be the norm for nodes with
nodes with conversion incapable interfaces. conversion incapable interfaces.
9.10. Bi-directional LSP 7.10. Bi-directional LSP
GMPLS allows establishment of bi-directional symmetric LSPs (not of GMPLS allows establishment of bi-directional symmetric LSPs (not of
asymmetric LSPs). A symmetric bi-directional LSP has the same asymmetric LSPs). A symmetric bi-directional LSP has the same
traffic engineering requirements including fate sharing, protection traffic engineering requirements including fate sharing, protection
and restoration, LSRs, and resource requirements (e.g. latency and and restoration, LSRs, and resource requirements (e.g., latency and
jitter) in each direction. jitter) in each direction.
In the remainder of this section, the term "initiator" is used to In the remainder of this section, the term "initiator" is used to
refer to a node that starts the establishment of an LSP; the term refer to a node that starts the establishment of an LSP; the term
"terminator" is used to refer to the node that is the target of the "terminator" is used to refer to the node that is the target of the
LSP. For a bi-directional LSPs, there is only one initiator and one LSP. For a bi-directional LSPs, there is only one initiator and one
terminator. terminator.
E. Mannie (Editor) et al. Standard Track 31
Normally to establish a bi-directional LSP when using RSVP-TE Normally to establish a bi-directional LSP when using RSVP-TE
[RFC3209] or CR-LDP [RFC3212] two unidirectional paths must be [RFC3209] or CR-LDP [RFC3212] two unidirectional paths must be
independently established. This approach has the following independently established. This approach has the following
disadvantages: disadvantages:
1. The latency to establish the bi-directional LSP is equal to one 1. The latency to establish the bi-directional LSP is equal to one
round trip signaling time plus one initiator-terminator signaling round trip signaling time plus one initiator-terminator signaling
transit delay. This not only extends the setup latency for transit delay. This not only extends the setup latency for
successful LSP establishment, but it extends the worst-case latency successful LSP establishment, but it extends the worst-case
for discovering an unsuccessful LSP to as much as two times the latency for discovering an unsuccessful LSP to as much as two
initiator-terminator transit delay. These delays are particularly times the initiator-terminator transit delay. These delays are
significant for LSPs that are established for restoration purposes. particularly significant for LSPs that are established for
restoration purposes.
2. The control overhead is twice that of a unidirectional LSP. This 2. The control overhead is twice that of a unidirectional LSP. This
is because separate control messages (e.g. Path and Resv) must be is because separate control messages (e.g., Path and Resv) must be
generated for both segments of the bi-directional LSP. generated for both segments of the bi-directional LSP.
3. Because the resources are established in separate segments, route 3. Because the resources are established in separate segments, route
selection is complicated. There is also additional potential race selection is complicated. There is also additional potential race
for conditions in assignment of resources, which decreases the for conditions in assignment of resources, which decreases the
overall probability of successfully establishing the bi-directional overall probability of successfully establishing the bi-
connection. directional connection.
4. It is more difficult to provide a clean interface for SONET/SDH 4. It is more difficult to provide a clean interface for SONET/SDH
equipment that may rely on bi-directional hop-by-hop paths for equipment that may rely on bi-directional hop-by-hop paths for
protection switching. Note that existing SONET/SDH equipment protection switching. Note that existing SONET/SDH equipment
transmits the control information in-band with the data. transmits the control information in-band with the data.
5. Bi-directional optical LSPs (or lightpaths) are seen as a 5. Bi-directional optical LSPs (or lightpaths) are seen as a
requirement for many optical networking service providers. requirement for many optical networking service providers.
With bi-directional LSPs both the downstream and upstream data With bi-directional LSPs both the downstream and upstream data paths,
paths, i.e. from initiator to terminator and terminator to i.e., from initiator to terminator and terminator to initiator, are
initiator, are established using a single set of signaling messages. established using a single set of signaling messages. This reduces
This reduces the setup latency to essentially one initiator- the setup latency to essentially one initiator-terminator round trip
terminator round trip time plus processing time, and limits the time plus processing time, and limits the control overhead to the
control overhead to the same number of messages as a unidirectional same number of messages as a unidirectional LSP.
LSP.
For bi-directional LSPs, two labels must be allocated. Bi- For bi-directional LSPs, two labels must be allocated. Bi-
directional LSP setup is indicated by the presence of an Upstream directional LSP setup is indicated by the presence of an Upstream
Label in the appropriate signaling message. Label in the appropriate signaling message.
9.11. Bi-directional LSP Contention Resolution 7.11. Bi-directional LSP Contention Resolution
Contention for labels may occur between two bi-directional LSP setup Contention for labels may occur between two bi-directional LSP setup
requests traveling in opposite directions. This contention occurs requests traveling in opposite directions. This contention occurs
when both sides allocate the same resources (ports) at effectively when both sides allocate the same resources (ports) at effectively
the same time. GMPLS signaling defines a procedure to resolve that the same time. GMPLS signaling defines a procedure to resolve that
contention: the node with the higher node ID will win the contention: the node with the higher node ID will win the contention.
contention. To reduce the probability of contention, some mechanisms To reduce the probability of contention, some mechanisms are also
are also suggested. suggested.
E. Mannie (Editor) et al. Standard Track 32 7.12. Rapid Notification of Failure
9.12. Rapid Notification of Failure
GMPLS defines several signaling extensions that enable expedited GMPLS defines several signaling extensions that enable expedited
notification of failures and other events to nodes responsible for notification of failures and other events to nodes responsible for
restoring failed LSPs, and error handling. restoring failed LSPs, and error handling.
1. Acceptable Label Set for notification on Label Error: 1. Acceptable Label Set for notification on Label Error:
There are cases in traditional MPLS and in GMPLS that result in an There are cases in traditional MPLS and in GMPLS that result in an
error message containing an "Unacceptable label value" indication. error message containing an "Unacceptable label value" indication.
When these cases occur, it can useful for the node generating the When these cases occur, it can useful for the node generating the
error message to indicate which labels would be acceptable. To cover error message to indicate which labels would be acceptable. To
this case, GMPLS introduces the ability to convey such information cover this case, GMPLS introduces the ability to convey such
via the "Acceptable Label Set". An Acceptable Label Set is carried information via the "Acceptable Label Set". An Acceptable Label
in appropriate protocol specific error messages. The format of an Set is carried in appropriate protocol specific error messages.
Acceptable Label Set is identical to a Label Set. The format of an Acceptable Label Set is identical to a Label Set.
2. Expedited notification: 2. Expedited notification:
Extensions to RSVP-TE enable expedited notification of failures and Extensions to RSVP-TE enable expedited notification of failures
other events to determined nodes. For CR-LDP, there is not currently and other events to determined nodes. For CR-LDP, there is not
a similar mechanism. The first extension identifies where event currently a similar mechanism. The first extension identifies
notifications are to be sent. The second provides for general where event notifications are to be sent. The second provides for
expedited event notification with a Notify message. Such extensions general expedited event notification with a Notify message. Such
can be used by fast restoration mechanisms. Notifications may be extensions can be used by fast restoration mechanisms.
requested in both the upstream and downstream directions. Notifications may be requested in both the upstream and downstream
directions.
The Notify message is a generalized notification mechanism that The Notify message is a generalized notification mechanism that
differs from the currently defined error messages in that it can be differs from the currently defined error messages in that it can
"targeted" to a node other than the immediate upstream or downstream be "targeted" to a node other than the immediate upstream or
neighbor. The Notify message does not replace existing error downstream neighbor. The Notify message does not replace existing
messages. The Notify message may be sent either (a) normally, where error messages. The Notify message may be sent either (a)
non-target nodes just forward the Notify message to the target node, normally, where non-target nodes just forward the Notify message
similar to ResvConf processing in [RFC2205]; or (b) encapsulated in to the target node, similar to ResvConf processing in [RFC2205];
a new IP header whose destination is equal to the target IP address. or (b) encapsulated in a new IP header whose destination is equal
to the target IP address.
3. Faster removal of intermediate states: 3. Faster removal of intermediate states:
A specific RSVP optimization allowing in some cases the faster A specific RSVP optimization allowing in some cases the faster
removal of intermediate states. This extension is used to deal with removal of intermediate states. This extension is used to deal
specific RSVP mechanisms. with specific RSVP mechanisms.
9.13. Link Protection 7.13. Link Protection
Protection information is carried in the new optional Protection Protection information is carried in the new optional Protection
Information Object/TLV. It currently indicates the desired link Information Object/TLV. It currently indicates the desired link
protection for each link of an LSP. If a particular protection type, protection for each link of an LSP. If a particular protection type,
i.e. 1+1, or 1:N, is requested, then a connection request is i.e., 1+1, or 1:N, is requested, then a connection request is
processed only if the desired protection type can be honored. Note processed only if the desired protection type can be honored. Note
that GMPLS advertises the protection capabilities of a link in the that GMPLS advertises the protection capabilities of a link in the
routing protocols. Path computation algorithms may consider this routing protocols. Path computation algorithms may consider this
information when computing paths for setting up LSPs. information when computing paths for setting up LSPs.
E. Mannie (Editor) et al. Standard Track 33
Protection information also indicates if the LSP is a primary or Protection information also indicates if the LSP is a primary or
secondary LSP. A secondary LSP is a backup to a primary LSP. The secondary LSP. A secondary LSP is a backup to a primary LSP. The
resources of a secondary LSP are normally not used until the primary resources of a secondary LSP are normally not used until the primary
LSP fails, but they may be used by other LSPs until the primary LSP LSP fails, but they may be used by other LSPs until the primary LSP
fails over the secondary LSP. At that point, any LSP that is using fails over the secondary LSP. At that point, any LSP that is using
the resources for the secondary LSP must be preempted. the resources for the secondary LSP must be preempted.
Six link protection types are currently defined as individual flags Six link protection types are currently defined as individual flags
and can be combined: enhanced, dedicated 1+1, dedicated 1:1, shared, and can be combined: enhanced, dedicated 1+1, dedicated 1:1, shared,
unprotected, extra traffic. See [RFC3471] section 7.1 for a precise unprotected, extra traffic. See [RFC3471] section 7.1 for a precise
definition of each. definition of each.
9.14. Explicit Routing and Explicit Label Control 7.14. Explicit Routing and Explicit Label Control
By using an explicit route, the path taken by an LSP can be By using an explicit route, the path taken by an LSP can be
controlled more or less precisely. Typically, the node at the head- controlled more or less precisely. Typically, the node at the head-
end of an LSP finds an explicit route and builds an Explicit Route end of an LSP finds an explicit route and builds an Explicit Route
Object (ERO)/ Explicit Route (ER) TLV that contains that route. Object (ERO)/ Explicit Route (ER) TLV that contains that route.
Possibly, the edge node does not build any explicit route, and just Possibly, the edge node does not build any explicit route, and just
transmit a signaling request to a default neighbor LSR (as IP/MPLS transmit a signaling request to a default neighbor LSR (as IP/MPLS
hosts would). For instance, an explicit route could be added to a hosts would). For instance, an explicit route could be added to a
signaling message by the first switching node, on behalf of the edge signaling message by the first switching node, on behalf of the edge
node. Note also that an explicit route is altered by intermediate node. Note also that an explicit route is altered by intermediate
LSRs during its progression towards the destination. LSRs during its progression towards the destination.
The explicit route is originally defined by MPLS-TE as a list of The explicit route is originally defined by MPLS-TE as a list of
abstract nodes (i.e. groups of nodes) along the explicit route. Each abstract nodes (i.e., groups of nodes) along the explicit route.
abstract node can be an IPv4 address prefix, an IPv6 address prefix, Each abstract node can be an IPv4 address prefix, an IPv6 address
or an AS number. This capability allows the generator of the prefix, or an AS number. This capability allows the generator of the
explicit route to have incomplete information about the details of explicit route to have incomplete information about the details of
the path. In the simplest case, an abstract node can be a full IP the path. In the simplest case, an abstract node can be a full IP
address (32 bits) that identifies a specific node (called a simple address (32 bits) that identifies a specific node (called a simple
abstract node). abstract node).
MPLS-TE allows strict and loose abstract nodes. The path between a MPLS-TE allows strict and loose abstract nodes. The path between a
strict node and its preceding node must include only network nodes strict node and its preceding node must include only network nodes
from the strict node and its preceding abstract node. The path from the strict node and its preceding abstract node. The path
between a loose node and its preceding abstract node may include between a loose node and its preceding abstract node may include
other network nodes that are not part of the loose node or its other network nodes that are not part of the loose node or its
preceding abstract node. preceding abstract node.
This explicit route was extended to include interface numbers as This explicit route was extended to include interface numbers as
abstract nodes to support unnumbered interfaces; and further abstract nodes to support unnumbered interfaces; and further extended
extended by GMPLS to include labels as abstract nodes. Having labels by GMPLS to include labels as abstract nodes. Having labels in an
in an explicit route is an important feature that allows controlling explicit route is an important feature that allows controlling the
the placement of an LSP with a very fine granularity. This is more placement of an LSP with a very fine granularity. This is more
likely to be used for TDM, LSC and FSC links. likely to be used for TDM, LSC and FSC links.
In particular, the explicit label control in the explicit route In particular, the explicit label control in the explicit route
allows terminating an LSP on a particular outgoing port of an egress allows terminating an LSP on a particular outgoing port of an egress
node. Indeed, a label sub-object/TLV must follow a sub-object/TLV node. Indeed, a label sub-object/TLV must follow a sub-object/TLV
containing the IP address, or the interface identifier (in case of containing the IP address, or the interface identifier (in case of
unnumbered interface), associated with the link on which it is to be unnumbered interface), associated with the link on which it is to be
used. used.
E. Mannie (Editor) et al. Standard Track 34
This can also be used when it is desirable to "splice" two LSPs This can also be used when it is desirable to "splice" two LSPs
together, i.e. where the tail of the first LSP would be "spliced" together, i.e., where the tail of the first LSP would be "spliced"
into the head of the second LSP. into the head of the second LSP.
When used together with an optimization algorithm, it can provide When used together with an optimization algorithm, it can provide
very detailed explicit routes, including the label (timeslot) to use very detailed explicit routes, including the label (timeslot) to use
on a link, in order to minimize the fragmentation of the SONET/SDH on a link, in order to minimize the fragmentation of the SONET/SDH
multiplex on the corresponding interface. multiplex on the corresponding interface.
9.15. Route Recording 7.15. Route Recording
In order to improve the reliability and the manageability of the LSP In order to improve the reliability and the manageability of the LSP
being established, the concept of the route recording was introduced being established, the concept of the route recording was introduced
in RSVP-TE to function as: in RSVP-TE to function as:
- First, a loop detection mechanism to discover L3 routing loops, or - First, a loop detection mechanism to discover L3 routing loops, or
loops inherent in the explicit route (this mechanism is strictly loops inherent in the explicit route (this mechanism is strictly
exclusive with the use of explicit routing objects). exclusive with the use of explicit routing objects).
- Second, a route recording mechanism collects up-to-date detailed - Second, a route recording mechanism collects up-to-date detailed
path information on a hop-by-hop basis during the LSP setup process. path information on a hop-by-hop basis during the LSP setup
This mechanism provides valuable information to the source and process. This mechanism provides valuable information to the
destination nodes. Any intermediate routing change at setup time, in source and destination nodes. Any intermediate routing change at
case of loose explicit routing, will be reported. setup time, in case of loose explicit routing, will be reported.
- Third, a recorded route can be used as input for an explicit - Third, a recorded route can be used as input for an explicit
route. This is useful if a source node receives the recorded route route. This is useful if a source node receives the recorded
from a destination node and applies it as an explicit route in order route from a destination node and applies it as an explicit route
to "pin down the path". in order to "pin down the path".
Within the GMPLS architecture, only the second and third functions Within the GMPLS architecture, only the second and third functions
are mainly applicable for TDM, LSC and FSC layers. are mainly applicable for TDM, LSC and FSC layers.
9.16. LSP Modification and LSP Re-routing 7.16. LSP Modification and LSP Re-routing
LSP modification and re-routing are two features already available LSP modification and re-routing are two features already available in
in MPLS-TE. GMPLS does not add anything new. Elegant re-routing is MPLS-TE. GMPLS does not add anything new. Elegant re-routing is
possible with the concept of "make-before-break" whereby an old path possible with the concept of "make-before-break" whereby an old path
is still used while a new path is set up by avoiding double is still used while a new path is set up by avoiding double
reservation of resources. Then, the node performing the re-routing reservation of resources. Then, the node performing the re-routing
can swap on the new path and close the old path. This feature is can swap on the new path and close the old path. This feature is
supported with RSVP-TE (using shared explicit filters) and CR-LDP supported with RSVP-TE (using shared explicit filters) and CR-LDP
(using the action indicator flag). (using the action indicator flag).
LSP modification consists in changing some LSP parameters, but LSP modification consists in changing some LSP parameters, but
normally without changing the route. It is supported using the same normally without changing the route. It is supported using the same
mechanism as re-routing. However, the semantic of LSP modification mechanism as re-routing. However, the semantic of LSP modification
will differ from one technology to the other. For instance, further will differ from one technology to the other. For instance, further
studies are required to understand the impact of dynamically studies are required to understand the impact of dynamically changing
changing some SONET/SDH circuit characteristics such as the some SONET/SDH circuit characteristics such as the bandwidth, the
bandwidth, the protection type, the transparency, the concatenation, protection type, the transparency, the concatenation, etc.
etc.
E. Mannie (Editor) et al. Standard Track 35 7.17. LSP Administrative Status Handling
9.17. LSP Administrative Status Handling
GMPLS provides the optional capability to indicate the GMPLS provides the optional capability to indicate the administrative
administrative status of an LSP by using a new Admin Status status of an LSP by using a new Admin Status object/TLV.
object/TLV. Administrative Status information is currently used in Administrative Status information is currently used in two ways.
two ways.
In the first usage, the Admin Status object/TLV is carried in a In the first usage, the Admin Status object/TLV is carried in a
Path/Label Request or Resv/Label Mapping message to indicate the Path/Label Request or Resv/Label Mapping message to indicate the
administrative state of an LSP. In this usage, Administrative Status administrative state of an LSP. In this usage, Administrative Status
information indicates the state of the LSP, which include "up" or information indicates the state of the LSP, which include "up" or
"down", if it in a "testing" mode, and if deletion is in progress. "down", if it in a "testing" mode, and if deletion is in progress.
Based on that administrative status, a node can take local Based on that administrative status, a node can take local decisions,
decisions, like inhibit alarm reporting when an LSP is in "down" or like inhibit alarm reporting when an LSP is in "down" or "testing"
"testing" states, or report alarms associated with the connection at states, or report alarms associated with the connection at a priority
a priority equal to or less than "Non service affecting". equal to or less than "Non service affecting".
It is possible that some nodes along an LSP will not support the It is possible that some nodes along an LSP will not support the
Admin Status Object/TLV. In the case of a non-supporting transit Admin Status Object/TLV. In the case of a non-supporting transit
node, the object will pass through the node unmodified and normal node, the object will pass through the node unmodified and normal
processing can continue. processing can continue.
In some circumstances, particularly optical networks, it is useful In some circumstances, particularly optical networks, it is useful to
to set the administrative status of an LSP to "being deleted" before set the administrative status of an LSP to "being deleted" before
tearing it down in order to avoid non-useful generation of alarms. tearing it down in order to avoid non-useful generation of alarms.
The ingress LSR precedes an LSP deletion by inserting an appropriate The ingress LSR precedes an LSP deletion by inserting an appropriate
Admin Status Object/TLV in a Path/Label Request (with the Admin Status Object/TLV in a Path/Label Request (with the
modification action indicator flag set to modify) message. Transit modification action indicator flag set to modify) message. Transit
LSRs process the Admin Status Object/TLV and forward it. The egress LSRs process the Admin Status Object/TLV and forward it. The egress
LSR answers in a Resv/Label Mapping (with the modification action LSR answers in a Resv/Label Mapping (with the modification action
indicator flag set to modify) message with the Admin Status object. indicator flag set to modify) message with the Admin Status object.
Upon receiving this message and object, the ingress node sends a Upon receiving this message and object, the ingress node sends a
PathTear/Release message downstream to remove the LSP and normal PathTear/Release message downstream to remove the LSP and normal
RSVP-TE/CR-LDP processing takes place. RSVP-TE/CR-LDP processing takes place.
In the second usage, the Admin Status object/TLV is carried in a In the second usage, the Admin Status object/TLV is carried in a
Notification/Label Mapping (with the modification action indicator Notification/Label Mapping (with the modification action indicator
flag set to modify) message to request that the ingress node change flag set to modify) message to request that the ingress node change
the administrative state of an LSP. This allows intermediate and the administrative state of an LSP. This allows intermediate and
egress nodes triggering the setting of administrative status. In egress nodes triggering the setting of administrative status. In
particular, this allows intermediate or egress LSRs requesting a particular, this allows intermediate or egress LSRs requesting a
release of an LSP initiated by the ingress node. release of an LSP initiated by the ingress node.
9.18. Control Channel Separation 7.18. Control Channel Separation
In GMPLS, a control channel can be separated from the data channel. In GMPLS, a control channel be separated from the data channel.
Indeed, the control channel can be implemented completely out-of- Indeed, the control channel can be implemented completely out-of-
band for various reason, e.g. when the data channel cannot carry in- band for various reason, e.g., when the data channel cannot carry
band control information. This issue was even originally introduced in-band control information. This issue was even originally
to MPLS in the context of link bundling. introduced to MPLS in the context of link bundling.
In traditional MPLS, there is an implicit one-to-one association of
a control channel to a data channel. When such an association is
E. Mannie (Editor) et al. Standard Track 36 In traditional MPLS, there is an implicit one-to-one association of a
control channel to a data channel. When such an association is
present, no additional or special information is required to present, no additional or special information is required to
associate a particular LSP setup transaction with a particular data associate a particular LSP setup transaction with a particular data
channel. channel.
Otherwise, it is necessary to convey additional information in Otherwise, it is necessary to convey additional information in
signaling to identify the particular data channel being controlled. signaling to identify the particular data channel being controlled.
GMPLS supports explicit data channel identification by providing GMPLS supports explicit data channel identification by providing
interface identification information. GMPLS allows the use of a interface identification information. GMPLS allows the use of a
number of interface identification schemes including IPv4 or IPv6 number of interface identification schemes including IPv4 or IPv6
addresses, interface indexes (for unnumbered interfaces) and addresses, interface indexes (for unnumbered interfaces) and
component interfaces (for bundled interfaces), unnumbered bundled component interfaces (for bundled interfaces), unnumbered bundled
interfaces are also supported. interfaces are also supported.
The choice of the data interface to use is always made by the sender The choice of the data interface to use is always made by the sender
of the Path/Label Request message, and indicated by including the of the Path/Label Request message, and indicated by including the
data channel's interface identifier in the message using a new IF_ID data channel's interface identifier in the message using a new
RSVP_HOP object sub-type/Interface TLV. RSVP_HOP object sub-type/Interface TLV.
For bi-directional LSPs, the sender chooses the data interface in For bi-directional LSPs, the sender chooses the data interface in
each direction. In all cases but bundling, the upstream interface is each direction. In all cases but bundling, the upstream interface is
implied by the downstream interface. For bundling, the Path/Label implied by the downstream interface. For bundling, the Path/Label
Request sender explicitly identifies the component interface used in Request sender explicitly identifies the component interface used in
each direction. The new object/TLV is used in Resv/Label Mapping each direction. The new object/TLV is used in Resv/Label Mapping
message to indicate the downstream node's usage of the indicated message to indicate the downstream node's usage of the indicated
interface(s). interface(s).
The new object/TLV can contain a list of embedded TLVs, each The new object/TLV can contain a list of embedded TLVs, each embedded
embedded TLV can be an IPv4 address, and IPv6 address, an interface TLV can be an IPv4 address, and IPv6 address, an interface index, a
index, a downstream component interface ID or an upstream component downstream component interface ID or an upstream component interface
interface ID. In the last three cases, the embedded TLV contains ID. In the last three cases, the embedded TLV contains itself an IP
itself an IP address plus an Interface ID, the IP address being used address plus an Interface ID, the IP address being used to identify
to identify the interface ID (it can be the router ID for instance). the interface ID (it can be the router ID for instance).
There are cases where it is useful to indicate a specific interface There are cases where it is useful to indicate a specific interface
associated with an error. To support these cases the IF_ID associated with an error. To support these cases the IF_ID
ERROR_SPEC RSVP Objects are defined. ERROR_SPEC RSVP Objects are defined.
10. Forwarding Adjacencies (FA) 8. Forwarding Adjacencies (FA)
To improve scalability of MPLS TE (and thus GMPLS) it may be useful To improve scalability of MPLS TE (and thus GMPLS) it may be useful
to aggregate multiple TE LSPs inside a bigger TE LSP. Intermediate to aggregate multiple TE LSPs inside a bigger TE LSP. Intermediate
nodes see the external LSP only. They don't have to maintain nodes see the external LSP only. They do not have to maintain
forwarding states for each internal LSP, less signaling messages forwarding states for each internal LSP, less signaling messages need
need to be exchanged and the external LSP can be somehow protected to be exchanged and the external LSP can be somehow protected instead
instead (or in addition) to the internal LSPs. This can considerably (or in addition) to the internal LSPs. This can considerably
increase the scalability of the signaling. increase the scalability of the signaling.
The aggregation is accomplished by (a) an LSR creating a TE LSP, (b) The aggregation is accomplished by (a) an LSR creating a TE LSP, (b)
the LSR forming a forwarding adjacency out of that LSP (advertising the LSR forming a forwarding adjacency out of that LSP (advertising
this LSP as a Traffic Engineering (TE) link into IS-IS/OSPF), (c) this LSP as a Traffic Engineering (TE) link into IS-IS/OSPF), (c)
allowing other LSRs to use forwarding adjacencies for their path allowing other LSRs to use forwarding adjacencies for their path
computation, and (d) nesting of LSPs originated by other LSRs into computation, and (d) nesting of LSPs originated by other LSRs into
that LSP (e.g. by using the label stack construct in the case of that LSP (e.g., by using the label stack construct in the case of
IP). IP).
E. Mannie (Editor) et al. Standard Track 37 ISIS/OSPF floods the information about "Forwarding Adjacencies" FAs
IS-IS/OSPF floods the information about "Forwarding Adjacencies" FAs just as it floods the information about any other links. Consequently
just as it floods the information about any other links. to this flooding, an LSR has in its TE link state database the
Consequently to this flooding, an LSR has in its TE link state information about not just conventional links, but FAs as well.
database the information about not just conventional links, but FAs
as well.
An LSR, when performing path computation, uses not just conventional An LSR, when performing path computation, uses not just conventional
links, but FAs as well. Once a path is computed, the LSR uses RSVP- links, but FAs as well. Once a path is computed, the LSR uses RSVP-
TE/CR-LDP for establishing label binding along the path. FAs need TE/CR-LDP for establishing label binding along the path. FAs need
simple extensions to signaling and routing protocols. simple extensions to signaling and routing protocols.
10.1. Routing and Forwarding Adjacencies 8.1. Routing and Forwarding Adjacencies
Forwarding adjacencies may be represented as either unnumbered or Forwarding adjacencies may be represented as either unnumbered or
numbered links. A FA can also be a bundle of LSPs between two nodes. numbered links. A FA can also be a bundle of LSPs between two nodes.
FAs are advertised as GMPLS TE links such as defined in [HIERARCHY]. FAs are advertised as GMPLS TE links such as defined in [HIERARCHY].
GMPLS TE links are advertised in OSPF and IS-IS such as defined in GMPLS TE links are advertised in OSPF and IS-IS such as defined in
[OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. These last two specifications [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. These last two specifications
enhance [OSPF-TE] and [ISIS-TE] that defines a base TE link. enhance [OSPF-TE] and [ISIS-TE] that defines a base TE link.
When a FA is created dynamically, its TE attributes are inherited When a FA is created dynamically, its TE attributes are inherited
from the FA-LSP that induced its creation. [HIERARCHY] specifies how from the FA-LSP that induced its creation. [HIERARCHY] specifies how
each TE parameter of the FA is inherited from the FA-LSP. Note that each TE parameter of the FA is inherited from the FA-LSP. Note that
the bandwidth of the FA must be at least as big as the FA-LSP that the bandwidth of the FA must be at least as big as the FA-LSP that
induced it, but may be bigger if only discrete bandwidths are induced it, but may be bigger if only discrete bandwidths are
available for the FA-LSP. In general, for dynamically provisioned available for the FA-LSP. In general, for dynamically provisioned
forwarding adjacencies, a policy-based mechanism may be needed to forwarding adjacencies, a policy-based mechanism may be needed to
associate attributes to forwarding adjacencies. associate attributes to forwarding adjacencies.
A FA advertisement could contain the information about the path A FA advertisement could contain the information about the path taken
taken by the FA-LSP associated with that FA. Other LSRs may use this by the FA-LSP associated with that FA. Other LSRs may use this
information for path computation. This information is carried in a information for path computation. This information is carried in a
new OSPF and IS-IS TLV called the Path TLV. new OSPF and IS-IS TLV called the Path TLV.
It is possible that the underlying path information might change It is possible that the underlying path information might change over
over time, via configuration updates, or dynamic route time, via configuration updates, or dynamic route modifications,
modifications, resulting in the change of that TLV. resulting in the change of that TLV.
If forwarding adjacencies are bundled (via link bundling), and if If forwarding adjacencies are bundled (via link bundling), and if the
the resulting bundled link carries a Path TLV, the underlying path resulting bundled link carries a Path TLV, the underlying path
followed by each of the FA-LSPs that form the component links must followed by each of the FA-LSPs that form the component links must be
be the same. the same.
It is expected that forwarding adjacencies will not be used for It is expected that forwarding adjacencies will not be used for
establishing IS-IS/OSPF peering relation between the routers at the establishing IS-IS/OSPF peering relation between the routers at the
ends of the adjacency. ends of the adjacency.
LSP hierarchy could exist both with the peer and with the overlay LSP hierarchy could exist both with the peer and with the overlay
models. With the peer model, the LSP hierarchy is realized via FAs models. With the peer model, the LSP hierarchy is realized via FAs
and an LSP is both created and used as a TE link by exactly the same and an LSP is both created and used as a TE link by exactly the same
instance of the control plane. Creating LSP hierarchies with instance of the control plane. Creating LSP hierarchies with
overlays doesn't involve the concept of FA. With the overlay model overlays does not involve the concept of FA. With the overlay model
E. Mannie (Editor) et al. Standard Track 38
an LSP created (and maintained) by one instance of the GMPLS control an LSP created (and maintained) by one instance of the GMPLS control
plane is used as a TE link by another instance of the GMPLS control plane is used as a TE link by another instance of the GMPLS control
plane. Moreover, the nodes using a TE link are expected to have a plane. Moreover, the nodes using a TE link are expected to have a
routing and signaling adjacency. routing and signaling adjacency.
10.2. Signaling Aspects 8.2. Signaling Aspects
For the purpose of processing the explicit route in a Path/Request For the purpose of processing the explicit route in a Path/Request
message of an LSP that is to be tunneled over a forwarding message of an LSP that is to be tunneled over a forwarding adjacency,
adjacency, an LSR at the head-end of the FA-LSP views the LSR at the an LSR at the head-end of the FA-LSP views the LSR at the tail of
tail of that FA-LSP as adjacent (one IP hop away). that FA-LSP as adjacent (one IP hop away).
10.3. Cascading of Forwarding Adjacencies 8.3. Cascading of Forwarding Adjacencies
With an integrated model, several layers are controlled using the With an integrated model, several layers are controlled using the
same routing and signaling protocols. A network may then have links same routing and signaling protocols. A network may then have links
with different multiplexing/demultiplexing capabilities. For with different multiplexing/demultiplexing capabilities. For
example, a node may be able to multiplex/demultiplex individual example, a node may be able to multiplex/demultiplex individual
packets on a given link, and may be able to multiplex/demultiplex packets on a given link, and may be able to multiplex/demultiplex
channels within a SONET payload on other links. channels within a SONET payload on other links.
A new OSPF and IS-IS sub-TLV has been defined to advertise the A new OSPF and IS-IS sub-TLV has been defined to advertise the
multiplexing capability of each interface: PSC, L2SC, TDM, LSC or multiplexing capability of each interface: PSC, L2SC, TDM, LSC or
FSC. This sub-TLV is called the Interface Switching Capability FSC. This sub-TLV is called the Interface Switching Capability
Descriptor sub-TLV, which complements the sub-TLVs defined in [OSPF- Descriptor sub-TLV, which complements the sub-TLVs defined in
TE-GMPLS] and [ISIS-TE-GMPLS]. The information carried in this sub-
TLV is used to construct LSP regions, and determine region's [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. The information carried in this
sub-TLV is used to construct LSP regions, and determine region's
boundaries. boundaries.
Path computation may take into account region boundaries when Path computation may take into account region boundaries when
computing a path for an LSP. For example, path computation may computing a path for an LSP. For example, path computation may
restrict the path taken by an LSP to only the links whose restrict the path taken by an LSP to only the links whose
multiplexing/demultiplexing capability is PSC. When an LSP need to multiplexing/demultiplexing capability is PSC. When an LSP need to
cross a region boundary, it can trigger the establishment of an FA cross a region boundary, it can trigger the establishment of an FA at
at the underlying layer (i.e. the L2SC layer). This can trigger a the underlying layer (i.e., the L2SC layer). This can trigger a
cascading of FAs between layers with the following obvious order: cascading of FAs between layers with the following obvious order:
L2SC, then TDM, then LSC, and then finally FSC. L2SC, then TDM, then LSC, and then finally FSC.
11. Routing and Signaling Adjacencies 9. Routing and Signaling Adjacencies
By definition, two nodes have a routing (IS-IS/OSPF) adjacency if By definition, two nodes have a routing (IS-IS/OSPF) adjacency if
they are neighbors in the IS-IS/OSPF sense. they are neighbors in the IS-IS/OSPF sense.
By definition, two nodes have a signaling (RSVP-TE/CR-LDP) adjacency By definition, two nodes have a signaling (RSVP-TE/CR-LDP) adjacency
if they are neighbors in the RSVP-TE/CR-LDP sense. Nodes A and B are if they are neighbors in the RSVP-TE/CR-LDP sense. Nodes A and B are
RSVP-TE neighbors if they directly exchange RSVP-TE messages RSVP-TE neighbors if they directly exchange RSVP-TE messages
(Path/Resv) (e.g., as described in sections 7.1.1 and 7.1.2 of (Path/Resv) (e.g., as described in sections 7.1.1 and 7.1.2 of
[HIERARCHY]). The neighbor relationship includes exchanging RSVP-TE [HIERARCHY]). The neighbor relationship includes exchanging RSVP-TE
Hellos. Hellos.
By definition, a Forwarding Adjacency (FA) is a TE Link between two By definition, a Forwarding Adjacency (FA) is a TE Link between two
GMPLS nodes whose path transits one or more other (G)MPLS nodes in GMPLS nodes whose path transits one or more other (G)MPLS nodes in
the same instance of the (G)MPLS control plane. If two nodes have the same instance of the (G)MPLS control plane. If two nodes have
one or more non-FA TE Links between them, these two nodes are one or more non-FA TE Links between them, these two nodes are
expected (although not required) to have a routing adjacency. If two
E. Mannie (Editor) et al. Standard Track 39
expected (although not required) to have a routing adjacency. If two
nodes do not have any non-FA TE Links between them, it is expected nodes do not have any non-FA TE Links between them, it is expected
(although not required) that these two nodes would not have a (although not required) that these two nodes would not have a routing
routing adjacency. To state the obvious, if the TE links between two adjacency. To state the obvious, if the TE links between two nodes
nodes are to be used for establishing LSPs, the two nodes must have are to be used for establishing LSPs, the two nodes must have a
a signaling adjacency. signaling adjacency.
If one wants to establish routing and/or signaling adjacency between If one wants to establish routing and/or signaling adjacency between
two nodes, there must be an IP path between them. This IP path can two nodes, there must be an IP path between them. This IP path can
be, for example, a TE Link with an interface switching capability of be, for example, a TE Link with an interface switching capability of
PSC, anything that looks likes an IP link (e.g., GRE tunnel, or a PSC, anything that looks likes an IP link (e.g., GRE tunnel, or a
(bi-directional) LSP that with an interface switching capability of (bi-directional) LSP that with an interface switching capability of
PSC). PSC).
A TE link may not be capable of being used directly for maintaining A TE link may not be capable of being used directly for maintaining
routing and/or signaling adjacencies. This is because GMPLS routing routing and/or signaling adjacencies. This is because GMPLS routing
and signaling adjacencies requires exchanging data on a per frame/ and signaling adjacencies requires exchanging data on a per frame/
packet basis, and a TE link (e.g. a link between OXCs) may not be packet basis, and a TE link (e.g., a link between OXCs) may not be
capable of exchanging data on a per packet basis. In this case, the capable of exchanging data on a per packet basis. In this case, the
routing and signaling adjacencies are maintained via a set of one or routing and signaling adjacencies are maintained via a set of one or
more control channels (see [LMP]). more control channels (see [LMP]).
Two nodes may have a TE link between them even if they don't have a Two nodes may have a TE link between them even if they do not have a
routing adjacency. Naturally, each node must run OSPF/IS-IS with routing adjacency. Naturally, each node must run OSPF/IS-IS with
GMPLS extensions in order for that TE link to be advertised. More GMPLS extensions in order for that TE link to be advertised. More
precisely, the node needs to run GMPLS extensions for TE Links with precisely, the node needs to run GMPLS extensions for TE Links with
an interface switching capability (see [GMPLS-ROUTING]) other than an interface switching capability (see [GMPLS-ROUTING]) other than
PSC. Moreover, this node needs to run either GMPLS or MPLS PSC. Moreover, this node needs to run either GMPLS or MPLS
extensions for TE links with an interface switching capability of extensions for TE links with an interface switching capability of
PSC. PSC.
The mechanisms for Control Channel Separation [RFC3471] should be The mechanisms for Control Channel Separation [RFC3471] should be
used (even if the IP path between two nodes is a TE link). I.e., used (even if the IP path between two nodes is a TE link). I.e.,
RSVP-TE/CR-LDP signaling should use the Interface_ID (IF_ID) object RSVP-TE/CR-LDP signaling should use the Interface_ID (IF_ID) object
to specify a particular TE link when establishing an LSP. to specify a particular TE link when establishing an LSP.
The IP path could consist of multiple IP hops. In this case, the The IP path could consist of multiple IP hops. In this case, the
mechanisms of sections 7.1.1 and 7.1.2 of [HIERARCHY] should be used mechanisms of sections 7.1.1 and 7.1.2 of [HIERARCHY] should be used
(in addition to Control Channel Separation). (in addition to Control Channel Separation).
12. Control Plane Fault Handling 10. Control Plane Fault Handling
Two major types of faults can impact a control plane. The first, Two major types of faults can impact a control plane. The first,
referred to as control channel fault, relates to the case where referred to as control channel fault, relates to the case where
control communication is lost between two neighboring nodes. If the control communication is lost between two neighboring nodes. If the
control channel is embedded with the data channel, data channel control channel is embedded with the data channel, data channel
recovery procedure should solve the problem. If the control channel recovery procedure should solve the problem. If the control channel
is independent of the data channel, additional procedures are is independent of the data channel, additional procedures are
required to recover from that problem. required to recover from that problem.
The second, referred to as nodal faults, relates to the case where The second, referred to as nodal faults, relates to the case where
node loses its control state (e.g., after a restart) but does not node loses its control state (e.g., after a restart) but does not
loose its data forwarding state. loose its data forwarding state.
E. Mannie (Editor) et al. Standard Track 40
In transport networks, such types of control plane faults should not In transport networks, such types of control plane faults should not
have service impact on the existing connections. Under such have service impact on the existing connections. Under such
circumstances, a mechanism must exist to detect a control circumstances, a mechanism must exist to detect a control
communication failure and a recovery procedure must guarantee communication failure and a recovery procedure must guarantee
connection integrity at both ends of the control channel. connection integrity at both ends of the control channel.
For a control channel fault, once communication is restored routing For a control channel fault, once communication is restored routing
protocols are naturally able to recover but the underlying signaling protocols are naturally able to recover but the underlying signaling
protocols must indicate that the nodes have maintained their state protocols must indicate that the nodes have maintained their state
through the failure. The signaling protocol must also ensure that through the failure. The signaling protocol must also ensure that
any state changes that were instantiated during the failure are any state changes that were instantiated during the failure are
synchronized between the nodes. synchronized between the nodes.
For a nodal fault, a node's control plane restarts and loses most of For a nodal fault, a node's control plane restarts and loses most of
its state information. In this case, both upstream and downstream its state information. In this case, both upstream and downstream
nodes must synchronize their state information with the restarted nodes must synchronize their state information with the restarted
node. In order for any resynchronization to occur the node node. In order for any resynchronization to occur the node
undergoing the restart will need to preserve some information, such undergoing the restart will need to preserve some information, such
as it's mappings of incoming to outgoing labels. as it's mappings of incoming to outgoing labels.
These issues are addressed in protocol specific fashions, see These issues are addressed in protocol specific fashions, see
[RFC3473], [RFC3472], [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. Note that [RFC3473], [RFC3472], [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. Note that
these cases only apply when there are mechanisms to detect data these cases only apply when there are mechanisms to detect data
channel failures independent of control channel failures. channel failures independent of control channel failures.
The LDP Fault tolerance (see [RFC3479]) specifies the procedures to The LDP Fault tolerance (see [RFC3479]) specifies the procedures to
recover from a control channel failure. [RFC3473] specifies how to recover from a control channel failure. [RFC3473] specifies how to
recover from both a control channel failure and a node failure. recover from both a control channel failure and a node failure.
13. LSP Protection and Restoration 11. LSP Protection and Restoration
This section discusses Protection and Restoration (P&R) issues for This section discusses Protection and Restoration (P&R) issues for
GMPLS LSPs. It is driven by the requirements outlined in [RFC3386] GMPLS LSPs. It is driven by the requirements outlined in [RFC3386]
and some of the principles outlined in [RFC3469]. It will be and some of the principles outlined in [RFC3469]. It will be
enhanced, as more GMPLS P&R mechanisms are defined. The scope of enhanced, as more GMPLS P&R mechanisms are defined. The scope of
this section is clarified hereafter: this section is clarified hereafter:
- This section is only applicable when a fault impacting LSP(s) - This section is only applicable when a fault impacting LSP(s)
happens in the data/transport plane. Section 11 deals with control happens in the data/transport plane. Section 10 deals with
plane fault handling for nodal and control channel faults. control plane fault handling for nodal and control channel faults.
- This section focuses on P&R at the TDM, LSC and FSC layers. There - This section focuses on P&R at the TDM, LSC and FSC layers. There
are specific P&R requirements at these layers not present at the are specific P&R requirements at these layers not present at the
PSC layer. PSC layer.
- This section focuses on intra-area P&R as opposed to inter-area - This section focuses on intra-area P&R as opposed to inter-area
P&R and even inter-domain P&R. Note that P&R can even be more P&R and even inter-domain P&R. Note that P&R can even be more
restricted, e.g. to a collection of like customer equipment, or a restricted, e.g., to a collection of like customer equipment, or a
collection of equipment of like capabilities, in one single collection of equipment of like capabilities, in one single
routing area. routing area.
- This section focuses on intra-layer P&R (horizontal hierarchy as - This section focuses on intra-layer P&R (horizontal hierarchy as
defined in [RFC3386]) as opposed to the inter-layer P&R (vertical defined in [RFC3386]) as opposed to the inter-layer P&R (vertical
hierarchy). hierarchy).
E. Mannie (Editor) et al. Standard Track 41 - P&R mechanisms are in general designed to handle single failures,
- P&R mechanisms are in general designed to handle single failures, which makes SRLG diversity a necessity. Recovery from multiple
which makes SRLG diversity a necessity. Recovery from multiple failures requires further study.
failures requires further study.
- Both mesh and ring-like topologies are supported. - Both mesh and ring-like topologies are supported.
In the following, we assume that: In the following, we assume that:
- TDM, LSC and FSC devices are more generally committing recovery - TDM, LSC and FSC devices are more generally committing recovery
resources in a non-best effort way. Recovery resources are either resources in a non-best effort way. Recovery resources are either
allocated (thus used) or at least logically reserved (whether used allocated (thus used) or at least logically reserved (whether used
or not by preemptable extra traffic but unavailable anyway for or not by preemptable extra traffic but unavailable anyway for
regular working traffic). regular working traffic).
- Shared P&R mechanisms are valuable to operators in order to
maximize their network utilization.
- Sending preemptable excess traffic on recovery resources is a - Shared P&R mechanisms are valuable to operators in order to
valuable feature for operators. maximize their network utilization.
13.1. Protection Escalation across Domains and Layers - Sending preemptable excess traffic on recovery resources is a
valuable feature for operators.
To describe the P&R architecture, one must consider two dimensions 11.1. Protection Escalation across Domains and Layers
of hierarchy [RFC3386]:
- A horizontal hierarchy consisting of multiple P&R domains, which To describe the P&R architecture, one must consider two dimensions of
is important in an LSP based protection scheme. The scope of P&R hierarchy [RFC3386]:
may extend over a link (or span), an administrative domain or sub-
network, an entire LSP.
An administrative domain may consist of a single P&R domain or as - A horizontal hierarchy consisting of multiple P&R domains, which
a concatenation of several smaller P&R domains. The operator can is important in an LSP based protection scheme. The scope of P&R
configure P&R domains, based on customers' requirements, and on may extend over a link (or span), an administrative domain or
network topology and traffic engineering constraints. sub-network, an entire LSP.
- A vertical hierarchy consisting of multiple layers of P&R with An administrative domain may consist of a single P&R domain or as
varying granularities (packet flows, STS trails, lightpaths, a concatenation of several smaller P&R domains. The operator can
fibers, etc). configure P&R domains, based on customers' requirements, and on
network topology and traffic engineering constraints.
In the absence of adequate P&R coordination, a fault may propagate - A vertical hierarchy consisting of multiple layers of P&R with
from one level to the next within a P&R hierarchy. It can lead to varying granularities (packet flows, STS trails, lightpaths,
"collisions" and simultaneous recovery actions may lead to race fibers, etc).
conditions, reduced resource utilization, or instabilities
[MANCHESTER]. Thus, a consistent escalation strategy is needed to
coordinate recovery across domains and layers. The fact that GMPLS
can be used at different layers could simplify this coordination.
There are two types of escalation strategies: bottom-up and top- In the absence of adequate P&R coordination, a fault may propagate
down. The bottom-up approach assumes that "lower-level" recovery from one level to the next within a P&R hierarchy. It can lead to
schemes are more expedient. Therefore we can inhibit or hold off "collisions" and simultaneous recovery actions may lead to race
higher-level P&R. The Top-down approach attempts service P&R at conditions, reduced resource utilization, or instabilities
the higher levels before invoking "lower level" P&R. Higher-layer [MANCHESTER]. Thus, a consistent escalation strategy is needed to
coordinate recovery across domains and layers. The fact that
GMPLS can be used at different layers could simplify this
coordination.
E. Mannie (Editor) et al. Standard Track 42 There are two types of escalation strategies: bottom-up and top-
P&R is service selective, and permits "per-CoS" or "per-LSP" re- down. The bottom-up approach assumes that "lower-level" recovery
routing. schemes are more expedient. Therefore we can inhibit or hold off
higher-level P&R. The Top-down approach attempts service P&R at
the higher levels before invoking "lower level" P&R. Higher-layer
P&R is service selective, and permits "per-CoS" or "per-LSP" re-
routing.
Service Level Agreements (SLAs) between network operators and their Service Level Agreements (SLAs) between network operators and their
clients are needed to determine the necessary time scales for P&R at clients are needed to determine the necessary time scales for P&R at
each layer and at each domain. each layer and at each domain.
13.2. Mapping of Services to P&R Resources 11.2. Mapping of Services to P&R Resources
The choice of a P&R scheme is a tradeoff between network utilization The choice of a P&R scheme is a tradeoff between network utilization
(cost) and service interruption time. In light of this tradeoff, (cost) and service interruption time. In light of this tradeoff,
network service providers are expected to support a range of network service providers are expected to support a range of
different service offerings or service levels. different service offerings or service levels.
One can classify LSPs into one of a small set of service levels. One can classify LSPs into one of a small set of service levels.
Among other things, these service levels define the reliability Among other things, these service levels define the reliability
characteristics of the LSP. The service level associated with a characteristics of the LSP. The service level associated with a
given LSP is mapped to one or more P&R schemes during LSP given LSP is mapped to one or more P&R schemes during LSP
establishment. An advantage that mapping is that an LSP may use establishment. An advantage that mapping is that an LSP may use
different P&E schemes in different segments of a network (e.g. some different P&E schemes in different segments of a network (e.g., some
links may be span protected, whilst other segments of the LSP may links may be span protected, whilst other segments of the LSP may
utilize ring protection). These details are likely to be service utilize ring protection). These details are likely to be service
provider specific. provider specific.
An alternative to using service levels is for an application to An alternative to using service levels is for an application to
specify the set of specific P&R mechanisms to be used when specify the set of specific P&R mechanisms to be used when
establishing the LSP. This allows greater flexibility in using establishing the LSP. This allows greater flexibility in using
different mechanisms to meet the application requirements. different mechanisms to meet the application requirements.
A differentiator between these service levels is service A differentiator between these service levels is service interruption
interruption time in case of network failures, which is defined as time in case of network failures, which is defined as the length of
the length of time between when a failure occurs and when time between when a failure occurs and when connectivity is re-
connectivity is re-established. The choice of service level (or P&R established. The choice of service level (or P&R scheme) should be
scheme) should be dictated by the service requirements of different dictated by the service requirements of different applications.
applications.
13.3. Classification of P&R Mechanism Characteristics 11.3. Classification of P&R Mechanism Characteristics
The following figure provides a classification of the possible The following figure provides a classification of the possible
provisioning types of recovery LSPs, and of the levels of provisioning types of recovery LSPs, and of the levels of overbooking
overbooking that is possible for them. that is possible for them.
+-Computed on +-Established +-Resources pre- +-Computed on +-Established +-Resources pre-
| demand | on demand | allocated | demand | on demand | allocated
| | | | | |
Recovery LSP | | | Recovery LSP | | |
Provisioning -+-Pre computed +-Pre established +-Resources allocated Provisioning -+-Pre computed +-Pre established +-Resources allocated
on demand on demand
+--- Dedicated (1:1, 1+1) +--- Dedicated (1:1, 1+1)
| |
| |
+--- Shared (1:N, Ring, Shared mesh) +--- Shared (1:N, Ring, Shared mesh)
E. Mannie (Editor) et al. Standard Track 43
| |
Level of | Level of |
Overbooking ---+--- Best effort Overbooking ---+--- Best effort
13.4. Different Stages in P&R 11.4. Different Stages in P&R
Recovery from a network fault or impairment takes place in several Recovery from a network fault or impairment takes place in several
stages as discussed in [RFC3469], including fault detection, fault stages as discussed in [RFC3469], including fault detection, fault
localization, notification, recovery (i.e. the P&R itself) and localization, notification, recovery (i.e., the P&R itself) and
reversion of traffic (i.e. returning the traffic to the original reversion of traffic (i.e., returning the traffic to the original
working LSP or to a new one). working LSP or to a new one).
- Fault detection is technology and implementation dependent. In - Fault detection is technology and implementation dependent. In
general, failures are detected by lower layer mechanisms (e.g. general, failures are detected by lower layer mechanisms (e.g.,
SONET/SDH, Loss-of-Light (LOL)). When a node detects a failure, an SONET/SDH, Loss-of-Light (LOL)). When a node detects a failure,
alarm may be passed up to a GMPLS entity, which will take an alarm may be passed up to a GMPLS entity, which will take
appropriate actions, or the alarm may be propagated at the lower appropriate actions, or the alarm may be propagated at the lower
layer (e.g. SONET/SDH AIS). layer (e.g., SONET/SDH AIS).
- Fault localization can be done with the help of GMPLS, e.g. using - Fault localization can be done with the help of GMPLS, e.g., using
LMP for fault localization (see section 8.4). LMP for fault localization (see section 6.4).
- Fault notification can also be achieved through GMPLS, e.g. using - Fault notification can also be achieved through GMPLS, e.g., using
GMPLS RSVP-TE/CR-LDP notification (see section 9.12). GMPLS RSVP-TE/CR-LDP notification (see section 7.12).
- This section focuses on the different mechanisms available for - This section focuses on the different mechanisms available for
recovery and reversion of traffic once fault detection, recovery and reversion of traffic once fault detection,
localization and notification have taken place. localization and notification have taken place.
13.5. Recovery Strategies 11.5. Recovery Strategies
Network P&R techniques can be divided into Protection and Network P&R techniques can be divided into Protection and
Restoration. In protection, resources between the protection Restoration. In protection, resources between the protection
endpoints are established before failure, and connectivity after endpoints are established before failure, and connectivity after
failure is achieved simply by switching performed at the protection failure is achieved simply by switching performed at the protection
end-points. In contrast, restoration uses signaling after failure to end-points. In contrast, restoration uses signaling after failure to
allocate resources along the recovery path. allocate resources along the recovery path.
- Protection aims at extremely fast reaction times and may rely on - Protection aims at extremely fast reaction times and may rely on
the use of overhead control fields for achieving end-point the use of overhead control fields for achieving end-point
coordination. Protection for SONET/SDH networks is described in coordination. Protection for SONET/SDH networks is described in
[ITUT-G.841] and [ANSI-T1.105]. Protection mechanisms can be [ITUT-G.841] and [ANSI-T1.105]. Protection mechanisms can be
further classified by the level of redundancy and sharing. further classified by the level of redundancy and sharing.
- Restoration mechanisms rely on signaling protocols to coordinate - Restoration mechanisms rely on signaling protocols to coordinate
switching actions during recovery, and may involve simple re- switching actions during recovery, and may involve simple re-
provisioning, i.e. signaling only at the time of recovery; or pre- provisioning, i.e., signaling only at the time of recovery; or
signaling, i.e., signaling prior to recovery. pre-signaling, i.e., signaling prior to recovery.
In addition, P&R can be applied on a local or end-to-end basis. In In addition, P&R can be applied on a local or end-to-end basis. In
the local approach, P&R is focused on the local proximity of the the local approach, P&R is focused on the local proximity of the
fault in order to reduce delay in restoring service. In the end-to- fault in order to reduce delay in restoring service. In the end-to-
E. Mannie (Editor) et al. Standard Track 44
end approach, the LSP originating and terminating nodes control end approach, the LSP originating and terminating nodes control
recovery. recovery.
Using these strategies, the following recovery mechanisms can be Using these strategies, the following recovery mechanisms can be
defined. defined.
13.6. Recovery mechanisms: Protection schemes 11.6. Recovery mechanisms: Protection schemes
Note that protection schemes are usually defined in technology Note that protection schemes are usually defined in technology
specific ways, but this does not preclude other solutions. specific ways, but this does not preclude other solutions.
- 1+1 Link Protection: Two pre-provisioned resources are used in - 1+1 Link Protection: Two pre-provisioned resources are used in
parallel. For example, data is transmitted simultaneously on two parallel. For example, data is transmitted simultaneously on two
parallel links and a selector is used at the receiving node to parallel links and a selector is used at the receiving node to
choose the best source (see also [GMPLS-FUNCT]). choose the best source (see also [GMPLS-FUNCT]).
- 1:N Link Protection: Working and protecting resources (N working, - 1:N Link Protection: Working and protecting resources (N working,
1 backup) are pre-provisioned. If a working resource fails, the 1 backup) are pre-provisioned. If a working resource fails, the
data is switched to the protecting resource, using a coordination data is switched to the protecting resource, using a coordination
mechanism (e.g. in overhead bytes). More generally, N working and mechanism (e.g., in overhead bytes). More generally, N working
M protecting resources can be assigned for M:N link protection and M protecting resources can be assigned for M:N link protection
(see also [GMPLS-FUNCT]). (see also [GMPLS-FUNCT]).
- Enhanced Protection: Various mechanisms such as protection rings - Enhanced Protection: Various mechanisms such as protection rings
can be used to enhance the level of protection beyond single link can be used to enhance the level of protection beyond single link
failures to include the ability to switch around a node failure or failures to include the ability to switch around a node failure or
multiple link failures within a span, based on a pre-established multiple link failures within a span, based on a pre-established
topology of protection resources (note: no reference available at topology of protection resources (note: no reference available at
publication time). publication time).
- 1+1 LSP Protection: Simultaneous data transmission on working and - 1+1 LSP Protection: Simultaneous data transmission on working and
protecting LSPs and tail-end selection can be applied (see also protecting LSPs and tail-end selection can be applied (see also
[GMPLS-FUNCT]). [GMPLS-FUNCT]).
13.7. Recovery mechanisms: Restoration schemes 11.7. Recovery mechanisms: Restoration schemes
Thanks to the use of a distributed control plane like GMPLS, Thanks to the use of a distributed control plane like GMPLS,
restoration is possible in multiple of tenths of milliseconds. It is restoration is possible in multiple of tenths of milliseconds. It is
much harder to achieve when only an NMS is used and can only be done much harder to achieve when only an NMS is used and can only be done
in that case in a multiple of seconds. in that case in a multiple of seconds.
- End-to-end LSP restoration with re-provisioning: an end-to-end - End-to-end LSP restoration with re-provisioning: an end-to-end
restoration path is established after failure. The restoration restoration path is established after failure. The restoration
path may be dynamically calculated after failure, or pre- path may be dynamically calculated after failure, or pre-
calculated before failure (often during LSP establishment). calculated before failure (often during LSP establishment).
Importantly, no signaling is used along the restoration path Importantly, no signaling is used along the restoration path
before failure, and no restoration bandwidth is reserved. before failure, and no restoration bandwidth is reserved.
Consequently, there is no guarantee that a given restoration path Consequently, there is no guarantee that a given restoration path
is available when a failure occurs. Thus, one may have to is available when a failure occurs. Thus, one may have to
crankback to search for an available path. crankback to search for an available path.
- End-to-end LSP restoration with pre-signaled recovery bandwidth
reservation and no label pre-selection: an end-to-end restoration
path is pre-calculated before failure and a signaling message is
E. Mannie (Editor) et al. Standard Track 45
sent along this pre-selected path to reserve bandwidth, but labels
are not selected (see also [GMPLS-FUNCT]).
The resources reserved on each link of a restoration path may be - End-to-end LSP restoration with pre-signaled recovery bandwidth
shared across different working LSPs that are not expected to fail reservation and no label pre-selection: an end-to-end restoration
simultaneously. Local node policies can be applied to define the path is pre-calculated before failure and a signaling message is
degree to which capacity is shared across independent failures. sent along this pre-selected path to reserve bandwidth, but labels
Upon failure detection, LSP signaling is initiated along the are not selected (see also [GMPLS-FUNCT]).
restoration path to select labels, and to initiate the appropriate
cross-connections.
- End-to-end LSP restoration with pre-signaled recovery bandwidth The resources reserved on each link of a restoration path may be
reservation and label pre-selection: An end-to-end restoration shared across different working LSPs that are not expected to fail
path is pre-calculated before failure and a signaling procedure is simultaneously. Local node policies can be applied to define the
initiated along this pre-selected path on which bandwidth is degree to which capacity is shared across independent failures.
reserved and labels are selected (see also [GMPLS-FUNCT]). Upon failure detection, LSP signaling is initiated along the
restoration path to select labels, and to initiate the appropriate
cross-connections.
The resources reserved on each link may be shared across different - End-to-end LSP restoration with pre-signaled recovery bandwidth
working LSPs that are not expected to fail simultaneously. In reservation and label pre-selection: An end-to-end restoration
networks based on TDM, LSC and FSC technology, LSP signaling is path is pre-calculated before failure and a signaling procedure is
used after failure detection to establish cross-connections at the initiated along this pre-selected path on which bandwidth is
intermediate switches on the restoration path using the pre- reserved and labels are selected (see also [GMPLS-FUNCT]).
selected labels.
- Local LSP restoration: the above approaches can be applied on a The resources reserved on each link may be shared across different
local basis rather than end-to-end, in order to reduce recovery working LSPs that are not expected to fail simultaneously. In
time (note: no reference available at publication time). networks based on TDM, LSC and FSC technology, LSP signaling is
used after failure detection to establish cross-connections at the
intermediate switches on the restoration path using the pre-
selected labels.
13.8. Schema Selection Criteria - Local LSP restoration: the above approaches can be applied on a
local basis rather than end-to-end, in order to reduce recovery
time (note: no reference available at publication time).
This section discusses criteria that could be used by the operator 11.8. Schema Selection Criteria
in order to make a choice among the various P&R mechanisms.
- Robustness: In general, the less pre-planning of the restoration This section discusses criteria that could be used by the operator in
path, the more robust the restoration scheme is to a variety of order to make a choice among the various P&R mechanisms.
failures, provided that adequate resources are available.
Restoration schemes with pre-planned paths will not be able to
recover from network failures that simultaneously affect both the
working and restoration paths. Thus, these paths should ideally be
chosen to be as disjoint as possible (i.e. SRLG and node
disjoint), so that any single failure event will not affect both
paths. The risk of simultaneous failure of the two paths can be
reduced by recalculating the restoration path whenever a failure
occurs along it.
The pre-selection of a label gives less flexibility for multiple - Robustness: In general, the less pre-planning of the restoration
failure scenarios than no label pre-selection. If failures occur path, the more robust the restoration scheme is to a variety of
that affect two LSPs that are sharing a label at a common node failures, provided that adequate resources are available.
along their restoration routes, then only one of these LSPs can be Restoration schemes with pre-planned paths will not be able to
recovered, unless the label assignment is changed. recover from network failures that simultaneously affect both the
working and restoration paths. Thus, these paths should ideally
be chosen to be as disjoint as possible (i.e., SRLG and node
disjoint), so that any single failure event will not affect both
paths. The risk of simultaneous failure of the two paths can be
reduced by recalculating the restoration path whenever a failure
occurs along it.
The robustness of a restoration scheme is also determined by the The pre-selection of a label gives less flexibility for multiple
amount of reserved restoration bandwidth - as the amount of failure scenarios than no label pre-selection. If failures occur
restoration bandwidth sharing increases (reserved bandwidth that affect two LSPs that are sharing a label at a common node
along their restoration routes, then only one of these LSPs can be
recovered, unless the label assignment is changed.
E. Mannie (Editor) et al. Standard Track 46 The robustness of a restoration scheme is also determined by the
decreases), the restoration scheme becomes less robust to amount of reserved restoration bandwidth - as the amount of
failures. Restoration schemes with pre-signaled bandwidth restoration bandwidth sharing increases (reserved bandwidth
reservation (with or without label pre-selection) can reserve decreases), the restoration scheme becomes less robust to
adequate bandwidth to ensure recovery from any specific set of failures. Restoration schemes with pre-signaled bandwidth
failure events, such as any single SRLG failure, any two SRLG reservation (with or without label pre-selection) can reserve
failures etc. Clearly, more restoration capacity is allocated if a adequate bandwidth to ensure recovery from any specific set of
greater degree of failure recovery is required. Thus, the degree failure events, such as any single SRLG failure, any two SRLG
to which the network is protected is determined by the policy that failures etc. Clearly, more restoration capacity is allocated if
defines the amount of reserved restoration bandwidth. a greater degree of failure recovery is required. Thus, the
degree to which the network is protected is determined by the
policy that defines the amount of reserved restoration bandwidth.
- Recovery time: In general, the more pre-planning of the - Recovery time: In general, the more pre-planning of the
restoration route, the more rapid the P&R scheme. Protection restoration route, the more rapid the P&R scheme. Protection
schemes generally recover faster than restoration schemes. schemes generally recover faster than restoration schemes.
Restoration with pre-signaled bandwidth reservation are likely to Restoration with pre-signaled bandwidth reservation are likely to
be (significantly) faster than path restoration with re- be (significantly) faster than path restoration with re-
provisioning, especially because of the elimination of any provisioning, especially because of the elimination of any
crankback. Local restoration will generally be faster than end-to- crankback. Local restoration will generally be faster than end-
end schemes. to-end schemes.
Recovery time objectives for SONET/SDH protection switching (not Recovery time objectives for SONET/SDH protection switching (not
including time to detect failure) are specified in [ITUT-G.841] at including time to detect failure) are specified in [ITUT-G.841] at
50 ms, taking into account constraints on distance, number of 50 ms, taking into account constraints on distance, number of
connections involved, and in the case of ring enhanced protection, connections involved, and in the case of ring enhanced protection,
number of nodes in the ring. number of nodes in the ring.
Recovery time objectives for restoration mechanisms are being Recovery time objectives for restoration mechanisms are being
defined through a separate effort [RFC3386]. defined through a separate effort [RFC3386].
- Resource Sharing: 1+1 and 1:N link and LSP protection require - Resource Sharing: 1+1 and 1:N link and LSP protection require
dedicated recovery paths with limited ability to share resources: dedicated recovery paths with limited ability to share resources:
1+1 allows no sharing, 1:N allows some sharing of protection 1+1 allows no sharing, 1:N allows some sharing of protection
resources and support of extra (preemptable) traffic. Flexibility resources and support of extra (pre-emptable) traffic.
is limited because of topology restrictions, e.g. fixed ring Flexibility is limited because of topology restrictions, e.g.,
topology for traditional enhanced protection schemes. fixed ring topology for traditional enhanced protection schemes.
The degree to which restoration schemes allow sharing amongst The degree to which restoration schemes allow sharing amongst
multiple independent failures is directly dictated by the size of multiple independent failures is directly dictated by the size of
the restoration pool. In restoration schemes with re-provisioning, the restoration pool. In restoration schemes with re-
a pool of restoration capacity can be defined from which all provisioning, a pool of restoration capacity can be defined from
restoration routes are selected after failure. Thus, the degree of which all restoration routes are selected after failure. Thus,
sharing is defined by the amount of available restoration the degree of sharing is defined by the amount of available
capacity. In restoration with pre-signaled bandwidth reservation, restoration capacity. In restoration with pre-signaled bandwidth
the amount of reserved restoration capacity is determined by the reservation, the amount of reserved restoration capacity is
local bandwidth reservation policies. In all restoration schemes, determined by the local bandwidth reservation policies. In all
pre-emptable resources can use spare restoration capacity when restoration schemes, pre-emptable resources can use spare
that capacity is not being used for failure recovery. restoration capacity when that capacity is not being used for
failure recovery.
E. Mannie (Editor) et al. Standard Track 47 12. Network Management
14. Network Management
Service Providers (SPs) use network management extensively to Service Providers (SPs) use network management extensively to
configure, monitor or provision various devices in their network. It configure, monitor or provision various devices in their network. It
is important to note that a SP's equipment may be distributed across is important to note that a SP's equipment may be distributed across
geographically separate sites thus making distributed management geographically separate sites thus making distributed management even
even more important. The service provider should utilize an NMS more important. The service provider should utilize an NMS system
system and standard management protocols such as SNMP (see and standard management protocols such as SNMP (see [RFC3410],
[RFC3410], [RFC3411] and [RFC3416]) and the relevant MIB modules as [RFC3411] and [RFC3416]) and the relevant MIB modules as standard
standard interfaces to configure, monitor and provision devices at interfaces to configure, monitor and provision devices at various
various locations. The service provider may also wish to use the locations. The service provider may also wish to use the command
command line interface (CLI) provided by vendors with their devices. line interface (CLI) provided by vendors with their devices. However,
However, this is not a standard or recommended solution because this is not a standard or recommended solution because there is no
there is no standard CLI language or interface, which results in N standard CLI language or interface, which results in N different CLIs
different CLIs in a network with devices from N different vendors. in a network with devices from N different vendors. In the context of
In the context of GMPLS, it is extremely important for standard GMPLS, it is extremely important for standard interfaces to the SP's
interfaces to the SP's devices (e.g. SNMP) to exist due to the devices (e.g., SNMP) to exist due to the nature of the technology
nature of the technology itself. Since GMPLS comprises many itself. Since GMPLS comprises many different layers of control-plane
different layers of control-plane and data-plane technology, it is and data-plane technology, it is important for management interfaces
important for management interfaces in this area to be flexible in this area to be flexible enough to allow the manager to manage
enough to allow the manager to manage GMPLS easily, and in a GMPLS easily, and in a standard way.
standard way.
14.1. Network Management Systems (NMS) 12.1. Network Management Systems (NMS)
The NMS system should maintain the collective information about each The NMS system should maintain the collective information about each
device within the system. Note that the NMS system may actually be device within the system. Note that the NMS system may actually be
comprised of several distributed applications (i.e. alarm comprised of several distributed applications (i.e., alarm
aggregators, configuration consoles, polling applications, etc.) aggregators, configuration consoles, polling applications, etc.)
that collectively comprises the SP's NMS. In this way, it can make that collectively comprises the SP's NMS. In this way, it can make
provisioning and maintenance decisions with the full knowledge of provisioning and maintenance decisions with the full knowledge of the
the entire SP's network. Configuration or provisioning information entire SP's network. Configuration or provisioning information
(i.e. requests for new services) could be entered into the NMS and (i.e., requests for new services) could be entered into the NMS and
subsequently distributed via SNMP to the remote devices. Thus, subsequently distributed via SNMP to the remote devices. Thus,
making the SP's task of managing the network much more compact and making the SP's task of managing the network much more compact and
effortless rather than having to manage each device individually effortless rather than having to manage each device individually
(i.e. via CLI). (i.e., via CLI).
Security and access control can be achieved using the SNMPv3 User- Security and access control can be achieved using the SNMPv3 User-
based Security Model (USM) [RFC3414] and the View-based Access based Security Model (USM) [RFC3414] and the View-based Access
Control Model (VACM) [RFC3415]. This approach can be very Control Model (VACM) [RFC3415]. This approach can be very
effectively used within a SP's network, since the SP has access to effectively used within a SP's network, since the SP has access to
and control over all devices within its domain. Standardized MIBs and control over all devices within its domain. Standardized MIBs
will need to be developed before this approach can be used will need to be developed before this approach can be used
ubiquitously to provision, configure and monitor devices in non- ubiquitously to provision, configure and monitor devices in non-
heterogeneous networks or across SP's network boundaries. heterogeneous networks or across SP's network boundaries.
14.2. Management Information Base (MIB) 12.2. Management Information Base (MIB)
In the context of GMPLS, it is extremely important for standard In the context of GMPLS, it is extremely important for standard
interfaces to devices to exist due to the nature of the technology interfaces to devices to exist due to the nature of the technology
itself. Since GMPLS comprises many different layers of control-plane itself. Since GMPLS comprises many different layers of control-plane
technology, it is important for SNMP MIB modules in this area to be technology, it is important for SNMP MIB modules in this area to be
flexible enough to allow the manager to manage the entire control flexible enough to allow the manager to manage the entire control
plane. This should be done using MIB modules that may cooperate
(i.e., coordinated row-creation on the agent) or through more
generalized MIB modules that aggregate some of the desired actions to
be taken and push those details down to the devices. It is important
to note that in certain circumstances, it may be necessary to
duplicate some small subset of manageable objects in new MIB modules
for management convenience. Control of some parts of GMPLS may also
be achieved using existing MIB interfaces (i.e., existing SONET MIB)
or using separate ones, which are yet to be defined. MIB modules may
have been previously defined in the IETF or ITU. Current MIB modules
may need to be extended to facilitate some of the new functionality
desired by GMPLS. In these cases, the working group should work on
new versions of these MIB modules so that these extensions can be
added.
E. Mannie (Editor) et al. Standard Track 48 12.3. Tools
plane. This should be done using MIB modules that may cooperate
(i.e. coordinated row-creation on the agent) or through more
generalized MIB modules that aggregate some of the desired actions
to be taken and push those details down to the devices. It is
important to note that in certain circumstances, it may be necessary
to duplicate some small subset of manageable objects in new MIB
modules for management convenience. Control of some parts of GMPLS
may also be achieved using existing MIB interfaces (i.e. existing
SONET MIB) or using separate ones, which are yet to be defined. MIB
modules may have been previously defined in the IETF or ITU. Current
MIB modules may need to be extended to facilitate some of the new
functionality desired by GMPLS. In these cases, the working group
should work on new versions of these MIB modules so that these
extensions can be added.
14.3. Tools
As in traditional networks, standard tools such as traceroute As in traditional networks, standard tools such as traceroute
[RFC1393] and ping [RFC2151] are needed for debugging and [RFC1393] and ping [RFC2151] are needed for debugging and performance
performance monitoring of GMPLS networks, and mainly for the control monitoring of GMPLS networks, and mainly for the control plane
plane topology, that will mimic the data plane topology. topology, that will mimic the data plane topology. Furthermore, such
Furthermore, such tools provide network reachability information. tools provide network reachability information. The GMPLS control
The GMPLS control protocols will need to expose certain pieces of protocols will need to expose certain pieces of information in order
information in order for these tools to function properly and to for these tools to function properly and to provide information
provide information germane to GMPLS. These tools should be made germane to GMPLS. These tools should be made available via the CLI.
available via the CLI. These tools should also be made available for These tools should also be made available for remote invocation via
remote invocation via the SNMP interface [RFC2925]. the SNMP interface [RFC2925].
14.4. Fault Correlation between Multiple Layers 12.4. Fault Correlation between Multiple Layers
Due to the nature of GMPLS, and that potential layers may be Due to the nature of GMPLS, and that potential layers may be involved
involved in the control and transmission of GMPLS data and control in the control and transmission of GMPLS data and control
information, it is required that a fault in one layer be passed to information, it is required that a fault in one layer be passed to
the adjacent higher and lower layers to notify them of the fault. the adjacent higher and lower layers to notify them of the fault.
However, due to nature of these many layers, it is possible and even However, due to nature of these many layers, it is possible and even
probable, that hundreds or even thousands of notifications may need probable, that hundreds or even thousands of notifications may need
to transpire between layers. This is undesirable for several to transpire between layers. This is undesirable for several
reasons. First, these notifications will overwhelm the device. reasons. First, these notifications will overwhelm the device.
Second, if the device(s) are programmed to emit SNMP Notifications Second, if the device(s) are programmed to emit SNMP Notifications
[RFC3417] then the large number of notifications the device may [RFC3417] then the large number of notifications the device may
attempt to emit may overwhelm the network with a storm of attempt to emit may overwhelm the network with a storm of
notifications. Furthermore, even if the device emits the notifications. Furthermore, even if the device emits the
notifications, the NMS that must process these notifications either notifications, the NMS that must process these notifications either
will be overwhelmed or will be processing redundant information. will be overwhelmed or will be processing redundant information. That
That is, if 1000 interfaces at layer B are stacked above a single is, if 1000 interfaces at layer B are stacked above a single
interface below it at layer A, and the interface at A goes down, the interface below it at layer A, and the interface at A goes down, the
interfaces at layer B should not emit notifications. Instead, the interfaces at layer B should not emit notifications. Instead, the
interface at layer A should emit a single notification. The NMS interface at layer A should emit a single notification. The NMS
receiving this notification should be able to correlate the fact receiving this notification should be able to correlate the fact that
that this interface has many others stacked above it and take this interface has many others stacked above it and take appropriate
appropriate action, if necessary. action, if necessary.
Devices that support GMPLS should provide mechanisms for
aggregating, summarizing, enabling and disabling of inter-layer
E. Mannie (Editor) et al. Standard Track 49 Devices that support GMPLS should provide mechanisms for aggregating,
notifications for the reasons described above. In the context of summarizing, enabling and disabling of inter-layer notifications for
SNMP MIB modules, all MIB modules that are used by GMPLS must the reasons described above. In the context of SNMP MIB modules, all
provide enable/disable objects for all notification objects. MIB modules that are used by GMPLS must provide enable/disable
Furthermore, these MIBs must also provide notification summarization objects for all notification objects. Furthermore, these MIBs must
objects or functionality (as described above) as well. NMS systems also provide notification summarization objects or functionality (as
and standard tools which process notifications or keep track of the described above) as well. NMS systems and standard tools which
many layers on any given devices must be capable of processing the process notifications or keep track of the many layers on any given
vast amount of information which may potentially be emitted by devices must be capable of processing the vast amount of information
network devices running GMPLS at any point in time. which may potentially be emitted by network devices running GMPLS at
any point in time.
15. Security Considerations 13. Security Considerations
GMPLS defines a control plane architecture for multiple technologies GMPLS defines a control plane architecture for multiple technologies
and types of network elements. In general, since LSPs established and types of network elements. In general, since LSPs established
using GMPLS may carry high volumes of data and consume significant using GMPLS may carry high volumes of data and consume significant
network resources, security mechanisms are required to safeguard the network resources, security mechanisms are required to safeguard the
underlying network against attacks on the control plane and/or underlying network against attacks on the control plane and/or
unauthorized usage of data transport resources. The GMPLS control unauthorized usage of data transport resources. The GMPLS control
plane should therefore include mechanisms that prevent or minimize plane should therefore include mechanisms that prevent or minimize
the risk of attackers being able to inject and/or snoop on control the risk of attackers being able to inject and/or snoop on control
traffic. These risks depend on the level of trust between nodes that traffic. These risks depend on the level of trust between nodes that
exchange GMPLS control messages, as well as the realization and exchange GMPLS control messages, as well as the realization and
physical characteristics of the control channel. For example, an in- physical characteristics of the control channel. For example, an in-
band, in-fiber control channel over SONET/SDH overhead bytes is, in band, in-fiber control channel over SONET/SDH overhead bytes is, in
general, considered less vulnerable than a control channel realized general, considered less vulnerable than a control channel realized
over an out-of-band IP network. over an out-of-band IP network.
Security mechanisms can provide authentication and confidentiality. Security mechanisms can provide authentication and confidentiality.
Authentication can provide origin verification, message integrity Authentication can provide origin verification, message integrity and
and replay protection, while confidentiality ensures that a third replay protection, while confidentiality ensures that a third party
party cannot decipher the contents of a message. In situations where cannot decipher the contents of a message. In situations where GMPLS
GMPLS deployment requires primarily authentication, the respective deployment requires primarily authentication, the respective
authentication mechanisms of the GMPLS component protocols may be authentication mechanisms of the GMPLS component protocols may be
used (see [RFC2747], [RFC3036], [RFC2385] and [LMP]). Additionally, used (see [RFC2747], [RFC3036], [RFC2385] and [LMP]). Additionally,
the IPsec suite of protocols (see [RFC2402], [RFC2406] and the IPsec suite of protocols (see [RFC2402], [RFC2406] and [RFC2409])
[RFC2409]) may be used to provide authentication, confidentiality or may be used to provide authentication, confidentiality or both, for a
both, for a GMPLS control channel. IPsec thus offers the benefits of GMPLS control channel. IPsec thus offers the benefits of combined
combined protection for all GMPLS component protocols as well as key protection for all GMPLS component protocols as well as key
management. management.
A related issue is that of the authorization of requests for A related issue is that of the authorization of requests for
resources by GMPLS-capable nodes. Authorization determines whether a resources by GMPLS-capable nodes. Authorization determines whether a
given party, presumable already authenticated, has a right to access given party, presumable already authenticated, has a right to access
the requested resources. This determination is typically a matter of the requested resources. This determination is typically a matter of
local policy control [RFC2753], for example by setting limits on the local policy control [RFC2753], for example by setting limits on the
total bandwidth available to some party in the presence of resource total bandwidth available to some party in the presence of resource
contention. Such policies may become quite complex as the number of contention. Such policies may become quite complex as the number of
users, types of resources and sophistication of authorization rules users, types of resources and sophistication of authorization rules
increases. increases.
After authenticating requests, control elements should match them After authenticating requests, control elements should match them
against the local authorization policy. These control elements must against the local authorization policy. These control elements must
be capable of making decisions based on the identity of the be capable of making decisions based on the identity of the
requester, as verified cryptographically and/or topologically. For requester, as verified cryptographically and/or topologically. For
E. Mannie (Editor) et al. Standard Track 50
example, decisions may depend on whether the interface through which example, decisions may depend on whether the interface through which
the request is made is an inter- or intra-domain one. The use of the request is made is an inter- or intra-domain one. The use of
appropriate local authorization policies may help in limiting the appropriate local authorization policies may help in limiting the
impact of security breaches in remote parts of a network. impact of security breaches in remote parts of a network.
Finally, it should be noted that GMPLS itself introduces no new Finally, it should be noted that GMPLS itself introduces no new
security considerations to the current MPLS-TE signaling (RSVP-TE, security considerations to the current MPLS-TE signaling (RSVP-TE,
CR-LDP), routing protocols (OSPF-TE, IS-IS-TE) or network management CR-LDP), routing protocols (OSPF-TE, IS-IS-TE) or network management
protocols (SNMP). protocols (SNMP).
16. Acknowledgements 14. Acknowledgements
This document is the work of numerous authors and consists of a This document is the work of numerous authors and consists of a
composition of a number of previous drafts in this area. composition of a number of previous documents in this area.
Many thanks to Ben Mack-Crane (Tellabs) for all the useful SONET/SDH Many thanks to Ben Mack-Crane (Tellabs) for all the useful SONET/SDH
discussions we had together. Thanks also to Pedro Falcao, Alexandre discussions we had together. Thanks also to Pedro Falcao, Alexandre
Geyssens, Michael Moelants, Xavier Neerdaels, and Philippe Noel from Geyssens, Michael Moelants, Xavier Neerdaels, and Philippe Noel from
Ebone for their SONET/SDH and optical technical advice and support. Ebone for their SONET/SDH and optical technical advice and support.
Finally, many thanks also to Krishna Mitra (Consultant), Curtis Finally, many thanks also to Krishna Mitra (Consultant), Curtis
Villamizar (Avici), Ron Bonica (WorldCom) and Bert Wijnen (Lucent) Villamizar (Avici), Ron Bonica (WorldCom), and Bert Wijnen (Lucent)
for its revision effort of Section 14. for their revision effort on Section 12.
17. Intellectual Property Considerations 15. References
This section is taken from Section 10.4 of [RFC2026]. 15.1. Normative References
The IETF takes no position regarding the validity or scope of any [RFC3031] Rosen, E., Viswanathan, A., and R. Callon,
intellectual property or other rights that might be claimed to "Multiprotocol Label Switching Architecture",
pertain to the implementation or use of the technology described in RFC 3031, January 2001.
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made
to obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification
can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
copyrights, patents or patent applications, or other proprietary Srinivasan, V., and G. Swallow, "RSVP-TE:
rights which may cover technology that may be required to practice Extensions to RSVP for LSP Tunnels", RFC 3209,
this standard. Please address the information to the IETF Executive December 2001.
Director.
18. References [RFC3212] Jamoussi, B., Andersson, L., Callon, R., Dantu,
R., Wu, L., Doolan, P., Worster, T., Feldman,
N., Fredette, A., Girish, M., Gray, E.,
Heinanen, J., Kilty, T., and A. Malis,
"Constraint-Based LSP Setup using LDP", RFC
3212, January 2002.
18.1 Normative References [RFC3471] Berger, L., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional
Description", RFC 3471, January 2003.
[ANSI-T1.105] "Synchronous Optical Network (SONET): Basic [RFC3472] Ashwood-Smith, P. and L. Berger, "Generalized
Description Including Multiplex Structure, Rates, Multi-Protocol Label Switching (GMPLS)
And Formats," ANSI T1.105, 2000. Signaling Constraint-based Routed Label
Distribution Protocol (CR-LDP) Extensions", RFC
3472, January 2003.
E. Mannie (Editor) et al. Standard Track 51 [RFC3473] Berger, L., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource
ReserVation Protocol-Traffic Engineering
(RSVP-TE) Extensions", RFC 3473, January 2003.
[BUNDLE] K.Kompella, Y.Rekhter and L.Berger, "Link Bundling 15.2. Informative References
in MPLS Traffic Engineering," Work in Progress,
draft-ietf-mpls-bundle-04.txt.
[GMPLS-FUNCT] J.P.Lang and B.Rajagopalan (Editors) et al., [ANSI-T1.105] "Synchronous Optical Network (SONET): Basic
"Generalized MPLS Recovery Functional Description Including Multiplex Structure,
Specification," Work in Progress, draft-ietf-ccamp- Rates, And Formats," ANSI T1.105, 2000.
gmpls-recovery-functional-01.txt.
[GMPLS-G709] D.Papadimitriou (Editor) et al., "GMPLS Signaling [BUNDLE] Kompella, K., Rekhter, Y., and L. Berger, "Link
Extensions for G.709 Optical Transport Networks Bundling in MPLS Traffic Engineering", Work in
Control," Work in progress, draft-ietf-ccamp-gmpls- Progress.
g709-03.txt.
[GMPLS-OVERLAY] G.Swallow et al., "GMPLS RSVP Support for the [GMPLS-FUNCT] Lang, J.P., Ed. and B. Rajagopalan, Ed.,
Overlay Model," Work in Progress, draft-ietf-ccamp- "Generalized MPLS Recovery Functional
gmpls-overlay-01.txt. Specification", Work in Progress.
[GMPLS-ROUTING] K.Kompella and Y.Rekhter (Editors) et al., "Routing [GMPLS-G709] Papadimitriou, D., Ed., "GMPLS Signaling
Extensions in Support of Generalized MPLS," Work in Extensions for G.709 Optical Transport Networks
Progress, draft-ietf-ccamp-gmpls-routing-05.txt. Control", Work in Progress.
[GMPLS-SONET-SDH] E.Mannie and D.Papadimitriou (Editors) et al., [GMPLS-OVERLAY] Swallow, G., Drake, J., Ishimatsu, H., and Y.
"Generalized MPLS Extensions for SONET and SDH Rekhter, "GMPLS UNI: RSVP Support for the
Control," Work in progress, draft-ietf-ccamp-gmpls- Overlay Model", Work in Progress.
sonet-sdh-08.txt.
[HIERARCHY] K.Kompella and Y.Rekhter, "LSP Hierarchy with [GMPLS-ROUTING] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing
Generalized MPLS TE," Work in Progress, draft-ietf- Extensions in Support of Generalized Multi-
mpls-lsp-hierarchy-08.txt. Protocol Label Switching", Work in Progress.
[ITUT-G.707] ITU-T, "Network Node Interface for the Synchronous [RFC3946] Mannie, E., Ed. and Papadimitriou D., Ed.,
Digital Hierarchy", Recommendation G.707, October "Generalized Multi-Protocol Label Switching
2000. (GMPLS) Extensions for Synchronous Optical
Network (SONET) and Synchronous Digital
Hierarchy (SDH) Control", RFC 3946, October
2004.
[ITUT-G.709] ITU-T, "Interface for the Optical Transport Network [HIERARCHY] Kompella, K. and Y. Rekhter, "LSP Hierarchy
(OTN)," Recommendation G.709 version 1.0 (and with Generalized MPLS TE", Work in Progress.
Amendment 1), February 2001 (and October 2001).
[ITUT-G.841] ITU-T, "Types and Characteristics of SDH Network [ISIS-TE] Smit, H. and T. Li, "Intermediate System to
Protection Architectures," Recommendation G.841, Intermediate System (IS-IS) Extensions for
October 1998. Traffic Engineering (TE)", RFC 3784, June 2004.
[LMP] J.P.Lang (Editor) et al., "Link Management Protocol [ISIS-TE-GMPLS] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS
(LMP)," Work in progress, draft-ietf-ccamp-lmp- Extensions in Support of Generalized Multi-
09.txt. Protocol Label Switching", Work in Progress.
[LMP-WDM] A.Fredette and J.P.Lang (Editors) et al., "LMP for [ITUT-G.707] ITU-T, "Network Node Interface for the
WDM Optical Line Systems (LMP-WDM)," Work in Synchronous Digital Hierarchy", Recommendation
progress, draft-ietf-ccamp-lmp-wdm-02.txt. G.707, October 2000.
[OSPF-TE-GMPLS] K.Kompella and Y.Rekhter (Editors), "OSPF Extensions [ITUT-G.709] ITU-T, "Interface for the Optical Transport
in Support of Generalized MPLS," Work in Progress, Network (OTN)," Recommendation G.709 version
1.0 (and Amendment 1), February 2001 (and
October 2001).
E. Mannie (Editor) et al. Standard Track 52 [ITUT-G.841] ITU-T, "Types and Characteristics of SDH
Network Protection Architectures,"
Recommendation G.841, October 1998.
[OSPF-TE] D.Katz, D.Yeung, and K.Kompella, "Traffic [LMP] Lang, J., Ed., "Link Management Protocol
Engineering Extensions to OSPF", Work in Progress, (LMP)", Work in Progress.
draft-katz-yeung-ospf-traffic-09.txt.
[RFC1393] G.Malkin, "Traceroute Using an IP Option", IETF RFC [LMP-WDM] Fredette, A., Ed. and J. Lang Ed., "Link
1393, January 1993. Management Protocol (LMP) for Dense Wavelength
Division Multiplexing (DWDM) Optical Line
Systems", Work in Progress.
[RFC2026] S.Bradner, "The Internet Standards Process -- Revision [MANCHESTER] J. Manchester, P. Bonenfant and C. Newton, "The
3," BCP 9, IETF RFC 2026, October 1996. Evolution of Transport Network Survivability,"
IEEE Communications Magazine, August 1999.
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate [OIF-UNI] The Optical Internetworking Forum, "User
Requirement Levels", BCP 14, IETF RFC 2119, March 1997. Network Interface (UNI) 1.0 Signaling
Specification - Implementation Agreement OIF-
UNI-01.0," October 2001.
[RFC2151] G.Kessler and S.Shepard, "A Primer On Internet and [OLI-REQ] Fredette, A., Ed., "Optical Link Interface
TCP/IP Tools and Utilities", IETF RFC 2151, June 1997. Requirements," Work in Progress.
[RFC2385] A.Heffernan, "Protection of BGP Sessions via the TCP [OSPF-TE-GMPLS] Kompella, K., Ed. and Y.
MD5 Signature Option," IETF RFC 2385, August 1998. Rekhter, Ed., "OSPF Extensions in Support of
Generalized Multi-Protocol Label Switching",
Work in Progress.
[RFC2402] S.Kent and R.Atkinson, "IP Authentication Header," IETF [OSPF-TE] Katz, D., Kompella, K., and D. Yeung, "Traffic
RFC 2402, November 1998. Engineering (TE) Extensions to OSPF Version 2",
RFC 3630, September 2003.
[RFC2406] S.Kent and R. Atkinson, "IP Encapsulating Security [RFC1393] Malkin, G., "Traceroute Using an IP Option",
Payload (ESP)," IETF RFC 2406, November 1998. RFC 1393, January 1993.
[RFC2409] D.Harkins and D.Carrel, "The Internet Key Exchange [RFC2151] Kessler, G. and S. Shepard, "A Primer On
(IKE)," IETF RFC 2409, November 1998. Internet and TCP/IP Tools and Utilities", RFC
2151, June 1997.
[RFC2747] F.Baker et al., "RSVP Cryptographic Authentication," [RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S.,
IETF RFC 2747, January 2000. and S. Jamin, "Resource ReSerVation Protocol
(RSVP) -- Version 1 Functional Specification",
RFC 2205, September 1997.
[RFC2753] R.Yavatkar, D.Pendarakis and R.Guerin, "A Framework for [RFC2385] Heffernan, A., "Protection of BGP Sessions via
Policy-based Admission Control," IETF RFC 2753, January the TCP MD5 Signature Option", RFC 2385, August
2000. 1998.
[RFC2925] K.White, "Definitions of Managed Objects for Remote [RFC2402] Kent, S. and R. Atkinson, "IP Authentication
Ping, Traceroute, and Lookup Operations," IETF RFC Header", RFC 2402, November 1998.
2925, September 2000.
[RFC3031] E.Rosen, A.Viswanathan, and R.Callon, "Multiprotocol [RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating
Label Switching Architecture," IETF RFC 3031, January Security Payload (ESP)", RFC 2406, November
2001. 1998.
[RFC3036] L.Andersson, P.Doolan, N.Feldman, A.Fredette, and [RFC2409] Harkins, D. and D. Carrel, "The Internet Key
B.Thomas, "LDP Specification," IETF RFC 3036, January Exchange (IKE)", RFC 2409, November 1998.
2001.
[RFC3209] D.Awduche, et al., "RSVP-TE: Extensions to RSVP for [RFC2702] Awduche, D., Malcolm, J.,
LSP Tunnels," IETF RFC 3209, December 2001. Agogbua, J., O'Dell, M., and J. McManus,
"Requirements for Traffic Engineering Over
MPLS", RFC 2702, September 1999.
[RFC3212] B.Jamoussi (Editor) et al., "Constraint-Based LSP Setup [RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP
using LDP," IETF RFC 3212, January 2002. Cryptographic Authentication", RFC 2747,
January 2000.
E. Mannie (Editor) et al. Standard Track 53 [RFC2753] Yavatkar, R., Pendarakis, D., and R. Guerin, "A
Framework for Policy-based Admission Control",
RFC 2753, January 2000.
[RFC3411] D.Harrington, R.Presuhn and B.Wijnen, "An Architecture [RFC2925] White, K., "Definitions of Managed Objects for
for Describing Simple Network Management Protocol Remote Ping, Traceroute, and Lookup
(SNMP) Management Frameworks," IETF RFC 3411, December Operations", RFC 2925, September 2000.
2002.
[RFC3414] U.Blumenthal and B.Wijnen, "User-based Security Model [RFC3036] Andersson, L., Doolan, P., Feldman, N.,
(USM) for version 3 of the Simple Network Management Fredette, A., and B. Thomas, "LDP
Protocol (SNMPv3)," IETF RFC 3414, December 2002. Specification", RFC 3036, January 2001.
[RFC3415] B.Wijnen, R.Presuhn, and K.McCloghrie, "View-based [RFC3386] Lai, W. and D. McDysan, "Network Hierarchy and
Access Control Model (VACM) for the Simple Network Multilayer Survivability", RFC 3386, November
Management Protocol (SNMP)," IETF RFC 3415, December 2002.
2002.
[RFC3416] R.Presuhn (Editor), "Version 2 of the Protocol [RFC3410] Case, J., Mundy, R., Partain, D., and B.
Operations for the Simple Network Management Protocol Stewart, "Introduction and Applicability
(SNMP)," IETF RFC 3416, December 2002. Statements for Internet-Standard Management
Framework", RFC 3410, December 2002.
[RFC3417] R.Presuhn (Editor), "Transport Mappings for the Simple [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Network Management Protocol (SNMP)," IETF RFC 3417, Architecture for Describing Simple Network
December 2002. Management Protocol (SNMP) Management
Frameworks", STD 62, RFC 3411, December 2002.
[RFC3477] K.Kompella and Y.Rekhter, "Signalling Unnumbered [RFC3414] Blumenthal, U. and B. Wijnen, "User-based
Links in Resource ReSerVation Protocol - Traffic Security Model (USM) for version 3 of the
Engineering (RSVP-TE)," IETF RFC 3477, January 2003. Simple Network Management Protocol (SNMPv3)",
STD 62, RFC 3414, December 2002.
[RFC3471] L.Berger (Editor) et al., "Generalized MPLS - [RFC3415] Wijnen, B., Presuhn, R., and K. McCloghrie,
Signaling Functional Description," IETF RFC 3471, "View-based Access Control Model (VACM) for the
January 2003. Simple Network Management Protocol (SNMP)", STD
62, RFC 3415, December 2002.
[RFC3472] P.Ashwood-Smith and L.Berger (Editors) et al., [RFC3416] Presuhn, R., "Version 2 of the Protocol
"Generalized MPLS Signaling - CR-LDP Extensions," IETF Operations for the Simple Network Management
RFC 3472, January 2003. Protocol (SNMP)", STD 62, RFC 3416, December
2002.
[RFC3473] L.Berger (Editor) et al., "Generalized MPLS [RFC3417] Presuhn, R., "Transport Mappings for the Simple
Signaling - RSVP-TE Extensions," IETF RFC 3473, January Network Management Protocol (SNMP)", STD 62,
2003. RFC 3417, December 2002.
[RFC3479] A.Farrel (Editor) et al., "Fault Tolerance for the [RFC3469] Sharma, V. and F. Hellstrand, "Framework for
Label Distribution Protocol (LDP)," IETF RFC 3479, Multi-Protocol Label Switching (MPLS)-based
February 2003. Recovery", RFC 3469, February 2003.
[RFC3480] K.Kompella, Y.Rekhter and A.Kullberg, "Signalling [RFC3477] Kompella, K. and Y. Rekhter, "Signalling
Unnumbered Links in CR-LDP," IETF RFC 3480, February Unnumbered Links in Resource ReSerVation
2003. Protocol - Traffic Engineering (RSVP-TE)", RFC
3477, January 2003.
18.2 Informative References [RFC3479] Farrel, A., "Fault Tolerance for the Label
Distribution Protocol (LDP)", RFC 3479,
February 2003.
[ISIS-TE] H.Smit and T.Li, "IS-IS extensions for Traffic [RFC3480] Kompella, K., Rekhter, Y., and A. Kullberg,
Engineering," Work in Progress, draft-ietf-isis- "Signalling Unnumbered Links in CR-LDP
traffic-04.txt. (Constraint-Routing Label Distribution
Protocol)", RFC 3480, February 2003.
[ISIS-TE-GMPLS] K.Kompella and Y.Rekhter (Editors), "IS-IS [SONET-SDH-GMPLS-FRM] Bernstein, G., Mannie, E., and V. Sharma,
"Framework for GMPLS-based Control of SDH/SONET
Networks", Work in Progress.
E. Mannie (Editor) et al. Standard Track 54 16. Contributors
Extensions in Support of Generalized MPLS," Work in
Progress, draft-ietf-isis-gmpls-extensions-16.txt.
[MANCHESTER] J.Manchester, P.Bonenfant and C.Newton, "The Evolution Peter Ashwood-Smith
of Transport Network Survivability," IEEE Nortel
Communications Magazine, August 1999. P.O. Box 3511 Station C,
Ottawa, ON K1Y 4H7, Canada
[OIF-UNI] The Optical Internetworking Forum, "User Network EMail: petera@nortelnetworks.com
Interface (UNI) 1.0 Signaling Specification -
Implementation Agreement OIF-UNI-01.0," October 2001.
[OLI-REQ] A.Fredette (Editor), "Optical Link Interface Eric Mannie
Requirements," Work in Progress. Consult
Phone: +32 2 648-5023
Mobile: +32 (0)495-221775
[RFC2702] D.Awduche, et al., "Requirements for Traffic EMail: eric_mannie@hotmail.com
Engineering Over MPLS," IETF RFC 2702, September 1999.
[RFC3386] W.Lai, D.McDysan, et al., "Network Hierarchy and Multi- Daniel O. Awduche
layer Survivability," IETF RFC 3386, November 2002. Consult
[RFC3410] J.Case, R.Mundy, D.Partain, and B. Stewart, EMail: awduche@awduche.com
"Introduction and Applicability Statements for
Internet-Standard Management Framework," IETF RFC 3410,
December 2002.
[RFC3469] V.Sharma and F.Hellstrand (Editors), "Framework for Thomas D. Nadeau
Multi-Protocol Label Switching (MPLS)-based Recovery," Cisco
IETF RFC 3469, February 2003. 250 Apollo Drive
Chelmsford, MA 01824, USA
[SONET-SDH-GMPLS-FRM] G.Bernstein, E.Mannie and V.Sharma, EMail: tnadeau@cisco.com
"Framework for GMPLS-based Control of SDH/SONET Ayan Banerjee
Networks," Work in Progress. Calient
5853 Rue Ferrari
San Jose, CA 95138, USA
19. Author's Address EMail: abanerjee@calient.net
Eric Mannie (Consult) Lyndon Ong
Phone: +32 2 658-5023 Ciena
Mobile: +32 (0)495-221775 10480 Ridgeview Ct
Email: eric_mannie@hotmail.com Cupertino, CA 95014, USA
20. Contributors EMail: lyong@ciena.com
Peter Ashwood-Smith (Nortel) Eric Mannie (Consult) Debashis Basak
P.O. Box 3511 Station C, Phone: +32 2 648-5023 Accelight
Ottawa, ON K1Y 4H7, Canada Mobile: +32 (0)495-221775 70 Abele Road, Bldg.1200
Email: petera@nortelnetworks.com Email: eric_mannie@hotmail.com Bridgeville, PA 15017, USA
Daniel O. Awduche (Consult) Thomas D. Nadeau (Cisco) EMail: dbasak@accelight.com
Email: awduche@awduche.com 250 Apollo Drive
Chelmsford, MA 01824, USA
Email: tnadeau@cisco.com
E. Mannie (Editor) et al. Standard Track 55 Dimitri Papadimitriou
Ayan Banerjee (Calient) Lyndon Ong (Ciena) Alcatel
5853 Rue Ferrari 10480 Ridgeview Ct Francis Wellesplein, 1
San Jose, CA 95138, USA Cupertino, CA 95014, USA B-2018 Antwerpen, Belgium
Email: abanerjee@calient.net Email: lyong@ciena.com
Debashis Basak (Accelight) Dimitri Papadimitriou (Alcatel) EMail: dimitri.papadimitriou@alcatel.be
70 Abele Road, Bldg.1200 Francis Wellesplein, 1
Bridgeville, PA 15017, USA B-2018 Antwerpen, Belgium
Email: dbasak@accelight.com Email:
dimitri.papadimitriou@alcatel.be
Lou Berger (Movaz) Dimitrios Pendarakis (Tellium) Lou Berger
7926 Jones Branch Drive 2 Crescent Place, P.O. Box 901 Movaz
MCLean VA, 22102, USA Oceanport, NJ 07757-0901, USA 7926 Jones Branch Drive
Email: lberger@movaz.com Email: dpendarakis@tellium.com MCLean VA, 22102, USA
Greg Bernstein (Grotto) Bala Rajagopalan (Tellium) EMail: lberger@movaz.com
Email: 2 Crescent Place, P.O. Box 901
gregb@grotto-networking.com Oceanport, NJ 07757-0901, USA
Email: braja@tellium.com
Sudheer Dharanikota (Consult) Yakov Rekhter (Juniper) Dimitrios Pendarakis
Email: sudheer@ieee.org 1194 N. Mathilda Ave. Tellium
Sunnyvale, CA 94089, USA 2 Crescent Place, P.O. Box 901
Email: yakov@juniper.net Oceanport, NJ 07757-0901, USA
John Drake (Calient) Debanjan Saha EMail: dpendarakis@tellium.com
5853 Rue Ferrari (IBM Watson Research Center) Greg Bernstein
San Jose, CA 95138, USA Email: dsaha@us.ibm.com Grotto
Email: jdrake@calient.net
Yanhe Fan (Axiowave) Hal Sandick EMail: gregb@grotto-networking.com
200 Nickerson Road Shepard M.S.
Marlborough, MA 01752, USA 2401 Dakota Street
Email: yfan@axiowave.com Durham, NC 27705, USA
Email: sandick@nc.rr.com
Don Fedyk (Nortel) Vishal Sharma (Metanoia) Bala Rajagopalan
600 Technology Park Drive 1600 Villa Street, Unit 352 Tellium
Billerica, MA 01821, USA Mountain View, CA 94041, USA 2 Crescent Place, P.O. Box 901
Email: Email: v.sharma@ieee.org Oceanport, NJ 07757-0901, USA
dwfedyk@nortelnetworks.com
Gert Grammel (Alcatel) George Swallow (Cisco) EMail: braja@tellium.com
Lorenzstrasse, 10 250 Apollo Drive
70435 Stuttgart, Germany Chelmsford, MA 01824, USA
Email: gert.grammel@alcatel.de Email: swallow@cisco.com
Dan Guo (Turin) Z. Bo Tang (Tellium) Sudheer Dharanikota
1415 N. McDowell Blvd, Petaluma, 2 Crescent Place, P.O. Box 901 Consult
CA 95454, USA Oceanport, NJ 07757-0901, USA
Email: dguo@turinnetworks.com Email: btang@tellium.com
E. Mannie (Editor) et al. Standard Track 56 EMail: sudheer@ieee.org
Kireeti Kompella (Juniper) Jennifer Yates (AT&T)
1194 N. Mathilda Ave. 180 Park Avenue
Sunnyvale, CA 94089, USA Florham Park, NJ 07932, USA
Email: kireeti@juniper.net Email: jyates@research.att.com
Alan Kullberg (NetPlane) George R. Young (Edgeflow) Yakov Rekhter
888 Washington 329 March Road Juniper
St.Dedham, MA 02026, USA Ottawa, Ontario, K2K 2E1, Canada 1194 N. Mathilda Ave.
Email: akullber@netplane.com Email: george.young@edgeflow.com Sunnyvale, CA 94089, USA
Jonathan P. Lang John Yu (Hammerhead Systems) EMail: yakov@juniper.net
(Rincon Networks) 640 Clyde Court
Email: jplang@ieee.org Mountain View, CA 94043, USA
Email: john@hammerheadsystems.com
Fong Liaw (Solas Research) Alex Zinin (Alcatel) John Drake
Solas Research, LLC 1420 North McDowell Ave Calient
Email: fongliaw@yahoo.com Petaluma, CA 94954, USA 5853 Rue Ferrari
Email: alex.zinin@alcatel.com San Jose, CA 95138, USA
EMail: jdrake@calient.net
Debanjan Saha
Tellium
2 Crescent Place
Oceanport, NJ 07757-0901, USA
EMail: dsaha@tellium.com
Yanhe Fan
Axiowave
200 Nickerson Road
Marlborough, MA 01752, USA
EMail: yfan@axiowave.com
Hal Sandick
Shepard M.S.
2401 Dakota Street
Durham, NC 27705, USA
EMail: sandick@nc.rr.com
Don Fedyk
Nortel
600 Technology Park Drive
Billerica, MA 01821, USA
EMail: dwfedyk@nortelnetworks.com
Vishal Sharma
Metanoia
1600 Villa Street, Unit 352
Mountain View, CA 94041, USA
EMail: v.sharma@ieee.org
Gert Grammel
Alcatel
Lorenzstrasse, 10
70435 Stuttgart, Germany
EMail: gert.grammel@alcatel.de
George Swallow
Cisco
250 Apollo Drive
Chelmsford, MA 01824, USA
EMail: swallow@cisco.com
Dan Guo
Turin
1415 N. McDowell Blvd,
Petaluma, CA 95454, USA
EMail: dguo@turinnetworks.com
Z. Bo Tang
Tellium
2 Crescent Place, P.O. Box 901
Oceanport, NJ 07757-0901, USA
EMail: btang@tellium.com
Kireeti Kompella
Juniper
1194 N. Mathilda Ave.
Sunnyvale, CA 94089, USA
EMail: kireeti@juniper.net
Jennifer Yates
AT&T
180 Park Avenue
Florham Park, NJ 07932, USA
EMail: jyates@research.att.com
Alan Kullberg
NetPlane
888 Washington
St.Dedham, MA 02026, USA
EMail: akullber@netplane.com
George R. Young
Edgeflow
329 March Road
Ottawa, Ontario, K2K 2E1, Canada
EMail: george.young@edgeflow.com
Jonathan P. Lang
Rincon Networks
EMail: jplang@ieee.org
John Yu
Hammerhead Systems
640 Clyde Court
Mountain View, CA 94043, USA
EMail: john@hammerheadsystems.com
Fong Liaw
Solas Research
Solas Research, LLC
EMail: fongliaw@yahoo.com
Alex Zinin
Alcatel
1420 North McDowell Ave
Petaluma, CA 94954, USA
EMail: alex.zinin@alcatel.com
17. Author's Address
Eric Mannie (Consultant)
Avenue de la Folle Chanson, 2
B-1050 Brussels, Belgium
Phone: +32 2 648-5023
Mobile: +32 (0)495-221775
EMail: eric_mannie@hotmail.com
E. Mannie (Editor) et al. Standard Track 57
Full Copyright Statement Full Copyright Statement
"Copyright (C) The Internet Society (date). All Rights Reserved. Copyright (C) The Internet Society (2004).
This document and translations of it may be copied and furnished to
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
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