draft-ietf-ccamp-gmpls-mln-reqs-08.txt   draft-ietf-ccamp-gmpls-mln-reqs-09.txt 
Network Working Group Kohei Shiomoto (NTT) Network Working Group Kohei Shiomoto (NTT)
Internet-Draft Dimitri Papadimitriou (Alcatel-Lucent) Internet-Draft Dimitri Papadimitriou (Alcatel-Lucent)
Intended Status: Informational Jean-Louis Le Roux (France Telecom) Intended Status: Informational Jean-Louis Le Roux (France Telecom)
Martin Vigoureux (Alcatel-Lucent) Martin Vigoureux (Alcatel-Lucent)
Deborah Brungard (AT&T) Deborah Brungard (AT&T)
Expires: July 2008 January 2008
Requirements for GMPLS-Based Multi-Region and Requirements for GMPLS-Based Multi-Region and
Multi-Layer Networks (MRN/MLN) Multi-Layer Networks (MRN/MLN)
draft-ietf-ccamp-gmpls-mln-reqs-08.txt draft-ietf-ccamp-gmpls-mln-reqs-09.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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Most of the initial efforts to utilize Generalized MPLS (GMPLS) Most of the initial efforts to utilize Generalized MPLS (GMPLS)
have been related to environments hosting devices with a single have been related to environments hosting devices with a single
switching capability. The complexity raised by the control of such switching capability. The complexity raised by the control of such
data planes is similar to that seen in classical IP/MPLS networks. data planes is similar to that seen in classical IP/MPLS networks.
By extending MPLS to support multiple switching technologies, GMPLS By extending MPLS to support multiple switching technologies, GMPLS
provides a comprehensive framework for the control of a multi- provides a comprehensive framework for the control of a multi-
layered network of either a single switching technology or multiple layered network of either a single switching technology or multiple
switching technologies. switching technologies.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
In GMPLS, a switching technology domain defines a region, and a In GMPLS, a switching technology domain defines a region, and a
network of multiple switching types is referred to in this document network of multiple switching types is referred to in this document
as a Multi-Region Network (MRN). When referring in general to a as a Multi-Region Network (MRN). When referring in general to a
layered network, which may consist of either a single or multiple layered network, which may consist of either a single or multiple
regions, this document uses the term, Multi-Layer Network (MLN). regions, this document uses the term, Multi-Layer Network (MLN).
This document defines a framework for GMPLS based multi-region / This document defines a framework for GMPLS based multi-region /
multi-layer networks and lists a set of functional requirements. multi-layer networks and lists a set of functional requirements.
Table of Contents Table of Contents
1. Introduction .................................................... 1. Introduction.................................................3
1.1. Scope ......................................................... 1.1. Scope......................................................4
2. Conventions Used in this Document ............................... 2. Conventions Used in this Document............................5
2.1. List of Acronyms .............................................. 2.1. List of Acronyms...........................................5
3. Positioning ..................................................... 3. Positioning..................................................6
3.1. Data Plane Layers and Control Plane Regions ................... 3.1. Data Plane Layers and Control Plane Regions................6
3.2. Service Layer Networks .. ..................................... 3.2. Service Layer Networks.....................................6
3.3. Vertical and Horizontal Interaction and Integration ........... 3.3. Vertical and Horizontal Interaction and Integration........7
3.4. Motivation .................................................... 3.4. Motivation.................................................8
4. Key Concepts of GMPLS-Based MLNs and MRNs ....................... 4. Key Concepts of GMPLS-Based MLNs and MRNs....................9
4.1. Interface Switching Capability ................................ 4.1. Interface Switching Capability.............................9
4.2. Multiple Interface Switching Capabilities ..................... 4.2. Multiple Interface Switching Capabilities.................10
4.2.1. Networks with Multi-Switching-Type-Capable Hybrid Nodes ..... 4.2.1. Networks with Multi-Switching-Type-Capable Hybrid Nodes.11
4.3. Integrated Traffic Engineering (TE) and Resource Control ...... 4.3. Integrated Traffic Engineering (TE) and Resource Control..11
4.3.1. Triggered Signaling ......................................... 4.3.1. Triggered Signaling.....................................12
4.3.2. FA-LSPs ..................................................... 4.3.2. FA-LSPs.................................................12
4.3.3. Virtual Network Topology (VNT) .............................. 4.3.3. Virtual Network Topology (VNT)..........................13
5. Requirements .................................................... 5. Requirements................................................14
5.1. Handling Single-Switching and Multi-Switching-Type-Capable 5.1. Handling Single-Switching and Multi-Switching-Type-Capable
Nodes ....................................................... Nodes.....................................................14
5.2. Advertisement of the Available Adjustment Resource ............ 5.2. Advertisement of the Available Adjustment Resource........14
5.3. Scalability ................................................... 5.3. Scalability...............................................15
5.4. Stability ..................................................... 5.4. Stability.................................................16
5.5. Disruption Minimization ....................................... 5.5. Disruption Minimization...................................16
5.6. LSP Attribute Inheritance ..................................... 5.6. LSP Attribute Inheritance.................................16
5.7. Computing Paths With and Without Nested Signaling ............. 5.7. Computing Paths With and Without Nested Signaling.........17
5.8. LSP Resource Utilization ...................................... 5.8. LSP Resource Utilization..................................18
5.8.1. FA-LSP Release and Setup .................................... 5.8.1. FA-LSP Release and Setup................................18
5.8.2. Virtual TE-Links ............................................ 5.8.2. Virtual TE-Links........................................19
5.9. Verification of the LSPs ...................................... 5.9. Verification of the LSPs..................................20
6. Security Considerations ......................................... 6. Security Considerations.....................................21
7. IANA Considerations ............................................ 7. IANA Considerations.........................................21
8. Acknowledgements ................................................ 8. Acknowledgements............................................21
9. References ...................................................... 9. References..................................................21
9.1. Normative Reference ........................................... 9.1. Normative Reference.......................................21
9.2. Informative References ........................................ 9.2. Informative References....................................22
10. Authors' Addresses.........................................23
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008 11. Contributors' Addresses....................................24
12. Intellectual Property Considerations.......................24
10. Authors' Addresses ............................................. 13. Full Copyright Statement...................................25
11. Contributors' Addresses ........................................
12. Intellectual Property Considerations ...........................
13. Full Copyright Statement .......................................
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
1. Introduction 1. Introduction
Generalized MPLS (GMPLS) extends MPLS to handle multiple switching Generalized MPLS (GMPLS) extends MPLS to handle multiple switching
technologies: packet switching, layer-2 switching, TDM switching, technologies: packet switching, layer-2 switching, TDM switching,
wavelength switching, and fiber switching (see [RFC3945]). The wavelength switching, and fiber switching (see [RFC3945]). The
Interface Switching Capability (ISC) concept is introduced for Interface Switching Capability (ISC) concept is introduced for
these switching technologies and is designated as follows: PSC these switching technologies and is designated as follows: PSC
(packet switch capable), L2SC (Layer-2 switch capable), TDM (Time (packet switch capable), L2SC (Layer-2 switch capable), TDM (Time
Division Multiplex capable), LSC (lambda switch capable), and FSC Division Multiplex capable), LSC (lambda switch capable), and FSC
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associated with PSC). However, more than one data plane layer can associated with PSC). However, more than one data plane layer can
be associated with the same region (e.g., both VC4 and VC12 are be associated with the same region (e.g., both VC4 and VC12 are
associated with TDM). Thus, a control plane region, identified by associated with TDM). Thus, a control plane region, identified by
its switching type value (e.g., TDM), can be sub-divided into its switching type value (e.g., TDM), can be sub-divided into
smaller granularity component networks based on "data plane smaller granularity component networks based on "data plane
switching layers". The Interface Switching Capability Descriptor switching layers". The Interface Switching Capability Descriptor
(ISCD) [RFC4202], identifying the interface switching capability (ISCD) [RFC4202], identifying the interface switching capability
(ISC), the encoding type, and the switching bandwidth granularity, (ISC), the encoding type, and the switching bandwidth granularity,
enables the characterization of the associated layers. enables the characterization of the associated layers.
In this document, we define a Multi Layer Network (MLN) to be a TE In this document, we define a Multi Layer Network (MLN) to be a
domain comprising multiple data plane switching layers either of Traffic Engineering (TE) domain comprising multiple data plane
the same ISC (e.g. TDM) or different ISC (e.g. TDM and PSC) and switching layers either of the same ISC (e.g., TDM) or different
controlled by a single GMPLS control plane instance. We further ISC (e.g., TDM and PSC) and controlled by a single GMPLS control
define a particular case of MLNs. A Multi Region Network (MRN) is plane instance. We further define a particular case of MLNs. A
defined as a TE domain supporting at least two different switching Multi Region Network (MRN) is defined as a TE domain supporting at
types (e.g., PSC and TDM), either hosted on the same device or on least two different switching types (e.g., PSC and TDM), either
different ones, and under the control of a single GMPLS control hosted on the same device or on different ones, and under the
plane instance. control of a single GMPLS control plane instance.
MLNs can be further categorized according to the distribution of MLNs can be further categorized according to the distribution of
the ISCs among the LSRs: the ISCs among the Label Switching Routers (LSRs):
- Each LSR may support just one ISC. - Each LSR may support just one ISC.
Such LSRs are known as single-switching-type-capable LSRs. Such LSRs are known as single-switching-type-capable LSRs.
The MLN may comprise a set of single-switching-type-capable LSRs The MLN may comprise a set of single-switching-type-capable LSRs
some of which support different ISCs. some of which support different ISCs.
- Each LSR may support more than one ISC at the same time. - Each LSR may support more than one ISC at the same time.
- - Such LSRs are known as multi-switching-type-capable LSRs, and
Such LSRs are known as multi-switching-type-capable LSRs, and
can be further classified as either "simplex" or "hybrid" nodes can be further classified as either "simplex" or "hybrid" nodes
as defined in Section 4.2. as defined in Section 4.2.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008 - The MLN may be constructed from any combination of single-
-
- - The MLN may be constructed from any combination of single-
switching-type-capable LSRs and multi-switching-type-capable switching-type-capable LSRs and multi-switching-type-capable
LSRs. LSRs.
Since GMPLS provides a comprehensive framework for the control of Since GMPLS provides a comprehensive framework for the control of
different switching capabilities, a single GMPLS instance may be different switching capabilities, a single GMPLS instance may be
used to control the MLN/MRN. This enables rapid service used to control the MLN/MRN. This enables rapid service
provisioning and efficient traffic engineering across all switching provisioning and efficient traffic engineering across all switching
capabilities. In such networks, TE Links are consolidated into a capabilities. In such networks, TE Links are consolidated into a
single Traffic Engineering Database (TED). Since this TED contains single Traffic Engineering Database (TED). Since this TED contains
the information relative to all the different regions and layers the information relative to all the different regions and layers
existing in the network, a path across multiple regions or layers existing in the network, a path across multiple regions or layers
can be computed using this TED. Thus optimization of network can be computed using this TED. Thus optimization of network
resources can be achieved across the whole MLN/MRN. resources can be achieved across the whole MLN/MRN.
Consider, for example, a MRN consisting of packet- switch capable Consider, for example, a MRN consisting of packet- switch capable
routers and TDM cross-connects. Assume that a packet LSP is routed routers and TDM cross-connects. Assume that a packet Label Switched
between source and destination packet-switch capable routers, and Path (LSP) is routed between source and destination packet-switch
that the LSP can be routed across the PSC-region (i.e., utilizing capable routers, and that the LSP can be routed across the PSC-
only resources of the packet region topology). If the performance region (i.e., utilizing only resources of the packet region
objective for the packet LSP is not satisfied, new TE links may be topology). If the performance objective for the packet LSP is not
created between the packet-switch capable routers across the TDM- satisfied, new TE links may be created between the packet-switch
region (for example, VC-12 links) and the LSP can be routed over capable routers across the TDM-region (for example, VC-12 links)
those TE links. Furthermore, even if the LSP can be successfully and the LSP can be routed over those TE links. Furthermore, even if
established across the PSC-region, TDM hierarchical LSPs across the the LSP can be successfully established across the PSC-region, TDM
TDM region between the packet-switch capable routers may be hierarchical LSPs across the TDM region between the packet-switch
established and used if doing so is necessary to meet the capable routers may be established and used if doing so is
operator's objectives for network resources availability (e.g., necessary to meet the operator's objectives for network resources
link bandwidth.The same considerations hold when VC4 LSPs are availability (e.g., link bandwidth). The same considerations hold
provisioned to provide extra flexibility for the VC12 and/or VC11 when VC4 LSPs are provisioned to provide extra flexibility for the
layers in an MLN. VC12 and/or VC11 layers in an MLN.
Sections 3 and 4 of this document provide further background
information of the concepts and motivation behind multi-region and
multi-layer networks. Section 5 presents detailed requirements for
protocols used to implement such networks.
1.1. Scope 1.1. Scope
This document describes the requirements to support multi-region/ Early sections of this document describe the motivations and
multi-layer networks. There is no intention to specify solution- reasoning that require the development and deployment of MRN/MLN.
specific and/or protocol elements in this document. The Later sections of this document set out the required features that
applicability of existing GMPLS protocols and any protocol the GMPLS control plane must offer to support MRN/MLN. There is no
extensions to the MRN/MLN is addressed in separate documents [MRN- intention to specify solution- specific and/or protocol elements in
EVAL]. this document. The applicability of existing GMPLS protocols and
any protocol extensions to the MRN/MLN is addressed in separate
documents [MRN-EVAL].
This document covers the elements of a single GMPLS control plane This document covers the elements of a single GMPLS control plane
instance controlling multiple layers within a given TE domain. A instance controlling multiple layers within a given TE domain. A
control plane instance can serve one, two or more layers. Other control plane instance can serve one, two or more layers. Other
possible approaches such as having multiple control plane instances possible approaches such as having multiple control plane instances
serving disjoint sets of layers are outside the scope of this serving disjoint sets of layers are outside the scope of this
document. It is most probable that such a MLN or MRN would be document. It is most probable that such a MLN or MRN would be
operated by a single Service Provider, but this document does not operated by a single Service Provider, but this document does not
exclude the possibility of two layers (or regions) being under exclude the possibility of two layers (or regions) being under
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
different administrative control (for example, by different Service different administrative control (for example, by different Service
Providers that share a single control plane instance) where the Providers that share a single control plane instance) where the
administrative domains are prepared to share a limited amount of administrative domains are prepared to share a limited amount of
information. information.
For such TE domain to interoperate with edge nodes/domains For such TE domain to interoperate with edge nodes/domains
supporting non-GMPLS interfaces (such as those defined by other supporting non-GMPLS interfaces (such as those defined by other
SDOs), an interworking function may be needed. Location and SDOs), an interworking function may be needed. Location and
specification of this function are outside the scope of this specification of this function are outside the scope of this
document (because interworking aspects are strictly under the document (because interworking aspects are strictly under the
responsibility of the interworking function). responsibility of the interworking function).
This document assumes that the interconnection of adjacent MRN/MLN This document assumes that the interconnection of adjacent MRN/MLN
TE domains makes use of [RFC4726] when their edges also support TE domains makes use of [RFC4726] when their edges also support
inter- domain GMPLS RSVP-TE extensions. inter- domain GMPLS RSVP-TE extensions.
2. Conventions Used in this Document 2. Conventions Used in this Document
Although this is not a protocol specification, the key words Although this is not a protocol specification, the key words "MUST",
"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD
"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are used in NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are used in this
this document to highlight requirements, and are to be interpreted document to highlight requirements, and are to be interpreted as
as described in RFC 2119 [RFC2119]. described in RFC 2119 [RFC2119].
2.1. List of Acronyms 2.1. List of Acronyms
ERO: Explicit Route Object
FA: Forwarding Adjacency FA: Forwarding Adjacency
FA-LSP: Forwarding Adjacency Label Switched Path FA-LSP: Forwarding Adjacency Label Switched Path
FSC: Fiber Switching Capable FSC: Fiber Switching Capable
ISC: Interface Switching Capability ISC: Interface Switching Capability
ISCD: Interface Switching Capability Descriptor ISCD: Interface Switching Capability Descriptor
L2SC: Layer-2 Switching Capable L2SC: Layer-2 Switching Capable
LSC: Lambda Switching Capable LSC: Lambda Switching Capable
LSP: Label Switched Path LSP: Label Switched Path
LSR: Label Switching Router LSR: Label Switching Router
MLN: Multi-Layer Network MLN: Multi-Layer Network
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TDM: Time-Division Switch Capable TDM: Time-Division Switch Capable
TE: Traffic Engineering TE: Traffic Engineering
TED: Traffic Engineering Database TED: Traffic Engineering Database
VNT: Virtual Network Topology VNT: Virtual Network Topology
3. Positioning 3. Positioning
A multi-region network (MRN) is always a multi-layer network (MLN) A multi-region network (MRN) is always a multi-layer network (MLN)
since the network devices on region boundaries bring together since the network devices on region boundaries bring together
different ISCs. A MLN, however, is not necessarily a MRN since different ISCs. A MLN, however, is not necessarily a MRN since
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
multiple layers could be fully contained within a single region. multiple layers could be fully contained within a single region.
For example, VC12, VC4, and VC4-4c are different layers of the TDM For example, VC12, VC4, and VC4-4c are different layers of the TDM
region. region.
3.1. Data Plane Layers and Control Plane Regions 3.1. Data Plane Layers and Control Plane Regions
A data plane layer is a collection of network resources capable of A data plane layer is a collection of network resources capable of
terminating and/or switching data traffic of a particular format terminating and/or switching data traffic of a particular format
[RFC4397]. These resources can be used for establishing LSPs for [RFC4397]. These resources can be used for establishing LSPs for
traffic delivery. For example, VC-11 and VC4-64c represent two traffic delivery. For example, VC-11 and VC4-64c represent two
different layers. different layers.
From the control plane viewpoint, an LSP region is defined as a set From the control plane viewpoint, an LSP region is defined as a set
of one or more data plane layers that share the same type of of one or more data plane layers that share the same type of
switching technology, that is, the same switching type. For example, switching technology, that is, the same switching type. For example,
VC-11, VC-4, and VC-4-7v layers are part of the same TDM region. VC-11, VC-4, and VC-4-7v layers are part of the same TDM region.
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A service provider's network may be divided into different service A service provider's network may be divided into different service
layers. The customer's network is considered from the provider's layers. The customer's network is considered from the provider's
perspective as the highest service layer. It interfaces to the perspective as the highest service layer. It interfaces to the
highest service layer of the service provider's network. highest service layer of the service provider's network.
Connectivity across the highest service layer of the service Connectivity across the highest service layer of the service
provider's network may be provided with support from successively provider's network may be provided with support from successively
lower service layers. Service layers are realized via a hierarchy lower service layers. Service layers are realized via a hierarchy
of network layers located generally in several regions and commonly of network layers located generally in several regions and commonly
arranged according to the switching capabilities of network devices. arranged according to the switching capabilities of network devices.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
For instance some customers purchase Layer 1 (i.e., transport) For instance some customers purchase Layer 1 (i.e., transport)
services from the service provider, some Layer 2 (e.g., ATM), while services from the service provider, some Layer 2 (e.g., ATM), while
others purchase Layer 3 (IP/MPLS) services. The service provider others purchase Layer 3 (IP/MPLS) services. The service provider
realizes the services by a stack of network layers located within realizes the services by a stack of network layers located within
one or more network regions. The network layers are commonly one or more network regions. The network layers are commonly
arranged according to the switching capabilities of the devices in arranged according to the switching capabilities of the devices in
the networks. Thus, a customer network may be provided on top of the networks. Thus, a customer network may be provided on top of
the GMPLS-based multi-region/multi-layer network. For example, a the GMPLS-based multi-region/multi-layer network. For example, a
Layer 1 service (realized via the network layers of TDM, and/or LSC, Layer 1 service (realized via the network layers of TDM, and/or LSC,
and/or FSC regions) may support a Layer 2 network (realized via ATM and/or FSC regions) may support a Layer 2 network (realized via ATM
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Services provided by a GMPLS-based multi-region/multi-layer network Services provided by a GMPLS-based multi-region/multi-layer network
are referred to as "Multi-region/Multi-layer network services". For are referred to as "Multi-region/Multi-layer network services". For
example, legacy IP and IP/MPLS networks can be supported on top of example, legacy IP and IP/MPLS networks can be supported on top of
multi-region/multi-layer networks. It has to be emphasized that multi-region/multi-layer networks. It has to be emphasized that
delivery of such diverse services is a strong motivator for the delivery of such diverse services is a strong motivator for the
deployment of multi-region/multi-layer networks. deployment of multi-region/multi-layer networks.
A customer network may be provided on top of a server GMPLS-based A customer network may be provided on top of a server GMPLS-based
MRN/MLN which is operated by a service provider. For example, a MRN/MLN which is operated by a service provider. For example, a
pure IP and/or an IP/MPLS network can be provided on top of GMPLS- pure IP and/or an IP/MPLS network can be provided on top of GMPLS-
based packet over optical networks [MPLS-GMPLS]. The relationship based packet over optical networks [RFC5146]. The relationship
between the networks is a client/server relationship and, such between the networks is a client/server relationship and, such
services are referred to as "MRN/MLN services". In this case, the services are referred to as "MRN/MLN services". In this case, the
customer network may form part of the MRN/MLN, or may be partially customer network may form part of the MRN/MLN, or may be partially
separated, for example to maintain separate routing information but separated, for example to maintain separate routing information but
retain common signaling. retain common signaling.
3.3. Vertical and Horizontal Interaction and Integration 3.3. Vertical and Horizontal Interaction and Integration
Vertical interaction is defined as the collaborative mechanisms Vertical interaction is defined as the collaborative mechanisms
within a network element that is capable of supporting more than within a network element that is capable of supporting more than
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layers are also a vertical interaction. Integration of these layers are also a vertical interaction. Integration of these
interactions as part of the control plane is referred to as interactions as part of the control plane is referred to as
vertical integration. Thus, this refers to the collaborative vertical integration. Thus, this refers to the collaborative
mechanisms within a single control plane instance driving multiple mechanisms within a single control plane instance driving multiple
network layers part of the same region or not. Such a concept is network layers part of the same region or not. Such a concept is
useful in order to construct a framework that facilitates efficient useful in order to construct a framework that facilitates efficient
network resource usage and rapid service provisioning in carrier network resource usage and rapid service provisioning in carrier
networks that are based on multiple layers, switching technologies, networks that are based on multiple layers, switching technologies,
or ISCs. or ISCs.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
Horizontal interaction is defined as the protocol exchange between Horizontal interaction is defined as the protocol exchange between
network controllers that manage transport nodes within a given network controllers that manage transport nodes within a given
layer or region. For instance, the control plane interaction layer or region. For instance, the control plane interaction
between two TDM network elements switching at OC-48 is an example between two TDM network elements switching at OC-48 is an example
of horizontal interaction. GMPLS protocol operations handle of horizontal interaction. GMPLS protocol operations handle
horizontal interactions within the same routing area. The case horizontal interactions within the same routing area. The case
where the interaction takes place across a domain boundary, such as where the interaction takes place across a domain boundary, such as
between two routing areas within the same network layer, is between two routing areas within the same network layer, is
evaluated as part of the inter- domain work [RFC4726], and is evaluated as part of the inter- domain work [RFC4726], and is
referred to as horizontal integration. Thus, horizontal integration referred to as horizontal integration. Thus, horizontal integration
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devices hosting more than one switching capability not only devices hosting more than one switching capability not only
increases the complexity of their interactions but also increases increases the complexity of their interactions but also increases
the total amount of processing individual instances would handle. the total amount of processing individual instances would handle.
- The unification of the addressing spaces helps in avoiding - The unification of the addressing spaces helps in avoiding
multiple identifiers for the same object (a link, for instance, multiple identifiers for the same object (a link, for instance,
or more generally, any network resource). On the other hand such or more generally, any network resource). On the other hand such
aggregation does not impact the separation between the control aggregation does not impact the separation between the control
plane and the data plane. plane and the data plane.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
- By maintaining a single routing protocol instance and a single TE - By maintaining a single routing protocol instance and a single TE
database per LSR, a unified control plane model removes the database per LSR, a unified control plane model removes the
requirement to maintain a dedicated routing topology per layer requirement to maintain a dedicated routing topology per layer
and therefore does not mandate a full mesh of routing adjacencies and therefore does not mandate a full mesh of routing adjacencies
as is the case with overlaid control planes. as is the case with overlaid control planes.
- The collaboration between technology layers where the control - The collaboration between technology layers where the control
channel is associated with the data channel (e.g. packet/framed channel is associated with the data channel (e.g. packet/framed
data planes) and technology layers where the control channel is data planes) and technology layers where the control channel is
not directly associated with the data channel (SONET/SDH, G.709, not directly associated with the data channel (SONET/SDH, G.709,
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[RFC4202]. An ISC is identified via a switching type. [RFC4202]. An ISC is identified via a switching type.
A switching type (also referred to as the switching capability A switching type (also referred to as the switching capability
type) describes the ability of a node to forward data of a type) describes the ability of a node to forward data of a
particular data plane technology, and uniquely identifies a network particular data plane technology, and uniquely identifies a network
region. The following ISC types (and, hence, regions) are defined: region. The following ISC types (and, hence, regions) are defined:
PSC, L2SC, TDM, LSC, and FSC. Each end of a data link (more PSC, L2SC, TDM, LSC, and FSC. Each end of a data link (more
precisely, each interface connecting a data link to a node) in a precisely, each interface connecting a data link to a node) in a
GMPLS network is associated with an ISC. GMPLS network is associated with an ISC.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
The ISC value is advertised as a part of the Interface Switching The ISC value is advertised as a part of the Interface Switching
Capability Descriptor (ISCD) attribute (sub-TLV) of a TE link end Capability Descriptor (ISCD) attribute (sub-TLV) of a TE link end
associated with a particular link interface [RFC4202]. Apart from associated with a particular link interface [RFC4202]. Apart from
the ISC, the ISCD contains information including the encoding type, the ISC, the ISCD contains information including the encoding type,
the bandwidth granularity, and the unreserved bandwidth on each of the bandwidth granularity, and the unreserved bandwidth on each of
eight priorities at which LSPs can be established. The ISCD does eight priorities at which LSPs can be established. The ISCD does
not "identify" network layers, it uniquely characterizes not "identify" network layers, it uniquely characterizes
information associated to one or more network layers. information associated to one or more network layers.
TE link end advertisements may contain multiple ISCDs. This can be TE link end advertisements may contain multiple ISCDs. This can be
skipping to change at page 12, line 4 skipping to change at page 11, line 7
external interfaces connected to the node have both PSC and TDM external interfaces connected to the node have both PSC and TDM
capabilities. capabilities.
Additionally, TE link advertisements issued by a simplex or a Additionally, TE link advertisements issued by a simplex or a
hybrid node may need to provide information about the node's hybrid node may need to provide information about the node's
internal adjustment capacity between the switching technologies internal adjustment capacity between the switching technologies
supported. The term "adjustment" capacity refers to the property of supported. The term "adjustment" capacity refers to the property of
an hybrid node to interconnect different switching capabilities it an hybrid node to interconnect different switching capabilities it
provides through its external interfaces.. This information allows provides through its external interfaces.. This information allows
path computation to select an end- to-end multi-layer or multi- path computation to select an end- to-end multi-layer or multi-
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
region path that includes links of different switching capabilities region path that includes links of different switching capabilities
that are joined by LSRs that can adapt the signal between the links. that are joined by LSRs that can adapt the signal between the links.
4.2.1. Networks with Multi-Switching-Type-Capable Hybrid Nodes 4.2.1. Networks with Multi-Switching-Type-Capable Hybrid Nodes
This type of network contains at least one hybrid node, zero or This type of network contains at least one hybrid node, zero or
more simplex nodes, and a set of single-switching-type-capable more simplex nodes, and a set of single-switching-type-capable
nodes. nodes.
Figure 1 shows an example hybrid node. The hybrid node has two Figure 1 shows an example hybrid node. The hybrid node has two
switching elements (matrices), which support, for instance, TDM and switching elements (matrices), which support, for instance, TDM and
PSC switching respectively. The node terminates a PSC and a TDM PSC switching respectively. The node terminates a PSC and a TDM
link (Link1 and Link2 respectively). It also has an internal link link (Link1 and Link2 respectively). It also has an internal link
connecting the two switching elements. connecting the two switching elements.
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The two switching elements are internally interconnected in such a The two switching elements are internally interconnected in such a
way that it is possible to terminate some of the resources of, say, way that it is possible to terminate some of the resources of, say,
Link2 and provide adjustment for PSC traffic received/sent over the Link2 and provide adjustment for PSC traffic received/sent over the
PSC interface (#b). This situation is modeled in GMPLS by PSC interface (#b). This situation is modeled in GMPLS by
connecting the local end of Link2 to the TDM switching element via connecting the local end of Link2 to the TDM switching element via
an additional interface realizing the termination/adjustment an additional interface realizing the termination/adjustment
function. There are two possible ways to set up PSC LSPs through function. There are two possible ways to set up PSC LSPs through
the hybrid node. Available resource advertisement (i.e., Unreserved the hybrid node. Available resource advertisement (i.e., Unreserved
and Min/Max LSP Bandwidth) should cover both of these methods. and Min/Max LSP Bandwidth) should cover both of these methods.
Network element
............................. .............................
: Network element :
: -------- : : -------- :
: | PSC | : : | PSC | :
Link1 -------------<->--|#a | : Link1 -------------<->--|#a | :
: | | : : | | :
: +--<->---|#b | : : +--<->---|#b | :
: | -------- : : | -------- :
: | ---------- : : | ---------- :
TDM : +--<->--|#c TDM | : TDM : +--<->--|#c TDM | :
+PSC : | | : +PSC : | | :
Link2 ------------<->--|#d | : Link2 ------------<->--|#d | :
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Figure 1. Hybrid node. Figure 1. Hybrid node.
4.3. Integrated Traffic Engineering (TE) and Resource Control 4.3. Integrated Traffic Engineering (TE) and Resource Control
In GMPLS-based multi-region/multi-layer networks, TE Links may be In GMPLS-based multi-region/multi-layer networks, TE Links may be
consolidated into a single Traffic Engineering Database (TED) for consolidated into a single Traffic Engineering Database (TED) for
use by the single control plane instance. Since this TED contains use by the single control plane instance. Since this TED contains
the information relative to all the layers of all regions in the the information relative to all the layers of all regions in the
network, a path across multiple layers (possibly crossing multiple network, a path across multiple layers (possibly crossing multiple
regions) can be computed using the information in this TED. Thus, regions) can be computed using the information in this TED. Thus,
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
optimization of network resources across the multiple layers of the optimization of network resources across the multiple layers of the
same region and across multiple regions can be achieved. same region and across multiple regions can be achieved.
These concepts allow for the operation of one network layer over These concepts allow for the operation of one network layer over
the topology (that is, TE links) provided by other network layers the topology (that is, TE links) provided by other network layers
(for example, the use of a lower layer LSC LSP carrying PSC LSPs). (for example, the use of a lower layer LSC LSP carrying PSC LSPs).
In turn, a greater degree of control and inter-working can be In turn, a greater degree of control and inter-working can be
achieved, including (but not limited too): achieved, including (but not limited too):
- Dynamic establishment of Forwarding Adjacency (FA) LSPs - Dynamic establishment of Forwarding Adjacency (FA) LSPs
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layer. From a signaling perspective, there are two alternatives to layer. From a signaling perspective, there are two alternatives to
establish the lower layer FA-LSP: static (pre-provisioned) and establish the lower layer FA-LSP: static (pre-provisioned) and
dynamic (triggered). A pre-provisioned FA-LSP may be initiated dynamic (triggered). A pre-provisioned FA-LSP may be initiated
either by the operator or automatically using features like TE either by the operator or automatically using features like TE
auto-mesh [RFC4972]. If such a lower layer LSP does not already auto-mesh [RFC4972]. If such a lower layer LSP does not already
exist, the LSP may be established dynamically. Such a mechanism is exist, the LSP may be established dynamically. Such a mechanism is
referred to as "triggered signaling". referred to as "triggered signaling".
4.3.2. FA-LSPs 4.3.2. FA-LSPs
Once an LSP is created across a layer from one layer border node Once an LSP is created across a layer from one layer border node to
to another, it can be used as a data link in an upper layer. another, it can be used as a data link in an upper layer.
Furthermore, it can be advertised as a TE-link, allowing other Furthermore, it can be advertised as a TE-link, allowing other
nodes to consider the LSP as a TE link for their path computation nodes to consider the LSP as a TE link for their path computation
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
[RFC4206]. An LSP created either statically or dynamically by one [RFC4206]. An LSP created either statically or dynamically by one
instance of the control plane and advertised as a TE link into the instance of the control plane and advertised as a TE link into the
same instance of the control plane is called a Forwarding Adjacency same instance of the control plane is called a Forwarding Adjacency
LSP (FA-LSP). The FA-LSP is advertised as a TE link, and that TE LSP (FA-LSP). The FA-LSP is advertised as a TE link, and that TE
link is called a Forwarding Adjacency (FA). An FA has the special link is called a Forwarding Adjacency (FA). An FA has the special
characteristic of not requiring a routing adjacency (peering) characteristic of not requiring a routing adjacency (peering)
between its end points yet still guaranteeing control plane between its end points yet still guaranteeing control plane
connectivity between the FA-LSP end points based on a signaling connectivity between the FA-LSP end points based on a signaling
adjacency. An FA is a useful and powerful tool for improving the adjacency. An FA is a useful and powerful tool for improving the
scalability of GMPLS Traffic Engineering (TE) capable networks scalability of GMPLS Traffic Engineering (TE) capable networks
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words, provides a virtual network topology (VNT) to the upper- words, provides a virtual network topology (VNT) to the upper-
layers. For instance, a set of LSPs, each of which is supported by layers. For instance, a set of LSPs, each of which is supported by
an LSC LSP, provides a virtual network topology to the layers of a an LSC LSP, provides a virtual network topology to the layers of a
PSC region, assuming that the PSC region is connected to the LSC PSC region, assuming that the PSC region is connected to the LSC
region. Note that a single lower-layer LSP is a special case of the region. Note that a single lower-layer LSP is a special case of the
VNT. The virtual network topology is configured by setting up or VNT. The virtual network topology is configured by setting up or
tearing down the lower layer LSPs. By using GMPLS signaling and tearing down the lower layer LSPs. By using GMPLS signaling and
routing protocols, the virtual network topology can be adapted to routing protocols, the virtual network topology can be adapted to
traffic demands. traffic demands.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
A lower-layer LSP appears as a TE-link in the VNT. Whether the A lower-layer LSP appears as a TE-link in the VNT. Whether the
diversely-routed lower-layer LSPs are used or not, the routes of diversely-routed lower-layer LSPs are used or not, the routes of
lower-layer LSPs are hidden from the upper layer in the VNT. Thus, lower-layer LSPs are hidden from the upper layer in the VNT. Thus,
the VNT simplifies the upper-layer routing and traffic engineering the VNT simplifies the upper-layer routing and traffic engineering
decisions by hiding the routes taken by the lower-layer LSPs. decisions by hiding the routes taken by the lower-layer LSPs.
However, hiding the routes of the lower-layer LSPs may lose However, hiding the routes of the lower-layer LSPs may lose
important information that is needed to make the higher-layer LSPs important information that is needed to make the higher-layer LSPs
reliable. For instance, the routing and traffic engineering in the reliable. For instance, the routing and traffic engineering in the
IP/MPLS layer does not usually consider how the IP/MPLS TE links IP/MPLS layer does not usually consider how the IP/MPLS TE links
are formed from optical paths that are routed in the fiber layer. are formed from optical paths that are routed in the fiber layer.
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performed by computing the new VNT from the traffic demand matrix performed by computing the new VNT from the traffic demand matrix
and optionally from the current VNT. Exact details are outside the and optionally from the current VNT. Exact details are outside the
scope of this document. However, this method may be tailored scope of this document. However, this method may be tailored
according to the service provider's policy regarding network according to the service provider's policy regarding network
performance and quality of service (delay, loss/disruption, performance and quality of service (delay, loss/disruption,
utilization, residual capacity, reliability). utilization, residual capacity, reliability).
5. Requirements 5. Requirements
5.1. Handling Single-Switching and Multi-Switching-Type-Capable Nodes 5.1. Handling Single-Switching and Multi-Switching-Type-Capable Nodes
The MRN/MLN can consist of single-switching-type-capable and
multi- switching-type-capable nodes. The path computation mechanism The MRN/MLN can consist of single-switching-type-capable and multi-
in the MLN SHOULD be able to compute paths consisting of any switching-type-capable nodes. The path computation mechanism in the
combination of such nodes. MLN should be able to compute paths consisting of any combination
of such nodes.
Both single-switching-type-capable and multi-switching-type-capable Both single-switching-type-capable and multi-switching-type-capable
(simplex or hybrid) nodes could play the role of layer boundary. (simplex or hybrid) nodes could play the role of layer boundary.
MRN/MLN Path computation SHOULD handle TE topologies built of any MRN/MLN Path computation should handle TE topologies built of any
combination of nodes. combination of nodes.
5.2. Advertisement of the Available Adjustment Resource 5.2. Advertisement of the Available Adjustment Resource
A hybrid node SHOULD maintain resources on its internal links (the A hybrid node should maintain resources on its internal links (the
links required for vertical (layer) integration) and SHOULD links required for vertical (layer) integration). Likewise, path
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008 computation elements should be prepared to use the availability of
advertise the resource information for those links. Likewise, path
computation elements SHOULD be prepared to use the availability of
termination/ adjustment resources as a constraint in MRN/MLN path termination/ adjustment resources as a constraint in MRN/MLN path
computations to reduce the higher layer LSP setup blocking computations to reduce the higher layer LSP setup blocking
probability caused by the lack of necessary termination/adjustment probability caused by the lack of necessary termination/adjustment
resources in the lower layer(s). resources in the lower layer(s).
The advertisement of the adjustment capability to terminate LSPs of The advertisement of the adjustment capability to terminate LSPs of
lower-region and forward traffic in the upper-region is REQUIRED, lower-region and forward traffic in the upper-region is REQUIRED,
as it provides critical information when performing multi-region as it provides critical information when performing multi-region
path computation. path computation.
The mechanism SHOULD cover the case where the upper-layer links The path computation mechanism should cover the case where the
which are directly connected to upper-layer switching element and upper-layer links which are directly connected to upper-layer
the ones which are connected through internal links between upper- switching element and the ones which are connected through internal
layer element and lower-layer element coexist (see Section 4.2.1). links between upper-layer element and lower-layer element coexist
(see Section 4.2.1).
5.3. Scalability 5.3. Scalability
The MRN/MLN relies on unified routing and traffic engineering The MRN/MLN relies on unified routing and traffic engineering
models. models.
- Unified routing model: By maintaining a single routing protocol - Unified routing model: By maintaining a single routing protocol
instance and a single TE database per LSR, a unified control instance and a single TE database per LSR, a unified control
plane model removes the requirement to maintain a dedicated plane model removes the requirement to maintain a dedicated
routing topology per layer, and therefore does not mandate a routing topology per layer, and therefore does not mandate a full
full mesh of routing adjacencies per layer. mesh of routing adjacencies per layer.
- Unified TE model: The TED in each LSR is populated with TE-links - Unified TE model: The TED in each LSR is populated with TE-links
from all layers of all regions (TE link interfaces on multiple- from all layers of all regions (TE link interfaces on multiple-
switching-capability LSRs can be advertised with multiple ISCDs). switching-capability LSRs can be advertised with multiple ISCDs).
This may lead to an increase in the amount of information that This may lead to an increase in the amount of information that
has to be flooded and stored within the network. has to be flooded and stored within the network.
Furthermore, path computation times, which may be of great Furthermore, path computation times, which may be of great
importance during restoration, will depend on the size of the TED. importance during restoration, will depend on the size of the TED.
skipping to change at page 17, line 5 skipping to change at page 16, line 5
- Number of nodes - Number of nodes
- Number of TE-links (including FA-LSPs) - Number of TE-links (including FA-LSPs)
- Number of LSPs - Number of regions and layers - Number of LSPs - Number of regions and layers
- Number of ISCDs per TE-link. - Number of ISCDs per TE-link.
Further, design of the routing protocols MUST NOT prevent TE Further, design of the routing protocols MUST NOT prevent TE
information filtering based on ISCDs. The path computation information filtering based on ISCDs. The path computation
mechanism and the signaling protocol SHOULD be able to operate on mechanism and the signaling protocol SHOULD be able to operate on
partial TE information. partial TE information.
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
Since TE Links can advertise multiple Interface Switching Since TE Links can advertise multiple Interface Switching
Capabilities (ISCs), the number of links can be limited (by Capabilities (ISCs), the number of links can be limited (by
combination) by using specific topological maps referred to as VNTs combination) by using specific topological maps referred to as VNTs
(Virtual Network Topologies). The introduction of virtual (Virtual Network Topologies). The introduction of virtual
topological maps leads us to consider the concept of emulation of topological maps leads us to consider the concept of emulation of
data plane overlays. data plane overlays.
5.4. Stability 5.4. Stability
Path computation is dependent on the network topology and Path computation is dependent on the network topology and
associated link state. The path computation stability of an upper associated link state. The path computation stability of an upper
layer may be impaired if the VNT changes frequently and/or if the layer may be impaired if the VNT changes frequently and/or if the
status and TE parameters (the TE metric, for instance) of links in status and TE parameters (the TE metric, for instance) of links in
the VNT changes frequently. In this context, robustness of the VNT the VNT changes frequently. In this context, robustness of the VNT
is defined as the capability to smooth changes that may occur and is defined as the capability to smooth changes that may occur and
avoid their propagation into higher layers. Changes to the VNT may avoid their propagation into higher layers. Changes to the VNT may
be caused by the creation, deletion, or modification of LSPs. be caused by the creation, deletion, or modification of LSPs.
Creation, deletion, and modification of LSPs MAY be triggered by Protocol mechanisms MUST be provided to enable creation, deletion,
adjacent layers or through operational actions to meet traffic and modification of LSPs triggered through operational actions.
demand changes, topology changes, signaling requests from the upper Protocol mechanisms SHOULD be provided to enable similar functions
layer, and network failures. Routing robustness SHOULD be traded triggered by adjacent layers. Protocol mechanisms MAY be provided
with adaptability with respect to the change of incoming traffic to enable similar functions to adapt to the environment changes
requests. such as traffic demand changes, topology changes, and network
failures. Routing robustness should be traded with adaptability of
those changes.
5.5. Disruption Minimization 5.5. Disruption Minimization
When reconfiguring the VNT according to a change in traffic demand, When reconfiguring the VNT according to a change in traffic demand,
the upper-layer LSP might be disrupted. Such disruption to the the upper-layer LSP might be disrupted. Such disruption to the
upper layers MUST be minimized. upper layers must be minimized.
When residual resource decreases to a certain level, some lower When residual resource decreases to a certain level, some lower
layer LSPs MAY be released according to local or network policies. layer LSPs may be released according to local or network policies.
There is a trade-off between minimizing the amount of resource There is a trade-off between minimizing the amount of resource
reserved in the lower layer and disrupting higher layer traffic reserved in the lower layer and disrupting higher layer traffic
(i.e. moving the traffic to other TE-LSPs so that some LSPs can be (i.e. moving the traffic to other TE-LSPs so that some LSPs can be
released). Such traffic disruption MAY be allowed, but MUST be released). Such traffic disruption may be allowed, but MUST be
under the control of policy that can be configured by the operator. under the control of policy that can be configured by the operator.
Any repositioning of traffic MUST be as non-disruptive as possible Any repositioning of traffic MUST be as non-disruptive as possible
(for example, using make-before-break). (for example, using make-before-break).
5.6. LSP Attribute Inheritance 5.6. LSP Attribute Inheritance
TE-Link parameters SHOULD be inherited from the parameters of the TE-Link parameters should be inherited from the parameters of the
LSP that provides the TE-link, and so from the TE-links in the LSP that provides the TE-link, and so from the TE-links in the
lower layer that are traversed by the LSP. lower layer that are traversed by the LSP.
These include: These include:
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
- Interface Switching Capability - Interface Switching Capability
- TE metric - TE metric
- Maximum LSP bandwidth per priority level - Maximum LSP bandwidth per priority level
- Unreserved bandwidth for all priority levels - Unreserved bandwidth for all priority levels
- Maximum Reservable bandwidth - Maximum Reservable bandwidth
- Protection attribute - Protection attribute
- Minimum LSP bandwidth (depending on the Switching Capability) - Minimum LSP bandwidth (depending on the Switching Capability)
- SRLG - SRLG
Inheritance rules MUST be applied based on specific policies. Inheritance rules must be applied based on specific policies.
Particular attention should be given to the inheritance of TE Particular attention should be given to the inheritance of TE
metric (which may be other than a strict sum of the metrics of the metric (which may be other than a strict sum of the metrics of the
component TE links at the lower layer), protection attributes, and component TE links at the lower layer), protection attributes, and
SRLG. SRLG.
As described earlier, hiding the routes of the lower-layer LSPs may As described earlier, hiding the routes of the lower-layer LSPs may
lose important information necessary to make LSPs in the higher lose important information necessary to make LSPs in the higher
layer network reliable. SRLGs may be used to identify which lower- layer network reliable. SRLGs may be used to identify which lower-
layer LSPs share the same failure risk so that the potential risk layer LSPs share the same failure risk so that the potential risk
of the VNT becoming disjoint can be minimized, and so that resource of the VNT becoming disjoint can be minimized, and so that resource
disjoint protection paths can be set up in the higher layer. How to disjoint protection paths can be set up in the higher layer. How to
inherit the SRLG information from the lower layer to the upper inherit the SRLG information from the lower layer to the upper
layer needs more discussion and is out of scope of this document. layer needs more discussion and is out of scope of this document.
5.7. Computing Paths With and Without Nested Signaling 5.7. Computing Paths With and Without Nested Signaling
Path computation MAY take into account LSP region and layer Path computation can take into account LSP region and layer
boundaries when computing a path for an LSP. For example, path boundaries when computing a path for an LSP. Path computation may
computation MAY restrict the path taken by an LSP to only the links restrict the path taken by an LSP to only the links whose interface
whose interface switching capability is PSC. switching capability is PSC. For example, suppose that a TDM-LSP is
routed over the topology composed of TE links of the same TDM layer.
Interface switching capability is used as a constraint in path In calculating the path for the LSP, the TED may be filtered to
computation. For example, a TDM-LSP is routed over the topology include only links where both end include requested LSP switching
composed of TE links of the same TDM layer. In calculating the path type. In this way hierarchical routing is done by using a TED
for the LSP, the TED MAY be filtered to include only links where filtered with respect to switching capability (that is, with
both end include requested LSP switching type. In this way respect to particular layer).
hierarchical routing is done by using a TED filtered with respect
to switching capability (that is, with respect to particular layer).
If triggered signaling is allowed, the path computation mechanism If triggered signaling is allowed, the path computation mechanism
MAY produce a route containing multiple layers/regions. The path is may produce a route containing multiple layers/regions. The path is
computed over the multiple layers/regions even if the path is not computed over the multiple layers/regions even if the path is not
"connected" in the same layer as the endpoints of the path exist. "connected" in the same layer as the endpoints of the path exist.
Note that here we assume that triggered signaling will be invoked Note that here we assume that triggered signaling will be invoked
to make the path "connected", when the upper-layer signaling to make the path "connected", when the upper-layer signaling
request arrives at the boundary node. request arrives at the boundary node.
The upper-layer signaling request may contain an ERO that includes The upper-layer signaling request MAY contain an ERO (Explicit
only hops in the upper layer, in which case the boundary node is Route Object) that includes only hops in the upper layer, in which
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008 case the boundary node is responsible for triggered creation of the
lower-layer FA-LSP using a path of its choice, or for the selection
responsible for triggered creation of the lower-layer FA-LSP using of any available lower layer LSP as a data link for the higher
a path of its choice, or for the selection of any available lower layer. This mechanism is appropriate for environments where the TED
layer LSP as a data link for the higher layer. This mechanism is is filtered in the higher layer, where separate routing instances
appropriate for environments where the TED is filtered in the are used per layer, or where administrative policies prevent the
higher layer, where separate routing instances are used per layer, higher layer from specifying paths through the lower layer.
or where administrative policies prevent the higher layer from
specifying paths through the lower layer.
Obviously, if the lower layer LSP has been advertised as a TE link Obviously, if the lower layer LSP has been advertised as a TE link
(virtual or real) into the higher layer, then the higher layer (virtual or real) into the higher layer, then the higher layer
signaling request may contain the TE link identifier and so signaling request MAY contain the TE link identifier and so
indicate the lower layer resources to be used. But in this case, indicate the lower layer resources to be used. But in this case,
the path of the lower layer LSP can be dynamically changed by the the path of the lower layer LSP can be dynamically changed by the
lower layer at any time. lower layer at any time.
Alternatively, the upper-layer signaling request may contain an ERO Alternatively, the upper-layer signaling request MAY contain an ERO
specifying the lower layer FA-LSP route. In this case, the boundary specifying the lower layer FA-LSP route. In this case, the boundary
node is responsible for decision as to which it should use the path node MAY decide whether it should use the path contained in the
contained in the strict ERO or it should re-compute the path within strict ERO or re-compute the path within the lower-layer.
in the lower-layer.
Even in case the lower-layer FA-LSPs are already established, a Even in the case that the lower-layer FA-LSPs are already
signaling request may also be encoded as loose ERO. In this established, a signaling request may also be encoded as a loose ERO.
situation, it is up to the boundary node to decide whether it In this situation, it is up to the boundary node to decide whether
should a new lower-layer FA-LSP or it should use the existing it should create a new lower-layer FA-LSP or it should use an
lower-layer FA-LSPs. existing lower-layer FA-LSPs.
The lower-layer FA-LSP can be advertised just as an FA-LSP in the The lower-layer FA-LSP can be advertised just as an FA-LSP in the
upper-layer or an IGP adjacency can be brought up on the lower- upper-layer or an IGP adjacency can be brought up on the lower-
layer FA-LSP. layer FA-LSP.
5.8. LSP Resource Utilization 5.8. LSP Resource Utilization
It MUST be possible to utilize network resources efficiently. Resource usage in all layers should be optimized as a whole (i.e.,
Particularly, resource usage in all layers SHOULD be optimized as a across all layers), in a coordinated manner, (i.e., taking all
whole (i.e., across all layers), in a coordinated manner, (i.e., layers into account). The number of lower-layer LSPs carrying
taking all layers into account). The number of lower-layer LSPs upper-layer LSPs should be minimized (note that multiple LSPs may
carrying upper-layer LSPs SHOULD be minimized (note that multiple be used for load balancing). Lower-layer LSPs that could have their
LSPs MAY be used for load balancing). Lower-layer LSPs that could traffic re-routed onto other LSPs are unnecessary and should be
have their traffic re-routed onto other LSPs are unnecessary and avoided.
SHOULD be avoided.
5.8.1. FA-LSP Release and Setup 5.8.1. FA-LSP Release and Setup
Statistical multiplexing can only be employed in PSC and L2SC
regions. A PSC or L2SC LSP may or may not consume the maximum
reservable bandwidth of the TE link (FA-LSP) that carries it. On
the other hand, a TDM, or LSC LSP always consumes a fixed amount of
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
bandwidth as long as it exists (and is fully instantiated) because
statistical multiplexing is not available.
If there is low traffic demand, some FA-LSPs that do not carry any If there is low traffic demand, some FA-LSPs that do not carry any
higher-layer LSP MAY be released so that lower-layer resources are higher-layer LSP may be released so that lower-layer resources are
released and can be assigned to other uses. Note that if a small released and can be assigned to other uses. Note that if a small
fraction of the available bandwidth of an FA-LSP is still in use, fraction of the available bandwidth of an FA-LSP is still in use,
the nested LSPs can also be re-routed to other FA-LSPs (optionally the nested LSPs can also be re-routed to other FA-LSPs (optionally
using the make-before-break technique) to completely free up the using the make-before-break technique) to completely free up the
FA-LSP. Alternatively, unused FA-LSPs MAY be retained for future FA-LSP. Alternatively, unused FA-LSPs may be retained for future
use. Release or retention of underutilized FA-LSPs is a policy use. Release or retention of underutilized FA-LSPs is a policy
decision. decision.
As part of the re-optimization process, the solution MUST allow As part of the re-optimization process, the solution MUST allow
rerouting of an FA-LSP while keeping interface identifiers of rerouting of an FA-LSP while keeping interface identifiers of
corresponding TE links unchanged. Further, this process MUST be corresponding TE links unchanged. Further, this process MUST be
possible while the FA-LSP is carrying traffic (higher layer LSPs) possible while the FA-LSP is carrying traffic (higher layer LSPs)
with minimal disruption to the traffic. with minimal disruption to the traffic.
Additional FA-LSPs MAY also be created based on policy, which might Additional FA-LSPs may also be created based on policy, which might
consider residual resources and the change of traffic demand across consider residual resources and the change of traffic demand across
the region. By creating the new FA-LSPs, the network performance the region. By creating the new FA-LSPs, the network performance
such as maximum residual capacity may increase. such as maximum residual capacity may increase.
As the number of FA-LSPs grows, the residual resource may decrease. As the number of FA-LSPs grows, the residual resource may decrease.
In this case, re-optimization of FA-LSPs MAY be invoked according In this case, re-optimization of FA-LSPs may be invoked according
to policy. to policy.
Any solution MUST include measures to protect against network Any solution MUST include measures to protect against network
destabilization caused by the rapid setup and teardown of LSPs as destabilization caused by the rapid setup and teardown of LSPs as
traffic demand varies near a threshold. traffic demand varies near a threshold.
Signaling of lower-layer LSPs SHOULD include a mechanism to rapidly Signaling of lower-layer LSPs SHOULD include a mechanism to rapidly
advertise the LSP as a TE link and to coordinate into which routing advertise the LSP as a TE link and to coordinate into which routing
instances the TE link should be advertised. instances the TE link should be advertised.
5.8.2. Virtual TE-Links 5.8.2. Virtual TE-Links
It may be considered disadvantageous to fully instantiate (i.e. It may be considered disadvantageous to fully instantiate (i.e.
pre- provision) the set of lower layer LSPs that provide the VNT pre- provision) the set of lower layer LSPs that provide the VNT
since this might reserve bandwidth that could be used for other since this might reserve bandwidth that could be used for other
LSPs in the absence of upper-layer traffic. LSPs in the absence of upper-layer traffic.
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instances the TE link should be advertised. instances the TE link should be advertised.
5.8.2. Virtual TE-Links 5.8.2. Virtual TE-Links
It may be considered disadvantageous to fully instantiate (i.e. It may be considered disadvantageous to fully instantiate (i.e.
pre- provision) the set of lower layer LSPs that provide the VNT pre- provision) the set of lower layer LSPs that provide the VNT
since this might reserve bandwidth that could be used for other since this might reserve bandwidth that could be used for other
LSPs in the absence of upper-layer traffic. LSPs in the absence of upper-layer traffic.
However, in order to allow path computation of upper-layer LSPs However, in order to allow path computation of upper-layer LSPs
across the lower-layer, the lower-layer LSPs MAY be advertised into across the lower-layer, the lower-layer LSPs may be advertised into
the upper-layer as though they had been fully established, but the upper-layer as though they had been fully established, but
without actually establishing them. Such TE links that represent without actually establishing them. Such TE links that represent
the possibility of an underlying LSP are termed "virtual TE-links." the possibility of an underlying LSP are termed "virtual TE-links."
It is an implementation choice at a layer boundary node whether to It is an implementation choice at a layer boundary node whether to
create real or virtual TE-links, and the choice if available in an create real or virtual TE-links, and the choice if available in an
implementation MUST be under the control of operator policy. Note implementation MUST be under the control of operator policy. Note
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
that there is no requirement to support the creation of virtual TE- that there is no requirement to support the creation of virtual TE-
links, since real TE-links (with established LSPs) may be used, and links, since real TE-links (with established LSPs) may be used, and
even if there are no TE-links (virtual or real) advertised to the even if there are no TE-links (virtual or real) advertised to the
higher layer, it is possible to route a higher layer LSP into a higher layer, it is possible to route a higher layer LSP into a
lower layer on the assumptions that proper hierarchical LSPs in the lower layer on the assumptions that proper hierarchical LSPs in the
lower layer will be dynamically created (triggered) as needed. lower layer will be dynamically created (triggered) as needed.
If an upper-layer LSP that makes use of a virtual TE-Link is set up, If an upper-layer LSP that makes use of a virtual TE-Link is set up,
the underlying LSP MUST be immediately signaled in the lower layer. the underlying LSP MUST be immediately signaled in the lower layer.
If virtual TE-Links are used in place of pre-established LSPs, the If virtual TE-Links are used in place of pre-established LSPs, the
TE-links across the upper-layer can remain stable using pre- TE-links across the upper-layer can remain stable using pre-
computed paths while wastage of bandwidth within the lower-layer computed paths while wastage of bandwidth within the lower-layer
and unnecessary reservation of adaptation resource at the border and unnecessary reservation of adaptation resource at the border
nodes can be avoided. nodes can be avoided.
The solution SHOULD provide operations to facilitate the build-up The solution SHOULD provide operations to facilitate the build-up
of such virtual TE-links, taking into account the (forecast) of such virtual TE-links, taking into account the (forecast)
traffic demand and available resource in the lower-layer. traffic demand and available resource in the lower-layer.
Virtual TE-links MAY be added, removed or modified dynamically (by Virtual TE-links can be added, removed or modified dynamically (by
changing their capacity) according to the change of the (forecast) changing their capacity) according to the change of the (forecast)
traffic demand and the available resource in the lower-layer. The traffic demand and the available resource in the lower-layer. It
maximum number of virtual TE links that can be defined SHOULD be MUST be possible to add, remove, and modify virtual TE-links in a
configurable. dynamic way.
Any solution MUST include measures to protect against network Any solution MUST include measures to protect against network
destabilization caused by the rapid changes in the virtual network destabilization caused by the rapid changes in the virtual network
topology as traffic demand varies near a threshold. topology as traffic demand varies near a threshold.
The concept of the VNT can be extended to allow the virtual TE- The concept of the VNT can be extended to allow the virtual TE-
links to form part of the VNT. The combination of the fully links to form part of the VNT. The combination of the fully
provisioned TE- links and the virtual TE-links defines the VNT provisioned TE- links and the virtual TE-links defines the VNT
provided by the lower layer. The VNT can be changed by setting up provided by the lower layer. The VNT can be changed by setting up
and/or tearing down virtual TE links as well as by modifying real and/or tearing down virtual TE links as well as by modifying real
skipping to change at page 21, line 54 skipping to change at page 20, line 40
In some situations, selective advertisement of the preferred In some situations, selective advertisement of the preferred
connectivity among a set of border nodes between layers may be connectivity among a set of border nodes between layers may be
appropriate. Further decreasing the number of advertisement of the appropriate. Further decreasing the number of advertisement of the
virtual connectivity can be achieved by abstracting the topology virtual connectivity can be achieved by abstracting the topology
(between border nodes) using models similar to those detailed in (between border nodes) using models similar to those detailed in
[RFC4847]. [RFC4847].
5.9. Verification of the LSPs 5.9. Verification of the LSPs
When a lower layer LSP is established for use as a data link by a When a lower layer LSP is established for use as a data link by a
higher layer, the LSP MAY be verified for correct connectivity and higher layer, the LSP may be verified for correct connectivity and
data integrity. Such mechanisms are data technology-specific and data integrity before it is made available for use. Such mechanisms
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008 are data technology-specific and are beyond the scope of this
document, but the GMPLS protocols SHOULD provide mechanisms for the
coordination of data link verification.
are beyond the scope of this document, but may be coordinated 5.10. Management
through the GMPLS control plane.
MIB modules exist for the modeling and management of GMPLS networks
[RFC4802], [RFC4803]. Some deployments of GMPLS networks may choose
to use MIB modules to operate individual network layers. In these
cases, operators may desire to coordinate layers through a further
MIB module. Multi-layer protocol solutions SHOULD be manageable
through MIB modules. A further MIB module to coordinate multiple
network layers may be produced.
OAM tools are important to the successful deployment of networks.
Protocol solutions for individual network layers SHOULD include
mechanisms for OAM or to make use of OAM features inherent in the
physical media of the layers. Multi-layer protocol solutions SHOULD
provide mechanisms to coordinate OAM mechanisms operating in each
layer.
6. Security Considerations 6. Security Considerations
The MLN/MRN architecture does not introduce any new security The MLN/MRN architecture does not introduce any new security
requirements over the general GMPLS architecture described in requirements over the general GMPLS architecture described in
[RFC3945]. Additional security considerations form MPLS and GMPLS [RFC3945]. Additional security considerations form MPLS and GMPLS
networks are described in [MPLS-SEC]. networks are described in [MPLS-SEC].
However, where the separate layers of a MLN/MRN network are However, where the separate layers of a MLN/MRN network are
operated as different administrative domains, additional security operated as different administrative domains, additional security
skipping to change at page 22, line 35 skipping to change at page 21, line 40
It is expected that solution documents will include a full analysis It is expected that solution documents will include a full analysis
of the security issues that any protocol extensions introduce. of the security issues that any protocol extensions introduce.
7. IANA Considerations 7. IANA Considerations
This informational document makes no requests to IANA for action. This informational document makes no requests to IANA for action.
8. Acknowledgements 8. Acknowledgements
The authors would like to thank Adrian Farrel and the participants The authors would like to thank Adrian Farrel and the participants
of ITU-T Study Group 15 Question 14 for their careful review. of ITU-T Study Group 15 Question 14 for their careful review. The
authors would like to thank the IESG review team for rigorous
review: special thanks to Tim Polk, Miguel Garcia, Jari Arkko, and
Dan Romascanu.
9. References 9. References
9.1. Normative Reference 9.1. Normative Reference
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3945] E. Mannie (Editor), "Generalized Multi-Protocol Label [RFC3945] E. Mannie (Editor), "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October 2004. Switching (GMPLS) Architecture", RFC 3945, October 2004.
[RFC4202] Kompella, K., and Rekhter, Y., "Routing Extensions in [RFC4202] Kompella, K., and Rekhter, Y., "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching Support of Generalized Multi-Protocol Label Switching
(GMPLS)," RFC4202, October 2005. (GMPLS)," RFC4202, October 2005.
[RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths [RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths
(LSP) Hierarchy with Generalized Multi-Protocol Label (LSP) Hierarchy with Generalized Multi-Protocol Label
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
Switching (GMPLS) Traffic Engineering (TE)," RFC4206, Switching (GMPLS) Traffic Engineering (TE)," RFC4206,
Oct. 2005. Oct. 2005.
[RFC4397] Bryskin, I., and Farrel, A., "A Lexicography for the [RFC4397] Bryskin, I., and Farrel, A., "A Lexicography for the
Interpretation of Generalized Multiprotocol Label Interpretation of Generalized Multiprotocol Label
Switching (GMPLS) Terminology within the Context of the Switching (GMPLS) Terminology within the Context of the
ITU-T's Automatically Switched Optical Network (ASON) ITU-T's Automatically Switched Optical Network (ASON)
Architecture", RFC 4397, February 2006. Architecture", RFC 4397, February 2006.
[RFC4726] Farrel, A., Vasseur, JP., and Ayyangar, A., "A [RFC4726] Farrel, A., Vasseur, JP., and Ayyangar, A., "A
skipping to change at page 23, line 31 skipping to change at page 22, line 39
[DYN-HIER] Shiomoto, K., Rabbat, R., Ayyangar, A., Farrel, A. [DYN-HIER] Shiomoto, K., Rabbat, R., Ayyangar, A., Farrel, A.
and Ali, Z., "Procedures for Dynamically Signaled and Ali, Z., "Procedures for Dynamically Signaled
Hierarchical Label Switched Paths", draft-ietf-ccamp- Hierarchical Label Switched Paths", draft-ietf-ccamp-
lsp-hierarchy-bis, work in progress. lsp-hierarchy-bis, work in progress.
[MRN-EVAL] Le Roux, J.L., Brungard, D., Oki, E., Papadimitriou, [MRN-EVAL] Le Roux, J.L., Brungard, D., Oki, E., Papadimitriou,
D., Shiomoto, K., Vigoureux, M., "Evaluation of D., Shiomoto, K., Vigoureux, M., "Evaluation of
Existing GMPLS Protocols Against Multi-Layer and Existing GMPLS Protocols Against Multi-Layer and
Multi-Region Network (MLN/MRN) Requirements", draft- Multi-Region Network (MLN/MRN) Requirements", draft-
ietf-ccamp-gmpls- mln-eval, work in progress. ietf-ccamp-gmpls- mln-eval, work in progress.
[MPLS-GMPLS]
K. Kumaki (Editor), "Interworking Requirements to [RFC5146] K. Kumaki (Editor), "Interworking Requirements to
Support Operation of MPLS-TE over GMPLS Networks", Support Operation of MPLS-TE over GMPLS Networks",
draft-ietf-ccamp-mpls-gmpls-interwork-reqts, work in RFC 5146, March 2008.
progress.
[MPLS-SEC] Fang, L., et al., "Security Framework for MPLS and [MPLS-SEC] Fang, L., et al., "Security Framework for MPLS and
GMPLS Networks", draft-ietf-mpls-mpls-and-gmpls- GMPLS Networks", draft-ietf-mpls-mpls-and-gmpls-
security-framework, work in progress. security-framework, work in progress.
[RFC4802] Nadeau, T., Ed. and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Traffic
Engineering Management Information Base", RFC 4802,
February 2007.
[RFC4803] Nadeau, T., Ed. and A. Farrel, Ed., "Generalized
Multiprotocol Label Switching (GMPLS) Label Switching
Router (LSR) Management Information Base", RFC 4803,
February 2007.
[RFC4847] T. Takeda (Editor), " Framework and Requirements for [RFC4847] T. Takeda (Editor), " Framework and Requirements for
Layer 1 Virtual Private Networks", RFC 4847, April Layer 1 Virtual Private Networks", RFC 4847, April
2007. 2007.
[RFC4972] Vasseur, JP., Le Roux, JL., et al., "Routing [RFC4972] Vasseur, JP., Le Roux, JL., et al., "Routing
Extensions for Discovery of Multiprotocol (MPLS) Extensions for Discovery of Multiprotocol (MPLS)
Label Switch Router (LSR) Traffic Engineering (TE) Label Switch Router (LSR) Traffic Engineering (TE)
Mesh Membership", RFC 4972, July 2007. Mesh Membership", RFC 4972, July 2007.
10. Authors' Addresses 10. Authors' Addresses
Kohei Shiomoto Kohei Shiomoto
NTT Network Service Systems Laboratories NTT Network Service Systems Laboratories
3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan
Email: shiomoto.kohei@lab.ntt.co.jp Email: shiomoto.kohei@lab.ntt.co.jp
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
Dimitri Papadimitriou Dimitri Papadimitriou
Alcatel-Lucent Alcatel-Lucent
Copernicuslaan 50, Copernicuslaan 50,
B-2018 Antwerpen, Belgium B-2018 Antwerpen, Belgium
Phone : +32 3 240 8491 Phone : +32 3 240 8491
Email: dimitri.papadimitriou@alcatel-lucent.be Email: dimitri.papadimitriou@alcatel-lucent.be
Jean-Louis Le Roux Jean-Louis Le Roux
France Telecom R&D, France Telecom R&D,
skipping to change at page 25, line 4 skipping to change at page 24, line 27
3-9-11 Midori-cho, 3-9-11 Midori-cho,
Musashino-shi, Musashino-shi,
Tokyo 180-8585, Tokyo 180-8585,
Japan Japan
Phone: +81 422 59 3441 Phone: +81 422 59 3441
Email: ichiro.inoue@lab.ntt.co.jp Email: ichiro.inoue@lab.ntt.co.jp
Emmanuel Dotaro Emmanuel Dotaro
Alcatel-Lucent Alcatel-Lucent
Route de Nozay, Route de Nozay,
draft-ietf-ccamp-gmpls-mln-reqs-08.txt January 2008
91461 Marcoussis cedex, 91461 Marcoussis cedex,
France France
Phone : +33 1 6963 4723 Phone : +33 1 6963 4723
Email: emmanuel.dotaro@alcatel-lucent.fr Email: emmanuel.dotaro@alcatel-lucent.fr
12. Intellectual Property Considerations 12. Intellectual Property Considerations
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described to pertain to the implementation or use of the technology described
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