draft-ietf-ccamp-sdhsonet-control-02.txt   draft-ietf-ccamp-sdhsonet-control-03.txt 
CCAMP Working Group G. Bernstein (Grotto Networking) CCAMP Working Group G. Bernstein (Grotto Networking)
Internet Draft E. Mannie (InterAir Link) Internet Draft E. Mannie (InterAir Link)
Document: <draft-ietf-ccamp-sdhsonet- V. Sharma (Metanoia, Inc.) Document: <draft-ietf-ccamp-sdhsonet- V. Sharma (Metanoia, Inc.)
control-02.txt> control-03.txt>
Category: Informational Category: Informational
Expires August 2003 February 2003 Expires January 2005 July 2004
Framework for GMPLS-based Control of SDH/SONET Networks Framework for GMPLS-based Control of SDH/SONET Networks
<draft-ietf-ccamp-sdhsonet-control-02.txt> <draft-ietf-ccamp-sdhsonet-control-03.txt>
Status of this Memo Status of this Memo
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1. Abstract Abstract
The suite of protocols that defines Multi-Protocol Label Switching The suite of protocols that defines Multi-Protocol Label Switching
(MPLS) is in the process of enhancement to generalize its (MPLS) is in the process of enhancement to generalize its
applicability to the control of non-packet based switching, that is, applicability to the control of non-packet based switching, that is,
optical switching. One area of prime consideration is to use these optical switching. One area of prime consideration is to use these
generalized MPLS (GMPLS) protocols in upgrading the control plane of generalized MPLS (GMPLS) protocols in upgrading the control plane of
optical transport networks. This document illustrates this process optical transport networks. This document illustrates this process
by describing those extensions to MPLS protocols that are directed by describing those extensions to MPLS protocols that are directed
towards controlling SONET/SDH networks. SONET/SDH networks make towards controlling SDH/SONET networks. SDH/SONET networks make
very good examples of this process since they possess a rich very good examples of this process since they possess a rich
multiplex structure, a variety of protection/restoration options, multiplex structure, a variety of protection/restoration options,
are well defined, and are widely deployed. The document discusses are well defined, and are widely deployed. The document discusses
extensions to MPLS routing protocols to disseminate information extensions to MPLS routing protocols to disseminate information
needed in transport path computation and network operations, needed in transport path computation and network operations,
together with the extensions to MPLS label distribution protocols together with the extensions to MPLS label distribution protocols
needed for the provisioning of transport circuits. New capabilities needed for the provisioning of transport circuits. New capabilities
that an MPLS control plane would bring to SONET/SDH networks, such that an MPLS control plane would bring to SDH/SONET networks, such
as new restoration methods and multi-layer circuit establishment, as new restoration methods and multi-layer circuit establishment,
are also discussed. are also discussed.
2. Conventions used in this document Bernstein/Mannie/Sharma Informational-January 2005 1
GMPLS based Control of SDH/SONET July 2004
Bernstein, Mannie, Sharma Informational-November 2002 1 1. Conventions used in this document................................2
GMPLS based Control of SDH/SONET February 2003 2. Introduction.....................................................3
2.1. MPLS Overview..................................................3
2.2. SDH/SONET Overview.............................................4
2.3. The Current State of Circuit Establishment in SDH/SONET
Networks.............................................................7
2.3.1. Administrative Tasks.......................................7
2.3.2. Manual Operations..........................................7
2.3.3. Planning Tool Operation....................................7
2.3.4. Circuit Provisioning.......................................8
2.4. Centralized Approach versus Distributed Approach...............8
2.4.1. Topology Discovery and Resource Dissemination..............9
2.4.2. Path Computation (Route Determination).....................9
2.4.3. Connection Establishment (Provisioning)...................10
2.5. Why SDH/SONET will not Disappear Tomorrow.....................11
3. GMPLS Applied to SDH/SONET......................................12
3.1. Controlling the SDH/SONET Multiplex...........................12
3.2. SDH/SONET LSR and LSP Terminology.............................13
4. Decomposition of the MPLS Circuit-Switching Problem Space.......13
5. GMPLS Routing for SDH/SONET.....................................14
5.1. Switching Capabilities........................................15
5.1.1. Switching Granularity.....................................15
5.1.2. Signal Concatenation Capabilities.........................16
5.1.3. SDH/SONET Transparency....................................17
5.2. Protection....................................................18
5.3. Available Capacity Advertisement..............................21
5.4. Path Computation..............................................22
6. LSP Provisioning/Signaling for SDH/SONET........................22
6.1. What do we Label in SDH/SONET? Frames or Circuits?............23
6.2. Label Structure in SDH/SONET..................................24
6.3. Signaling Elements............................................24
7. Summary and Conclusions.........................................26
8. Security Considerations.........................................27
9. Acknowledgments.................................................27
10. Author's Addresses..............................................27
11. References......................................................27
11.1. Normative References........................................27
11.2. Informative References......................................28
12. Intellectual Property Considerations............................29
12.1. IPR Disclosure Acknowledgement..............................29
13. Full Copyright Statement........................................29
1. Conventions used in this document
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119 [2]. this document are to be interpreted as described in RFC-2119 [2].
3. Introduction 2. Introduction
The CCAMP Working Group of the IETF is currently working on The CCAMP Working Group of the IETF is currently working on
extending MPLS [3] protocols to support multiple network layers and extending MPLS [3] protocols to support multiple network layers and
new services. This extended MPLS, which was initially known as new services. This extended MPLS, which was initially known as
Multi-Protocol Lambda Switching, is now better referred to as Multi-Protocol Lambda Switching, is now better referred to as
Generalized MPLS (or GMPLS). The authors of this work are among the Generalized MPLS (or GMPLS).
co-authors of the GMPLS specifications, and focus mainly on those
aspects of GMPLS that relate to the control of SDH/SONET networks.
The GMPLS effort is, in effect, extending IP technology to control The GMPLS effort is, in effect, extending IP/MPLS technology to
and manage lower layers. Using the same framework and similar control and manage lower layers. Using the same framework and
signaling and routing protocols to control multiple layers can not similar signaling and routing protocols to control multiple layers
only reduce the overall complexity of designing, deploying and can not only reduce the overall complexity of designing, deploying
maintaining networks, but can also make it possible to operate two and maintaining networks, but can also make it possible to operate
contiguous layers by using either an overlay model, a peer model, or two contiguous layers by using either an overlay model, a peer
an integrated model. The benefits of using a peer or an overlay model, or an integrated model. The benefits of using a peer or an
model between the IP layer and its underlying layer(s) will have to overlay model between the IP layer and its underlying layer(s) will
be clarified and evaluated in the future. In the mean time, GMPLS have to be clarified and evaluated in the future. In the mean time,
could be used for controlling each layer independently. GMPLS could be used for controlling each layer independently.
The goal of this work is to highlight how GMPLS could be used to The goal of this work is to highlight how MPLS could be used to
dynamically establish, maintain, and tear down SDH/SONET circuits. dynamically establish, maintain, and tear down SDH/SONET circuits.
The objective of using these extended MPLS protocols is to provide The objective of using these extended IP/MPLS protocols is to
at least the same kinds of SDH/SONET services as are provided today, provide at least the same kinds of SDH/SONET services as are
but using signaling instead of provisioning via centralized provided today, but using signaling instead of provisioning via
management to establish those services. This will allow operators to centralized management to establish those services. This will allow
propose new services, and will allow clients to create SONET/SDH operators to propose new services, and will allow clients to create
paths on-demand, in real-time, through the provider network. We SDH/SONET paths on-demand, in real-time, through the provider
first review the essential properties of SDH/SONET networks and network. We first review the essential properties of SDH/SONET
their operations, and we show how the label concept in MPLS can be networks and their operations, and we show how the label concept in
extended to the SONET/SDH case. We then look at important MPLS can be extended to the SDH/SONET case. We then look at
information to be disseminated by a link state routing protocol and important information to be disseminated by a link state routing
look at the important signal attributes that need to be conveyed by protocol and look at the important signal attributes that need to be
a label distribution protocol. Finally, we look at some outstanding conveyed by a label distribution protocol. Finally, we look at some
issues and future possibilities. outstanding issues and future possibilities.
3.1. MPLS Overview 2.1. MPLS Overview
A major advantage of the MPLS architecture [3] for use as a general A major advantage of the MPLS architecture [3] for use as a general
network control plane is its clear separation between the forwarding network control plane is its clear separation between the forwarding
(or data) plane, the signaling (or connection control) plane, and (or data) plane, the signaling (or connection control) plane, and
the routing (or topology discovery/resource status) plane. This the routing (or topology discovery/resource status) plane. This
allows the work on MPLS extensions to focus on the forwarding and allows the work on MPLS extensions to focus on the forwarding and
signaling planes, while allowing well-known IP routing protocols to signaling planes, while allowing well-known IP routing protocols to
be reused in the routing plane. This clear separation also allows be reused in the routing plane. This clear separation also allows
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GMPLS based Control of SDH/SONET February 2003
for MPLS to be used to control networks that do not have a packet- for MPLS to be used to control networks that do not have a packet-
based forwarding plane. based forwarding plane.
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An MPLS network consists of MPLS nodes called Label Switch Routers An MPLS network consists of MPLS nodes called Label Switch Routers
(LSRs) connected via circuits called Label Switched Paths (LSPs). An (LSRs) connected via circuits called Label Switched Paths (LSPs). An
LSP is unidirectional and could be of several different types such LSP is unidirectional and could be of several different types such
as point-to-point, point-to-multipoint, and multipoint-to-point. as point-to-point, point-to-multipoint, and multipoint-to-point.
Border LSRs in an MPLS network act either as ingress or egress LSRs Border LSRs in an MPLS network act either as ingress or egress LSRs
depending on the direction of the traffic being forwarded. depending on the direction of the traffic being forwarded.
Each LSP is associated with a Fowarding Equivalence Class (FEC), Each LSP is associated with a Fowarding Equivalence Class (FEC),
which may be thought of as a set of packets that receive identical which may be thought of as a set of packets that receive identical
forwarding treatment at an LSR. The simplest example of an FEC might forwarding treatment at an LSR. The simplest example of an FEC might
skipping to change at line 148 skipping to change at line 192
purpose, the ingress LSR attaches an appropriate label to the purpose, the ingress LSR attaches an appropriate label to the
packet, and forwards the packet to the next hop. The label may be packet, and forwards the packet to the next hop. The label may be
attached to a packet in different ways. For example, it may be in attached to a packet in different ways. For example, it may be in
the form of a header encapsulating the packet (the "shim" header) or the form of a header encapsulating the packet (the "shim" header) or
it may be written in the VPI/VCI field (or DLCI field) of the layer it may be written in the VPI/VCI field (or DLCI field) of the layer
2 encapsulation of the packet. In case of SDH/SONET networks, we 2 encapsulation of the packet. In case of SDH/SONET networks, we
will see that a label is simply associated with a segment of a will see that a label is simply associated with a segment of a
circuit, and is mainly used in the signaling plane to identify this circuit, and is mainly used in the signaling plane to identify this
segment (e.g. a time-slot) between two adjacent nodes. segment (e.g. a time-slot) between two adjacent nodes.
When a packet reaches a core packet LSR, this LSR uses the label as When a packet reaches a packet LSR, this LSR uses the label as an
an index into a forwarding table to determine the next hop and the index into a forwarding table to determine the next hop and the
corresponding outgoing label (and, possibly, the QoS treatment to be corresponding outgoing label (and, possibly, the QoS treatment to be
given to the packet), writes the new label into the packet, and given to the packet), writes the new label into the packet, and
forwards the packet to the next hop. When the packet reaches the forwards the packet to the next hop. When the packet reaches the
egress LSR, the label is removed and the packet is forwarded using egress LSR, the label is removed and the packet is forwarded using
appropriate forwarding, such as normal IP forwarding. We will see appropriate forwarding, such as normal IP forwarding. We will see
that for a SONET/SDH network these operations do not occur in quite that for a SDH/SONET network these operations do not occur in quite
the same way. the same way.
3.2. SDH/SONET Overview 2.2. SDH/SONET Overview
There are currently two different multiplexing technologies in use There are currently two different multiplexing technologies in use
in optical networks: wavelength division multiplexing (WDM) and time in optical networks: wavelength division multiplexing (WDM) and time
division multiplexing (TDM). This work focuses on TDM technology. division multiplexing (TDM). This work focuses on TDM technology.
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SDH and SONET are two TDM standards widely used by operators to SDH and SONET are two TDM standards widely used by operators to
transport and multiplex different tributary signals over optical transport and multiplex different tributary signals over optical
links, thus creating a multiplexing structure, which we call the links, thus creating a multiplexing structure, which we call the
SDH/SONET multiplex. SDH, which was developed by the ETSI and later SDH/SONET multiplex.
standardized by the ITU-T [4], is now used worldwide, while SONET,
which was standardized by the ANSI [5], is mainly used in the US. ITU-T (G.707) [4] includes both the European ETSI SDH hierarchy and
However, these two standards have several similarities, and to some the USA ANSI SONET hierarchy [5]. The ETSI SDH and SONET standards
extent SONET can be viewed as a subset of SDH. Internetworking regarding frame structures and higher-order multiplexing are the
between the two is possible using gateways. same. There are some regional differences in terminology, on the use
of some overhead bytes, and lower-order multiplexing. Interworking
between the two lower-order hierarchies is possible using gateways.
The fundamental signal in SDH is the STM-1 that operates at a rate The fundamental signal in SDH is the STM-1 that operates at a rate
of about 155 Mbps, while the fundamental signal in SONET is the STS- of about 155 Mbps, while the fundamental signal in SONET is the STS-
1 that operates at a rate of about 51 Mbps. These two signals are 1 that operates at a rate of about 51 Mbps. These two signals are
made of contiguous frames that consist of transport overhead made of contiguous frames that consist of transport overhead
(header) and payload. To solve synchronization issues, the actual (header) and payload. To solve synchronization issues, the actual
data is not transported directly in the payload but rather in data is not transported directly in the payload but rather in
another internal frame that is allowed to float over two successive another internal frame that is allowed to float over two successive
SDH/SONET payloads. This internal frame is named a Virtual Container SDH/SONET payloads. This internal frame is named a Virtual Container
(VC) in SDH and a Synchronous Payload Envelope (SPE) in SONET. (VC) in SDH and a Synchronous Payload Envelope (SPE) in SONET.
skipping to change at line 197 skipping to change at line 243
The SDH/SONET architecture identifies three different layers, each The SDH/SONET architecture identifies three different layers, each
of which corresponds to one level of communication between SDH/SONET of which corresponds to one level of communication between SDH/SONET
equipment. These are, starting with the lowest, the regenerator equipment. These are, starting with the lowest, the regenerator
section/section layer, the multiplex section/line layer, and (at the section/section layer, the multiplex section/line layer, and (at the
top) the path layer. Each of these layers in turn has its own top) the path layer. Each of these layers in turn has its own
overhead (header). The transport overhead of a SDH/SONET frame is overhead (header). The transport overhead of a SDH/SONET frame is
mainly sub-divided in two parts that contain the regenerator mainly sub-divided in two parts that contain the regenerator
section/section overhead and the multiplex section/line overhead. In section/section overhead and the multiplex section/line overhead. In
addition, a pointer (in the form of the H1, H2 and H3 bytes) addition, a pointer (in the form of the H1, H2 and H3 bytes)
indicates the beginning of the VC/SPE in the payload of the overall indicates the beginning of the VC/SPE in the payload of the overall
STM/SDH frame. STM/STS frame.
The VC/SPE itself is made up of a header (the path overhead) and a The VC/SPE itself is made up of a header (the path overhead) and a
payload. This payload can be further subdivided into sub-elements payload. This payload can be further subdivided into sub-elements
(signals) in a fairly complex way. In the case of SDH, the STM-1 (signals) in a fairly complex way. In the case of SDH, the STM-1
frame may contain either one VC-4 or three multiplexed VC-3s. The frame may contain either one VC-4 or three multiplexed VC-3s. The
SONET multiplex is a pure tree, while the SDH multiplex is not a SONET multiplex is a pure tree, while the SDH multiplex is not a
pure tree, since it contains a node that can be attached to two pure tree, since it contains a node that can be attached to two
parent nodes. The structure of the SONET/SDH multiplex is shown in parent nodes. The structure of the SDH/SONET multiplex is shown in
Figure 1. In addition, we show reference points in this figure that Figure 1. In addition, we show reference points in this figure that
are explained in later sections. are explained in later sections.
xN x1 xN x1
STM-N<----AUG<----AU-4<--VC4<------------------------------C-4 E4 STM-N<----AUG<----AU-4<--VC4<------------------------------C-4 E4
^ ^ ^ ^
Ix3 Ix3 Ix3 Ix3
I I x1 I I x1
I -----TUG-3<----TU-3<---VC-3<---I I -----TUG-3<----TU-3<---VC-3<---I
I ^ C-3 DS3/E3 I ^ C-3 DS3/E3
-------AU-3<---VC-3<-- I ---------------------I
^ I
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STM-0<------------AU-3<---VC-3<-- I ---------------------I
^ I
Ix7 Ix7 Ix7 Ix7
I I x1 I I x1
-----TUG-2<---TU-2<---VC-2<---C-2 DS2/T2 -----TUG-2<---TU-2<---VC-2<---C-2 DS2/T2
^ ^ ^ ^
I I x3 I I x3
I I----TU-12<---VC-12<--C-12 E1 I I----TU-12<---VC-12<--C-12 E1
I I
I x4 I x4
I-------TU-11<---VC-11<--C-11 DS1/T1 I-------TU-11<---VC-11<--C-11 DS1/T1
skipping to change at line 269 skipping to change at line 315
is to identify the elements that can be switched from an input is to identify the elements that can be switched from an input
multiplex on one interface to an output multiplex on another multiplex on one interface to an output multiplex on another
interface. The only elements that can be switched are those that can interface. The only elements that can be switched are those that can
be re-aligned via a pointer, i.e. a VC-x in the case of SDH and a be re-aligned via a pointer, i.e. a VC-x in the case of SDH and a
SPE in the case of SONET. SPE in the case of SONET.
An STM-N/STS-N signal is formed from N x STM-1/STS-1 signals via An STM-N/STS-N signal is formed from N x STM-1/STS-1 signals via
byte interleaving. The VCs/SPEs in the N interleaved frames are byte interleaving. The VCs/SPEs in the N interleaved frames are
independent and float according to their own clocking. To transport independent and float according to their own clocking. To transport
tributary signals in excess of the basic STM-1/STS-1 signal rates, tributary signals in excess of the basic STM-1/STS-1 signal rates,
the VCs/SPEs can be concatenated, i.e., glued together. In this case
their relationship with respect to each other is fixed in time and
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GMPLS based Control of SDH/SONET February 2003 GMPLS based Control of SDH/SONET July 2004
the VCs/SPEs can be concatenated, i.e., glued together. In this case
their relationship with respect to each other is fixed in time and
hence this relieves, when possible, an end system of any inverse hence this relieves, when possible, an end system of any inverse
multiplexing bonding processes. Different types of concatenations multiplexing bonding processes. Different types of concatenations
are defined in SDH/SONET. are defined in SDH/SONET.
For example, standard SONET concatenation allows the concatenation For example, standard SONET concatenation allows the concatenation
of M x STS-1 signals within an STS-N signal with M <= N, and M = 3, of M x STS-1 signals within an STS-N signal with M <= N, and M = 3,
12, 48, 192,...). The SPEs of these M x STS-1s can be concatenated 12, 48, 192,...). The SPEs of these M x STS-1s can be concatenated
to form an STS-Mc. The STS-Mc notation is short hand for describing to form an STS-Mc. The STS-Mc notation is short hand for describing
an STS-M signal whose SPEs have been concatenated. an STS-M signal whose SPEs have been concatenated.
3.3. The Current State of Circuit Establishment in SDH/SONET Networks 2.3. The Current State of Circuit Establishment in SDH/SONET Networks
In present day SDH and SONET networks, the networks are primarily In present day SDH and SONET networks, the networks are primarily
statically configured. When a client of an operator requests a statically configured. When a client of an operator requests a
point-to-point circuit, the request sets in motion a process that point-to-point circuit, the request sets in motion a process that
can last for several weeks or more. This process is composed of a can last for several weeks or more. This process is composed of a
chain of shorter administrative and technical tasks, some of which chain of shorter administrative and technical tasks, some of which
can be fully automated, resulting in significant improvements in can be fully automated, resulting in significant improvements in
provisioning time and in operational savings. In the best case, the provisioning time and in operational savings. In the best case, the
entire process can be fully automated allowing, for example, entire process can be fully automated allowing, for example,
customer premise equipment (CPE) to contact a SDH/SONET switch to customer premise equipment (CPE) to contact a SDH/SONET switch to
request a circuit. Currently, the provisioning process involves the request a circuit. Currently, the provisioning process involves the
following tasks. following tasks.
3.3.1. Administrative Tasks 2.3.1. Administrative Tasks
The administrative tasks represent a significant part of the The administrative tasks represent a significant part of the
provisioning time. Most of them can be automated using IT provisioning time. Most of them can be automated using IT
applications, e.g., a client still has to fill a form to request a applications, e.g., a client still has to fill a form to request a
circuit. This form can be filled via a Web-based application and can circuit. This form can be filled via a Web-based application and can
be automatically processed by the operator. A further enhancement is be automatically processed by the operator. A further enhancement is
to allow the client's equipment to coordinate with the operator's to allow the client's equipment to coordinate with the operator's
network directly and request the desired circuit. This could be network directly and request the desired circuit. This could be
achieved through a signaling protocol at the interface between the achieved through a signaling protocol at the interface between the
client equipment and an operator switch, i.e., at the UNI, where client equipment and an operator switch, i.e., at the UNI, where
GMPLS signaling [6], [7], [8] can be used. GMPLS signaling [6], [7], [8] can be used.
3.3.2. Manual Operations 2.3.2. Manual Operations
Another significant part of the time may be consumed by manual Another significant part of the time may be consumed by manual
operations that involve installing the right interface in the CPE operations that involve installing the right interface in the CPE
and installing the right cable or fiber between the CPE and the and installing the right cable or fiber between the CPE and the
operator switch. This time can be especially significant when a operator switch. This time can be especially significant when a
client is in a different time zone than the operator's main office. client is in a different time zone than the operator's main office.
This first-time connection time is frequently accounted for in the This first-time connection time is frequently accounted for in the
overall establishment time. overall establishment time.
3.3.3. Planning Tool Operation 2.3.3. Planning Tool Operation
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GMPLS based Control of SDH/SONET July 2004
Another portion of the time is consumed by planning tools that run Another portion of the time is consumed by planning tools that run
simulations using heuristic algorithms to find an optimized simulations using heuristic algorithms to find an optimized
placement for the required circuits. These planning tools can placement for the required circuits. These planning tools can
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GMPLS based Control of SDH/SONET February 2003
require a significant running time, sometimes on the order of days. require a significant running time, sometimes on the order of days.
These simulations are, in general, executed for a set of demands for These simulations are, in general, executed for a set of demands for
circuits, i.e., a batch mode, to improve the optimality of network circuits, i.e., a batch mode, to improve the optimality of network
resource usage and other parameters. Today, we do not really have a resource usage and other parameters. Today, we do not really have a
means to reduce this simulation time. On the contrary, to support means to reduce this simulation time. On the contrary, to support
fast, on-line, circuit establishment, this phase may be invoked more fast, on-line, circuit establishment, this phase may be invoked more
frequently, i.e., we will not "batch up" as many connection frequently, i.e., we will not "batch up" as many connection
requests before we plan out the corresponding circuits. This means requests before we plan out the corresponding circuits. This means
that the network may need to be re-optimized periodically, implying that the network may need to be re-optimized periodically, implying
that the signaling should support re-optimization with minimum that the signaling should support re-optimization with minimum
impact to existing services. impact to existing services.
3.3.4. Circuit Provisioning 2.3.4. Circuit Provisioning
Once the first three steps discussed above have been completed, the Once the first three steps discussed above have been completed, the
operator must provision the circuits using the outputs of the operator must provision the circuits using the outputs of the
planning process. The time required for provisioning varies greatly. planning process. The time required for provisioning varies greatly.
It can be fairly short, on the order of a few minutes, if the It can be fairly short, on the order of a few minutes, if the
operators already have tools that help them to do the provisioning operators already have tools that help them to do the provisioning
over heterogeneous equipment. Otherwise, the process can take days. over heterogeneous equipment. Otherwise, the process can take days.
Developing these tools for each new piece of equipment and each Developing these tools for each new piece of equipment and each
vendor is a significant burden on the service provider. A vendor is a significant burden on the service provider. A
standardized interface for provisioning, such as GMPLS signaling, standardized interface for provisioning, such as GMPLS signaling,
skipping to change at line 370 skipping to change at line 415
When a circuit is provisioned, it is not delivered directly to a When a circuit is provisioned, it is not delivered directly to a
client. Rather, the operator first tests its performance and client. Rather, the operator first tests its performance and
behavior and if successful, delivers the circuit to the client. This behavior and if successful, delivers the circuit to the client. This
testing phase lasts, in general, for up to 24 hours. The operator testing phase lasts, in general, for up to 24 hours. The operator
installs test equipment at each end and uses pre-defined test installs test equipment at each end and uses pre-defined test
streams to verify performance. If successful, the circuit is streams to verify performance. If successful, the circuit is
officially accepted by the client. To speed up the verification officially accepted by the client. To speed up the verification
(sometimes known as "proving") process, it would be necessary to (sometimes known as "proving") process, it would be necessary to
support some form of automated performance testing. support some form of automated performance testing.
3.4. Centralized Approach versus Distributed Approach 2.4. Centralized Approach versus Distributed Approach
Whether a centralized approach or a distributed approach will be Whether a centralized approach or a distributed approach will be
used to control SDH/SONET networks is an open question, since each used to control SDH/SONET networks is an open question, since each
approach has its merits. The application of GMPLS to SONET/SDH approach has its merits. The application of MPLS to SDH/SONET
networks does not preclude either model, although MPLS is itself a networks does not preclude either model, although MPLS is itself a
distributed technology. distributed technology.
The basic tradeoff between the centralized and distributed The basic tradeoff between the centralized and distributed
approaches is that of complexity of the network elements versus that approaches is that of complexity of the network elements versus that
of the network management system (NMS). Since adding functionality of the network management system (NMS). Since adding functionality
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to existing SDH/SONET network elements may not be possible, a to existing SDH/SONET network elements may not be possible, a
centralized approach may be needed in some cases. The main issue centralized approach may be needed in some cases. The main issue
facing centralized control via an NMS is one of scalability. For facing centralized control via an NMS is one of scalability. For
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instance, this approach may be limited in the number of network instance, this approach may be limited in the number of network
elements that can be managed (e.g., one thousand). It is, therefore, elements that can be managed (e.g., one thousand). It is, therefore,
quite common for operators to deploy several NMSÆs in parallel at quite common for operators to deploy several NMSÆs in parallel at
the Network Management Layer, each managing a different zone. In the Network Management Layer, each managing a different zone. In
that case, however, a Service Management Layer must be built on the that case, however, a Service Management Layer must be built on the
top of several individual NMSÆs to take care of end-to-end on-demand top of several individual NMSÆs to take care of end-to-end on-demand
services. On the other hand, in a complex and/or dense network, services. On the other hand, in a complex and/or dense network,
restoration could be faster with a distributed approach than with a restoration could be faster with a distributed approach than with a
centralized approach. centralized approach.
Let's now look at how the major control plane functional components Let's now look at how the major control plane functional components
are handled via the centralized and distributed approaches: are handled via the centralized and distributed approaches:
3.4.1. Topology Discovery and Resource Dissemination 2.4.1. Topology Discovery and Resource Dissemination
Currently NMS's maintain a consistent view of all the networking Currently NMS's maintain a consistent view of all the networking
layers under their purview. This can include the physical topology, layers under their purview. This can include the physical topology,
such as information about fibers and ducts. Since most of this such as information about fibers and ducts. Since most of this
information is entered manually, it remains error prone. information is entered manually, it remains error prone.
A link state GMPLS routing protocol, on the other hand, could perform
automatic topology discovery and dissemination the topology as well as
resource status. This information would be available to all nodes in
the network, and hence also the NMS. Hence one can look at a continuum
of functionality between manually provisioned topology information (of
which there will always be some) and fully automated discovery and
dissemination as in a link state protocol. Note that, unlike the IP
datagram case, a link state routing protocol applied to the SDH/SONET
network does not have any service impacting implications. This is
because in the SDH/SONET case, the circuit is source-routed (so there
can be no loops), and no traffic is transmitted until a circuit has
been established, and an acknowledgement received at the source.
3.4.2. Path Computation (Route Determination) A link state GMPLS routing protocol, on the other hand, could
perform automatic topology discovery and dissemination the topology
as well as resource status. This information would be available to
all nodes in the network, and hence also the NMS. Hence one can
look at a continuum of functionality between manually provisioned
topology information (of which there will always be some) and fully
automated discovery and dissemination as in a link state protocol.
Note that, unlike the IP datagram case, a link state routing
protocol applied to the SDH/SONET network does not have any service
impacting implications. This is because in the SDH/SONET case, the
circuit is source-routed (so there can be no loops), and no traffic
is transmitted until a circuit has been established, and an
acknowledgement received at the source.
2.4.2. Path Computation (Route Determination)
In the SDH/SONET case, unlike the IP datagram case, there is no need In the SDH/SONET case, unlike the IP datagram case, there is no need
for network elements to all perform the same path calculation [9]. for network elements to all perform the same path calculation [9].
In addition, path determination is an area for vendors to provide a In addition, path determination is an area for vendors to provide a
potentially significant value addition in terms of network potentially significant value addition in terms of network
efficiency, reliability, and service differentiation. In this sense, efficiency, reliability, and service differentiation. In this sense,
a centralized approach to path computation may be easier to operate a centralized approach to path computation may be easier to operate
and upgrade. For example, new features such as new types of path and upgrade. For example, new features such as new types of path
diversity or new optimization algorithms can be introduced with a diversity or new optimization algorithms can be introduced with a
simple NMS software upgrade. On the other hand, updating switches simple NMS software upgrade. On the other hand, updating switches
with new path computation software is a more complicated task. In with new path computation software is a more complicated task. In
addition, many of the algorithms can be fairly computationally addition, many of the algorithms can be fairly computationally
intensive and may be completely unsuitable for the embedded intensive and may be completely unsuitable for the embedded
processing environment available on most switches. In restoration processing environment available on most switches. In restoration
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scenarios, the ability to perform a reasonably sophisticated level scenarios, the ability to perform a reasonably sophisticated level
of path computation on the network element can be particularly of path computation on the network element can be particularly
useful for restoring traffic during major network faults. useful for restoring traffic during major network faults.
3.4.3. Connection Establishment (provisioning) 2.4.3. Connection Establishment (Provisioning)
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The actual setting up of circuits, i.e., a coupled collection of The actual setting up of circuits, i.e., a coupled collection of
cross connects across a network, can be done either via the NMS cross connects across a network, can be done either via the NMS
setting up individual cross connects or via a "soft permanent LSP" setting up individual cross connects or via a "soft permanent LSP"
(SPLSP) type approach. In the SPLSP approach, the NMS may just kick (SPLSP) type approach. In the SPLSP approach, the NMS may just kick
off the connection at the "ingress" switch with GMPLS signaling off the connection at the "ingress" switch with GMPLS signaling
setting up the connection from that point onward. Connection setting up the connection from that point onward. Connection
establishment is the trickiest part to distribute, however, since establishment is the trickiest part to distribute, however, since
errors in the connection setup/tear down process are service errors in the connection setup/tear down process are service
impacting. impacting.
The table below compares the two approaches to connection The table below compares the two approaches to connection
establishment. establishment.
Distributed approach Centralized approach Distributed approach Centralized approach
Control plane like MPLS or Management plane like TMN or Packet-based control plane Management plane like TMN or
PNNI SNMP (like MPLS or PNNI) useful? SNMP
Do we really need it? Being Always needed! Already there, Do we really need it? Being Always needed! Already there,
added/specified by several proven and understood. added/specified by several proven and understood.
standardization bodies standardization bodies
High survivability (e.g. in Potential single point(s) of High survivability (e.g. in Potential single point(s) of
case of partition) failure case of partition) failure
Distributed load Bottleneck: #requests and Distributed load Bottleneck: #requests and
actions to/from NMS actions to/from NMS
skipping to change at line 490 skipping to change at line 538
Requires enhanced routing Better consistency Requires enhanced routing Better consistency
protocol (traffic protocol (traffic
engineering) engineering)
Ideal for inter-domain Not inter-domain friendly Ideal for inter-domain Not inter-domain friendly
Suitable for very dynamic For less dynamic demands Suitable for very dynamic For less dynamic demands
demands (longer lived) demands (longer lived)
Probably faster to restore, Probably slower to restore,but Probably faster to restore, Probably slower to restore,but
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but more difficult to have could effect reliable but more difficult to have could effect reliable
reliable restoration. restoration. reliable restoration. restoration.
High scalability Limited scalability: #nodes, High scalability Limited scalability: #nodes,
(hierarchical) links, circuits, messages (hierarchical) links, circuits, messages
Planning (optimization) Planning is a background Planning (optimization) Planning is a background
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harder to achieve centralized activity harder to achieve centralized activity
Easier future integration Easier future integration
with other control plane with other control plane
layers layers
Table 1. Qualitative comparison between centralized and distributed Table 1. Qualitative comparison between centralized and distributed
approaches. approaches.
3.5. Why SDH/SONET will not Disappear Tomorrow 2.5. Why SDH/SONET will not Disappear Tomorrow
As IP traffic becomes the dominant traffic transported over the As IP traffic becomes the dominant traffic transported over the
transport infrastructure, it is useful to compare the statistical transport infrastructure, it is useful to compare the statistical
multiplexing of IP with the time division multiplexing of SDH and multiplexing of IP with the time division multiplexing of SDH and
SONET. SONET.
Consider, for instance, a scenario where IP over WDM is used Consider, for instance, a scenario where IP over WDM is used
everywhere and lambdas are optically switched. In such a case, a everywhere and lambdas are optically switched. In such a case, a
carrier's carrier would sell dynamically controlled lambdas with carrier's carrier would sell dynamically controlled lambdas with
each customers building their own IP backbones over these lambdas. each customers building their own IP backbones over these lambdas.
skipping to change at line 546 skipping to change at line 594
SDH and SONET possess a rich multiplexing hierarchy that permits SDH and SONET possess a rich multiplexing hierarchy that permits
fairly fine granularity and that provides a very cheap and simple fairly fine granularity and that provides a very cheap and simple
physical separation of the transported traffic between circuits, physical separation of the transported traffic between circuits,
i.e., QoS. Moreover, even IP datagrams cannot be transported i.e., QoS. Moreover, even IP datagrams cannot be transported
directly over a wavelength. A framing or encapsulation is always directly over a wavelength. A framing or encapsulation is always
required to delimit IP datagrams. The Total Length field of an IP required to delimit IP datagrams. The Total Length field of an IP
header cannot be trusted to find the start of a new datagram, since header cannot be trusted to find the start of a new datagram, since
it could be corrupted and would result in a loss of synchronization. it could be corrupted and would result in a loss of synchronization.
The typical framing used today for IP over DWDM is defined in The typical framing used today for IP over DWDM is defined in
RFC1619/RFC2615 and known as POS (Packet Over SONET/SDH), i.e., IP
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RFC1619/RFC2615 and known as POS (Packet Over SDH/SONET), i.e., IP
over PPP (in HDLC-like format) over SDH/SONET. SDH and SONET are over PPP (in HDLC-like format) over SDH/SONET. SDH and SONET are
actually efficient encapsulations for IP. For instance, with an actually efficient encapsulations for IP. For instance, with an
average IP datagram length of 350 octets, an IP over GBE average IP datagram length of 350 octets, an IP over GBE
encapsulation using an 8B/10B encoding results in 28% overhead, an encapsulation using an 8B/10B encoding results in 28% overhead, an
IP/ATM/SDH encapsulation results in 22% overhead and an IP/PPP/SDH IP/ATM/SDH encapsulation results in 22% overhead and an IP/PPP/SDH
encapsulation results in only 6% overhead. (New simplified encapsulation results in only 6% overhead.
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encapsulations could reduce this overhead to as low as 3%, but the
gain is not huge compared to SDH and SONET, which have other
benefits as well.)
Any encapsulation of IP over WDM should at least provide error Any encapsulation of IP over WDM should, in the data plane, at least
monitoring capabilities (to detect signal degradation), error provide error monitoring capabilities (to detect signal
correction capabilities, such as FEC (Forward Error Correction) that degradation); error correction capabilities, such as FEC (Forward
are particularly needed for ultra long haul transmission, sufficient Error Correction) that are particularly needed for ultra long haul
timing information, to allow robust synchronization (that is, to transmission; sufficient timing information, to allow robust
detect the beginning of a packet), and capacity to transport synchronization (that is, to detect the beginning of a packet). In
signaling, routing and management messages, in order to control the the case where associated signaling is used (that is the control and
optical switches. SDH and SONET cover all these aspects natively, data plane topologies are congruent) the encapsulation should also
except FEC, which tends to be supported in a proprietary way. provide the capacity to transport signaling, routing and management
messages, in order to control the optical switches. Rather SDH and
SONET cover all these aspects natively, except FEC, which tends to
be supported in a proprietary way. (We note, however, that
associated signaling is not a requirement for the GMPLS-based
control of SDH/SONET networks. Rather, it is just one option. Non-
associated signaling, as would happen with an out-of-band control
plane network is another equally valid option.)
Since IP encapsulated in SDH/SONET is efficient and widely used, the Since IP encapsulated in SDH/SONET is efficient and widely used, the
only real difference between an IP over WDM network and an IP over only real difference between an IP over WDM network and an IP over
SDH over WDM network is the layers at which the switching or SDH over WDM network is the layers at which the switching or
forwarding can take place. In the first case, it can take place at forwarding can take place. In the first case, it can take place at
the IP and optical layers. In the second case, it can take place at the IP and optical layers. In the second case, it can take place at
the IP, SDH/SONET, and optical layers. the IP, SDH/SONET, and optical layers.
Almost all transmission networks today are based on SDH or SONET. A Almost all transmission networks today are based on SDH or SONET. A
client is connected either directly through an SDH or SONET client is connected either directly through an SDH or SONET
interface or through a PDH interface, the PDH signal being interface or through a PDH interface, the PDH signal being
transported between the ingress and the egress interfaces over SDH transported between the ingress and the egress interfaces over SDH
or SONET. What we are arguing here is that it makes sense to do or SONET. What we are arguing here is that it makes sense to do
switching or forwarding at all these layers. switching or forwarding at all these layers.
4. GMPLS Applied to SDH/SONET 3. GMPLS Applied to SDH/SONET
4.1. Controlling the SDH/SONET Multiplex 3.1. Controlling the SDH/SONET Multiplex
Controlling the SDH/SONET multiplex implies deciding which of the Controlling the SDH/SONET multiplex implies deciding which of the
different switchable components of the SDH/SONET multiplex do we different switchable components of the SDH/SONET multiplex do we
wish to control using GMPLS. Essentially, every SDH/SONET element wish to control using GMPLS. Essentially, every SDH/SONET element
that is referenced by a pointer can be switched. These component that is referenced by a pointer can be switched. These component
signals are the VC-4, VC-3, VC-2, VC-12 and VC-11 in the SDH case; signals are the VC-4, VC-3, VC-2, VC-12 and VC-11 in the SDH case;
and the VT and STS SPEs in the SONET case. The SONET case is a bit and the VT and STS SPEs in the SONET case. The SPEs in SONET do not
difficult to explain since, unlike in SDH, SPEs in SONET do not have have individual names, although they can be referred to simply as
individual names. We will refer to them by identifying the structure VT-N SPEs. We will refer to them by identifying the structure that
that contains them, namely the STS-1, VT-6, VT-3, VT-2 and VT-1.5. contains them, namely STS-1, VT-6, VT-3, VT-2 and VT-1.5.
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The STS-1 SPE corresponds to a VC-3, a VT-6 SPE corresponds to a VC- The STS-1 SPE corresponds to a VC-3, a VT-6 SPE corresponds to a VC-
2, a VT-2 SPE corresponds to a VC-12, and a VT-1.5 SPE corresponds 2, a VT-2 SPE corresponds to a VC-12, and a VT-1.5 SPE corresponds
to a VC-11. The SONET VT-3 SPE has no correspondence in SDH, however to a VC-11. The SONET VT-3 SPE has no correspondence in SDH, however
SDH's VC-4 corresponds to SONET's STS-3c SPE. SDH's VC-4 corresponds to SONET's STS-3c SPE.
In addition, it is possible to concatenate some of the structures In addition, it is possible to concatenate some of the structures
that contain these elements to build larger elements. For instance, that contain these elements to build larger elements. For instance,
SDH allows the concatenation of X contiguous AU-4s to build a VC-4- SDH allows the concatenation of X contiguous AU-4s to build a VC-4-
Xc and of m contiguous TU-2s to build a VC-2-mc. In that case, a VC- Xc and of m contiguous TU-2s to build a VC-2-mc. In that case, a VC-
4-Xc or a VC-2-mc can be switched and controlled by MPLS. Note that 4-Xc or a VC-2-mc can be switched and controlled by GMPLS. Note that
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SDH also defines virtual (non-contiguous) concatenation of TU- 2s, SDH also defines virtual (non-contiguous) concatenation of TU- 2s,
but in that case each constituent VC-2 is switched individually. but in that case each constituent VC-2 is switched individually.
4.2. SDH/SONET LSR and LSP Terminology 3.2. SDH/SONET LSR and LSP Terminology
Let a SDH or SONET Terminal Multiplexer (TM), Add-Drop Multiplexer Let a SDH or SONET Terminal Multiplexer (TM), Add-Drop Multiplexer
(ADM) or cross-connect (i.e. a switch) be called an SDH/SONET LSR. A (ADM) or cross-connect (i.e. a switch) be called an SDH/SONET LSR. A
SDH/SONET path or circuit between two SDH/SONET LSRs now becomes a SDH/SONET path or circuit between two SDH/SONET LSRs now becomes a
GMPLS LSP. An SDH/SONET LSP is a logical connection between the GMPLS LSP. An SDH/SONET LSP is a logical connection between the
point at which a tributary signal (client layer) is adapted into its point at which a tributary signal (client layer) is adapted into its
virtual container, and the point at which it is extracted from its virtual container, and the point at which it is extracted from its
virtual container. virtual container.
To establish such an LSP, a signaling protocol is required to To establish such an LSP, a signaling protocol is required to
skipping to change at line 640 skipping to change at line 691
no merging is possible with SDH/SONET signals. no merging is possible with SDH/SONET signals.
To facilitate the signaling and setup of SDH/SONET circuits, an To facilitate the signaling and setup of SDH/SONET circuits, an
SDH/SONET LSR must, therefore, identify each possible signal SDH/SONET LSR must, therefore, identify each possible signal
individually per interface, since each signal corresponds to a individually per interface, since each signal corresponds to a
potential LSP that can be established through the SDH/SONET LSR. It potential LSP that can be established through the SDH/SONET LSR. It
turns out, however, that not all SDH signals correspond to an LSP turns out, however, that not all SDH signals correspond to an LSP
and therefore not all of them need be identified. In fact, only and therefore not all of them need be identified. In fact, only
those signals that can be switched need identification. those signals that can be switched need identification.
5. Decomposition of the MPLS Circuit-Switching Problem Space 4. Decomposition of the MPLS Circuit-Switching Problem Space
Although those familiar with MPLS may be familiar with its Although those familiar with MPLS may be familiar with its
application in a variety of application areas, e.g., ATM, Frame application in a variety of application areas, e.g., ATM, Frame
Relay, and so on, here we quickly review its decomposition when Relay, and so on, here we quickly review its decomposition when
applied to the optical switching problem space. applied to the optical switching problem space.
(i) Information needed to compute paths must be made globally (i) Information needed to compute paths must be made globally
available throughout the network. Since this is done via the link available throughout the network. Since this is done via the link
state routing protocol, any information of this nature must either state routing protocol, any information of this nature must either
be in the existing link state advertisements (LSAs) or the LSAs must be in the existing link state advertisements (LSAs) or the LSAs must
be supplemented to convey this information. For example, if it is be supplemented to convey this information. For example, if it is
desirable to offer different levels of service in a network based on desirable to offer different levels of service in a network based on
whether a circuit is routed over SDH/SONET lines that are ring whether a circuit is routed over SDH/SONET lines that are ring
protected versus being routed over those that are not ring protected protected versus being routed over those that are not ring protected
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(differentiation based on reliability), the type of protection on a (differentiation based on reliability), the type of protection on a
SDH/SONET line would be an important topological parameter that SDH/SONET line would be an important topological parameter that
would have to be distributed via the link state routing protocol. would have to be distributed via the link state routing protocol.
(ii) Information that is only needed between two "adjacent" switches (ii) Information that is only needed between two "adjacent" switches
for the purposes of connection establishment is appropriate for for the purposes of connection establishment is appropriate for
distribution via one of the label distribution protocols. In fact, distribution via one of the label distribution protocols. In fact,
this information can be thought of as the "virtual" label. For this information can be thought of as the "virtual" label. For
example, in SONET networks, when distributing information to example, in SONET networks, when distributing information to
switches concerning an end-to-end STS-1 path traversing a network, switches concerning an end-to-end STS-1 path traversing a network,
it is critical that adjacent switches agree on the multiplex entry it is critical that adjacent switches agree on the multiplex entry
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used by this STS-1 (but this information is only of local used by this STS-1 (but this information is only of local
significance between those two switches). Hence, the multiplex entry significance between those two switches). Hence, the multiplex entry
number in this case can be used as a virtual label. Note that the number in this case can be used as a virtual label. Note that the
label is virtual, in that it is not appended to the payload in any label is virtual, in that it is not appended to the payload in any
way, but it is still a label in the sense that it uniquely way, but it is still a label in the sense that it uniquely
identifies the signal locally on the link between the two switches. identifies the signal locally on the link between the two switches.
(iii) Information that all switches in the path need to know about a (iii) Information that all switches in the path need to know about a
circuit will also be distributed via the label distribution circuit will also be distributed via the label distribution
protocol. Examples of such information include bandwidth, priority, protocol. Examples of such information include bandwidth, priority,
and preemption for instance. and preemption for instance.
(iv) Information intended only for end systems of the connection. (iv) Information intended only for end systems of the connection.
Some of the payload type information in may fall into this category. Some of the payload type information in may fall into this category.
6. MPLS Routing for SDH/SONET 5. GMPLS Routing for SDH/SONET
Modern transport networks based on SONET/SDH excel at Modern transport networks based on SDH/SONET excel at
interoperability in the performance monitoring (PM) and fault interoperability in the performance monitoring (PM) and fault
management (FM) areas [10], [11]. They do not, however, inter- management (FM) areas [10], [11]. They do not, however, inter-
operate in the areas of topology discovery or resource status. operate in the areas of topology discovery or resource status.
Although link state routing protocols, such as IS-IS and OSPF, have Although link state routing protocols, such as IS-IS and OSPF, have
been used for some time in the IP world to compute destination-based been used for some time in the IP world to compute destination-based
next hops for routes (without routing loops), they are particularly next hops for routes (without routing loops), they are particularly
valuable for providing timely topology and network status valuable for providing timely topology and network status
information in a distributed manner, i.e., at any network node. If information in a distributed manner, i.e., at any network node. If
resource utilization information is disseminated along with the link resource utilization information is disseminated along with the link
status (as was done in ATM's PNNI routing protocol) then a very status (as was done in ATM's PNNI routing protocol) then a very
complete picture of network status is available to a network complete picture of network status is available to a network
operator for use in planning, provisioning and operations. operator for use in planning, provisioning and operations.
The information needed to compute the path a connection will take The information needed to compute the path a connection will take
through a network is important to distribute via the routing through a network is important to distribute via the routing
protocol. In the optical TDM case, this information includes, but protocol. In the TDM case, this information includes, but is not
is not limited to: the available capacity of the network links, the limited to: the available capacity of the network links, the
switching and termination capabilities of the nodes and interfaces, switching and termination capabilities of the nodes and interfaces,
and the protection properties of the link. This is what is being and the protection properties of the link. This is what is being
proposed in the GMPLS extensions to IP routing protocols [12], [13], proposed in the GMPLS extensions to IP routing protocols
[14]. [12],[13],[14].
When applying routing to circuit switched networks it is useful to When applying routing to circuit switched networks it is useful to
compare and contrast this situation with the datagram routing case compare and contrast this situation with the datagram routing case
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[15]. In the case of routing datagrams, all routes on all nodes [15]. In the case of routing datagrams, all routes on all nodes
must be calculated exactly the same to avoid loops and "black must be calculated exactly the same to avoid loops and "black
holes". In circuit switching, this is not the case since routes are holes". In circuit switching, this is not the case since routes are
established per circuit and are fixed for that circuit. Hence, established per circuit and are fixed for that circuit. Hence,
unlike the datagram case, routing is not service impacting in the unlike the datagram case, routing is not service impacting in the
circuit switched case. This is helpful, because, to accommodate the circuit switched case. This is helpful, because, to accommodate the
optical layer, routing protocols need to be supplemented with new optical layer, routing protocols need to be supplemented with new
information, much more than the datagram case. This information is information, much more than the datagram case. This information is
also likely to be used in different ways for implementing different also likely to be used in different ways for implementing different
user services. Due to the increase in information transferred in user services. Due to the increase in information transferred in
the routing protocol, it may be useful to separate the relatively the routing protocol, it may be useful to separate the relatively
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static parameters concerning a link from those that may be subject static parameters concerning a link from those that may be subject
to frequent changes. The current GMPLS routing extensions to frequent changes. The current GMPLS routing extensions
[12],[13],[14] do not make such a separation, however. [12],[13],[14] do not make such a separation, however.
6.1. Switching Capabilities Indeed, from the carriers' perspective, the up-to-date dissemination
of all link properties is essential and desired, and the use of a
link-state routing protocol to distribute this information provides
timely and efficient delivery. If GMPLS-based networks got to the
point that bandwidth updates happen very frequently, it makes sense,
from an efficiency point of view, to separate them out for update.
This situation is not yet seen in actual networks; however, if GMPLS
signaling is put into widespread use then the need could arise.
The main switching capabilities that characterize a SONET/SDH end 5.1. Switching Capabilities
The main switching capabilities that characterize a SDH/SONET end
system and thus need to be advertised via the link state routing system and thus need to be advertised via the link state routing
protocol are: the switching granularity, supported forms of protocol are: the switching granularity, supported forms of
concatenation, and the level of transparency. concatenation, and the level of transparency.
6.1.1. Switching Granularity 5.1.1. Switching Granularity
From references [4], [5] and the overview section on SONET/SDH we From references [4],[5] and the overview section on SDH/SONET we see
see that there are a number of different signals that compose the that there are a number of different signals that compose the
SONET/SDH hierarchies. Those signals that are referenced via a SDH/SONET hierarchies. Those signals that are referenced via a
pointer, i.e., the VCs in SDH and the SPEs in SONET are those that pointer, i.e., the VCs in SDH and the SPEs in SONET are those that
will actually be switched within a SONET/SDH network. These signals will actually be switched within a SDH/SONET network. These signals
are subdivided into lower order signals and higher order signals as are subdivided into lower order signals and higher order signals as
shown in Table 2. shown in Table 2.
Table 2. SDH/SONET switched signal groupings. Table 2. SDH/SONET switched signal groupings.
Signal Type SDH SONET Signal Type SDH SONET
Lower Order VC-11, VC-12, VC-2 VT-1.5 SPE, VT-2 SPE, Lower Order VC-11, VC-12, VC-2 VT-1.5 SPE, VT-2 SPE,
VT-3 SPE, VT-6 SPE VT-3 SPE, VT-6 SPE
Higher VC-3, VC-4 STS-1 SPE Higher VC-3, VC-4 STS-1 SPE, STS-3c SPE
Order Order
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Manufacturers today differ in the types of switching capabilities Manufacturers today differ in the types of switching capabilities
their systems support. Many manufacturers today switch signals their systems support. Many manufacturers today switch signals
starting at VC-4 for SDH or STS-1 for SONET (i.e. the basic frame) starting at VC-4 for SDH or STS-1 for SONET (i.e. the basic frame)
and above (see Section 6.1.2 on concatenation), but they do not and above (see Section 5.1.2 on concatenation), but they do not
switch lower order signals. Some of them only allow the switching of switch lower order signals. Some of them only allow the switching of
entire aggregates (concatenated or not) of signals such as 16 VC-4s, entire aggregates (concatenated or not) of signals such as 16 VC-4s,
i.e. a complete STM-16, and nothing finer. Some go down to the VC-3 i.e. a complete STM-16, and nothing finer. Some go down to the VC-3
level for SDH. Finally, some offer highly integrated switches that level for SDH. Finally, some offer highly integrated switches that
switch at the VC-3/STS-1 level down to lower order signals such as switch at the VC-3/STS-1 level down to lower order signals such as
VC-12s. In order to cover the needs of all manufacturers and VC-12s. In order to cover the needs of all manufacturers and
operators, GMPLS signaling [6],[7],[8] covers both higher order and operators, GMPLS signaling [6],[7],[8] covers both higher order and
lower order signals. lower order signals.
6.1.2. Signal Concatenation Capabilities 5.1.2. Signal Concatenation Capabilities
As stated in the SONET/SDH overview, to transport tributary signals As stated in the SDH/SONET overview, to transport tributary signals
with rates in excess of the basic STM-1/STS-1 signal, the VCs/SPEs with rates in excess of the basic STM-1/STS-1 signal, the VCs/SPEs
can be concatenated, i.e., glued together. Different types of can be concatenated, i.e., glued together. Different types of
concatenations are defined: contiguous standard concatenation, concatenations are defined: contiguous standard concatenation,
arbitrary concatenation, and virtual concatenation with different arbitrary concatenation, and virtual concatenation with different
rules concerning their size, placement, and binding. rules concerning their size, placement, and binding.
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Standard SONET concatenation allows the concatenation of M x STS-1 Standard SONET concatenation allows the concatenation of M x STS-1
signals within an STS-N signal with M <= N, and M = 3, 12, 48, 192, signals within an STS-N signal with M <= N, and M = 3, 12, 48, 192,
...). The SPEs of these M x STS-1s can be concatenated to form an ...). The SPEs of these M x STS-1s can be concatenated to form an
STS-Mc. The STS-Mc notation is short hand for describing an STS-M STS-Mc. The STS-Mc notation is short hand for describing an STS-M
signal whose SPEs have been concatenated. The multiplexing signal whose SPEs have been concatenated. The multiplexing
procedures for SDH and SONET are given in references [4] and [5], procedures for SDH and SONET are given in references [4] and [5],
respectively. Constraints are imposed on the size of STS-Mc signals, respectively. Constraints are imposed on the size of STS-Mc signals,
i.e., they must be a multiple of 3, and on their starting location i.e., they must be a multiple of 3, and on their starting location
and interleaving. and interleaving.
skipping to change at line 813 skipping to change at line 873
(where the rest of the signal gets put in terms of STS-1 slot (where the rest of the signal gets put in terms of STS-1 slot
numbers) leads to the requirement for re-grooming (due to bandwidth numbers) leads to the requirement for re-grooming (due to bandwidth
fragmentation). fragmentation).
Due to these disadvantages some SONET framer manufacturers now Due to these disadvantages some SONET framer manufacturers now
support "flexible" or arbitrary concatenation, i.e., no restrictions support "flexible" or arbitrary concatenation, i.e., no restrictions
on the size of an STS-Mc (as long as M <= N) and no constraints on on the size of an STS-Mc (as long as M <= N) and no constraints on
the STS-1 timeslots used to convey it, i.e., the signals can use any the STS-1 timeslots used to convey it, i.e., the signals can use any
combination of available time slots. combination of available time slots.
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Standard and flexible concatenations are network services, while Standard and flexible concatenations are network services, while
virtual concatenation is a SONET/SDH end-system service recently virtual concatenation is a SDH/SONET end-system service approved by
approved by the committee T1 of ANSI and ITU-T. The essence of this the Committee T1 of ANSI [5] and the ITU-T [4]. The essence of this
service is to have SONET/SDH end systems "glue" together the VCs or service is to have SDH/SONET end systems "glue" together the VCs or
SPEs of separate signals rather than requiring that he signals be SPEs of separate signals rather than requiring that he signals be
carried through the network as a single unit. In one example of carried through the network as a single unit. In one example of
virtual concatenation, two end systems supporting this feature could virtual concatenation, two end systems supporting this feature could
essentially "inverse multiplex" two STS-1s into a virtual STS-2c for essentially "inverse multiplex" two STS-1s into a STS-1-2v for the
the efficient transport of 100 Mbps Ethernet traffic. Note that this efficient transport of 100 Mbps Ethernet traffic. Note that this
inverse multiplexing process can be significantly easier to inverse multiplexing process (or virtual concatenation) can be
implement with SONET/SDH signals rather than packets. Since virtual significantly easier to implement with SDH/SONET signals rather than
concatenation is provided by end systems, it is compatible with packets, because timing and in-order delivery of frames is more
existing SONET/SDH networks. Virtual concatenation is defined for easily ensured with SDH/SONET signals than it is with packets, where
both higher order signals and low order signals. Table 3 shows the more sophisticated techniques are needed.
nomenclature and capacity for several lower-order virtually
concatenated signals contained within different higher-order Since virtual concatenation is provided by end systems, it is
signals. compatible with existing SDH/SONET networks. Virtual concatenation
is defined for both higher order signals and low order signals.
Table 3 shows the nomenclature and capacity for several lower-order
virtually concatenated signals contained within different higher-
order signals.
Table 3 Capacity of Virtually Concatenated VTn-Xv (9/G.707) Table 3 Capacity of Virtually Concatenated VTn-Xv (9/G.707)
Carried In X Capacity In steps Carried In X Capacity In steps
of of
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VT1.5/ STS-1/VC-3 1 to 28 1600kbit/s to 1600kbit/s VT1.5/ STS-1/VC-3 1 to 28 1600kbit/s to 1600kbit/s
VC-11-Xv 44800kbit/s VC-11-Xv 44800kbit/s
VT2/ STS-1/VC-3 1 to 21 2176kbit/s to 2176kbit/s VT2/ STS-1/VC-3 1 to 21 2176kbit/s to 2176kbit/s
VC-12-Xv 45696kbit/s VC-12-Xv 45696kbit/s
VT1.5/ STS-3c/VC-4 1 to 64 1600kbit/s to 1600kbit/s VT1.5/ STS-3c/VC-4 1 to 64 1600kbit/s to 1600kbit/s
VC-11-Xv 102400kbit/s VC-11-Xv 102400kbit/s
VT2/ STS-3c/VC-4 1 to 63 2176kbit/s to 2176kbit/s VT2/ STS-3c/VC-4 1 to 63 2176kbit/s to 2176kbit/s
VC-12-Xv 137088kbit/s VC-12-Xv 137088kbit/s
6.1.3. SDH/SONET Transparency 5.1.3. SDH/SONET Transparency
The purposed of SONET/SDH is to carry its payload signals in a The purposed of SDH/SONET is to carry its payload signals in a
transparent manner. This can include some of the layers of SONET transparent manner. This can include some of the layers of SONET
itself. For example, situations where the path overhead can never be itself. For example, situations where the path overhead can never be
touched, since it actually belongs to the client. This was another touched, since it actually belongs to the client. This was another
reason for not coding an explicit label in the SDH/SONET path reason for not coding an explicit label in the SDH/SONET path
overhead. It may be useful to transport, multiplex and/or switch overhead. It may be useful to transport, multiplex and/or switch
lower layers of the SONET signal transparently. lower layers of the SONET signal transparently.
As mentioned in the introduction, SONET overhead is broken into As mentioned in the introduction, SONET overhead is broken into
three layers: Section, Line and Path. Each of these layers is three layers: Section, Line and Path. Each of these layers is
concerned with fault and performance monitoring. The Section concerned with fault and performance monitoring. The Section
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overhead is primarily concerned with framing, while the Line overhead is primarily concerned with framing, while the Line
overhead is primarily concerned with multiplexing and protection. To overhead is primarily concerned with multiplexing and protection. To
perform multiplexing, a SONET network element should be line perform pipe multiplexing (that is, multiplexing of 50 Mbps or 150
terminating. However, not all SONET multiplexers/switches perform Mbps chunks), a SONET network element should be line terminating.
SONET pointer adjustments on all the STS-1s contained within a However, not all SONET multiplexers/switches perform SONET pointer
higher order SONET signal passing through them. Alternatively, if adjustments on all the STS-1s contained within a higher order SONET
they perform pointer adjustments, they do not terminate the line signal passing through them. Alternatively, if they perform pointer
overhead. For example, a multiplexer may take four SONET STS-48 adjustments, they do not terminate the line overhead. For example, a
signals and multiplex them onto an STS-192 without performing multiplexer may take four SONET STS-48 signals and multiplex them
standard line pointer adjustments on the individual STS-1s. This onto an STS-192 without performing standard line pointer adjustments
can be looked at as a service since it may be desirable to pass on the individual STS-1s. This can be looked at as a service since
SONET signals, like an STS-12 or STS-48, with some level of it may be desirable to pass SONET signals, like an STS-12 or STS-48,
transparency through a network and still take advantage of TDM with some level of transparency through a network and still take
technology. Transparent multiplexing and switching can also be advantage of TDM technology. Transparent multiplexing and switching
viewed as a constraint, since some multiplexers and switches may not can also be viewed as a constraint, since some multiplexers and
switch with as fine a granularity as others. Table 4 summarizes the switches may not switch with as fine a granularity as others. Table
levels of SONET/SDH transparency. 4 summarizes the levels of SDH/SONET transparency.
Table 4. SONET/SDH transparency types and their properties. Table 4. SDH/SONET transparency types and their properties.
Transparency Type Comments Transparency Type Comments
Path Layer (or Line Standard higher order SONET path Path Layer (or Line Standard higher order SONET path
Terminating) switching. Line overhead is terminated Terminating) switching. Line overhead is terminated
or modified. or modified.
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Line Level (or Section Preserves line overhead and switches Line Level (or Section Preserves line overhead and switches
Terminating) the entire line multiplex as a whole. Terminating) the entire line multiplex as a whole.
Section overhead is terminated or Section overhead is terminated or
modified. modified.
Section layer Preserves all section overhead, Section layer Preserves all section overhead,
Basically does not touch any of the Basically does not modify/terminate
SONET/SDH bits. any of the SDH/SONET overhead bits.
6.2. Protection 5.2. Protection
SONET and SDH networks offer a variety of protection options at both SONET and SDH networks offer a variety of protection options at both
the SONET line (SDH multiplex section) and SONET/SDH path level the SONET line (SDH multiplex section) and SDH/SONET path level
[10],[11]. Standardized SONET line level protection techniques [10],[11]. Standardized SONET line level protection techniques
include: Linear 1+1 and linear 1:N automatic protection switching include: Linear 1+1 and linear 1:N automatic protection switching
(APS) and both two-fiber and four-fiber bi-directional line switched (APS) and both two-fiber and four-fiber bi-directional line switched
rings (BLSRs). At the path layer, SONET offers uni-directional path rings (BLSRs). At the path layer, SONET offers uni-directional path
switched ring protection. Both ring and 1:N line protection also switched ring protection. Likewise, standardized SDH multiplex
allow for "extra traffic" to be carried over the protection line section protection techniques include linear 1+1 and 1:N automatic p
when that line is not being used, i.e., when it is not carrying protection switching and both two-fiber and four-fiber bi-
traffic for a failed working line. These protection methods are directional MS-SPRings (Multiplex Section-Shared Protection Rings).
summarized in Table 5. It should be noted that these protection At the path layer, SDH offers SNCP (sub-network connection
methods are completely separate from any MPLS layer protection or protection) ring protection.
restoration mechanisms.
Table 5. Common SONET/SDH protection mechanisms. Both ring and 1:N line protection also allow for "extra traffic" to
be carried over the protection line when that line is not being
used, i.e., when it is not carrying traffic for a failed working
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line. These protection methods are summarized in Table 5. It should
be noted that these protection methods are completely separate from
any MPLS layer protection or restoration mechanisms.
Table 5. Common SDH/SONET protection mechanisms.
Protection Type Extra Comments Protection Type Extra Comments
Traffic Traffic
Optionally Optionally
Supported Supported
1+1 No Requires no coordination 1+1 No Requires no coordination
Unidirectional between the two ends of the Unidirectional between the two ends of the
circuit. Dedicated circuit. Dedicated
protection line. protection line.
skipping to change at line 946 skipping to change at line 1021
1:N Yes One Protection line shared 1:N Yes One Protection line shared
by N working lines by N working lines
4F-BLSR (4 Yes Dedicated protection, with 4F-BLSR (4 Yes Dedicated protection, with
fiber bi- alternative ring path. fiber bi- alternative ring path.
directional directional
line switched line switched
ring) ring)
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2F-BLSR (2 Yes Dedicated protection, with 2F-BLSR (2 Yes Dedicated protection, with
fiber bi- alternative ring path fiber bi- alternative ring path
directional directional
line switched line switched
ring) ring)
UPSR (uni- No Dedicated protection via UPSR (uni- No Dedicated protection via
directional alternative ring path. directional alternative ring path.
path switched Typically used in access path switched Typically used in access
ring) networks. ring) networks.
It may be desirable to route some connections over lines that It may be desirable to route some connections over lines that
support protection of a given type, while others may be routed over support protection of a given type, while others may be routed over
unprotected lines, or as "extra traffic" over protection lines. unprotected lines, or as "extra traffic" over protection lines.
Also, to assist in the configuration of these various protection Also, to assist in the configuration of these various protection
methods it can be extremely valuable to advertise the link methods it can be extremely valuable to advertise the link
protection attributes in the routing protocol, as is done in the protection attributes in the routing protocol, as is done in the
current GMPLS routing protocols. For example, suppose that a 1:N current GMPLS routing protocols. For example, suppose that a 1:N
protection group is being configured via two nodes. One must make protection group is being configured via two nodes. One must make
sure that the lines are "numbered the same" with respect to both sure that the lines are "numbered the same" with respect to both
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ends of the connection or else the APS (K1/K2 byte) protocol will ends of the connection or else the APS (K1/K2 byte) protocol will
not correctly operate. not correctly operate.
Table 6. Parameters defining protection mechanisms. Table 6. Parameters defining protection mechanisms.
Protection Comments Protection Comments
Related Link Related Link
Information Information
Protection Type Indicates which of the protection types Protection Type Indicates which of the protection types
skipping to change at line 1000 skipping to change at line 1076
number protection line. number protection line.
Extra Traffic Yes or No Extra Traffic Yes or No
Supported Supported
Layer If this protection parameter is specific to Layer If this protection parameter is specific to
SONET then this parameter is unneeded, SONET then this parameter is unneeded,
otherwise it would indicate the signal otherwise it would indicate the signal
layer that the protection is applied. layer that the protection is applied.
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An open issue concerning protection is the extent of information An open issue concerning protection is the extent of information
regarding protection that must be disseminated. The contents of regarding protection that must be disseminated. The contents of
Table 6 represent one extreme while a simple enumerated list of: Table 6 represent one extreme while a simple enumerated list of:
Extra-Traffic/Protection line, Unprotected, Shared (1:N)/Working Extra-Traffic/Protection line, Unprotected, Shared (1:N)/Working
line, Dedicated (1:1, 1+1)/Working Line, Enhanced (Ring) /Working line, Dedicated (1:1, 1+1)/Working Line, Enhanced (Ring) /Working
Line, represents the other. Line, represents the other.
There is also a potential implication for link bundling [16], that There is also a potential implication for link bundling [16], [18]
is, for each link, the routing protocol could advertise whether that that is, for each link, the routing protocol could advertise whether
link is a working or protection link and possibly some parameters that link is a working or protection link and possibly some
from Table 6. A possible drawback of this scheme is that the routing parameters from Table 6. A possible drawback of this scheme is that
protocol would be burdened with advertising properties even for the routing protocol would be burdened with advertising properties
those protection links in the network that could not, in fact, be even for those protection links in the network that could not, in
used for routing working traffic, e.g., dedicated protection links. fact, be used for routing working traffic, e.g., dedicated
An alternative method would be to bundle the working and protection protection links. An alternative method would be to bundle the
links together, and advertise the bundle instead. Now, for each working and protection links together, and advertise the bundle
bundled link, the protocol would have to advertise the amount of instead. Now, for each bundled link, the protocol would have to
bandwidth available on its working links, as well as the amount of advertise the amount of bandwidth available on its working links, as
bandwidth available on those protection links within the bundle that well as the amount of bandwidth available on those protection links
were capable of carrying "extra traffic." This would reduce the
amount of information to be advertised. An issue here would be to
decide which types of working and protection links to bundle
together. For instance, it might be preferable to bundle working
links (and their corresponding protection links) that are "shared"
protected separately from working links that are "dedicated"
protected.
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within the bundle that were capable of carrying "extra traffic."
This would reduce the amount of information to be advertised. An
issue here would be to decide which types of working and protection
links to bundle together. For instance, it might be preferable to
bundle working links (and their corresponding protection links) that
are "shared" protected separately from working links that are
"dedicated" protected.
5.3. Available Capacity Advertisement
Each SDH/SONET LSR must maintain an internal table per interface Each SDH/SONET LSR must maintain an internal table per interface
that indicates each signal in the multiplex structure that is that indicates each signal in the multiplex structure that is
allocated at that interface. This internal table is the most allocated at that interface. This internal table is the most
complete and accurate view of the link usage and available capacity. complete and accurate view of the link usage and available capacity.
For use in path computation, this information needs to be advertised For use in path computation, this information needs to be advertised
in some way to all others SONET/SDH LSRs in the same domain. There in some way to all others SDH/SONET LSRs in the same domain. There
is a trade off to be reached concerning: the amount of detail in the is a trade off to be reached concerning: the amount of detail in the
available capacity information to be reported via a link state available capacity information to be reported via a link state
routing protocol, the frequency or conditions under which this routing protocol, the frequency or conditions under which this
information is updated, the percentage of connection establishments information is updated, the percentage of connection establishments
that are unsuccessful on their first attempt due to the granularity that are unsuccessful on their first attempt due to the granularity
of the advertised information, and the extent to which network of the advertised information, and the extent to which network
resources can be optimized. There are different levels of resources can be optimized. There are different levels of
summarization that are being considered today for the available summarization that are being considered today for the available
capacity information. At one extreme, all signals that are allocated capacity information. At one extreme, all signals that are allocated
on an interface could be advertised, while at the other extreme, a on an interface could be advertised, while at the other extreme, a
single aggregated value of the available bandwidth per link could be single aggregated value of the available bandwidth per link could be
advertised. advertised.
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Consider first the relatively simple structure of SONET and its most Consider first the relatively simple structure of SONET and its most
common current and planned usage. DS1s and DS3s are the signals most common current and planned usage. DS1s and DS3s are the signals most
often carried within a SONET STS-1. Either a single DS3 occupies often carried within a SONET STS-1. Either a single DS3 occupies
the STS-1 or up to 28 DS1s (4 each within the 7 VT groups) are the STS-1 or up to 28 DS1s (4 each within the 7 VT groups) are
carried within the STS-1. With a reasonable VT1.5 placement carried within the STS-1. With a reasonable VT1.5 placement
algorithm within each node it may be possible to just report on algorithm within each node it may be possible to just report on
aggregate bandwidth usage in terms of number of whole STS-1s aggregate bandwidth usage in terms of number of whole STS-1s
(dedicated to DS3s) used and the number of STS-1s dedicated to (dedicated to DS3s) used and the number of STS-1s dedicated to
carrying DS1s allocated for this purpose. This way a network carrying DS1s allocated for this purpose. This way a network
optimization program could try to determine the optimal placement of optimization program could try to determine the optimal placement of
DS3s and DS1s to minimize wasted bandwidth due to half-empty STS-1s DS3s and DS1s to minimize wasted bandwidth due to half-empty STS-1s
at various places within the transport network. Similarly consider at various places within the transport network. Similarly consider
the set of super rate SONET signals (STS-Nc). If the links between the set of super rate SONET signals (STS-Nc). If the links between
the two switches support flexible concatenation then the reporting the two switches support flexible concatenation then the reporting
is particularly straightforward since any of the STS-1s within an is particularly straightforward since any of the STS-1s within an
STS-M can be used to comprise the transported STS- Nc. However, if STS-M can be used to comprise the transported STS- Nc. However, if
only standard concatenation is supported then reporting gets only standard concatenation is supported then reporting gets
trickier since there are constraints on where the STS-1s can be trickier since there are constraints on where the STS-1s can be
placed. SDH has still more options and constraints, hence it is not placed. SDH has still more options and constraints, hence it is not
yet clear which is the best way to advertise bandwidth resource yet clear which is the best way to advertise bandwidth resource
availability/usage in SONET/SDH. At present, the GMPLS routing availability/usage in SDH/SONET. At present, the GMPLS routing
protocol extensions define minimum and maximum values for available protocol extensions define minimum and maximum values for available
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bandwidth, which allows a remote node to make some deductions about bandwidth, which allows a remote node to make some deductions about
the amount of capacity available at a remote link and the types of the amount of capacity available at a remote link and the types of
signals it can accommodate. However, due to the multiplexed nature signals it can accommodate. However, due to the multiplexed nature
of the signals, the authors are of the opinion that reporting of of the signals, the authors are of the opinion that reporting of
bandwidth particular to signal types rather than as a single bandwidth particular to signal types rather than as a single
aggregate bit rate is probably very desirable. aggregate bit rate is probably very desirable. For more details on
why this is so, we refer the reader to ITU-T G.7715.1 [19] and to
Chapter 12 of [20].
6.4. Path Computation 5.4. Path Computation
Although a link state routing protocol can be used to obtain network Although a link state routing protocol can be used to obtain network
topology and resource information, this does not imply the use of an topology and resource information, this does not imply the use of an
"open shortest path first" route [9]. The path must be open in the "open shortest path first" route [9]. The path must be open in the
sense that the links must be capable of supporting the desired sense that the links must be capable of supporting the desired
signal type and that capacity must be available to carry the signal type and that capacity must be available to carry the
signal. Other constraints may include hop count, total delay signal. Other constraints may include hop count, total delay
(mostly propagation), and underlying protection. In addition, it may (mostly propagation), and underlying protection. In addition, it may
be desirable to route traffic in order to optimize overall network be desirable to route traffic in order to optimize overall network
capacity, or reliability, or some combination of the two. Dikstra's capacity, or reliability, or some combination of the two. Dikstra's
skipping to change at line 1108 skipping to change at line 1188
a batch of connections between a set of endpoints in order to a batch of connections between a set of endpoints in order to
optimize network link utilization. One can think of this along the optimize network link utilization. One can think of this along the
lines of global or local optimization of the network in time. lines of global or local optimization of the network in time.
Due to the complexity of some of the connection routing algorithms Due to the complexity of some of the connection routing algorithms
(high dimensionality, non-linear integer programming problems) and (high dimensionality, non-linear integer programming problems) and
various criteria by which one may optimize a network, it may not be various criteria by which one may optimize a network, it may not be
possible or desirable to run these algorithms on network nodes. possible or desirable to run these algorithms on network nodes.
However, it may still be desirable to have some basic path However, it may still be desirable to have some basic path
computation ability running on the network nodes, particularly for computation ability running on the network nodes, particularly for
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use during restoration situations. Such an approach is in line with use during restoration situations. Such an approach is in line with
the use of MPLS for traffic engineering, but is much different than the use of MPLS for traffic engineering, but is much different than
typical OSPF or IS-IS usage where all nodes must run the same typical OSPF or IS-IS usage where all nodes must run the same
routing algorithm. routing algorithm.
7. LSP Provisioning/Signaling for SDH/SONET 6. LSP Provisioning/Signaling for SDH/SONET
Traditionally, end-to-end circuit connections in SDH/SONET networks Traditionally, end-to-end circuit connections in SDH/SONET networks
have been set up via network management systems (NMSs), which issue have been set up via network management systems (NMSs), which issue
commands (usually under the control of a human operator) to the commands (usually under the control of a human operator) to the
various network elements involved in the circuit, via an equipment various network elements involved in the circuit, via an equipment
vendor's element management system (EMS). Very little multi-vendor vendor's element management system (EMS). Very little multi-vendor
interoperability has been achieved via management systems. Hence, end- interoperability has been achieved via management systems. Hence,
to-end circuits in a multi-vendor environment typically require the end-to-end circuits in a multi-vendor environment typically require
use of multiple management systems and the infamous configuration via the use of multiple management systems and the infamous configuration
"yellow sticky notes". As discussed in Section 2, a common signaling via "yellow sticky notes". As discussed in Section 3, a common
protocol, such as RSVP with TE extensions or CR- LDP appropriately signaling protocol, such as RSVP with TE extensions or CR- LDP
extended for circuit switching applications, could therefore help to appropriately extended for circuit switching applications, could
solve these interoperability problems. In this section, we examine the therefore help to solve these interoperability problems. In this
various components involved in the automated provisioning of SONET/SDH
LSPs.
7.1.1. What do we Label in SDH/SONET? Frames or Circuits? Bernstein/Mannie/Sharma Expires January 2005 22
GMPLS based Control of SDH/SONET July 2004
section, we examine the various components involved in the automated
provisioning of SDH/SONET LSPs.
6.1. What do we Label in SDH/SONET? Frames or Circuits?
MPLS was initially introduced to control asynchronous technologies MPLS was initially introduced to control asynchronous technologies
like IP, where a label was attached to each individual block of like IP, where a label was attached to each individual block of
data, such as an IP packet or a Frame Relay frame. SONET and SDH, data, such as an IP packet or a Frame Relay frame. SONET and SDH,
however, are synchronous technologies that define a multiplexing however, are synchronous technologies that define a multiplexing
structure (see Section 3), which we referred to as the SDH (or structure (see Section 4), which we referred to as the SDH (or
SONET) multiplex. This multiplex involves a hierarchy of signals, SONET) multiplex. This multiplex involves a hierarchy of signals,
lower order signals embedded within successive higher order ones lower order signals embedded within successive higher order ones
(see Fig. 1). Thus, depending on its level in the hierarchy, each (see Fig. 1). Thus, depending on its level in the hierarchy, each
signal consists of frames that repeat periodically, with a certain signal consists of frames that repeat periodically, with a certain
number of byte time slots per frame. number of byte time slots per frame.
The question then arises: is it these frames that we label in GMPLS? The question then arises: is it these frames that we label in GMPLS?
It will be seen in what follows that each SONET or SDH "frame" It will be seen in what follows that each SONET or SDH "frame"
need not have its own label, nor is it necessary to switch frames need not have its own label, nor is it necessary to switch frames
individually. Rather, the unit that is switched is a "flow" individually. Rather, the unit that is switched is a "flow"
comprised of a continuous sequence of time slots that appear at a comprised of a continuous sequence of time slots that appear at a
given position in a frame. That is, we switch an individual SONET or given position in a frame. That is, we switch an individual SONET or
SDH signal, and a label associated with each given signal. SDH signal, and a label associated with each given signal.
For instance, the payload of an SDH STM-1 frame does not fully For instance, the payload of an SDH STM-1 frame does not fully
contain a complete unit of user data. In fact, the user data is contain a complete unit of user data. In fact, the user data is
contained in a virtual container (VC) that is allowed to float over contained in a virtual container (VC) that is allowed to float over
two contiguous frames for synchronization purposes. A pointer in the two contiguous frames for synchronization purposes. The H1-H2-H3 Au-
Section Overhead (SOH) indicates the beginning of the VC in the n pointer bytes in the SDH overhead indicates the beginning of the
payload. Thus, frames are now inter-related, since each consecutive VC in the payload. Thus, frames are now inter-related, since each
pair may share a common virtual container. From the point of view of consecutive pair may share a common virtual container. From the
GMPLS, therefore, it is not the successive frames that are treated point of view of GMPLS, therefore, it is not the successive frames
that are treated independently or labeled, but rather the entire
Bernstein, Mannie, Sharma Expires August 2003 21 user signal. An identical argument applies to SONET.
GMPLS based Control of SDH/SONET February 2003
independently or labeled, but rather the entire user signal. An
identical argument applies to SONET.
Observe also that the GMPLS signaling used to control the SDH/SONET Observe also that the GMPLS signaling used to control the SDH/SONET
multiplex must honor its hierarchy. In other words, the SDH/SONET multiplex must honor its hierarchy. In other words, the SDH/SONET
layer should not be viewed as homogeneous and flat, because this layer should not be viewed as homogeneous and flat, because this
would limit the scope of the services that SDH/SONET can provide. would limit the scope of the services that SDH/SONET can provide.
Instead, GMPLS tunnels should be used to dynamically and Instead, GMPLS tunnels should be used to dynamically and
hierarchically control the SDH/SONET multiplex. For example, one hierarchically control the SDH/SONET multiplex. For example, one
unstructured VC-4 LSP may be established between two nodes, and unstructured VC-4 LSP may be established between two nodes, and
later lower order LSPs (e.g. VC-12) may be created within that later lower order LSPs (e.g. VC-12) may be created within that
higher order LSP. This VC-4 LSP can, in fact, be established higher order LSP. This VC-4 LSP can, in fact, be established
between two non-adjacent internal nodes in an SDH network, and later between two non-adjacent internal nodes in an SDH network, and later
advertised by a routing protocol as a new (virtual) link called a advertised by a routing protocol as a new (virtual) link called a
Forwarding Adjacency (FA). Forwarding Adjacency (FA) [17].
A SONET/SDH-LSR will have to identify each possible signal A SDH/SONET-LSR will have to identify each possible signal
individually per interface to fulfill the GMPLS operations. In order individually per interface to fulfill the GMPLS operations. In order
to stay transparent the LSR obviously should not touch the SONET/SDH to stay transparent the LSR obviously should not touch the SDH/SONET
overheads; this is why an explicit label is not encoded in the overheads; this is why an explicit label is not encoded in the
SDH/SONET overheads. Rather, a label is associated with each SDH/SONET overheads. Rather, a label is associated with each
Bernstein/Mannie/Sharma Expires January 2005 23
GMPLS based Control of SDH/SONET July 2004
individual signal. This approach is similar to the one considered individual signal. This approach is similar to the one considered
for lambda switching, except that it is more complex, since SONET for lambda switching, except that it is more complex, since SONET
and SDH define a richer multiplexing structure. Therefore a label and SDH define a richer multiplexing structure. Therefore a label
is associated with each signal, and is locally unique for each is associated with each signal, and is locally unique for each
signal at each interface. This signal could, and will most probably, signal at each interface. This signal could, and will most probably,
occupy different time-slots at different interfaces. occupy different time-slots at different interfaces.
7.2. Label Structure in SDH/SONET 6.2. Label Structure in SDH/SONET
The signaling protocol used to establish an SDH/SONET LSP must have The signaling protocol used to establish an SDH/SONET LSP must have
specific information elements in it to map a label to the particular specific information elements in it to map a label to the particular
signal type that it represents, and to the position of that signal signal type that it represents, and to the position of that signal
in the SONET/SDH multiplex. As we will see shortly, with a in the SDH/SONET multiplex. As we will see shortly, with a
carefully chosen label structure, the label itself can be made to carefully chosen label structure, the label itself can be made to
function as this information element. function as this information element.
In general, there are two ways to assign labels for signals between In general, there are two ways to assign labels for signals between
neighboring SDH/SONET LSRs. One way is for the labels to be neighboring SDH/SONET LSRs. One way is for the labels to be
allocated completely independently of any SDH/SONET semantics; e.g. allocated completely independently of any SDH/SONET semantics; e.g.
labels could just be unstructured 16 or 32 bit numbers. In that labels could just be unstructured 16 or 32 bit numbers. In that
case, in the absence of appropriate binding information, a label case, in the absence of appropriate binding information, a label
gives no visible information about the flow that it represents. From gives no visible information about the flow that it represents. From
a management and debugging point of view, therefore, it becomes a management and debugging point of view, therefore, it becomes
difficult to match a label with the corresponding signal, since , as difficult to match a label with the corresponding signal, since , as
we saw in Section 7.1.1, the label is not coded in the SDH/SONET we saw in Section 6.1, the label is not coded in the SDH/SONET
overhead of the signal. overhead of the signal.
Another way is to use the well-defined and finite structure of the Another way is to use the well-defined and finite structure of the
SDH/SONET multiplexing tree to devise a signal numbering scheme that SDH/SONET multiplexing tree to devise a signal numbering scheme that
makes use of the multiplex as a naming tree, and assigns each makes use of the multiplex as a naming tree, and assigns each
multiplex entry a unique associated value. This allows the unique multiplex entry a unique associated value. This allows the unique
identification of each multiplex entry (signal) in terms of its type identification of each multiplex entry (signal) in terms of its type
Bernstein, Mannie, Sharma Expires August 2003 22
GMPLS based Control of SDH/SONET February 2003
and position in the multiplex tree. By using this multiplex entry and position in the multiplex tree. By using this multiplex entry
value itself as the label, we automatically add SDH/SONET semantics value itself as the label, we automatically add SDH/SONET semantics
to the label! Thus, simply by examining the label, one can now to the label! Thus, simply by examining the label, one can now
directly deduce the signal that it represents, as well as its directly deduce the signal that it represents, as well as its
position in the SDH/SONET multiplex. We refer to this as position in the SDH/SONET multiplex. We refer to this as
multiplex-based labeling. This is the idea that was incorporated in multiplex-based labeling. This is the idea that was incorporated in
the GMPLS signaling specifications for SDH/SONET [17]. the GMPLS signaling specifications for SDH/SONET [18].
7.3. Signaling Elements 6.3. Signaling Elements
In the preceding sections, we defined the meaning of a SDH/SONET In the preceding sections, we defined the meaning of a SDH/SONET
label and specified its structure. A question that arises naturally label and specified its structure. A question that arises naturally
at this point is the following. In an LSP or connection setup at this point is the following. In an LSP or connection setup
request, how do we specify the signal for which we want to establish request, how do we specify the signal for which we want to establish
a path (and for which we desire a label)? a path (and for which we desire a label)?
Clearly, information that is required to completely specify the Clearly, information that is required to completely specify the
desired signal and its characteristics must be transferred via the desired signal and its characteristics must be transferred via the
label distribution protocol, so that the switches along the path can label distribution protocol, so that the switches along the path can
be configured to correctly handle and switch the signal. This be configured to correctly handle and switch the signal. This
information is specified in three parts [17], each of which refers
Bernstein/Mannie/Sharma Expires January 2005 24
GMPLS based Control of SDH/SONET July 2004
information is specified in three parts [18], each of which refers
to a different network layer. to a different network layer.
1. GENERALIZED_LABEL REQUEST (as in [6], [7]), which contains three
parts: LSP Encoding Type, Switching Type, and G-PID.
The first specifies the nature/type of the LSP or the desired The first specifies the nature/type of the LSP or the desired
SDH/SONET channel, in terms of the particular signal (or collection SDH/SONET channel, in terms of the particular signal (or collection
of signals) within the SDH/SONET multiplex that the LSP represents, of signals) within the SDH/SONET multiplex that the LSP represents,
and is used by all the nodes along the path of the LSP. and is used by all the nodes along the path of the LSP.
The second specifies the payload carried by the LSP or SDH/SONET The second specifies certain link selection constraints, which
control, at each hop, the selection of the underlying link that is
used to transport this LSP.
The third specifies the payload carried by the LSP or SDH/SONET
channel, in terms of the termination and adaptation functions channel, in terms of the termination and adaptation functions
required at the end points, and is used by the source and required at the end points, and is used by the source and
destination nodes of the LSP. destination nodes of the LSP.
The third specifies certain link selection constraints, which 2. SONET/SDH TRAFFIC_PARAMETERS (as in [17], Section 2.1) used as a
control, at each hop, the selection of the underlying link that is SENDER_TSPEC/FLOWSPEC, which contains 6 parts: Signal Type,
used to transport this LSP. (Requested Contiguous Concatenation (RCC), Number of Contiguous
Components (NCC), Number of Virtual Components (NVC)), Multiplier
(MT), Transparency, and Profile.
8. Summary and Conclusions The Signal Type indicates the type of elementary signal comprising
the LSP, while the remaining fields indicate transforms that can be
applied to the basic signal to build the final signal that
corresponds to the LSP actually being requested. For instance (see
[18] for details):
- Contiguous concatenation (by using the RCC and NCC
fields) can be optionally applied on the Elementary Signal,
resulting in a contiguously concatenated signal.
- Then, virtual concatenation (by using the NVC field) can be
optionally applied on the Elementary Signal resulting in
a virtually concatenated signal.
- Third, some transparency (by using the Transparency field)
can be optionally specified when requesting a frame as
signal rather than an SPE or VC based signal.
- Fourth, a multiplication (by using the Multiplier field)
can be optionally applied either directly 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.
Transparency indicates precisely which fields in these overheads
must be delivered unmodified at the other end of the LSP. An ingress
Bernstein/Mannie/Sharma Expires January 2005 25
GMPLS based Control of SDH/SONET July 2004
LSR requesting transparency will pass these overhead fields that
must be delivered to the egress LSR without any change. From the
ingress and egress LSRs point of views, these fields must be seen as
unmodified.
Transparency is not applied at the interfaces with the initiating
and terminating LSRs, but is only applied between intermediate LSRs.
The transparency field is used to request an LSP that supports the
requested transparency type; it may also be used to setup the
transparency process to be applied at each intermediate LSR.
Finally, the profile field is intended particular capabilities that
must be supported for the LSP, for example monitoring capabilities.
No standard profile is currently defined, however.
3. UPSTREAM_LABEL for Bi-directional LSP's (as in [6], [7]).
4. Local Link Selection e.g. IF_ID_RSVP_HOP Object (as in [7]).
7. Summary and Conclusions
We provided a detailed account of the issues involved in applying We provided a detailed account of the issues involved in applying
MPLS-based control to TDM networks. generalized MPLS-based control (GMPLS) to TDM networks.
We began with a brief overview of MPLS and SDH/SONET networks, We began with a brief overview of MPLS and SDH/SONET networks,
discussing current circuit establishment in TDM networks, and discussing current circuit establishment in TDM networks, and
arguing why SDH/SONET technologies will not be "outdated" in the arguing why SDH/SONET technologies will not be "outdated" in the
foreseeable future. Next, we looked at MPLS applied to SDH/SONET foreseeable future. Next, we looked at IP/MPLS applied to SDH/SONET
networks, where we considered why such an application makes sense, networks, where we considered why such an application makes sense,
and reviewed some MPLS terminology as applied to TDM networks. We and reviewed some MPLS terminology as applied to TDM networks.
considered the two main areas of application of MPLS methods to TDM
networks, namely routing and signaling. We reviewed in detail the
switching capabilities of TDM equipment, and the requirement to
Bernstein, Mannie, Sharma Expires August 2003 23 We considered the two main areas of application of IP/MPLS methods
GMPLS based Control of SDH/SONET February 2003 to TDM networks, namely routing and signaling, and discussed how
Generalized MPLS routing and signaling are used in the context of
TDM networks. We reviewed in detail the switching capabilities of
TDM equipment, and the requirement to learn about the protection
capabilities of underlying links, and how these influence the
available capacity advertisement in TDM networks.
learn about the protection capabilities of underlying links, and how We focused briefly on path computation methods, pointing out that
these influence the available capacity advertisement in TDM these were not subject to standardization. We then examined optical
networks. We focused briefly on path computation methods, pointing path provisioning or signaling, considering the issue of what
out that these were not subject to standardization. We then examined constitutes an appropriate label for TDM circuits and how this label
optical path provisioning or signaling, considering the issue of should be structured, and we focused on the importance of
what constitutes an appropriate label for TDM circuits and how this
label should be structured, and we focused on the importance of
hierarchical label allocation in a TDM network. Finally, we reviewed hierarchical label allocation in a TDM network. Finally, we reviewed
the signaling elements involved when setting up an optical TDM the signaling elements involved when setting up an TDM circuit,
circuit, focusing on the nature of the LSP, the type of payload it focusing on the nature of the LSP, the type of payload it carries,
carries, and the characteristics of the links that the LSP wishes to and the characteristics of the links that the LSP wishes to use at
use at each hop along its path for achieving a certain reliability. each hop along its path for achieving a certain reliability.
9. Security Considerations Bernstein/Mannie/Sharma Expires January 2005 26
GMPLS based Control of SDH/SONET July 2004
8. Security Considerations
This draft raises no new security issues in the MPLS specifications. This draft raises no new security issues in the MPLS specifications.
10.Acknowledgments 9. Acknowledgments
We acknowledge all the participants of the MPLS and CCAMP WGs, whose We acknowledge all the participants of the MPLS and CCAMP WGs, whose
constant enquiry about GMPLS issues in TDM networks motivated the constant enquiry about GMPLS issues in TDM networks motivated the
writing of this document, and whose questions helped shape its writing of this document, and whose questions helped shape its
contents. Also, thanks to Kireeti Kompella for his careful reading contents. Also, thanks to Kireeti Kompella for his careful reading
of the last version of this draft, and for his helpful comments and of the last version of this draft, and for his helpful comments and
feedback. feedback, and to Dimitri Papadimitriou for his review on behalf of
the Routing Area Directorate, which provided many useful inputs to
help update the document to confirm to the standards evolutions
since this document passed last call.
11.Author's Addresses 10.Author's Addresses
Greg Bernstein Greg Bernstein
Grotto Networking Grotto Networking
Phone: +1 510 573-2237 Phone: +1 510 573-2237
E-mail: greg@ciena.com E-mail: gregb@grotto-networking.com
Eric Mannie Eric Mannie
InterAir Link InterAir Link
Phone: +32 2 790 34 25 Phone: +32 2 790 34 25
E-mail: eric_mannie@hotmail.com E-mail: eric_mannie@hotmail.com
Vishal Sharma Vishal Sharma
Metanoia, Inc. Metanoia, Inc.
1600 Villa Street, Unit 352 888 Villa Street, Suite 200B
Mountain View, CA 94041 Mountain View, CA 94041
Phone: +1 408 530 8313
Phone: +1 650 386 6723
Email: v.sharma@ieee.org Email: v.sharma@ieee.org
Bernstein, Mannie, Sharma Expires August 2003 24 11.References
GMPLS based Control of SDH/SONET February 2003
Full Copyright Statement
"Copyright (C) The Internet Society (date). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into
12.References 11.1. Normative References
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP [1] Bradner, S., "The Internet Standards Process -- Revision 3",
9, RFC 2026, October 1996. BCP 9, RFC 2026, October 1996.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[3] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol Label [3] Rosen, E., Viswanathan, A., and Callon, R., "Multiprotocol
Switching Architecture", RFC 3031, January 2001. Label Switching Architecture", RFC 3031, January 2001.
Bernstein/Mannie/Sharma Expires January 2005 27
GMPLS based Control of SDH/SONET July 2004
[4] G.707, Network Node Interface for the Synchronous Digital [4] G.707, Network Node Interface for the Synchronous Digital
Hierarchy (SDH), International Telecommunication Union, 03/96. Hierarchy (SDH), International Telecommunication Union, March
1996.
[5] Synchronous Optical Network (SONET) Basic Description including [5] ANSI T1.105-1995, Synchronous Optical Network (SONET) Basic
Multiplex Structure, Rates, and Formats, ANSI T1.105-1995. Description including Multiplex Structure, Rates, and Formats,
American National Standards Institute.
[6] Berger, L. (Editor), "Generalized MPLS - - Signaling Functional [6] Berger, L. (Editor), "Generalized MPLS - - Signaling Functional
Description," RFC 3472, January 2003. Description," RFC 3471, January 2003.
[7] Berger, L. (Editor), "Generalized MPLS Signaling - - RSVP-TE [7] Berger, L. (Editor), "Generalized MPLS Signaling - - RSVP-TE
Extensions," RFC 3473, January 2003. Extensions," RFC 3473, January 2003.
[8] Berger, L. (Editor), "Generalized MPLS Signaling - - CR-LDP [8] Berger, L. (Editor), "Generalized MPLS Signaling - - CR-LDP
Extensions," RFC 3473, January 2003. Extensions," RFC 3473, January 2003.
[9] Bernstein, G., Yates, J., Saha, D., "IP-Centric Control and [9] Bernstein, G., Yates, J., Saha, D., "IP-Centric Control and
Management of Optical Transport Networks," IEEE Communications Management of Optical Transport Networks," IEEE Communications
Mag., Vol. 40, Issue 10, October 2000. Mag., Vol. 40, Issue 10, October 2000.
[10] ANSI T1.105.01-1995, Synchronous Optical Network (SONET) [10] ANSI T1.105.01-1995, Synchronous Optical Network (SONET)
Automatic Protection Switching, American National Standards Automatic Protection Switching, American National Standards
Institute. Institute.
Bernstein, Mannie, Sharma Expires August 2003 25
GMPLS based Control of SDH/SONET February 2003
[11] G.841, Types and Characteristics of SDH Network Protection [11] G.841, Types and Characteristics of SDH Network Protection
Architectures, ITU-T, 07/95. Architectures, ITU-T, July 1995.
11.2. Informative References
[12] Kompella, K., et al, "Routing Extensions in Support of [12] Kompella, K., et al, "Routing Extensions in Support of
Generalize MPLS, " Internet Draft, Work-in-Progress, draft-ietf- Generalized MPLS," Internet Draft, Work-in-Progress, draft-
ccamp-gmpls-routing-05.txt, August 2002. ietf-ccamp-gmpls-routing-09.txt, October 2003.
[13] Kompella, K., et al, "OSPF Extensions in Support of Generalize [13] Kompella, K., et al, "OSPF Extensions in Support of Generalized
MPLS," Internet Draft, Work-in-Progress, draft-ietf-ccamp-ospf- MPLS," Internet Draft, Work-in-Progress, draft-ietf-ccamp-
extensions-09.txt, December 2002. ospf-extensions-12.txt, October 2003.
[14] Kompella, K., et al, "IS-IS Extensions in Support of Generalize [14] Kompella, K., et al, "IS-IS Extensions in Support of
MPLS," Internet Draft, Work-in-Progress, draft-ietf-isis-gmpls- Generalized MPLS," Internet Draft, Work-in-Progress, draft-
extensions-16.txt, August 2002. ietf-isis-gmpls-extensions-16.txt, August 2002.
[15] Bernstein, G., Sharma, V., Ong, L., ææInter-domain Optical [15] Bernstein, G., Sharma, V., Ong, L., "Inter-domain Optical
Routing,ÆÆ OSA J. of Optical Networking, vol. 1, no. 2, pp. 80-92. Routing, " OSA J. of Optical Networking, vol. 1, no. 2, pp. 80-
92.
[16] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling in [16] Kompella, K., Rekhter, Y., and Berger, L., "Link Bundling in
MPLS Traffic Engineering", Internet Draft, Work-in-Progress, MPLS Traffic Engineering", Internet Draft, Work-in-Progress,
draft-ietf-mpls-bundle-04.txt, July 2002. draft-ietf-mpls-bundle-04.txt, July 2002.
[17] Mannie, E. (Editor), "GMPLS Extensions for SONET and SDH [17] Kompella, K., Rekhter, Y., "LSP Hierarchy with Generalized
MPLS-TE", Internet Draft, Work-in-Progress, draft-ietf-mpls-
lsp-hierarchy-08.txt, September 2002.
Bernstein/Mannie/Sharma Expires January 2005 28
GMPLS based Control of SDH/SONET July 2004
[18] Mannie, E. (Editor), "GMPLS Extensions for SONET and SDH
Control", Internet Draft, Work-in-Progress, draft-ietf-ccamp- Control", Internet Draft, Work-in-Progress, draft-ietf-ccamp-
gmpls-sonet-sdh-07.txt, October 2002. gmpls-sonet-sdh-08.txt, February 2003.
Bernstein, Mannie, Sharma Expires August 2003 26 [19] G.7715.1, ASON Routing Architecture and Requirements for Link-
State Protocols, International Telecommunications Union,
February 2004.
[20] Bernstein, G., Rajagopalan, R., and Saha, D., "Optical Network
Control: Protocols, Architectures, and Standards," Addison-
Wesley, July 2003.
12.Intellectual Property Considerations
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology described
in this document or the extent to which any license under such
rights might or might not be available; nor does it represent that
it has made any independent effort to identify any such rights.
Information on the procedures with respect to rights in RFC
documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
12.1. IPR Disclosure Acknowledgement
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance
with RFC 3668.
13.Full Copyright Statement
"Copyright (C) The Internet Society (2004). This document is
subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights."
Bernstein/Mannie/Sharma Expires January 2005 29
GMPLS based Control of SDH/SONET July 2004
"This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE Of
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
Bernstein/Mannie/Sharma Expires January 2005 30
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