Network Working Group                         Eric Mannie - Editor
   Internet Draft
   Category: Standard Track

   Expiration date: November 2003                            May 2003

          Generalized Multi-Protocol Label Switching Architecture


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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   Future data and transmission networks will consist of elements such
   as routers, switches, Dense Wavelength Division Multiplexing (DWDM)
   systems, Add-Drop Multiplexors (ADMs), photonic cross-connects
   (PXCs), optical cross-connects (OXCs), etc. that will use
   Generalized Multi-Protocol Label Switching (GMPLS) to dynamically
   provision resources and to provide network survivability using
   protection and restoration techniques.

   This document describes the architecture of GMPLS. GMPLS extends
   MPLS to encompass time-division (e.g. SONET/SDH, PDH, G.709),
   wavelength (lambdas), and spatial switching (e.g. incoming port or
   fiber to outgoing port or fiber). The focus of GMPLS is on the
   control plane of these various layers since each of them can use
   physically diverse data or forwarding planes. The intention is to
   cover both the signaling and the routing part of that control plane.

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1. Table of Contents

   Status of this Memo .............................................. 1
   Abstract ......................................................... 1
   1. Table of Contents ............................................. 2
   2. Conventions used in this document ............................. 3
   3. Introduction .................................................. 3
   3.1. Acronyms & Abbreviations .................................... 4
   3.2. Multiple Types of Switching and Forwarding Hierarchies ...... 4
   3.3. Extension of the MPLS Control Plane ......................... 6
   3.4. GMPLS Key Extensions to MPLS-TE ............................. 9
   4. Routing and Addressing Mode .................................. 10
   4.1. Addressing of PSC and non-PSC layers ....................... 11
   4.2. GMPLS Scalability Enhancements ............................. 11
   4.3. TE Extensions to IP Routing Protocols ...................... 12
   5. Unnumbered Links ............................................. 13
   5.1. Unnumbered Forwarding Adjacencies .......................... 14
   6. Link Bundling ................................................ 14
   6.1. Restrictions on Bundling ................................... 15
   6.2. Routing Considerations for Bundling ........................ 15
   6.3. Signaling Considerations ................................... 16
   6.3.1 Mechanism 1: Implicit Indication .......................... 16
   6.3.2 Mechanism 2: Explicit Indication by Numbered Interface ID . 16
   6.3.3 Mechanism 3: Explicit Indication by Unnumbered Interface ID 16
   6.4. Unnumbered Bundled Link .................................... 17
   6.5. Forming Bundled Links ...................................... 17
   7. Relationship with the UNI .................................... 18
   7.1. Relationship with the OIF UNI .............................. 18
   7.2. Reachability across the UNI ................................ 19
   8. Link Management .............................................. 19
   8.1. Control Channel and Control Channel Management ............. 20
   8.2. Link Property Correlation .................................. 21
   8.3. Link Connectivity Verification ............................. 21
   8.4. Fault Management ........................................... 22
   8.5. LMP for DWDM Optical Line Systems (OLSs) ................... 23
   9. Generalized Signaling ........................................ 24
   9.1. Overview: How to Request an LSP ............................ 25
   9.2. Generalized Label Request .................................. 26
   9.3. SONET/SDH Traffic Parameters ............................... 27
   9.4. G.709 Traffic Parameters ................................... 28
   9.5. Bandwidth Encoding ......................................... 29
   9.6. Generalized Label .......................................... 29
   9.7. Waveband Switching ......................................... 30
   9.8. Label Suggestion by the Upstream ........................... 30
   9.9. Label Restriction by the Upstream .......................... 31
   9.10. Bi-directional LSP ........................................ 31
   9.11. Bi-directional LSP Contention Resolution .................. 32
   9.12. Rapid Notification of Failure ............................. 33
   9.13. Link Protection ........................................... 33
   9.14. Explicit Routing and Explicit Label Control ............... 34
   9.15. Route Recording ........................................... 35
   9.16. LSP Modification and LSP Re-routing ....................... 35
   9.17. LSP Administrative Status Handling ........................ 36
   9.18. Control Channel Separation ................................ 36

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   10. Forwarding Adjacencies (FA) ................................. 37
   10.1. Routing and Forwarding Adjacencies ........................ 38
   10.2. Signaling Aspects ......................................... 39
   10.3. Cascading of Forwarding Adjacencies ....................... 39
   11. Routing and Signaling Adjacencies ........................... 39
   12. Control Plane Fault Handling ................................ 40
   13. LSP Protection and Restoration .............................. 41
   13.1. Protection Escalation across Domains and Layers ........... 42
   13.2. Mapping of Services to P&R Resources ...................... 43
   13.3. Classification of P&R Mechanism Characteristics ........... 43
   13.4. Different Stages in P&R ................................... 44
   13.5. Recovery Strategies ....................................... 44
   13.6. Recovery mechanisms: Protection schemes ................... 45
   13.7. Recovery mechanisms: Restoration schemes .................. 45
   13.8. Schema Selection Criteria ................................. 46
   14. Network Management .......................................... 48
   14.1. Network Management Systems (NMS) .......................... 48
   14.2. Management Information Base (MIB) ......................... 48
   14.3. Tools ..................................................... 49
   14.4. Fault Correlation Between Multiple Layers ................. 49
   15. Security Considerations ..................................... 50
   16. Acknowledgements ............................................ 51
   17. Intellectual Property Considerations ........................ 51
   18. References .................................................. 51
   18.1 Normative References ....................................... 51
   18.2 Information References ..................................... 54
   19. Author's Address ............................................ 55
   20. Contributors ................................................ 55
   Full Copyright Statement ........................................ 58

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   this document are to be interpreted as described in [RFC2119].

3. Introduction

   The architecture described in this document covers the main building
   blocks needed to build a consistent control plane for multiple
   switching layers. It does not restrict the way that these layers
   work together. Different models can be applied: e.g. overlay,
   augmented or integrated. Moreover, each pair of contiguous layers
   may collaborate in different ways, resulting in a number of possible
   combinations, at the discretion of manufacturers and operators.

   This architecture clearly separates the control plane and the
   forwarding plane. In addition, it also clearly separates the control
   plane in two parts, the signaling plane containing the signaling
   protocols and the routing plane containing the routing protocols.

   This document is a generalization of the Multi-Protocol Label
   Switching (MPLS) architecture [RFC3031], and in some cases may
   differ slightly from that architecture since non packet-based

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   forwarding planes are now considered. It is not the intention of
   this document to describe concepts already described in the current
   MPLS architecture. The goal is to describe specific concepts of
   Generalized MPLS (GMPLS).

   However, some of the concepts explained hereafter are not part of
   the current MPLS architecture and are applicable to both MPLS and
   GMPLS (i.e. link bundling, unnumbered links, and LSP hierarchy).
   Since these concepts were introduced together with GMPLS and since
   they are of paramount importance for an operational GMPLS network,
   they will be discussed here.

   The organization of the remainder of this document is as follows. We
   begin with an introduction of GMPLS. We then present the specific
   GMPLS building blocks and explain how they can be combined together
   to build an operational GMPLS network. Specific details of the
   separate building blocks can be found in the corresponding

3.1. Acronyms & Abbreviations

   AS           Autonomous System
   BGP          Border Gateway Protocol
   CR-LDP       Constraint-based Routing LDP
   CSPF         Constraint-based Shortest Path First
   DWDM         Dense Wavelength Division Multiplexing
   FA           Forwarding Adjacency
   GMPLS        Generalized Multi-Protocol Label Switching
   IGP          Interior Gateway Protocol
   LDP          Label Distribution Protocol
   LMP          Link Management Protocol
   LSA          Link State Advertisement
   LSR          Label Switching Router
   LSP          Label Switched Path
   MIB          Management Information Base
   MPLS         Multi-Protocol Label Switching
   NMS          Network Management System
   OXC          Optical Cross-Connect
   PXC          Photonic Cross-Connect
   RSVP         ReSource reserVation Protocol
   SDH          Synchronous Digital Hierarchy
   SONET        Synchronous Optical Networks
   STM(-N)      Synchronous Transport Module (-N)
   STS(-N)      Synchronous Transport Signal-Level N (SONET)
   TDM          Time Division Multiplexing
   TE           Traffic Engineering

3.2. Multiple Types of Switching and Forwarding Hierarchies

   Generalized MPLS (GMPLS) differs from traditional MPLS in that it
   supports multiple types of switching, i.e. the addition of support
   for TDM, lambda, and fiber (port) switching. The support for the
   additional types of switching has driven GMPLS to extend certain
   base functions of traditional MPLS and, in some cases, to add

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   functionality. These changes and additions impact basic LSP
   properties: how labels are requested and communicated, the
   unidirectional nature of LSPs, how errors are propagated, and
   information provided for synchronizing the ingress and egress LSRs.

   The MPLS architecture [RFC3031] was defined to support the
   forwarding of data based on a label. In this architecture, Label
   Switching Routers (LSRs) were assumed to have a forwarding plane
   that is capable of (a) recognizing either packet or cell boundaries,
   and (b) being able to process either packet headers (for LSRs
   capable of recognizing packet boundaries) or cell headers (for LSRs
   capable of recognizing cell boundaries).

   The original MPLS architecture is here being extended to include
   LSRs whose forwarding plane recognizes neither packet, nor cell
   boundaries, and therefore, can't forward data based on the
   information carried in either packet or cell headers. Specifically,
   such LSRs include devices where the switching decision is based on
   time slots, wavelengths, or physical ports. So, the new set of LSRs,
   or more precisely interfaces on these LSRs, can be subdivided into
   the following classes:

   1. Packet Switch Capable (PSC) interfaces:

   Interfaces that recognize packet boundaries and can forward data
   based on the content of the packet header. Examples include
   interfaces on routers that forward data based on the content of the
   IP header and interfaces on routers that switch data based on the
   content of the MPLS "shim" header.

   2. Layer-2 Switch Capable (L2SC) interfaces:

   Interfaces that recognize frame/cell boundaries and can switch data
   based on the content of the frame/cell header. Examples include
   interfaces on Ethernet bridges that switch data based on the content
   of the MAC header and interfaces on ATM-LSRs that forward data based
   on the ATM VPI/VCI.

   3. Time-Division Multiplex Capable (TDM) interfaces:

   Interfaces that switch data based on the data's time slot in a
   repeating cycle. An example of such an interface is that of a
   SONET/SDH Cross-Connect (XC), Terminal Multiplexer (TM), or Add-Drop
   Multiplexer (ADM). Other examples include interfaces providing G.709
   TDM capabilities (the "digital wrapper") and PDH interfaces.

   4. Lambda Switch Capable (LSC) interfaces:

   Interfaces that switch data based on the wavelength on which the
   data is received. An example of such an interface is that of a
   Photonic Cross-Connect (PXC) or Optical Cross-Connect (OXC) that can
   operate at the level of an individual wavelength. Additional
   examples include PXC interfaces that can operate at the level of a

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   group of wavelengths, i.e. a waveband and G.709 interfaces providing
   optical capabilities.

   5. Fiber-Switch Capable (FSC) interfaces:

   Interfaces that switch data based on a position of the data in the
   (real world) physical spaces. An example of such an interface is
   that of a PXC or OXC that can operate at the level of a single or
   multiple fibers.

   A circuit can be established only between, or through, interfaces of
   the same type. Depending on the particular technology being used for
   each interface, different circuit names can be used, e.g. SDH
   circuit, optical trail, light-path, etc. In the context of GMPLS,
   all these circuits are referenced by a common name: Label Switched
   Path (LSP).

   The concept of nested LSP (LSP within LSP), already available in the
   traditional MPLS, facilitates building a forwarding hierarchy, i.e.
   a hierarchy of LSPs. This hierarchy of LSPs can occur on the same
   interface, or between different interfaces.

   For example, a hierarchy can be built if an interface is capable of
   multiplexing several LSPs from the same technology (layer), e.g. a
   lower order SONET/SDH LSP (e.g. VT2/VC-12) nested in a higher order
   SONET/SDH LSP (e.g. STS-3c/VC-4). Several levels of signal (LSP)
   nesting are defined in the SONET/SDH multiplexing hierarchy.

   The nesting can also occur between interface types. At the top of
   the hierarchy are FSC interfaces, followed by LSC interfaces,
   followed by TDM interfaces, followed by L2SC, and followed by PSC
   interfaces. This way, an LSP that starts and ends on a PSC interface
   can be nested (together with other LSPs) into an LSP that starts and
   ends on a L2SC interface. This LSP, in turn, can be nested (together
   with other LSPs) into an LSP that starts and ends on a TDM
   interface. In turn, this LSP can be nested (together with other
   LSPs) into an LSP that starts and ends on a LSC interface, which in
   turn can be nested (together with other LSPs) into an LSP that
   starts and ends on a FSC interface.

3.3. Extension of the MPLS Control Plane

   The establishment of LSPs that span only Packet Switch Capable (PSC)
   or Layer-2 Switch Capable (L2SC) interfaces is defined for the
   original MPLS and/or MPLS-TE control planes. GMPLS extends these
   control planes to support each of the five classes of interfaces
   (i.e. layers) defined in the previous section.

   Note that the GMPLS control plane supports an overlay model, an
   augmented model, and a peer (integrated) model. In the near term,
   GMPLS appears to be very suitable for controlling each layer
   independently. This elegant approach will facilitate the future
   deployment of other models.

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   The GMPLS control plane is made of several building blocks are
   described in more detail in the following sections. These building
   blocks are based on well-known signaling and routing protocols that
   have been extended and/or modified to support GMPLS. They use IPv4
   and/or IPv6 addresses. Only one new specialized protocol is required
   to support the operations of GMPLS, a signaling protocol for link
   management [LMP].

   GMPLS is indeed based on the Traffic Engineering (TE) extensions to
   MPLS, a.k.a. MPLS-TE [RFC2702]. This, because most of the
   technologies that can be used below the PSC level requires some
   traffic engineering. The placement of LSPs at these levels needs in
   general to consider several constraints (such as framing, bandwidth,
   protection capability, etc) and to bypass the legacy Shortest-Path
   First (SPF) algorithm. Note, however, that this is not mandatory and
   that in some cases SPF routing can be applied.

   In order to facilitate constrained-based SPF routing of LSPs, nodes
   that perform LSP establishment need more information about the links
   in the network than standard intra-domain routing protocols provide.
   These TE attributes are distributed using the transport mechanisms
   already available in IGPs (e.g. flooding) and taken into
   consideration by the LSP routing algorithm. Optimization of the LSP
   routes may also require some external simulations using heuristics
   that serve as input for the actual path calculation and LSP
   establishment process.

   By definition, a TE link is a representation in the IS-IS/OSPF Link
   State advertisements and in the link state database of certain
   physical resources, and their properties, between two GMPLS nodes.
   TE Links are used by the GMPLS control plane (routing and signaling)
   for establishing LSPs.

   Extensions to traditional routing protocols and algorithms are
   needed to uniformly encode and carry TE link information, and
   explicit routes (e.g. source routes) are required in the signaling.
   In addition, the signaling must now be capable of transporting the
   required circuit (LSP) parameters such as the bandwidth, the type of
   signal, the desired protection and/or restoration, the position in a
   particular multiplex, etc. Most of these extensions have already
   been defined for PSC and L2SC traffic engineering with MPLS. GMPLS
   primarily defines additional extensions for TDM, LSC, and FSC
   traffic engineering. A very few elements are technology specific.

   Thus, GMPLS extends the two signaling protocols defined for MPLS-TE
   signaling, i.e. RSVP-TE [RFC3209] and CR-LDP [RFC3212]. However,
   GMPLS does not specify which one of these two signaling protocols
   must be used. It is the role of manufacturers and operators to
   evaluate the two possible solutions for their own interest.

   Since GMPLS signalling is based on RSVP-TE and CR-LDP, it mandates a
   downstream-on-demand label allocation and distribution, with ingress
   initiated ordered control. Liberal label retention is normally used,
   but conservative label retention mode could also be used.

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   Furthermore, there is no restriction on the label allocation
   strategy, it can be request/signaling driven (obvious for circuit
   switching technologies), traffic/data driven, or even topology
   driven. There is also no restriction on the route selection;
   explicit routing is normally used (strict or loose) but hop-by-hop
   routing could be used as well.

   GMPLS also extends two traditional intra-domain link-state routing
   protocols already extended for TE purposes, i.e. OSPF-TE [OSPF-TE]
   and IS-IS-TE [ISIS-TE]. However, if explicit (source) routing is
   used, the routing algorithms used by these protocols no longer need
   to be standardized. Extensions for inter-domain routing (e.g. BGP)
   are for further study.

   The use of technologies like DWDM (Dense Wavelength Division
   Multiplexing) implies that we can now have a very large number of
   parallel links between two directly adjacent nodes (hundreds of
   wavelengths, or even thousands of wavelengths if multiple fibers are
   used). Such a large number of links was not originally considered
   for an IP or MPLS control plane, although it could be done. Some
   slight adaptations of that control plane are thus required if we
   want to better reuse it in the GMPLS context.

   For instance, the traditional IP routing model assumes the
   establishment of a routing adjacency over each link connecting two
   adjacent nodes. Having such a large number of adjacencies does not
   scale well. Each node needs to maintain each of its adjacencies one
   by one, and link state routing information must be flooded
   throughout the network.

   To solve this issue the concept of link bundling was introduced.
   Moreover, the manual configuration and control of these links, even
   if they are unnumbered, becomes impractical. The Link Management
   Protocol (LMP) was specified to solve these issues.

   LMP runs between data plane adjacent nodes and is used to manage TE
   links. Specifically, LMP provides mechanisms to maintain control
   channel connectivity (IP Control Channel Maintenance), verify the
   physical connectivity of the data-bearing links (Link Verification),
   correlate the link property information (Link Property Correlation),
   and manage link failures (Fault Localization and Fault
   Notification). A unique feature of LMP is that it is able to
   localize faults in both opaque and transparent networks (i.e.
   independent of the encoding scheme and bit rate used for the data).

   LMP is defined in the context of GMPLS, but is specified
   independently of the GMPLS signaling specification since it is a
   local protocol running between data-plane adjacent nodes.
   Consequently, LMP can be used in other contexts with non-GMPLS
   signaling protocols.

   MPLS signaling and routing protocols require at least one bi-
   directional control channel to communicate even if two adjacent
   nodes are connected by unidirectional links. Several control

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   channels can be used. LMP can be used to establish, maintain and
   manage these control channels.

   GMPLS does not specify how these control channels must be
   implemented, but GMPLS requires IP to transport the signaling and
   routing protocols over them. Control channels can be either in-band
   or out-of-band, and several solutions can be used to carry IP. Note
   also that one type of LMP message (the Test message) is used in-band
   in the data plane and may not be transported over IP, but this is a
   particular case, needed to verify connectivity in the data plane.

3.4. GMPLS Key Extensions to MPLS-TE

   Some key extensions brought by GMPLS to MPLS-TE are highlighted in
   the following. Some of them are key advantages of GMPLS to control
   TDM, LSC and FSC layers.

   - In MPLS-TE, links traversed by an LSP can include an intermix of
   links with heterogeneous label encoding (e.g. links between routers,
   links between routers and ATM-LSRs, and links between ATM-LSRs.
   GMPLS extends this by including links where the label is encoded as
   a time slot, or a wavelength, or a position in the (real world)
   physical space.

   - In MPLS-TE, an LSP that carries IP has to start and end on a
   router. GMPLS extends this by requiring an LSP to start and end on
   similar type of interfaces.

   - The type of a payload that can be carried in GMPLS by an LSP is
   extended to allow such payloads as SONET/SDH, G.709, 1Gb or 10Gb
   Ethernet, etc.

   - The use of Forwarding Adjacencies (FA) provides a mechanism that
   can improve bandwidth utilization, when bandwidth allocation can be
   performed only in discrete units. It offers also a mechanism to
   aggregate forwarding state, thus allowing the number of required
   labels to be reduced.

   - GMPLS allows suggesting a label by an upstream node to reduce the
   setup latency. This suggestion may be overridden by a downstream
   node but in some cases, at the cost of higher LSP setup time.

   - GMPLS extends on the notion of restricting the range of labels
   that may be selected by a downstream node. In GMPLS, an upstream
   node may restrict the labels for an LSP along either a single hop or
   the entire LSP path. This feature is useful in photonic networks
   where wavelength conversion may not be available.

   - While traditional TE-based (and even LDP-based) LSPs are
   unidirectional, GMPLS supports the establishment of bi-directional

   - GMPLS supports the termination of an LSP on a specific egress
   port, i.e. the port selection at the destination side.

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   - GMPLS with RSVP-TE supports an RSVP specific mechanism for rapid
   failure notification.

   Note also some other key differences between MPLS-TE and GMPLS:

   - For TDM, LSC and FSC interfaces, bandwidth allocation for an LSP
   can be performed only in discrete units.

   - It is expected to have (much) fewer labels on TDM, LSC or FSC
   links than on PSC or L2SC links, because the former are physical
   labels instead of logical labels.

4. Routing and Addressing Model

   GMPLS is based on the IP routing and addressing models. This assumes
   that IPv4 and/or IPv6 addresses are used to identify interfaces but
   also that traditional (distributed) IP routing protocols are reused.
   Indeed, the discovery of the topology and the resource state of all
   links in a routing domain is achieved via these routing protocols.

   Since control and data planes are de-coupled in GMPLS, control-plane
   neighbors (i.e. IGP-learnt neighbors) may not be data-plane
   neighbors. Hence, mechanisms like LMP are needed to associate TE
   links with neighboring nodes.

   IP addresses are not used only to identify interfaces of IP hosts
   and routers, but more generally to identify any PSC and non-PSC
   interfaces. Similarly, IP routing protocols are used to find routes
   for IP datagrams with a SPF algorithm; they are also used to find
   routes for non-PSC circuits by using a CSPF algorithm.

   However, some additional mechanisms are needed to increase the
   scalability of these models and to deal with specific traffic
   engineering requirements of non-PSC layers. These mechanisms will be
   introduced in the following.

   Re-using existing IP routing protocols allows for non-PSC layers
   taking advantage of all the valuable developments that took place
   since years for IP routing, in particular, in the context of intra-
   domain routing (link-state routing) and inter-domain routing (policy

   In an overlay model, each particular non-PSC layer can be seen as a
   set of Autonomous Systems (ASs) interconnected in an arbitrary way.
   Similarly to the traditional IP routing, each AS is managed by a
   single administrative authority. For instance, an AS can be an
   SONET/SDH network operated by a given carrier. The set of
   interconnected ASs can be viewed as SONET/SDH internetworks.

   Exchange of routing information between ASs can be done via an
   inter-domain routing protocol like BGP-4. There is obviously a huge
   value of re-using well-known policy routing facilities provided by
   BGP in a non-PSC context. Extensions for BGP traffic engineering

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   (BGP-TE) in the context of non-PSC layers are left for further

   Each AS can be sub-divided in different routing domains, and each
   can run a different intra-domain routing protocol. In turn, each
   routing-domain can be divided in areas.

   A routing domain is made of GMPLS enabled nodes (i.e. a network
   device including a GMPLS entity). These nodes can be either edge
   nodes (i.e. hosts, ingress LSRs or egress LSRs), or internal LSRs.
   An example of non-PSC host is an SONET/SDH Terminal Multiplexer
   (TM). Another example is an SONET/SDH interface card within an IP
   router or ATM switch.

   Note that traffic engineering in the intra-domain requires the use
   of link-state routing protocols like OSPF or IS-IS.

   GMPLS defines extensions to these protocols. These extensions are
   needed to disseminate specific TDM, LSC and FSC static and dynamic
   characteristics related to nodes and links. The current focus is on
   intra-area traffic engineering. However, inter-area traffic
   engineering is also under investigation.

4.1. Addressing of PSC and non-PSC Layers

   The fact that IPv4 and/or IPv6 addresses are used doesn't imply at
   all that they should be allocated in the same addressing space than
   public IPv4 and/or IPv6 addresses used for the Internet. Private IP
   addresses can be used if they don't require to be exchanged with any
   other operator; public IP addresses are otherwise required. Of
   course, if an integrated model is used, two layers could share the
   same addressing space. Finally, TE links may be "unnumbered" i.e.
   not have any IP addresses, in case IP addresses are not available,
   or the overhead of managing them is considered too high.

   Note that there is a benefit of using public IPv4 and/or IPv6
   Internet addresses for non-PSC layers if an integrated model with
   the IP layer is foreseen.

   If we consider the scalability enhancements proposed in the next
   section, the IPv4 (32 bits) and the IPv6 (128 bits) addressing
   spaces are both more than sufficient to accommodate any non-PSC
   layer. We can reasonably expect to have much less non-PSC devices
   (e.g. SONET/SDH nodes) than we have today IP hosts and routers.

4.2. GMPLS Scalability Enhancements

   TDM, LSC and FSC layers introduce new constraints on the IP
   addressing and routing models since several hundreds of parallel
   physical links (e.g. wavelengths) can now connect two nodes. Most of
   the carriers already have today several tens of wavelengths per
   fiber between two nodes. New generation of DWDM systems will allow
   several hundreds of wavelengths per fiber.

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   It becomes rather impractical to associate an IP address with each
   end of each physical link, to represent each link as a separate
   routing adjacency, and to advertise and to maintain link states for
   each of these links. For that purpose, GMPLS enhances the MPLS
   routing and addressing models to increase their scalability.

   Two optional mechanisms can be used to increase the scalability of
   the addressing and the routing: unnumbered links and link bundling.
   These two mechanisms can also be combined. They require extensions
   to signaling (RSVP-TE and CR-LDP) and routing (OSPF-TE and IS-IS-TE)

4.3. TE Extensions to IP Routing Protocols

   Traditionally, a TE link is advertised as an adjunct to a "regular"
   OSPF or IS-IS link, i.e., an adjacency is brought up on the link.
   When the link is up, both the regular IGP properties of the link
   (basically, the SPF metric) and the TE properties of the link are
   then advertised.

   However, GMPLS challenges this notion in three ways:

   - First, links that are non-PSC may yet have TE properties; however,
   an OSPF adjacency could not be brought up directly on such links.

   - Second, an LSP can be advertised as a point-to-point TE link in
   the routing protocol, i.e. as a Forwarding Adjacency (FA); thus, an
   advertised TE link need no longer be between two OSPF direct
   neighbors. Forwarding Adjacencies (FA) are further described in
   Section 10.

   - Third, a number of links may be advertised as a single TE link
   (e.g. for improved scalability), so again, there is no longer a one-
   to-one association of a regular adjacency and a TE link.

   Thus, we have a more general notion of a TE link. A TE link is a
   logical link that has TE properties. Some of these properties may be
   configured on the advertising LSR, others may be obtained from other
   LSRs by means of some protocol, and yet others may be deduced from
   the component(s) of the TE link.

   An important TE property of a TE link is related to the bandwidth
   accounting for that link. GMPLS will define different accounting
   rules for different non-PSC layers. Generic bandwidth attributes are
   however defined by the TE routing extensions and by GMPLS, such as
   the unreserved bandwidth, the maximum reservable bandwidth and the
   maximum LSP bandwidth.

   It is expected in a dynamic environment to have frequent changes of
   bandwidth accounting information. A flexible policy for triggering
   link state updates based on bandwidth thresholds and link-dampening
   mechanism can be implemented.

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   TE properties associated with a link should also capture protection
   and restoration related characteristics. For instance, shared
   protection can be elegantly combined with bundling. Protection and
   restoration are mainly generic mechanisms also applicable to MPLS.
   It is expected that they will first be developed for MPLS and later
   on generalized to GMPLS.

   A TE link between a pair of LSRs doesn't imply the existence of an
   IGP adjacency between these LSRs. A TE link must also have some
   means by which the advertising LSR can know of its liveness (e.g. by
   using LMP hellos). When an LSR knows that a TE link is up, and can
   determine the TE link's TE properties, the LSR may then advertise
   that link to its GMPLS enhanced OSPF or IS-IS neighbors using the TE
   objects/TLVs. We call the interfaces over which GMPLS enhanced OSPF
   or IS-IS adjacencies are established "control channels".

5. Unnumbered Links

   Unnumbered links (or interfaces) are links (or interfaces) that do
   not have IP addresses. Using such links involves two capabilities:
   the ability to specify unnumbered links in MPLS TE signaling, and
   the ability to carry (TE) information about unnumbered links in IGP
   TE extensions of IS-IS-TE and OSPF-TE.

   A. The ability to specify unnumbered links in MPLS TE signaling
     requires extensions to RSVP-TE [RFC3477] and CR-LDP [RFC3480]. The
     MPLS-TE signaling doesn't provide support for unnumbered links,
     because it doesn't provide a way to indicate an unnumbered link in
     its Explicit Route Object/TLV and in its Record Route Object
     (there is no such TLV for CR-LDP). GMPLS defines simple extensions
     to indicate an unnumbered link in these two Objects/TLVs, using a
     new Unnumbered Interface ID sub-object/sub-TLV.

     Since unnumbered links are not identified by an IP address, then
     for the purpose of MPLS TE each end need some other identifier,
     local to the LSR to which the link belongs. LSRs at the two end-
     points of an unnumbered link exchange with each other the
     identifiers they assign to the link. Exchanging the identifiers
     may be accomplished by configuration, by means of a protocol such
     as LMP ([LMP]), by means of RSVP-TE/CR-LDP (especially in the case
     where a link is a Forwarding Adjacency, see below), or by means of
     IS-IS or OSPF extensions ([ISIS-TE-GMPLS], [OSPF-TE-GMPLS]).

     Consider an (unnumbered) link between LSRs A and B. LSR A chooses
     an identifier for that link. So does LSR B. From A's perspective
     we refer to the identifier that A assigned to the link as the
     "link local identifier" (or just "local identifier"), and to the
     identifier that B assigned to the link as the "link remote
     identifier" (or just "remote identifier"). Likewise, from B's
     perspective the identifier that B assigned to the link is the
     local identifier, and the identifier that A assigned to the link
     is the remote identifier.

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     The new Unnumbered Interface ID sub-object/sub-TLV for the ER
     Object/TLV contains the Router ID of the LSR at the upstream end
     of the unnumbered link and the link local identifier with respect
     to that upstream LSR.

     The new Unnumbered Interface ID sub-object for the RR Object
     contains the link local identifier with respect to the LSR that
     adds it in the RR Object.

   B. The ability to carry (TE) information about unnumbered links in
     IGP TE extensions requires new sub-TLVs for the extended IS
     reachability TLV defined in IS-IS-TE and for the TE LSA (which is
     an opaque LSA) defined in OSPF-TE. A Link Local Identifier sub-TLV
     and a Link Remote Identifier sub-TLV are defined.

5.1. Unnumbered Forwarding Adjacencies

   If an LSR that originates an LSP advertises this LSP as an
   unnumbered FA in IS-IS or OSPF, or the LSR uses this FA as an
   unnumbered component link of a bundled link, the LSR must allocate
   an Interface ID to that FA. If the LSP is bi-directional, the tail
   end does the same and allocates an Interface ID to the reverse FA.

   Signaling has been enhanced to carry the Interface ID of a FA in the
   new LSP Tunnel Interface ID object/TLV. This object/TLV contains the
   Router ID (of the LSR that generates it) and the Interface ID. It is
   called the Forward Interface ID when it appears in a Path/REQUEST
   message, and it is called the Reverse Interface ID when it appears
   in the Resv/MAPPING message.

6. Link Bundling

   The concept of link bundling is essential in certain networks
   employing the GMPLS control plane as is defined in [BUNDLE]. A
   typical example is an optical meshed network where adjacent optical
   cross-connects (LSRs) are connected by several hundreds of parallel
   wavelengths. In this network, consider the application of link state
   routing protocols, like OSPF or IS-IS, with suitable extensions for
   resource discovery and dynamic route computation. Each wavelength
   must be advertised separately to be used, except if link bundling is

   When a pair of LSRs is connected by multiple links, it is possible
   to advertise several (or all) of these links as a single link into
   OSPF and/or IS-IS. This process is called link bundling, or just
   bundling. The resulting logical link is called a bundled link as its
   physical links are called component links (and are identified by
   interface indexes).

   The result is that a combination of three identifiers ((bundled)
   link identifier, component link identifier, label) is sufficient to
   unambiguously identify the appropriate resources used by an LSP.

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   The purpose of link bundling is to improve routing scalability by
   reducing the amount of information that has to be handled by OSPF
   and/or IS-IS. This reduction is accomplished by performing
   information aggregation/abstraction. As with any other information
   aggregation/abstraction, this results in losing some of the
   information. To limit the amount of losses one need to restrict the
   type of the information that can be aggregated/abstracted.

6.1. Restrictions on Bundling

   The following restrictions are required for bundling links. All
   component links in a bundle must begin and end on the same pair of
   LSRs; and share some common characteristics or properties defined in
   [OSPF-TE] and [ISIS-TE], i.e. they must have the same:

   - Link Type (i.e. point-to-point or multi-access),
   - TE Metric (i.e. an administrative cost),
   - Set of Resource Classes at each end of the links (i.e. colors).

   Note that a FA may also be a component link. In fact, a bundle can
   consist of a mix of point-to-point links and FAs, but all sharing
   some common properties.

6.2. Routing Considerations for Bundling

   A bundled link is just another kind of TE link such as those defined
   by [GMPLS-ROUTING]. The liveness of the bundled link is determined
   by the liveness of each its component links. A bundled link is alive
   when at least one of its component links is alive. The liveness of a
   component link can be determined by any of several means: IS-IS or
   OSPF hellos over the component link, or RSVP Hello (hop local), or
   LMP hellos (link local), or from layer 1 or layer 2 indications.

   Note that (according to the RSVP-TE specification [RFC3209]) the
   RSVP Hello mechanism is intended to be used when notification of
   link layer failures is not available and unnumbered links are not
   used, or when the failure detection mechanisms provided by the link
   layer are not sufficient for timely node failure detection.

   Once a bundled link is determined to be alive, it can be advertised
   as a TE link and the TE information can be flooded. If IS-IS/OSPF
   hellos are run over the component links, IS-IS/OSPF flooding can be
   restricted to just one of the component links.

   Note that advertising a (bundled) TE link between a pair of LSRs
   doesn't imply that there is an IGP adjacency between these LSRs that
   is associated with just that link. In fact, in certain cases a TE
   link between a pair of LSRs could be advertised even if there is no
   IGP adjacency at all between the LSR (e.g. when the TE link is an

   Forming a bundled link consist in aggregating the identical TE
   parameters of each individual component link to produce aggregated

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   TE parameters. A TE link as defined by [GMPLS-ROUTING] has many
   parameters; adequate aggregation rules must be defined for each one.

   Some parameters can be sums of component characteristics such as the
   unreserved bandwidth and the maximum reservable bandwidth. Bandwidth
   information is an important part of a bundle advertisement and it
   must be clearly defined since an abstraction is done.

   A GMPLS node with bundled links must apply admission control on a
   per-component link basis.

6.3. Signaling Considerations

   Typically, an LSP's explicit route (e.g. contained in an explicit
   route Object/TLV) will choose the bundled link to be used for the
   LSP, but not the component link(s). This because information about
   the bundled link is flooded but information about the component
   links is not.

   The choice of the component link to use is always made by an
   upstream node. If the LSP is bi-directional, the upstream node
   chooses a component link in each direction.

   Three mechanisms for indicating this choice to the downstream node
   are possible.

6.3.1. Mechanism 1: Implicit Indication

   This mechanism requires that each component link has a dedicated
   signaling channel (e.g., the link is a Sonet/SDH link using the DCC
   for in-band signaling). The upstream node tells the receiver which
   component link to use by sending the message over the chosen
   component link's dedicated signaling channel. Note that this
   signaling channel can be in-band or out-of-band. In this last case,
   the association between the signaling channel and that component
   link need to be explicitly configured.

6.3.2. Mechanism 2: Explicit Indication by Numbered Interface ID

   This mechanism requires that the component link has a unique remote
   IP address. The upstream node indicates the choice of the component
   link by including a new IF_ID RSVP_HOP object/IF_ID TLV carrying
   either an IPv4 or an IPv6 address in the Path/Label Request message
   (see [RFC3473]/[RFC3472], respectively). For a bi-directional LSP, a
   component link is provided for each direction by the upstream node.

   This mechanism does not require each component link to have its own
   control channel. In fact, it doesn't even require the whole
   (bundled) link to have its own control channel.

6.3.3. Mechanism 3: Explicit Indication by Unnumbered Interface ID

   With this mechanism, each component link that is unnumbered is
   assigned a unique Interface Identifier (32 bits value). The upstream

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   node indicates the choice of the component link by including a new
   IF_ID RSVP_HOP object/IF_ID TLV in the Path/Label Request message
   (see [RFC3473]/[RFC3472], respectively).

   This object/TLV carries the component interface ID in the downstream
   direction for a unidirectional LSP, and in addition, the component
   interface ID in the upstream direction for a bi-directional LSP.

   The two LSRs at each end of the bundled link exchange these
   identifiers. Exchanging the identifiers may be accomplished by
   configuration, by means of a protocol such as LMP (preferred
   solution), by means of RSVP-TE/CR-LDP (especially in the case where
   a component link is a Forwarding Adjacency), or by means of IS-IS or
   OSPF extensions.

   This mechanism does not require each component link to have its own
   control channel. In fact, it doesn't even require the whole
   (bundled) link to have its own control channel.

6.4. Unnumbered Bundled Link

   A bundled link may itself be numbered or unnumbered independent of
   whether the component links are numbered or not. This affects how
   the bundled link is advertised in IS-IS/OSPF and the format of LSP
   EROs that traverse the bundled link. Furthermore, unnumbered
   Interface Identifiers for all unnumbered outgoing links of a given
   LSR (whether component links, Forwarding Adjacencies or bundled
   links) must be unique in the context of that LSR.

6.5. Forming Bundled Links

   The generic rule for bundling component links is to place those
   links that are correlated in some manner in the same bundle. If
   links may be correlated based on multiple properties then the
   bundling may be applied sequentially based on these properties. For
   instance, links may be first grouped based on the first property.
   Each of these groups may be then divided into smaller groups based
   on the second property and so on. The main principle followed in
   this process is that the properties of the resulting bundles should
   be concisely summarizable. Link bundling may be done automatically
   or by configuration. Automatic link bundling can apply bundling
   rules sequentially to produce bundles.

   For instance, the first property on which component links may be
   correlated could be the Interface Switching Capability [GMPLS-
   ROUTING], the second property could be the Encoding [GMPLS-ROUTING],
   the third property could be the Administrative Weight (cost), the
   fourth property could be the Resource Classes and finally links may
   be correlated based on other metrics such as SRLG (Shared Risk Link

   When routing an alternate path for protection purposes, the general
   principle followed is that the alternate path is not routed over any
   link belonging to an SRLG that belongs to some link of the primary

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   path. Thus, the rule to be followed is to group links belonging to
   exactly the same set of SRLGs.

   This type of sequential sub-division may result in a number of
   bundles between two adjacent nodes. In practice, however, the link
   properties may not be very heterogeneous among component links
   between two adjacent nodes. Thus, the number of bundles in practice
   may not be large.

7. Relationship with the UNI

   The interface between an edge GMPLS node and a GMPLS LSR on the
   network side may be referred to as a User to Network Interface
   (UNI), while the interface between two-network side LSRs may be
   referred to as a Network to Network Interface (NNI).

   GMPLS does not specify separately a UNI and an NNI. Edge nodes are
   connected to LSRs on the network side, and these LSRs are in turn
   connected between them. Of course, the behavior of an edge node is
   not exactly the same as the behavior of an LSR on the network side.
   Note also, that an edge node may run a routing protocol, however it
   is expected that in most of the cases it will not (see also section
   7.2 and the section about signaling with an explicit route).

   Conceptually, a difference between UNI and NNI make sense either if
   both interface uses completely different protocols, or if they use
   the same protocols but with some outstanding differences. In the
   first case, separate protocols are often defined successively, with
   more or less success.

   The GMPLS approach consisted in building a consistent model from day
   one, considering both the UNI and NNI interfaces at the same time
   [GMPLS-OVERLAY]. For that purpose, a very few specific UNI
   particularities have been ignored in a first time. GMPLS has been
   enhanced to support such particularities at the UNI by some other
   standardization bodies (see hereafter).

7.1. Relationship with the OIF UNI

   This section is only given for reference to the OIF work related to
   GMPLS. The current OIF UNI specification [OIF-UNI] defines an
   interface between a client SONET/SDH equipment and an SONET/SDH
   network, each belonging to a distinct administrative authority. It
   is designed for an overlay model. The OIF UNI defines additional
   mechanisms on the top of GMPLS for the UNI.

   For instance, the OIF service discovery procedure is a precursor to
   obtaining UNI services. Service discovery allows a client to
   determine the static parameters of the interconnection with the
   network, including the UNI signaling protocol, the type of
   concatenation, the transparency level as well as the type of
   diversity (node, link, SRLG) supported by the network.

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   Since the current OIF UNI interface does not cover photonic
   networks, G.709 Digital Wrapper, etc, it is from that perspective a
   subset of the GMPLS Architecture at the UNI.

7.2. Reachability across the UNI

   This section discusses the selection of an explicit route by an edge
   node. The selection of the first LSR by an edge node connected to
   multiple LSRs is part of that problem.

   An edge node (host or LSR) can participate more or less deeply in
   the GMPLS routing. Four different routing models can be supported at
   the UNI: configuration based, partial peering, silent listening and
   full peering.

   - Configuration based: this routing model requires the manual or
   automatic configuration of an edge node with a list of neighbor LSRs
   sorted by preference order. Automatic configuration can be achieved
   using DHCP for instance. No routing information is exchanged at the
   UNI, except maybe the ordered list of LSRs. The only routing
   information used by the edge node is that list. The edge node sends
   by default an LSP request to the preferred LSR. ICMP redirects could
   be send by this LSR to redirect some LSP requests to another LSR
   connected to the edge node. GMPLS does not preclude that model.

   - Partial peering: limited routing information (mainly reachability)
   can be exchanged across the UNI using some extensions in the
   signaling plane. The reachability information exchanged at the UNI
   may be used to initiate edge node specific routing decision over the
   network. GMPLS does not have any capability to support this model

   - Silent listening: the edge node can silently listen to routing
   protocols and take routing decisions based on the information
   obtained. An edge node receives the full routing information,
   including traffic engineering extensions. One LSR should forward
   transparently all routing PDUs to the edge node. An edge node can
   now compute a complete explicit route taking into consideration all
   the end-to-end routing information. GMPLS does not preclude this

   - Full peering: in addition to silent listening, the edge node
   participates within the routing, establish adjacencies with its
   neighbors and advertises LSAs. This is useful only if there are
   benefits for edge nodes to advertise themselves traffic engineering
   information. GMPLS does not preclude this model.

8. Link Management

   In the context of GMPLS, a pair of nodes (e.g., a photonic switch)
   may be connected by tens of fibers, and each fiber may be used to
   transmit hundreds of wavelengths if DWDM is used. Multiple fibers
   and/or multiple wavelengths may also be combined into one or more
   bundled links for routing purposes. Furthermore, to enable

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   communication between nodes for routing, signaling, and link
   management, control channels must be established between a node

   Link management is a collection of useful procedures between
   adjacent nodes that provide local services such as control channel
   management, link connectivity verification, link property
   correlation, and fault management. The Link Management Protocol
   (LMP) [LMP] has been defined to fulfill these operations. LMP has
   been initiated in the context of GMPLS but is a generic toolbox that
   can be also used in other contexts.

   In GMPLS, the control channels between two adjacent nodes are no
   longer required to use the same physical medium as the data links
   between those nodes. Moreover, the control channels that are used to
   exchange the GMPLS control-plane information exist independently of
   the links they manage. Hence, LMP was designed to manage the data
   links, independently of the termination capabilities of those data

   Control channel management and link property correlation procedures
   are mandatory per LMP. Link connectivity verification and fault
   management procedures are optional.

8.1. Control Channel and Control Channel Management

   LMP control channel management is used to establish and maintain
   control channels between nodes. Control channels exist independently
   of TE links, and can be used to exchange MPLS control-plane
   information such as signaling, routing, and link management

   An "LMP adjacency" is formed between two nodes that support the same
   LMP capabilities. Multiple control channels may be active
   simultaneously for each adjacency. A control channel can be either
   explicitly configured or automatically selected, however, LMP
   currently assume that control channels are explicitly configured
   while the configuration of the control channel capabilities can be
   dynamically negotiated.

   For the purposes of LMP, the exact implementation of the control
   channel is left unspecified. The control channel(s) between two
   adjacent nodes is no longer required to use the same physical medium
   as the data-bearing links between those nodes. For example, a
   control channel could use a separate wavelength or fiber, an
   Ethernet link, or an IP tunnel through a separate management

   A consequence of allowing the control channel(s) between two nodes
   to be physically diverse from the associated data-bearing links is
   that the health of a control channel does not necessarily correlate
   to the health of the data-bearing links, and vice-versa. Therefore,
   new mechanisms have been developed in LMP to manage links, both in
   terms of link provisioning and fault isolation.

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   LMP does not specify the signaling transport mechanism used in the
   control channel, however it states that messages transported over a
   control channel must be IP encoded. Furthermore, since the messages
   are IP encoded, the link level encoding is not part of LMP. A 32-bit
   non-zero integer Control Channel Identifier (CCId) is assigned to
   each direction of a control channel.

   Each control channel individually negotiates its control channel
   parameters and maintains connectivity using a fast Hello protocol.
   The latter is required if lower-level mechanisms are not available
   to detect link failures.

   The Hello protocol of LMP is intended to be a lightweight keep-alive
   mechanism that will react to control channel failures rapidly so
   that IGP Hellos are not lost and the associated link-state
   adjacencies are not removed uselessly.

   The Hello protocol consists of two phases: a negotiation phase and a
   keep-alive phase. The negotiation phase allows negotiation of some
   basic Hello protocol parameters, like the Hello frequency. The keep-
   alive phase consists of a fast lightweight bi-directional Hello
   message exchange.

   If a group of control channels share a common node pair and support
   the same LMP capabilities, then LMP control channel messages (except
   Configuration messages, and Hello's) may be transmitted over any of
   the active control channels without coordination between the local
   and remote nodes.

   For LMP, it is essential that at least one control channel is always
   available. In case of control channel failure, it may be possible to
   use an alternate active control channel without coordination.

8.2. Link Property Correlation

   As part of LMP, a link property correlation exchange is defined.
   The exchange is used to aggregate multiple data-bearing links (i.e.
   component links) into a bundled link and exchange, correlate, or
   change TE link parameters. The link property correlation exchange
   may be done at any time a link is up and not in the Verification
   process (see next section).

   It allows for instance to add component links to a link bundle,
   change link's minimum/maximum reservable bandwidth, change port
   identifiers, or change component identifiers in a bundle. This
   mechanism is supported by an exchange of link summary messages.

8.3. Link Connectivity Verification

   Link connectivity verification is an optional procedure that may be
   used to verify the physical connectivity of data-bearing links as
   well as to exchange the link identifiers that are used in the GMPLS

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   This procedure should be performed initially when a data-bearing
   link is first established, and subsequently, on a periodic basis for
   all unallocated (free) data-bearing links.

   The verification procedure consists of sending Test messages in-band
   over the data-bearing links. This requires that the unallocated
   links must be opaque; however, multiple degrees of opaqueness (e.g.,
   examining overhead bytes, terminating the payload, etc.), and hence
   different mechanisms to transport the Test messages, are specified.
   Note that the Test message is the only LMP message that is
   transmitted over the data-bearing link, and that Hello messages
   continue to be exchanged over the control channel during the link
   verification process. Data-bearing links are tested in the transmit
   direction as they are unidirectional. As such, it is possible for
   LMP neighboring nodes to exchange the Test messages simultaneously
   in both directions.

   To initiate the link verification procedure, a node must first
   notify the adjacent node that it will begin sending Test messages
   over a particular data-bearing link, or over the component links of
   a particular bundled link. The node must also indicate the number of
   data-bearing links that are to be verified; the interval at which
   the test messages will be sent; the encoding scheme, the transport
   mechanisms that are supported, the data rate for Test messages; and,
   in the case where the data-bearing links correspond to fibers, the
   wavelength over which the Test messages will be transmitted.
   Furthermore, the local and remote bundled link identifiers are
   transmitted at this time to perform the component link association
   with the bundled link identifiers.

8.4. Fault Management

   Fault management is an important requirement from the operational
   point of view. Fault management includes usually: fault detection,
   fault localization and fault notification. When a failure occurs and
   is detected (fault detection), an operator needs to know exactly
   where it happened (fault localization) and a source node may need to
   be notified in order to take some actions (fault notification).

   Note that fault localization can also be used to support some
   specific (local) protection/restoration mechanisms.

   In new technologies such as transparent photonic switching currently
   no method is defined to locate a fault, and the mechanism by which
   the fault information is propagated must be sent "out of band" (via
   the control plane).

   LMP provides a fault localization procedure that can be used to
   rapidly localize link failures, by notifying a fault up to the node
   upstream of that fault (i.e. through a fault notification

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   A downstream LMP neighbor that detects data link failures will send
   an LMP message to its upstream neighbor notifying it of the failure.
   When an upstream node receives a failure notification, it can
   correlate the failure with the corresponding input ports to
   determine if the failure is between the two nodes. Once the failure
   has been localized, the signaling protocols can be used to initiate
   link or path protection/restoration procedures.

8.5 LMP for DWDM Optical Line Systems (OLSs)

   In an all-optical environment, LMP focuses on peer communications
   (e.g. OXC-to-OXC). A great deal of information about a link between
   two OXCs is known by the OLS (Optical Line System or WDM Terminal
   multiplexer). Exposing this information to the control plane can
   improve network usability by further reducing required manual
   configuration, and by greatly enhancing fault detection and

   LMP-WDM [LMP-WDM] defines extensions to LMP for use between an OXC
   and an OLS. These extensions are intended to satisfy the Optical
   Link Interface Requirements described in [OLI-REQ].

   Fault detection is particularly an issue when the network is using
   all-optical photonic switches (PXC). Once a connection is
   established, PXCs have only limited visibility into the health of
   the connection. Although the PXC is all-optical, long-haul OLSs
   typically terminate channels electrically and regenerate them
   optically. This provides an opportunity to monitor the health of a
   channel between PXCs. LMP-WDM can then be used by the OLS to provide
   this information to the PXC.

   In addition to the link information known to the OLS that is
   exchanged through LMP-WDM, some information known to the OXC may
   also be exchanged with the OLS through LMP-WDM. This information is
   useful for alarm management and link monitoring (e.g. trace
   monitoring). Alarm management is important because the
   administrative state of a connection, known to the OXC (e.g. this
   information may be learned through the Admin Status object of GMPLS
   signaling [RFC3471]), can be used to suppress spurious alarms. For
   example, the OXC may know that a connection is "up", "down", in a
   "testing" mode, or being deleted ("deletion-in-progress"). The OXC
   can use this information to inhibit alarm reporting from the OLS
   when a connection is "down", "testing", or being deleted.

   It is important to note that an OXC may peer with one or more OLSs
   and an OLS may peer with one or more OXCs. Although there are many
   similarities between an OXC-OXC LMP session and an OXC-OLS LMP
   session, particularly for control management and link verification,
   there are some differences as well. These differences can primarily
   be attributed to the nature of an OXC-OLS link, and the purpose of
   OXC-OLS LMP sessions. The OXC-OXC links can be used to provide the
   basis for GMPLS signaling and routing at the optical layer. The
   information exchanged over LMP-WDM sessions is used to augment
   knowledge about the links between OXCs.

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   In order for the information exchanged over the OXC-OLS LMP sessions
   to be used by the OXC-OXC session, the information must be
   coordinated by the OXC. However, the OXC-OXC and OXC-OLS LMP
   sessions are run independently and must be maintained separately.
   One critical requirement when running an OXC-OLS LMP session is the
   ability of the OLS to make a data link transparent when not doing
   the verification procedure. This is because the same data link may
   be verified between OXC-OLS and between OXC-OXC. The verification
   procedure of LMP is used to coordinate the Test procedure (and hence
   the transparency/opaqueness of the data links). To maintain
   independence between the sessions, it must be possible for the LMP
   sessions to come up in any order. In particular, it must be possible
   for an OXC-OXC LMP session to come up without an OXC-OLS LMP session
   being brought up, and vice-versa.

9. Generalized Signaling

   The GMPLS signaling extends certain base functions of the RSVP-TE
   and CR-LDP signaling and, in some cases, adds functionality. These
   changes and additions impact basic LSP properties: how labels are
   requested and communicated, the unidirectional nature of LSPs, how
   errors are propagated, and information provided for synchronizing
   the ingress and egress.

   The core GMPLS signaling specification is available in three parts:

      1. A signaling functional description [RFC3471].
      2. RSVP-TE extensions [RFC3473].
      3. CR-LDP extensions [RFC3472].

   In addition, independent parts are available per technology:

      1. GMPLS extensions for SONET and SDH control [GMPLS-SONET-SDH].
      2. GMPLS extensions for G.709 control [GMPLS-G709].

   The following MPLS profile expressed in terms of MPLS features
   [RFC3031] applies to GMPLS:

      - Downstream-on-demand label allocation and distribution.
      - Ingress initiated ordered control.
      - Liberal (typical), or conservative (could) label retention
      - Request, traffic/data, or topology driven label allocation
      - Explicit routing (typical), or hop-by-hop routing.

   The GMPLS signaling defines the following new building blocks on the
   top of MPLS-TE:

      1. A new generic label request format.
      2. Labels for TDM, LSC and FSC interfaces, generically known as
         Generalized Label.
      3. Waveband switching support.

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      4. Label suggestion by the upstream for optimization purposes
         (e.g. latency).
      5. Label restriction by the upstream to support some optical
      6. Bi-directional LSP establishment with contention resolution.
      7. Rapid failure notification extensions.
      8. Protection information currently focusing on link protection,
         plus primary and secondary LSP indication.
      9. Explicit routing with explicit label control for a fine
         degree of control.
     10. Specific traffic parameters per technology.
     11. LSP administrative status handling.
     12. Control channel separation.

   These building blocks will be described in more details in the
   following. A complete specification can be found in the
   corresponding documents.

   Note that GMPLS is highly generic and has many options. Only
   building blocks 1, 2 and 10 are mandatory, and only within the
   specific format that is needed. Typically, building blocks 6 and 9
   should be implemented. Building blocks 3, 4, 5, 7, 8, 11 and 12 are

   A typical SONET/SDH switching network would implement building
   blocks: 1, 2 (the SONET/SDH label), 6, 9, 10 and 11. Building blocks
   7 and 8 are optional since protection can be achieved using SONET/
   SDH overhead bytes.

   A typical wavelength switching network would implement building
   blocks: 1, 2 (the generic format), 4, 5, 6, 7, 8, 9 and 11. Building
   block 3 is only needed in the particular case of waveband switching.

   A typical fiber switching network would implement building blocks:
   1, 2 (the generic format), 6, 7, 8, 9 and 11.

   A typical MPLS-IP network would not implement any of these building
   blocks, since the absence of building block 1 would indicate regular
   MPLS-IP. Note however that building block 1 and 8 can be used to
   signal MPLS-IP as well. In that case, the MPLS-IP network can
   benefit from the link protection type (not available in CR-LDP, some
   very basic form being available in RSVP-TE). Building block 2 is
   here a regular MPLS label and no new label format is required.

   GMPLS does not specify any profile for RSVP-TE and CR-LDP
   implementations that have to support GMPLS - except for what is
   directly related to GMPLS procedures. It is to the manufacturer to
   decide which are the optional elements and procedures of RSVP-TE and
   CR-LDP that need to be implemented. Some optional MPLS-TE elements
   can be useful for TDM, LSC and FSC layers, for instance the setup
   and holding priorities that are inherited from MPLS-TE.

9.1. Overview: How to Request an LSP

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   A TDM, LSC or FSC LSP is established by sending a PATH/Label Request
   message downstream to the destination. This message contains a
   Generalized Label Request with the type of LSP (i.e. the layer
   concerned), and its payload type. An Explicit Route Object (ERO) is
   also normally added to the message, but this can be added and/or
   completed by the first/default LSR.

   The requested bandwidth is encoded in the RSVP-TE SENDER_TSPEC
   object, or in the CR-LDP Traffic Parameters TLV. Specific parameters
   for a given technology are given in these traffic parameters, such
   as the type of signal, concatenation and/or transparency for a
   SONET/SDH LSP. For some other technology there be could just one
   bandwidth parameter indicating the bandwidth as a floating-point

   The requested local protection per link may be requested using the
   Protection Information Object/TLV. The end-to-end LSP protection is
   for further study and is introduced LSP protection/restoration
   section (see after).

   If the LSP is a bi-directional LSP, an Upstream Label is also
   specified in the Path/Label Request message. This label will be the
   one to use in the upstream direction.

   Additionally, a Suggested Label, a Label Set and a Waveband Label
   can also be included in the message. Other operations are defined in

   The downstream node will send back a Resv/Label Mapping message
   including one Generalized Label object/TLV that can contain several
   Generalized Labels. For instance, if a concatenated SONET/SDH signal
   is requested, several labels can be returned.

   In case of SONET/SDH virtual concatenation, a list of labels is
   returned. Each label identifying one element of the virtual
   concatenated signal. This limits virtual concatenation to remain
   within a single (component) link.

   In case of any type of SONET/SDH contiguous concatenation, only one
   label is returned. That label is the lowest signal of the contiguous
   concatenated signal (given an order specified in [GMPLS-SONET-SDH]).

   In case of SONET/SDH "multiplication", i.e. co-routing of circuits
   of the same type but without concatenation but all belonging to the
   same LSP, the explicit ordered list of all signals that take part in
   the LSP is returned.

9.2. Generalized Label Request

   The Generalized Label Request is a new object/TLV to be added in an
   RSVP-TE Path message instead of the regular Label Request, or in a
   CR-LDP Request message in addition to the already existing TLVs.
   Only one label request can be used per message, so a single LSP can
   be requested at a time per signaling message.

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   The Generalized Label Request gives three major characteristics
   (parameters) required to support the LSP being requested: the LSP
   Encoding Type, the Switching Type that must be used and the LSP
   payload type called Generalized PID (G-PID).

   The LSP Encoding Type indicates the encoding type that will be used
   with the data associated with the LSP, i.e. the type of technology
   being considered. For instance, it can be SDH, SONET, Ethernet, ANSI
   PDH, etc. It represents the nature of the LSP, and not the nature of
   the links that the LSP traverses. This is used hop-by-hop by each

   A link may support a set of encoding formats, where support means
   that a link is able to carry and switch a signal of one or more of
   these encoding formats. The Switching Type indicates then the type
   of switching that should be performed on a particular link for that
   LSP. This information is needed for links that advertise more than
   one type of switching capability.

   Nodes must verify that the type indicated in the Switching Type is
   supported on the corresponding incoming interface; otherwise, the
   node must generate a notification message with a "Routing
   problem/Switching Type" indication.

   The LSP payload type (G-PID) identifies the payload carried by the
   LSP, i.e. an identifier of the client layer of that LSP. For some
   technologies, it also indicates the mapping used by the client
   layer, e.g. byte synchronous mapping of E1. This must be interpreted
   according to the LSP encoding type and is used by the nodes at the
   endpoints of the LSP to know to which client layer a request is
   destined, and in some cases by the penultimate hop.

   Other technology specific parameters are not transported in the
   Generalized Label Request but in technology specific traffic
   parameters as explained hereafter. Currently, two set of traffic
   parameters are defined, one for SONET/SDH and one for G.709.

   Note that it is expected than specific traffic parameters will be
   defined in the future for photonic (all optical) switching.

9.3. SONET/SDH Traffic Parameters

   The GMPLS SONET/SDH traffic parameters [GMPLS-SONET-SDH] specify a
   powerful set of capabilities for SONET [ANSI T1.105] and SDH [ITU-T

   The first traffic parameter specifies the type of the elementary
   SONET/SDH signal that comprises the requested LSP, e.g. VC-11, VT6,
   VC-4, STS-3c, etc. Several transforms can then be applied
   successively on the elementary Signal to build the final signal
   being actually requested for the LSP.

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   These transforms are the contiguous concatenation, the virtual
   concatenation, the transparency and the multiplication. Each one is
   optional. They must be applied strictly in the following order:

   - First, contiguous concatenation can be optionally applied on the
     Elementary Signal, resulting in a contiguously concatenated
   - Second, virtual concatenation can be optionally applied either
     directly on the elementary Signal, or on the contiguously
     concatenated signal obtained from the previous phase.
   - Third, some transparency can be optionally specified when
     requesting a frame as signal rather than a container. Several
     transparency packages are defined.
   - Fourth, a multiplication 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.

   For RSVP-TE, the SONET/SDH traffic parameters are carried in a new
   SENDER_TSPEC and FLOWSPEC. The same format is used for both. There
   is no Adspec associated with the SENDER_TSPEC, it is omitted or a
   default value is used. The content of the FLOWSPEC object received
   in a Resv message should be identical to the content of the
   SENDER_TSPEC of the corresponding Path message. In other words, the
   receiver is normally not allowed to change the values of the traffic
   parameters. However, some level of negotiation may be achieved as
   explained in [GMPLS-SONET-SDH].

   For CR-LDP, the SONET/SDH traffic parameters are simply carried in a
   new TLV.

   Note that a general discussion on SONET/SDH and GMPLS can be found

9.4. G.709 Traffic Parameters

   Simply said, an [ITU-T G.709] based network is decomposed in two
   major layers: an optical layer (i.e. made of wavelengths) and a
   digital layer. These two layers are divided into sub-layers and
   switching occurs at two specific sub-layers: at the OCh (Optical
   Channel) optical layer and at the ODU (Optical channel Data Unit)
   electrical layer. The ODUk notation is used to denote ODUs at
   different bandwidths.

   The GMPLS G.709 traffic parameters [GMPLS-G709] specify a powerful
   set of capabilities for ITU-T G.709 networks.

   The first traffic parameter specifies the type of the elementary
   G.709 signal that comprises the requested LSP, e.g. ODU1, OCh at 40
   Gbps, etc. Several transforms can then be applied successively on
   the elementary Signal to build the final signal being actually
   requested for the LSP.

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   These transforms are the virtual concatenation and the
   multiplication. Each one of these transforms is optional. They must
   be applied strictly in the following order:

   - First, virtual concatenation can be optionally applied directly on
     the elementary Signal,
   - Second, a multiplication can be optionally applied, either
     directly on the elementary Signal, or on the virtually
     concatenated signal obtained from the first phase.

   Additional ODUk Multiplexing traffic parameters allow indicating an
   ODUk mapping (ODUj into ODUk) for an ODUk multiplexing LSP request.
   G.709 supports the following multiplexing capabilities: ODUj into
   ODUk (k > j) and ODU1 with ODU2 multiplexing into ODU3.

   For RSVP-TE, the G.709 traffic parameters are carried in a new
   SENDER-TSPEC and FLOWSPEC. The same format is used for both. There
   is no Adspec associated with the SENDER_TSPEC, it is omitted or a
   default value is used. The content of the FLOWSPEC object received
   in a Resv message should be identical to the content of the
   SENDER_TSPEC of the corresponding Path message.

   For CR-LDP, the G.709 traffic parameters are simply carried in a new

9.5. Bandwidth Encoding

   Some technologies that do not have (yet) specific traffic parameters
   just require a bandwidth encoding transported in a generic form.
   Bandwidth is carried in 32-bit number in IEEE floating-point format
   (the unit is bytes per second). Values are carried in a per protocol
   specific manner. For non-packet LSPs, it is useful to define
   discrete values to identify the bandwidth of the LSP.

   It should be noted that this bandwidth encoding do not apply to
   SONET/SDH and G.709, for which the traffic parameters fully define
   the requested SONET/SDH or G.709 signal.

   The bandwidth is coded in the Peak Data Rate field of Int-Serv
   objects for RSVP-TE in the SENDER_TSPEC and FLOWSPEC objects and in
   the Peak and Committed Data Rate fields of the CR-LDP Traffic
   Parameters TLV.

9.6. Generalized Label

   The Generalized Label extends the traditional MPLS label by allowing
   the representation of not only labels that travel in-band with
   associated data packets, but also (virtual) labels that identify
   time-slots, wavelengths, or space division multiplexed positions.

   For example, the Generalized Label may identify (a) a single fiber
   in a bundle, (b) a single waveband within fiber, (c) a single
   wavelength within a waveband (or fiber), or (d) a set of time-slots
   within a wavelength (or fiber). It may also be a generic MPLS label,

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   a Frame Relay label, or an ATM label (VCI/VPI). The format of a
   label can be as simple as an integer value such as a wavelength
   label or can be more elaborated such as an SONET/SDH or a G.709

   SDH and SONET define each a multiplexing structure. These
   multiplexing structures will be used as naming trees to create
   unique labels. Such a label will identify the exact position (times-
   lot(s)) of a signal in a multiplexing structure. Since the SONET
   multiplexing structure may be seen as a subset of the SDH
   multiplexing structure, the same format of label is used for SDH and
   SONET. A similar concept is applied to build a label at the G.709
   ODU layer.

   Since the nodes sending and receiving the Generalized Label know
   what kinds of link they are using, the Generalized Label does not
   identify its type. Instead, the nodes are expected to know from the
   context what type of label to expect.

   A Generalized Label only carries a single level of label i.e. it is
   non-hierarchical. When multiple levels of labels (LSPs within LSPs)
   are required, each LSP must be established separately.

9.7. Waveband Switching

   A special case of wavelength switching is waveband switching. A
   waveband represents a set of contiguous wavelengths, which can be
   switched together to a new waveband. For optimization reasons, it
   may be desirable for a photonic cross-connect to optically switch
   multiple wavelengths as a unit. This may reduce the distortion on
   the individual wavelengths and may allow tighter separation of the
   individual wavelengths. A Waveband label is defined to support this
   special case.

   Waveband switching naturally introduces another level of label
   hierarchy and as such the waveband is treated the same way, all
   other upper layer labels are treated. As far as the MPLS protocols
   are concerned, there is little difference between a waveband label
   and a wavelength label. Exception is that semantically the waveband
   can be subdivided into wavelengths whereas the wavelength can only
   be subdivided into time or statistically multiplexed labels.

   In the context of waveband switching, the generalized label used to
   indicate a waveband contains three fields, a waveband ID, a Start
   Label and an End Label. The Start and End Labels are channel
   identifiers from the sender perspective that identify respectively,
   the lowest value wavelength and the highest value wavelength making
   up the waveband.

9.8. Label Suggestion by the Upstream

   GMPLS allows for a label to be optionally suggested by an upstream
   node. This suggestion may be overridden by a downstream node but in
   some cases, at the cost of higher LSP setup time. The suggested

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   label is valuable when establishing LSPs through certain kinds of
   optical equipment where there may be a lengthy (in electrical terms)
   delay in configuring the switching fabric. For example, micro
   mirrors may have to be elevated or moved, and this physical motion
   and subsequent damping takes time. If the labels and hence switching
   fabric are configured in the reverse direction (the norm), the Resv/
   MAPPING message may need to be delayed by 10's of milliseconds per
   hop in order to establish a usable forwarding path. It can be
   important for restoration purposes where alternate LSPs may need to
   be rapidly established as a result of network failures.

9.9. Label Restriction by the Upstream

   An upstream node can optionally restrict (limit) the choice of label
   of a downstream node to a set of acceptable labels. Giving lists
   and/or ranges of inclusive (acceptable) or exclusive (unacceptable)
   labels in a Label Set provides this restriction. If not applied, all
   labels from the valid label range may be used. There are at least
   four cases where a label restriction is useful in the "optical"

   Case 1: the end equipment is only capable of transmitting and
   receiving on a small specific set of wavelengths/wavebands.

   Case 2: there is a sequence of interfaces, which cannot support
   wavelength conversion and require the same wavelength be used end-
   to-end over a sequence of hops, or even an entire path.

   Case 3: it is desirable to limit the amount of wavelength conversion
   being performed to reduce the distortion on the optical signals.

   Case 4: two ends of a link support different sets of wavelengths.

   The receiver of a Label Set must restrict its choice of labels to
   one that is in the Label Set. A Label Set may be present across
   multiple hops. In this case, each node generates its own outgoing
   Label Set, possibly based on the incoming Label Set and the node's
   hardware capabilities. This case is expected to be the norm for
   nodes with conversion incapable interfaces.

9.10. Bi-directional LSP

   GMPLS allows establishment of bi-directional symmetric LSPs (not of
   asymmetric LSPs). A symmetric bi-directional LSP has the same
   traffic engineering requirements including fate sharing, protection
   and restoration, LSRs, and resource requirements (e.g. latency and
   jitter) in each direction.

   In the remainder of this section, the term "initiator" is used to
   refer to a node that starts the establishment of an LSP; the term
   "terminator" is used to refer to the node that is the target of the
   LSP. For a bi-directional LSPs, there is only one initiator and one

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   Normally to establish a bi-directional LSP when using RSVP-TE
   [RFC3209] or CR-LDP [RFC3212] two unidirectional paths must be
   independently established. This approach has the following

   1. The latency to establish the bi-directional LSP is equal to one
   round trip signaling time plus one initiator-terminator signaling
   transit delay. This not only extends the setup latency for
   successful LSP establishment, but it extends the worst-case latency
   for discovering an unsuccessful LSP to as much as two times the
   initiator-terminator transit delay. These delays are particularly
   significant for LSPs that are established for restoration purposes.

   2. The control overhead is twice that of a unidirectional LSP. This
   is because separate control messages (e.g. Path and Resv) must be
   generated for both segments of the bi-directional LSP.

   3. Because the resources are established in separate segments, route
   selection is complicated. There is also additional potential race
   for conditions in assignment of resources, which decreases the
   overall probability of successfully establishing the bi-directional

   4. It is more difficult to provide a clean interface for SONET/SDH
   equipment that may rely on bi-directional hop-by-hop paths for
   protection switching. Note that existing SONET/SDH equipment
   transmits the control information in-band with the data.

   5. Bi-directional optical LSPs (or lightpaths) are seen as a
   requirement for many optical networking service providers.

   With bi-directional LSPs both the downstream and upstream data
   paths, i.e. from initiator to terminator and terminator to
   initiator, are established using a single set of signaling messages.
   This reduces the setup latency to essentially one initiator-
   terminator round trip time plus processing time, and limits the
   control overhead to the same number of messages as a unidirectional

   For bi-directional LSPs, two labels must be allocated. Bi-
   directional LSP setup is indicated by the presence of an Upstream
   Label in the appropriate signaling message.

9.11. Bi-directional LSP Contention Resolution

   Contention for labels may occur between two bi-directional LSP setup
   requests traveling in opposite directions. This contention occurs
   when both sides allocate the same resources (ports) at effectively
   the same time. GMPLS signaling defines a procedure to resolve that
   contention: the node with the higher node ID will win the
   contention. To reduce the probability of contention, some mechanisms
   are also suggested.

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9.12. Rapid Notification of Failure

   GMPLS defines several signaling extensions that enable expedited
   notification of failures and other events to nodes responsible for
   restoring failed LSPs, and error handling.

   1. Acceptable Label Set for notification on Label Error:

   There are cases in traditional MPLS and in GMPLS that result in an
   error message containing an "Unacceptable label value" indication.
   When these cases occur, it can useful for the node generating the
   error message to indicate which labels would be acceptable. To cover
   this case, GMPLS introduces the ability to convey such information
   via the "Acceptable Label Set". An Acceptable Label Set is carried
   in appropriate protocol specific error messages. The format of an
   Acceptable Label Set is identical to a Label Set.

   2. Expedited notification:

   Extensions to RSVP-TE enable expedited notification of failures and
   other events to determined nodes. For CR-LDP, there is not currently
   a similar mechanism. The first extension identifies where event
   notifications are to be sent. The second provides for general
   expedited event notification with a Notify message. Such extensions
   can be used by fast restoration mechanisms. Notifications may be
   requested in both the upstream and downstream directions.

   The Notify message is a generalized notification mechanism that
   differs from the currently defined error messages in that it can be
   "targeted" to a node other than the immediate upstream or downstream
   neighbor. The Notify message does not replace existing error
   messages. The Notify message may be sent either (a) normally, where
   non-target nodes just forward the Notify message to the target node,
   similar to ResvConf processing in [RFC2205]; or (b) encapsulated in
   a new IP header whose destination is equal to the target IP address.

   3. Faster removal of intermediate states:

   A specific RSVP optimization allowing in some cases the faster
   removal of intermediate states. This extension is used to deal with
   specific RSVP mechanisms.

9.13. Link Protection

   Protection information is carried in the new optional Protection
   Information Object/TLV. It currently indicates the desired link
   protection for each link of an LSP. If a particular protection type,
   i.e. 1+1, or 1:N, is requested, then a connection request is
   processed only if the desired protection type can be honored. Note
   that GMPLS advertises the protection capabilities of a link in the
   routing protocols. Path computation algorithms may consider this
   information when computing paths for setting up LSPs.

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   Protection information also indicates if the LSP is a primary or
   secondary LSP. A secondary LSP is a backup to a primary LSP. The
   resources of a secondary LSP are normally not used until the primary
   LSP fails, but they may be used by other LSPs until the primary LSP
   fails over the secondary LSP. At that point, any LSP that is using
   the resources for the secondary LSP must be preempted.

   Six link protection types are currently defined as individual flags
   and can be combined: enhanced, dedicated 1+1, dedicated 1:1, shared,
   unprotected, extra traffic. See [RFC3471] section 7.1 for a precise
   definition of each.

9.14. Explicit Routing and Explicit Label Control

   By using an explicit route, the path taken by an LSP can be
   controlled more or less precisely. Typically, the node at the head-
   end of an LSP finds an explicit route and builds an Explicit Route
   Object (ERO)/ Explicit Route (ER) TLV that contains that route.
   Possibly, the edge node does not build any explicit route, and just
   transmit a signaling request to a default neighbor LSR (as IP/MPLS
   hosts would). For instance, an explicit route could be added to a
   signaling message by the first switching node, on behalf of the edge
   node. Note also that an explicit route is altered by intermediate
   LSRs during its progression towards the destination.

   The explicit route is originally defined by MPLS-TE as a list of
   abstract nodes (i.e. groups of nodes) along the explicit route. Each
   abstract node can be an IPv4 address prefix, an IPv6 address prefix,
   or an AS number. This capability allows the generator of the
   explicit route to have incomplete information about the details of
   the path. In the simplest case, an abstract node can be a full IP
   address (32 bits) that identifies a specific node (called a simple
   abstract node).

   MPLS-TE allows strict and loose abstract nodes. The path between a
   strict node and its preceding node must include only network nodes
   from the strict node and its preceding abstract node. The path
   between a loose node and its preceding abstract node may include
   other network nodes that are not part of the loose node or its
   preceding abstract node.

   This explicit route was extended to include interface numbers as
   abstract nodes to support unnumbered interfaces; and further
   extended by GMPLS to include labels as abstract nodes. Having labels
   in an explicit route is an important feature that allows controlling
   the placement of an LSP with a very fine granularity. This is more
   likely to be used for TDM, LSC and FSC links.

   In particular, the explicit label control in the explicit route
   allows terminating an LSP on a particular outgoing port of an egress
   node. Indeed, a label sub-object/TLV must follow a sub-object/TLV
   containing the IP address, or the interface identifier (in case of
   unnumbered interface), associated with the link on which it is to be

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   This can also be used when it is desirable to "splice" two LSPs
   together, i.e. where the tail of the first LSP would be "spliced"
   into the head of the second LSP.

   When used together with an optimization algorithm, it can provide
   very detailed explicit routes, including the label (timeslot) to use
   on a link, in order to minimize the fragmentation of the SONET/SDH
   multiplex on the corresponding interface.

9.15. Route Recording

   In order to improve the reliability and the manageability of the LSP
   being established, the concept of the route recording was introduced
   in RSVP-TE to function as:

   - First, a loop detection mechanism to discover L3 routing loops, or
   loops inherent in the explicit route (this mechanism is strictly
   exclusive with the use of explicit routing objects).

   - Second, a route recording mechanism collects up-to-date detailed
   path information on a hop-by-hop basis during the LSP setup process.
   This mechanism provides valuable information to the source and
   destination nodes. Any intermediate routing change at setup time, in
   case of loose explicit routing, will be reported.

   - Third, a recorded route can be used as input for an explicit
   route. This is useful if a source node receives the recorded route
   from a destination node and applies it as an explicit route in order
   to "pin down the path".

   Within the GMPLS architecture, only the second and third functions
   are mainly applicable for TDM, LSC and FSC layers.

9.16. LSP Modification and LSP Re-routing

   LSP modification and re-routing are two features already available
   in MPLS-TE. GMPLS does not add anything new. Elegant re-routing is
   possible with the concept of "make-before-break" whereby an old path
   is still used while a new path is set up by avoiding double
   reservation of resources. Then, the node performing the re-routing
   can swap on the new path and close the old path. This feature is
   supported with RSVP-TE (using shared explicit filters) and CR-LDP
   (using the action indicator flag).

   LSP modification consists in changing some LSP parameters, but
   normally without changing the route. It is supported using the same
   mechanism as re-routing. However, the semantic of LSP modification
   will differ from one technology to the other. For instance, further
   studies are required to understand the impact of dynamically
   changing some SONET/SDH circuit characteristics such as the
   bandwidth, the protection type, the transparency, the concatenation,

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9.17. LSP Administrative Status Handling

   GMPLS provides the optional capability to indicate the
   administrative status of an LSP by using a new Admin Status
   object/TLV. Administrative Status information is currently used in
   two ways.

   In the first usage, the Admin Status object/TLV is carried in a
   Path/Label Request or Resv/Label Mapping message to indicate the
   administrative state of an LSP. In this usage, Administrative Status
   information indicates the state of the LSP, which include "up" or
   "down", if it in a "testing" mode, and if deletion is in progress.

   Based on that administrative status, a node can take local
   decisions, like inhibit alarm reporting when an LSP is in "down" or
   "testing" states, or report alarms associated with the connection at
   a priority equal to or less than "Non service affecting".

   It is possible that some nodes along an LSP will not support the
   Admin Status Object/TLV. In the case of a non-supporting transit
   node, the object will pass through the node unmodified and normal
   processing can continue.

   In some circumstances, particularly optical networks, it is useful
   to set the administrative status of an LSP to "being deleted" before
   tearing it down in order to avoid non-useful generation of alarms.
   The ingress LSR precedes an LSP deletion by inserting an appropriate
   Admin Status Object/TLV in a Path/Label Request (with the
   modification action indicator flag set to modify) message. Transit
   LSRs process the Admin Status Object/TLV and forward it. The egress
   LSR answers in a Resv/Label Mapping (with the modification action
   indicator flag set to modify) message with the Admin Status object.
   Upon receiving this message and object, the ingress node sends a
   PathTear/Release message downstream to remove the LSP and normal
   RSVP-TE/CR-LDP processing takes place.

   In the second usage, the Admin Status object/TLV is carried in a
   Notification/Label Mapping (with the modification action indicator
   flag set to modify) message to request that the ingress node change
   the administrative state of an LSP. This allows intermediate and
   egress nodes triggering the setting of administrative status. In
   particular, this allows intermediate or egress LSRs requesting a
   release of an LSP initiated by the ingress node.

9.18. Control Channel Separation

   In GMPLS, a control channel can be separated from the data channel.
   Indeed, the control channel can be implemented completely out-of-
   band for various reason, e.g. when the data channel cannot carry in-
   band control information. This issue was even originally introduced
   to MPLS in the context of link bundling.

   In traditional MPLS, there is an implicit one-to-one association of
   a control channel to a data channel. When such an association is

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   present, no additional or special information is required to
   associate a particular LSP setup transaction with a particular data

   Otherwise, it is necessary to convey additional information in
   signaling to identify the particular data channel being controlled.
   GMPLS supports explicit data channel identification by providing
   interface identification information. GMPLS allows the use of a
   number of interface identification schemes including IPv4 or IPv6
   addresses, interface indexes (for unnumbered interfaces) and
   component interfaces (for bundled interfaces), unnumbered bundled
   interfaces are also supported.

   The choice of the data interface to use is always made by the sender
   of the Path/Label Request message, and indicated by including the
   data channel's interface identifier in the message using a new IF_ID
   RSVP_HOP object sub-type/Interface TLV.

   For bi-directional LSPs, the sender chooses the data interface in
   each direction. In all cases but bundling, the upstream interface is
   implied by the downstream interface. For bundling, the Path/Label
   Request sender explicitly identifies the component interface used in
   each direction. The new object/TLV is used in Resv/Label Mapping
   message to indicate the downstream node's usage of the indicated

   The new object/TLV can contain a list of embedded TLVs, each
   embedded TLV can be an IPv4 address, and IPv6 address, an interface
   index, a downstream component interface ID or an upstream component
   interface ID. In the last three cases, the embedded TLV contains
   itself an IP address plus an Interface ID, the IP address being used
   to identify the interface ID (it can be the router ID for instance).

   There are cases where it is useful to indicate a specific interface
   associated with an error. To support these cases the IF_ID
   ERROR_SPEC RSVP Objects are defined.

10. Forwarding Adjacencies (FA)

   To improve scalability of MPLS TE (and thus GMPLS) it may be useful
   to aggregate multiple TE LSPs inside a bigger TE LSP. Intermediate
   nodes see the external LSP only. They don't have to maintain
   forwarding states for each internal LSP, less signaling messages
   need to be exchanged and the external LSP can be somehow protected
   instead (or in addition) to the internal LSPs. This can considerably
   increase the scalability of the signaling.

   The aggregation is accomplished by (a) an LSR creating a TE LSP, (b)
   the LSR forming a forwarding adjacency out of that LSP (advertising
   this LSP as a Traffic Engineering (TE) link into IS-IS/OSPF), (c)
   allowing other LSRs to use forwarding adjacencies for their path
   computation, and (d) nesting of LSPs originated by other LSRs into
   that LSP (e.g. by using the label stack construct in the case of

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   IS-IS/OSPF floods the information about "Forwarding Adjacencies" FAs
   just as it floods the information about any other links.
   Consequently to this flooding, an LSR has in its TE link state
   database the information about not just conventional links, but FAs
   as well.

   An LSR, when performing path computation, uses not just conventional
   links, but FAs as well. Once a path is computed, the LSR uses RSVP-
   TE/CR-LDP for establishing label binding along the path. FAs need
   simple extensions to signaling and routing protocols.

10.1. Routing and Forwarding Adjacencies

   Forwarding adjacencies may be represented as either unnumbered or
   numbered links. A FA can also be a bundle of LSPs between two nodes.

   FAs are advertised as GMPLS TE links such as defined in [HIERARCHY].
   GMPLS TE links are advertised in OSPF and IS-IS such as defined in
   [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. These last two specifications
   enhance [OSPF-TE] and [ISIS-TE] that defines a base TE link.

   When a FA is created dynamically, its TE attributes are inherited
   from the FA-LSP that induced its creation. [HIERARCHY] specifies how
   each TE parameter of the FA is inherited from the FA-LSP. Note that
   the bandwidth of the FA must be at least as big as the FA-LSP that
   induced it, but may be bigger if only discrete bandwidths are
   available for the FA-LSP. In general, for dynamically provisioned
   forwarding adjacencies, a policy-based mechanism may be needed to
   associate attributes to forwarding adjacencies.

   A FA advertisement could contain the information about the path
   taken by the FA-LSP associated with that FA. Other LSRs may use this
   information for path computation. This information is carried in a
   new OSPF and IS-IS TLV called the Path TLV.

   It is possible that the underlying path information might change
   over time, via configuration updates, or dynamic route
   modifications, resulting in the change of that TLV.

   If forwarding adjacencies are bundled (via link bundling), and if
   the resulting bundled link carries a Path TLV, the underlying path
   followed by each of the FA-LSPs that form the component links must
   be the same.

   It is expected that forwarding adjacencies will not be used for
   establishing IS-IS/OSPF peering relation between the routers at the
   ends of the adjacency.

   LSP hierarchy could exist both with the peer and with the overlay
   models. With the peer model, the LSP hierarchy is realized via FAs
   and an LSP is both created and used as a TE link by exactly the same
   instance of the control plane. Creating LSP hierarchies with
   overlays doesn't involve the concept of FA. With the overlay model

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   an LSP created (and maintained) by one instance of the GMPLS control
   plane is used as a TE link by another instance of the GMPLS control
   plane. Moreover, the nodes using a TE link are expected to have a
   routing and signaling adjacency.

10.2. Signaling Aspects

   For the purpose of processing the explicit route in a Path/Request
   message of an LSP that is to be tunneled over a forwarding
   adjacency, an LSR at the head-end of the FA-LSP views the LSR at the
   tail of that FA-LSP as adjacent (one IP hop away).

10.3. Cascading of Forwarding Adjacencies

   With an integrated model, several layers are controlled using the
   same routing and signaling protocols. A network may then have links
   with different multiplexing/demultiplexing capabilities. For
   example, a node may be able to multiplex/demultiplex individual
   packets on a given link, and may be able to multiplex/demultiplex
   channels within a SONET payload on other links.

   A new OSPF and IS-IS sub-TLV has been defined to advertise the
   multiplexing capability of each interface: PSC, L2SC, TDM, LSC or
   FSC. This sub-TLV is called the Interface Switching Capability
   Descriptor sub-TLV, which complements the sub-TLVs defined in [OSPF-
   TE-GMPLS] and [ISIS-TE-GMPLS]. The information carried in this sub-
   TLV is used to construct LSP regions, and determine region's

   Path computation may take into account region boundaries when
   computing a path for an LSP. For example, path computation may
   restrict the path taken by an LSP to only the links whose
   multiplexing/demultiplexing capability is PSC. When an LSP need to
   cross a region boundary, it can trigger the establishment of an FA
   at the underlying layer (i.e. the L2SC layer). This can trigger a
   cascading of FAs between layers with the following obvious order:
   L2SC, then TDM, then LSC, and then finally FSC.

11. Routing and Signaling Adjacencies

   By definition, two nodes have a routing (IS-IS/OSPF) adjacency if
   they are neighbors in the IS-IS/OSPF sense.

   By definition, two nodes have a signaling (RSVP-TE/CR-LDP) adjacency
   if they are neighbors in the RSVP-TE/CR-LDP sense. Nodes A and B are
   RSVP-TE neighbors if they directly exchange RSVP-TE messages
   (Path/Resv) (e.g., as described in sections 7.1.1 and 7.1.2 of
   [HIERARCHY]). The neighbor relationship includes exchanging RSVP-TE

   By definition, a Forwarding Adjacency (FA) is a TE Link between two
   GMPLS nodes whose path transits one or more other (G)MPLS nodes in
   the same instance of the (G)MPLS control plane. If two nodes have
   one or more non-FA TE Links between them, these two nodes are

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   expected (although not required) to have a routing adjacency. If two
   nodes do not have any non-FA TE Links between them, it is expected
   (although not required) that these two nodes would not have a
   routing adjacency. To state the obvious, if the TE links between two
   nodes are to be used for establishing LSPs, the two nodes must have
   a signaling adjacency.

   If one wants to establish routing and/or signaling adjacency between
   two nodes, there must be an IP path between them.  This IP path can
   be, for example, a TE Link with an interface switching capability of
   PSC, anything that looks likes an IP link (e.g., GRE tunnel, or a
   (bi-directional) LSP that with an interface switching capability of

   A TE link may not be capable of being used directly for maintaining
   routing and/or signaling adjacencies. This is because GMPLS routing
   and signaling adjacencies requires exchanging data on a per frame/
   packet basis, and a TE link (e.g. a link between OXCs) may not be
   capable of exchanging data on a per packet basis. In this case, the
   routing and signaling adjacencies are maintained via a set of one or
   more control channels (see [LMP]).

   Two nodes may have a TE link between them even if they don't have a
   routing adjacency. Naturally, each node must run OSPF/IS-IS with
   GMPLS extensions in order for that TE link to be advertised. More
   precisely, the node needs to run GMPLS extensions for TE Links with
   an interface switching capability (see [GMPLS-ROUTING]) other than
   PSC. Moreover, this node needs to run either GMPLS or MPLS
   extensions for TE links with an interface switching capability of

   The mechanisms for Control Channel Separation [RFC3471] should be
   used (even if the IP path between two nodes is a TE link). I.e.,
   RSVP-TE/CR-LDP signaling should use the Interface_ID (IF_ID) object
   to specify a particular TE link when establishing an LSP.

   The IP path could consist of multiple IP hops. In this case, the
   mechanisms of sections 7.1.1 and 7.1.2 of [HIERARCHY] should be used
   (in addition to Control Channel Separation).

12. Control Plane Fault Handling

   Two major types of faults can impact a control plane. The first,
   referred to as control channel fault, relates to the case where
   control communication is lost between two neighboring nodes. If the
   control channel is embedded with the data channel, data channel
   recovery procedure should solve the problem. If the control channel
   is independent of the data channel, additional procedures are
   required to recover from that problem.

   The second, referred to as nodal faults, relates to the case where
   node loses its control state (e.g., after a restart) but does not
   loose its data forwarding state.

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   In transport networks, such types of control plane faults should not
   have service impact on the existing connections. Under such
   circumstances, a mechanism must exist to detect a control
   communication failure and a recovery procedure must guarantee
   connection integrity at both ends of the control channel.

   For a control channel fault, once communication is restored routing
   protocols are naturally able to recover but the underlying signaling
   protocols must indicate that the nodes have maintained their state
   through the failure. The signaling protocol must also ensure that
   any state changes that were instantiated during the failure are
   synchronized between the nodes.

   For a nodal fault, a node's control plane restarts and loses most of
   its state information. In this case, both upstream and downstream
   nodes must synchronize their state information with the restarted
   node. In order for any resynchronization to occur the node
   undergoing the restart will need to preserve some information, such
   as it's mappings of incoming to outgoing labels.

   These issues are addressed in protocol specific fashions, see
   [RFC3473], [RFC3472], [OSPF-TE-GMPLS] and [ISIS-TE-GMPLS]. Note that
   these cases only apply when there are mechanisms to detect data
   channel failures independent of control channel failures.

   The LDP Fault tolerance (see [RFC3479]) specifies the procedures to
   recover from a control channel failure. [RFC3473] specifies how to
   recover from both a control channel failure and a node failure.

13. LSP Protection and Restoration

   This section discusses Protection and Restoration (P&R) issues for
   GMPLS LSPs. It is driven by the requirements outlined in [RFC3386]
   and some of the principles outlined in [RFC3469]. It will be
   enhanced, as more GMPLS P&R mechanisms are defined. The scope of
   this section is clarified hereafter:

   - This section is only applicable when a fault impacting LSP(s)
     happens in the data/transport plane. Section 11 deals with control
     plane fault handling for nodal and control channel faults.

   - This section focuses on P&R at the TDM, LSC and FSC layers. There
     are specific P&R requirements at these layers not present at the
     PSC layer.

   - This section focuses on intra-area P&R as opposed to inter-area
     P&R and even inter-domain P&R. Note that P&R can even be more
     restricted, e.g. to a collection of like customer equipment, or a
     collection of equipment of like capabilities, in one single
     routing area.

   - This section focuses on intra-layer P&R (horizontal hierarchy as
     defined in [RFC3386]) as opposed to the inter-layer P&R (vertical

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   - P&R mechanisms are in general designed to handle single failures,
     which makes SRLG diversity a necessity. Recovery from multiple
     failures requires further study.

   - Both mesh and ring-like topologies are supported.

   In the following, we assume that:

   - TDM, LSC and FSC devices are more generally committing recovery
     resources in a non-best effort way. Recovery resources are either
     allocated (thus used) or at least logically reserved (whether used
     or not by preemptable extra traffic but unavailable anyway for
     regular working traffic).

   - Shared P&R mechanisms are valuable to operators in order to
     maximize their network utilization.

   - Sending preemptable excess traffic on recovery resources is a
     valuable feature for operators.

13.1. Protection Escalation across Domains and Layers

   To describe the P&R architecture, one must consider two dimensions
   of hierarchy [RFC3386]:

   - A horizontal hierarchy consisting of multiple P&R domains, which
     is important in an LSP based protection scheme. The scope of P&R
     may extend over a link (or span), an administrative domain or sub-
     network, an entire LSP.

     An administrative domain may consist of a single P&R domain or as
     a concatenation of several smaller P&R domains. The operator can
     configure P&R domains, based on customers' requirements, and on
     network topology and traffic engineering constraints.

   - A vertical hierarchy consisting of multiple layers of P&R with
     varying granularities (packet flows, STS trails, lightpaths,
     fibers, etc).

     In the absence of adequate P&R coordination, a fault may propagate
     from one level to the next within a P&R hierarchy. It can lead to
     "collisions" and simultaneous recovery actions may lead to race
     conditions, reduced resource utilization, or instabilities
     [MANCHESTER]. Thus, a consistent escalation strategy is needed to
     coordinate recovery across domains and layers. The fact that GMPLS
     can be used at different layers could simplify this coordination.

     There are two types of escalation strategies: bottom-up and top-
     down. The bottom-up approach assumes that "lower-level" recovery
     schemes are more expedient. Therefore we can inhibit or hold off
     higher-level P&R. The Top-down approach attempts service P&R at
     the higher levels before invoking "lower level" P&R. Higher-layer

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     P&R is service selective, and permits "per-CoS" or "per-LSP" re-

   Service Level Agreements (SLAs) between network operators and their
   clients are needed to determine the necessary time scales for P&R at
   each layer and at each domain.

13.2. Mapping of Services to P&R Resources

   The choice of a P&R scheme is a tradeoff between network utilization
   (cost) and service interruption time. In light of this tradeoff,
   network service providers are expected to support a range of
   different service offerings or service levels.

   One can classify LSPs into one of a small set of service levels.
   Among other things, these service levels define the reliability
   characteristics of the LSP. The service level associated with a
   given LSP is mapped to one or more P&R schemes during LSP
   establishment. An advantage that mapping is that an LSP may use
   different P&E schemes in different segments of a network (e.g. some
   links may be span protected, whilst other segments of the LSP may
   utilize ring protection). These details are likely to be service
   provider specific.

   An alternative to using service levels is for an application to
   specify the set of specific P&R mechanisms to be used when
   establishing the LSP. This allows greater flexibility in using
   different mechanisms to meet the application requirements.

   A differentiator between these service levels is service
   interruption time in case of network failures, which is defined as
   the length of time between when a failure occurs and when
   connectivity is re-established. The choice of service level (or P&R
   scheme) should be dictated by the service requirements of different

13.3. Classification of P&R Mechanism Characteristics

   The following figure provides a classification of the possible
   provisioning types of recovery LSPs, and of the levels of
   overbooking that is possible for them.

                 +-Computed on  +-Established     +-Resources pre-
                 | demand       | on demand       | allocated
                 |              |                 |
   Recovery LSP  |              |                 |
   Provisioning -+-Pre computed +-Pre established +-Resources allocated
                                                    on demand

                  +--- Dedicated (1:1, 1+1)
                  +--- Shared (1:N, Ring, Shared mesh)

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   Level of       |
   Overbooking ---+--- Best effort

13.4. Different Stages in P&R

   Recovery from a network fault or impairment takes place in several
   stages as discussed in [RFC3469], including fault detection, fault
   localization, notification, recovery (i.e. the P&R itself) and
   reversion of traffic (i.e. returning the traffic to the original
   working LSP or to a new one).

   - Fault detection is technology and implementation dependent. In
     general, failures are detected by lower layer mechanisms (e.g.
     SONET/SDH, Loss-of-Light (LOL)). When a node detects a failure, an
     alarm may be passed up to a GMPLS entity, which will take
     appropriate actions, or the alarm may be propagated at the lower
     layer (e.g. SONET/SDH AIS).

   - Fault localization can be done with the help of GMPLS, e.g. using
     LMP for fault localization (see section 8.4).

   - Fault notification can also be achieved through GMPLS, e.g. using
     GMPLS RSVP-TE/CR-LDP notification (see section 9.12).

   - This section focuses on the different mechanisms available for
     recovery and reversion of traffic once fault detection,
     localization and notification have taken place.

13.5. Recovery Strategies

   Network P&R techniques can be divided into Protection and
   Restoration. In protection, resources between the protection
   endpoints are established before failure, and connectivity after
   failure is achieved simply by switching performed at the protection
   end-points. In contrast, restoration uses signaling after failure to
   allocate resources along the recovery path.

   - Protection aims at extremely fast reaction times and may rely on
     the use of overhead control fields for achieving end-point
     coordination. Protection for SONET/SDH networks is described in
     [ITUT-G.841] and [ANSI-T1.105]. Protection mechanisms can be
     further classified by the level of redundancy and sharing.

   - Restoration mechanisms rely on signaling protocols to coordinate
     switching actions during recovery, and may involve simple re-
     provisioning, i.e. signaling only at the time of recovery; or pre-
     signaling, i.e., signaling prior to recovery.

   In addition, P&R can be applied on a local or end-to-end basis. In
   the local approach, P&R is focused on the local proximity of the
   fault in order to reduce delay in restoring service. In the end-to-

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   end approach, the LSP originating and terminating nodes control

   Using these strategies, the following recovery mechanisms can be

13.6. Recovery mechanisms: Protection schemes

   Note that protection schemes are usually defined in technology
   specific ways, but this does not preclude other solutions.

   - 1+1 Link Protection: Two pre-provisioned resources are used in
     parallel. For example, data is transmitted simultaneously on two
     parallel links and a selector is used at the receiving node to
     choose the best source (see also [GMPLS-FUNCT]).

   - 1:N Link Protection: Working and protecting resources (N working,
     1 backup) are pre-provisioned. If a working resource fails, the
     data is switched to the protecting resource, using a coordination
     mechanism (e.g. in overhead bytes). More generally, N working and
     M protecting resources can be assigned for M:N link protection
     (see also [GMPLS-FUNCT]).

   - Enhanced Protection: Various mechanisms such as protection rings
     can be used to enhance the level of protection beyond single link
     failures to include the ability to switch around a node failure or
     multiple link failures within a span, based on a pre-established
     topology of protection resources (note: no reference available at
     publication time).

   - 1+1 LSP Protection: Simultaneous data transmission on working and
     protecting LSPs and tail-end selection can be applied (see also

13.7. Recovery mechanisms: Restoration schemes

   Thanks to the use of a distributed control plane like GMPLS,
   restoration is possible in multiple of tenths of milliseconds. It is
   much harder to achieve when only an NMS is used and can only be done
   in that case in a multiple of seconds.

   - End-to-end LSP restoration with re-provisioning: an end-to-end
     restoration path is established after failure. The restoration
     path may be dynamically calculated after failure, or pre-
     calculated before failure (often during LSP establishment).
     Importantly, no signaling is used along the restoration path
     before failure, and no restoration bandwidth is reserved.
     Consequently, there is no guarantee that a given restoration path
     is available when a failure occurs. Thus, one may have to
     crankback to search for an available path.

   - End-to-end LSP restoration with pre-signaled recovery bandwidth
     reservation and no label pre-selection: an end-to-end restoration
     path is pre-calculated before failure and a signaling message is

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     sent along this pre-selected path to reserve bandwidth, but labels
     are not selected (see also [GMPLS-FUNCT]).

     The resources reserved on each link of a restoration path may be
     shared across different working LSPs that are not expected to fail
     simultaneously. Local node policies can be applied to define the
     degree to which capacity is shared across independent failures.
     Upon failure detection, LSP signaling is initiated along the
     restoration path to select labels, and to initiate the appropriate

   - End-to-end LSP restoration with pre-signaled recovery bandwidth
     reservation and label pre-selection: An end-to-end restoration
     path is pre-calculated before failure and a signaling procedure is
     initiated along this pre-selected path on which bandwidth is
     reserved and labels are selected (see also [GMPLS-FUNCT]).

     The resources reserved on each link may be shared across different
     working LSPs that are not expected to fail simultaneously. In
     networks based on TDM, LSC and FSC technology, LSP signaling is
     used after failure detection to establish cross-connections at the
     intermediate switches on the restoration path using the pre-
     selected labels.

   - Local LSP restoration: the above approaches can be applied on a
     local basis rather than end-to-end, in order to reduce recovery
     time (note: no reference available at publication time).

13.8. Schema Selection Criteria

   This section discusses criteria that could be used by the operator
   in order to make a choice among the various P&R mechanisms.

   - Robustness: In general, the less pre-planning of the restoration
     path, the more robust the restoration scheme is to a variety of
     failures, provided that adequate resources are available.
     Restoration schemes with pre-planned paths will not be able to
     recover from network failures that simultaneously affect both the
     working and restoration paths. Thus, these paths should ideally be
     chosen to be as disjoint as possible (i.e. SRLG and node
     disjoint), so that any single failure event will not affect both
     paths. The risk of simultaneous failure of the two paths can be
     reduced by recalculating the restoration path whenever a failure
     occurs along it.

     The pre-selection of a label gives less flexibility for multiple
     failure scenarios than no label pre-selection. If failures occur
     that affect two LSPs that are sharing a label at a common node
     along their restoration routes, then only one of these LSPs can be
     recovered, unless the label assignment is changed.

     The robustness of a restoration scheme is also determined by the
     amount of reserved restoration bandwidth - as the amount of
     restoration bandwidth sharing increases (reserved bandwidth

E. Mannie (Editor) et al.    Standard Track                          46

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     decreases), the restoration scheme becomes less robust to
     failures. Restoration schemes with pre-signaled bandwidth
     reservation (with or without label pre-selection) can reserve
     adequate bandwidth to ensure recovery from any specific set of
     failure events, such as any single SRLG failure, any two SRLG
     failures etc. Clearly, more restoration capacity is allocated if a
     greater degree of failure recovery is required. Thus, the degree
     to which the network is protected is determined by the policy that
     defines the amount of reserved restoration bandwidth.

   - Recovery time: In general, the more pre-planning of the
     restoration route, the more rapid the P&R scheme. Protection
     schemes generally recover faster than restoration schemes.
     Restoration with pre-signaled bandwidth reservation are likely to
     be (significantly) faster than path restoration with re-
     provisioning, especially because of the elimination of any
     crankback. Local restoration will generally be faster than end-to-
     end schemes.

     Recovery time objectives for SONET/SDH protection switching (not
     including time to detect failure) are specified in [ITUT-G.841] at
     50 ms, taking into account constraints on distance, number of
     connections involved, and in the case of ring enhanced protection,
     number of nodes in the ring.

     Recovery time objectives for restoration mechanisms are being
     defined through a separate effort [RFC3386].

   - Resource Sharing: 1+1 and 1:N link and LSP protection require
     dedicated recovery paths with limited ability to share resources:
     1+1 allows no sharing, 1:N allows some sharing of protection
     resources and support of extra (preemptable) traffic. Flexibility
     is limited because of topology restrictions, e.g. fixed ring
     topology for traditional enhanced protection schemes.

     The degree to which restoration schemes allow sharing amongst
     multiple independent failures is directly dictated by the size of
     the restoration pool. In restoration schemes with re-provisioning,
     a pool of restoration capacity can be defined from which all
     restoration routes are selected after failure. Thus, the degree of
     sharing is defined by the amount of available restoration
     capacity. In restoration with pre-signaled bandwidth reservation,
     the amount of reserved restoration capacity is determined by the
     local bandwidth reservation policies. In all restoration schemes,
     pre-emptable resources can use spare restoration capacity when
     that capacity is not being used for failure recovery.

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14. Network Management

   Service Providers (SPs) use network management extensively to
   configure, monitor or provision various devices in their network. It
   is important to note that a SP's equipment may be distributed across
   geographically separate sites thus making distributed management
   even more important. The service provider should utilize an NMS
   system and standard management protocols such as SNMP (see
   [RFC3410], [RFC3411] and [RFC3416]) and the relevant MIB modules as
   standard interfaces to configure, monitor and provision devices at
   various locations. The service provider may also wish to use the
   command line interface (CLI) provided by vendors with their devices.
   However, this is not a standard or recommended solution because
   there is no standard CLI language or interface, which results in N
   different CLIs in a network with devices from N different vendors.
   In the context of GMPLS, it is extremely important for standard
   interfaces to the SP's devices (e.g. SNMP) to exist due to the
   nature of the technology itself. Since GMPLS comprises many
   different layers of control-plane and data-plane technology, it is
   important for management interfaces in this area to be flexible
   enough to allow the manager to manage GMPLS easily, and in a
   standard way.

14.1. Network Management Systems (NMS)

   The NMS system should maintain the collective information about each
   device within the system. Note that the NMS system may actually be
   comprised of several distributed applications (i.e. alarm
   aggregators, configuration consoles, polling applications, etc.)
   that collectively comprises the SP's NMS. In this way, it can make
   provisioning and maintenance decisions with the full knowledge of
   the entire SP's network. Configuration or provisioning information
   (i.e. requests for new services) could be entered into the NMS and
   subsequently distributed via SNMP to the remote devices. Thus,
   making the SP's task of managing the network much more compact and
   effortless rather than having to manage each device individually
   (i.e. via CLI).

   Security and access control can be achieved using the SNMPv3 User-
   based Security Model (USM) [RFC3414] and the View-based Access
   Control Model (VACM) [RFC3415]. This approach can be very
   effectively used within a SP's network, since the SP has access to
   and control over all devices within its domain. Standardized MIBs
   will need to be developed before this approach can be used
   ubiquitously to provision, configure and monitor devices in non-
   heterogeneous networks or across SP's network boundaries.

14.2. Management Information Base (MIB)

   In the context of GMPLS, it is extremely important for standard
   interfaces to devices to exist due to the nature of the technology
   itself. Since GMPLS comprises many different layers of control-plane
   technology, it is important for SNMP MIB modules in this area to be
   flexible enough to allow the manager to manage the entire control

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   plane. This should be done using MIB modules that may cooperate
   (i.e. coordinated row-creation on the agent) or through more
   generalized MIB modules that aggregate some of the desired actions
   to be taken and push those details down to the devices. It is
   important to note that in certain circumstances, it may be necessary
   to duplicate some small subset of manageable objects in new MIB
   modules for management convenience. Control of some parts of GMPLS
   may also be achieved using existing MIB interfaces (i.e. existing
   SONET MIB) or using separate ones, which are yet to be defined. MIB
   modules may have been previously defined in the IETF or ITU. Current
   MIB modules may need to be extended to facilitate some of the new
   functionality desired by GMPLS. In these cases, the working group
   should work on new versions of these MIB modules so that these
   extensions can be added.

14.3. Tools

   As in traditional networks, standard tools such as traceroute
   [RFC1393] and ping [RFC2151] are needed for debugging and
   performance monitoring of GMPLS networks, and mainly for the control
   plane topology, that will mimic the data plane topology.
   Furthermore, such tools provide network reachability information.
   The GMPLS control protocols will need to expose certain pieces of
   information in order for these tools to function properly and to
   provide information germane to GMPLS. These tools should be made
   available via the CLI. These tools should also be made available for
   remote invocation via the SNMP interface [RFC2925].

14.4. Fault Correlation between Multiple Layers

   Due to the nature of GMPLS, and that potential layers may be
   involved in the control and transmission of GMPLS data and control
   information, it is required that a fault in one layer be passed to
   the adjacent higher and lower layers to notify them of the fault.
   However, due to nature of these many layers, it is possible and even
   probable, that hundreds or even thousands of notifications may need
   to transpire between layers. This is undesirable for several
   reasons. First, these notifications will overwhelm the device.
   Second, if the device(s) are programmed to emit SNMP Notifications
   [RFC3417] then the large number of notifications the device may
   attempt to emit may overwhelm the network with a storm of
   notifications. Furthermore, even if the device emits the
   notifications, the NMS that must process these notifications either
   will be overwhelmed or will be processing redundant information.
   That is, if 1000 interfaces at layer B are stacked above a single
   interface below it at layer A, and the interface at A goes down, the
   interfaces at layer B should not emit notifications. Instead, the
   interface at layer A should emit a single notification. The NMS
   receiving this notification should be able to correlate the fact
   that this interface has many others stacked above it and take
   appropriate action, if necessary.

   Devices that support GMPLS should provide mechanisms for
   aggregating, summarizing, enabling and disabling of inter-layer

E. Mannie (Editor) et al.    Standard Track                          49

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   notifications for the reasons described above. In the context of
   SNMP MIB modules, all MIB modules that are used by GMPLS must
   provide enable/disable objects for all notification objects.
   Furthermore, these MIBs must also provide notification summarization
   objects or functionality (as described above) as well. NMS systems
   and standard tools which process notifications or keep track of the
   many layers on any given devices must be capable of processing the
   vast amount of information which may potentially be emitted by
   network devices running GMPLS at any point in time.

15. Security Considerations

   GMPLS defines a control plane architecture for multiple technologies
   and types of network elements. In general, since LSPs established
   using GMPLS may carry high volumes of data and consume significant
   network resources, security mechanisms are required to safeguard the
   underlying network against attacks on the control plane and/or
   unauthorized usage of data transport resources. The GMPLS control
   plane should therefore include mechanisms that prevent or minimize
   the risk of attackers being able to inject and/or snoop on control
   traffic. These risks depend on the level of trust between nodes that
   exchange GMPLS control messages, as well as the realization and
   physical characteristics of the control channel. For example, an in-
   band, in-fiber control channel over SONET/SDH overhead bytes is, in
   general, considered less vulnerable than a control channel realized
   over an out-of-band IP network.

   Security mechanisms can provide authentication and confidentiality.
   Authentication can provide origin verification, message integrity
   and replay protection, while confidentiality ensures that a third
   party cannot decipher the contents of a message. In situations where
   GMPLS deployment requires primarily authentication, the respective
   authentication mechanisms of the GMPLS component protocols may be
   used (see [RFC2747], [RFC3036], [RFC2385] and [LMP]). Additionally,
   the IPsec suite of protocols (see [RFC2402], [RFC2406] and
   [RFC2409]) may be used to provide authentication, confidentiality or
   both, for a GMPLS control channel. IPsec thus offers the benefits of
   combined protection for all GMPLS component protocols as well as key

   A related issue is that of the authorization of requests for
   resources by GMPLS-capable nodes. Authorization determines whether a
   given party, presumable already authenticated, has a right to access
   the requested resources. This determination is typically a matter of
   local policy control [RFC2753], for example by setting limits on the
   total bandwidth available to some party in the presence of resource
   contention. Such policies may become quite complex as the number of
   users, types of resources and sophistication of authorization rules

   After authenticating requests, control elements should match them
   against the local authorization policy. These control elements must
   be capable of making decisions based on the identity of the
   requester, as verified cryptographically and/or topologically. For

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   example, decisions may depend on whether the interface through which
   the request is made is an inter- or intra-domain one. The use of
   appropriate local authorization policies may help in limiting the
   impact of security breaches in remote parts of a network.

   Finally, it should be noted that GMPLS itself introduces no new
   security considerations to the current MPLS-TE signaling (RSVP-TE,
   CR-LDP), routing protocols (OSPF-TE, IS-IS-TE) or network management
   protocols (SNMP).

16. Acknowledgements

   This document is the work of numerous authors and consists of a
   composition of a number of previous drafts in this area.

   Many thanks to Ben Mack-Crane (Tellabs) for all the useful SONET/SDH
   discussions we had together. Thanks also to Pedro Falcao, Alexandre
   Geyssens, Michael Moelants, Xavier Neerdaels, and Philippe Noel from
   Ebone for their SONET/SDH and optical technical advice and support.
   Finally, many thanks also to Krishna Mitra (Consultant), Curtis
   Villamizar (Avici), Ron Bonica (WorldCom) and Bert Wijnen (Lucent)
   for its revision effort of Section 14.

17. Intellectual Property Considerations

   This section is taken from Section 10.4 of [RFC2026].

   The IETF takes no position regarding the validity or scope of any
   intellectual property 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; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances
   of licenses to be made available, or the result of an attempt made
   to obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification
   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive

18. References

18.1 Normative References

   [ANSI-T1.105]   "Synchronous Optical Network (SONET): Basic
                   Description Including Multiplex Structure, Rates,
                   And Formats," ANSI T1.105, 2000.

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   [BUNDLE]        K.Kompella, Y.Rekhter and L.Berger, "Link Bundling
                   in MPLS Traffic Engineering," Work in Progress,

   [GMPLS-FUNCT]   J.P.Lang and B.Rajagopalan (Editors) et al.,
                   "Generalized MPLS Recovery Functional
                   Specification," Work in Progress, draft-ietf-ccamp-

   [GMPLS-G709]    D.Papadimitriou (Editor) et al., "GMPLS Signaling
                   Extensions for G.709 Optical Transport Networks
                   Control," Work in progress, draft-ietf-ccamp-gmpls-

   [GMPLS-OVERLAY] G.Swallow et al., "GMPLS RSVP Support for the
                   Overlay Model," Work in Progress, draft-ietf-ccamp-

   [GMPLS-ROUTING] K.Kompella and Y.Rekhter (Editors) et al., "Routing
                   Extensions in Support of Generalized MPLS," Work in
                   Progress, draft-ietf-ccamp-gmpls-routing-05.txt.

   [GMPLS-SONET-SDH] E.Mannie and D.Papadimitriou (Editors) et al.,
                   "Generalized MPLS Extensions for SONET and SDH
                   Control," Work in progress, draft-ietf-ccamp-gmpls-

   [HIERARCHY]     K.Kompella and Y.Rekhter, "LSP Hierarchy with
                   Generalized MPLS TE," Work in Progress, draft-ietf-

   [ITUT-G.707]    ITU-T, "Network Node Interface for the Synchronous
                   Digital Hierarchy", Recommendation G.707, October

   [ITUT-G.709]    ITU-T, "Interface for the Optical Transport Network
                   (OTN)," Recommendation G.709 version 1.0 (and
                   Amendment 1), February 2001 (and October 2001).

   [ITUT-G.841]    ITU-T, "Types and Characteristics of SDH Network
                   Protection Architectures," Recommendation G.841,
                   October 1998.

   [LMP]           J.P.Lang (Editor) et al., "Link Management Protocol
                   (LMP)," Work in progress, draft-ietf-ccamp-lmp-

   [LMP-WDM]       A.Fredette and J.P.Lang (Editors) et al., "LMP for
                   WDM Optical Line Systems (LMP-WDM)," Work in
                   progress, draft-ietf-ccamp-lmp-wdm-02.txt.

   [OSPF-TE-GMPLS] K.Kompella and Y.Rekhter (Editors), "OSPF Extensions
                   in Support of Generalized MPLS," Work in Progress,

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   [OSPF-TE]    D.Katz, D.Yeung, and K.Kompella, "Traffic
                Engineering Extensions to OSPF", Work in Progress,

   [RFC1393]    G.Malkin, "Traceroute Using an IP Option", IETF RFC
                1393, January 1993.

   [RFC2026]    S.Bradner, "The Internet Standards Process -- Revision
                3," BCP 9, IETF RFC 2026, October 1996.

   [RFC2119]    S.Bradner, "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, IETF RFC 2119, March 1997.

   [RFC2151]    G.Kessler and S.Shepard, "A Primer On Internet and
                TCP/IP Tools and Utilities", IETF RFC 2151, June 1997.

   [RFC2385]    A.Heffernan, "Protection of BGP Sessions via the TCP
                MD5 Signature Option," IETF RFC 2385, August 1998.

   [RFC2402]    S.Kent and R.Atkinson, "IP Authentication Header," IETF
                RFC 2402, November 1998.

   [RFC2406]    S.Kent and R. Atkinson, "IP Encapsulating Security
                Payload (ESP)," IETF RFC 2406, November 1998.

   [RFC2409]    D.Harkins and D.Carrel, "The Internet Key Exchange
                (IKE)," IETF RFC 2409, November 1998.

   [RFC2747]    F.Baker et al., "RSVP Cryptographic Authentication,"
                IETF RFC 2747, January 2000.

   [RFC2753]    R.Yavatkar, D.Pendarakis and R.Guerin, "A Framework for
                Policy-based Admission Control," IETF RFC 2753, January

   [RFC2925]    K.White, "Definitions of Managed Objects for Remote
                Ping, Traceroute, and Lookup Operations," IETF RFC
                2925, September 2000.

   [RFC3031]    E.Rosen, A.Viswanathan, and R.Callon, "Multiprotocol
                Label Switching Architecture," IETF RFC 3031, January

   [RFC3036]    L.Andersson, P.Doolan, N.Feldman, A.Fredette, and
                B.Thomas, "LDP Specification," IETF RFC 3036, January

   [RFC3209]    D.Awduche, et al., "RSVP-TE: Extensions to RSVP for
                LSP Tunnels," IETF RFC 3209, December 2001.

   [RFC3212]    B.Jamoussi (Editor) et al., "Constraint-Based LSP Setup
                using LDP," IETF RFC 3212, January 2002.

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   [RFC3411]    D.Harrington, R.Presuhn and B.Wijnen, "An Architecture
                for Describing Simple Network Management Protocol
                (SNMP) Management Frameworks," IETF RFC 3411, December

   [RFC3414]    U.Blumenthal and B.Wijnen, "User-based Security Model
                (USM) for version 3 of the Simple Network Management
                Protocol (SNMPv3)," IETF RFC 3414, December 2002.

   [RFC3415]    B.Wijnen, R.Presuhn, and K.McCloghrie, "View-based
                Access Control Model (VACM) for the Simple Network
                Management Protocol (SNMP)," IETF RFC 3415, December

   [RFC3416]    R.Presuhn (Editor), "Version 2 of the Protocol
                Operations for the Simple Network Management Protocol
                (SNMP)," IETF RFC 3416, December 2002.

   [RFC3417]    R.Presuhn (Editor), "Transport Mappings for the Simple
                Network Management Protocol (SNMP)," IETF RFC 3417,
                December 2002.

   [RFC3477]    K.Kompella and Y.Rekhter, "Signalling Unnumbered
                Links in Resource ReSerVation Protocol - Traffic
                Engineering (RSVP-TE)," IETF RFC 3477, January 2003.

   [RFC3471]    L.Berger (Editor) et al., "Generalized MPLS -
                Signaling Functional Description," IETF RFC 3471,
                January 2003.

   [RFC3472]    P.Ashwood-Smith and L.Berger (Editors) et al.,
                "Generalized MPLS Signaling - CR-LDP Extensions," IETF
                RFC 3472, January 2003.

   [RFC3473]    L.Berger (Editor) et al., "Generalized MPLS
                Signaling - RSVP-TE Extensions," IETF RFC 3473, January

   [RFC3479]    A.Farrel (Editor) et al., "Fault Tolerance for the
                Label Distribution Protocol (LDP)," IETF RFC 3479,
                February 2003.

   [RFC3480]    K.Kompella, Y.Rekhter and A.Kullberg, "Signalling
                Unnumbered Links in CR-LDP," IETF RFC 3480, February

18.2 Informative References

   [ISIS-TE]    H.Smit and T.Li, "IS-IS extensions for Traffic
                Engineering," Work in Progress, draft-ietf-isis-

   [ISIS-TE-GMPLS] K.Kompella and Y.Rekhter (Editors), "IS-IS

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                Extensions in Support of Generalized MPLS," Work in
                Progress, draft-ietf-isis-gmpls-extensions-16.txt.

   [MANCHESTER] J.Manchester, P.Bonenfant and C.Newton, "The Evolution
                of Transport Network Survivability," IEEE
                Communications Magazine, August 1999.

   [OIF-UNI]    The Optical Internetworking Forum, "User Network
                Interface (UNI) 1.0 Signaling Specification -
                Implementation Agreement OIF-UNI-01.0," October 2001.

   [OLI-REQ]    A.Fredette (Editor), "Optical Link Interface
                Requirements," Work in Progress.

   [RFC2702]    D.Awduche, et al., "Requirements for Traffic
                Engineering Over MPLS," IETF RFC 2702, September 1999.

   [RFC3386]    W.Lai, D.McDysan, et al., "Network Hierarchy and Multi-
                layer Survivability," IETF RFC 3386, November 2002.

   [RFC3410]    J.Case, R.Mundy, D.Partain, and B. Stewart,
                "Introduction and Applicability Statements for
                Internet-Standard Management Framework," IETF RFC 3410,
                December 2002.

   [RFC3469]    V.Sharma and F.Hellstrand (Editors), "Framework for
                Multi-Protocol Label Switching (MPLS)-based Recovery,"
                IETF RFC 3469, February 2003.

   [SONET-SDH-GMPLS-FRM] G.Bernstein, E.Mannie and V.Sharma,
                "Framework for GMPLS-based Control of SDH/SONET
                Networks," Work in Progress.

19. Author's Address

   Eric Mannie (Consult)
   Phone:  +32 2 658-5023
   Mobile: +32 (0)495-221775

20. Contributors

   Peter Ashwood-Smith (Nortel)      Eric Mannie (Consult)
   P.O. Box 3511 Station C,          Phone:  +32 2 648-5023
   Ottawa, ON K1Y 4H7, Canada        Mobile: +32 (0)495-221775
   Email:  Email:

   Daniel O. Awduche (Consult)       Thomas D. Nadeau (Cisco)
   Email:        250 Apollo Drive
                                     Chelmsford, MA 01824, USA

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   Ayan Banerjee (Calient)           Lyndon Ong (Ciena)
   5853 Rue Ferrari                  10480 Ridgeview Ct
   San Jose, CA 95138, USA           Cupertino, CA 95014, USA
   Email:      Email:

   Debashis Basak (Accelight)        Dimitri Papadimitriou (Alcatel)
   70 Abele Road, Bldg.1200          Francis Wellesplein, 1
   Bridgeville, PA 15017, USA        B-2018 Antwerpen, Belgium
   Email:       Email:

   Lou Berger (Movaz)                Dimitrios Pendarakis (Tellium)
   7926 Jones Branch Drive           2 Crescent Place, P.O. Box 901
   MCLean VA, 22102, USA             Oceanport, NJ 07757-0901, USA
   Email:          Email:

   Greg Bernstein (Grotto)           Bala Rajagopalan (Tellium)
   Email:                            2 Crescent Place, P.O. Box 901       Oceanport, NJ 07757-0901, USA

   Sudheer Dharanikota (Consult)     Yakov Rekhter (Juniper)
   Email:           1194 N. Mathilda Ave.
                                     Sunnyvale, CA 94089, USA

   John Drake (Calient)              Debanjan Saha
   5853 Rue Ferrari                  (IBM Watson Research Center)
   San Jose, CA 95138, USA           Email:

   Yanhe Fan (Axiowave)              Hal Sandick
   200 Nickerson Road                Shepard M.S.
   Marlborough, MA 01752, USA        2401 Dakota Street
   Email:          Durham, NC 27705, USA

   Don Fedyk (Nortel)                Vishal Sharma (Metanoia)
   600 Technology Park Drive         1600 Villa Street, Unit 352
   Billerica, MA 01821, USA          Mountain View, CA 94041, USA
   Email:                            Email:

   Gert Grammel (Alcatel)            George Swallow (Cisco)
   Lorenzstrasse, 10                 250 Apollo Drive
   70435 Stuttgart, Germany          Chelmsford, MA 01824, USA
   Email:    Email:

   Dan Guo (Turin)                   Z. Bo Tang (Tellium)
   1415 N. McDowell Blvd, Petaluma,  2 Crescent Place, P.O. Box 901
   CA 95454, USA                     Oceanport, NJ 07757-0901, USA
   Email:     Email:

E. Mannie (Editor) et al.    Standard Track                          56

draft-ietf-ccamp-gmpls-architecture-07.txt                     May 2003

   Kireeti Kompella (Juniper)        Jennifer Yates (AT&T)
   1194 N. Mathilda Ave.             180 Park Avenue
   Sunnyvale, CA 94089, USA          Florham Park, NJ 07932, USA
   Email:        Email:

   Alan Kullberg (NetPlane)          George R. Young (Edgeflow)
   888 Washington                    329 March Road
   St.Dedham, MA 02026, USA          Ottawa, Ontario, K2K 2E1, Canada
   Email:      Email:

   Jonathan P. Lang                  John Yu (Hammerhead Systems)
   (Rincon Networks)                 640 Clyde Court
   Email:            Mountain View, CA 94043, USA

   Fong Liaw (Solas Research)        Alex Zinin (Alcatel)
   Solas Research, LLC               1420 North McDowell Ave
   Email:         Petaluma, CA 94954, USA

E. Mannie (Editor) et al.    Standard Track                          57

draft-ietf-ccamp-gmpls-architecture-07.txt                     May 2003

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