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Requirements for GMPLS-Based Multi-Region and Multi-Layer Networks (MRN/MLN)

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 5212.
Authors Jean-Louis Le Roux , Kohei Shiomoto , Martin Vigoureux , Dimitri Papadimitriou , Deborah Brungard
Last updated 2018-12-20 (Latest revision 2008-05-28)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
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IESG IESG state Became RFC 5212 (Informational)
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Responsible AD Ross Callon
Send notices to (None)
Network Working Group                               Kohei Shiomoto (NTT)
Internet-Draft                    Dimitri Papadimitriou (Alcatel-Lucent)
Intended Status: Informational       Jean-Louis Le Roux (France Telecom)
Created: May 28, 2008                  Martin Vigoureux (Alcatel-Lucent)
Expires: November 28, 2008                       Deborah Brungard (AT&T)

               Requirements for GMPLS-Based Multi-Region and
                      Multi-Layer Networks (MRN/MLN)


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   Most of the initial efforts to utilize Generalized MPLS (GMPLS)
   have been related to environments hosting devices with a single
   switching capability. The complexity raised by the control of such
   data planes is similar to that seen in classical IP/MPLS networks.
   By extending MPLS to support multiple switching technologies, GMPLS
   provides a comprehensive framework for the control of a multi-
   layered network of either a single switching technology or multiple
   switching technologies.

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    In GMPLS, a switching technology domain defines a region, and a
    network of multiple switching types is referred to in this document
    as a Multi-Region Network (MRN). When referring in general to a
    layered network, which may consist of either a single or multiple
    regions, this document uses the term, Multi-Layer Network (MLN).
    This document defines a framework for GMPLS based multi-region /
    multi-layer networks and lists a set of functional requirements.

Table of Contents
    1. Introduction.................................................3
    1.1. Scope......................................................4
    2. Conventions Used in this Document............................5
    2.1. List of Acronyms...........................................5
    3. Positioning..................................................6
    3.1. Data Plane Layers and Control Plane Regions................6
    3.2. Service Layer Networks.....................................6
    3.3. Vertical and Horizontal Interaction and Integration........7
    3.4. Motivation.................................................8
    4. Key Concepts of GMPLS-Based MLNs and MRNs....................9
    4.1. Interface Switching Capability.............................9
    4.2. Multiple Interface Switching Capabilities.................10
    4.2.1. Networks with Multi-Switching-Type-Capable Hybrid Nodes.11
    4.3. Integrated Traffic Engineering (TE) and Resource Control..11
    4.3.1. Triggered Signaling.....................................12
    4.3.2. FA-LSPs.................................................12
    4.3.3. Virtual Network Topology (VNT)..........................13
    5. Requirements................................................14
    5.1. Handling Single-Switching and Multi-Switching-Type-Capable
    5.2. Advertisement of the Available Adjustment Resource........14
    5.3. Scalability...............................................15
    5.4. Stability.................................................16
    5.5. Disruption Minimization...................................16
    5.6. LSP Attribute Inheritance.................................16
    5.7. Computing Paths With and Without Nested Signaling.........17
    5.8. LSP Resource Utilization..................................18
    5.8.1. FA-LSP Release and Setup................................18
    5.8.2. Virtual TE-Links........................................19
    5.9. Verification of the LSPs..................................20
    5.10. Management...............................................20
    6. Security Considerations.....................................23
    7. IANA Considerations.........................................23
    8. Acknowledgements............................................23
    9. References..................................................23
    9.1. Normative Reference.......................................23
    9.2. Informative References....................................24
    10. Authors' Addresses.........................................25
    11. Contributors' Addresses....................................26
    12. Intellectual Property Considerations.......................26
    13. Full Copyright Statement...................................27

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1. Introduction

   Generalized MPLS (GMPLS) extends MPLS to handle multiple switching
   technologies: packet switching, layer-2 switching, TDM switching,
   wavelength switching, and fiber switching (see [RFC3945]). The
   Interface Switching Capability (ISC) concept is introduced for
   these switching technologies and is designated as follows: PSC
   (packet switch capable), L2SC (Layer-2 switch capable), TDM (Time
   Division Multiplex capable), LSC (lambda switch capable), and FSC
   (fiber switch capable).

   The representation, in a GMPLS control plane, of a switching
   technology domain is referred to as a region [RFC4206]. A switching
   type describes the ability of a node to forward data of a
   particular data plane technology, and uniquely identifies a network
   region. A layer describes a data plane switching granularity level
   (e.g., VC4, VC-12). A data plane layer is associated with a region
   in the control plane (e.g., VC4 is associated with TDM, MPLS is
   associated with PSC). However, more than one data plane layer can
   be associated with the same region (e.g., both VC4 and VC12 are
   associated with TDM). Thus, a control plane region, identified by
   its switching type value (e.g., TDM), can be sub-divided into
   smaller granularity component networks based on "data plane
   switching layers". The Interface Switching Capability Descriptor
   (ISCD) [RFC4202], identifying the interface switching capability
   (ISC), the encoding type, and the switching bandwidth granularity,
   enables the characterization of the associated layers.

   In this document, we define a Multi Layer Network (MLN) to be a
   Traffic Engineering (TE) domain comprising multiple data plane
   switching layers either of the same ISC (e.g., TDM) or different
   ISC (e.g., TDM and PSC) and controlled by a single GMPLS control
   plane instance. We further define a particular case of MLNs. A
   Multi Region Network (MRN) is defined as a TE domain supporting at
   least two different switching types (e.g., PSC and TDM), either
   hosted on the same device or on different ones, and under the
   control of a single GMPLS control plane instance.

   MLNs can be further categorized according to the distribution of
   the ISCs among the Label Switching Routers (LSRs):

   - Each LSR may support just one ISC.
     Such LSRs are known as single-switching-type-capable LSRs.
     The MLN may comprise a set of single-switching-type-capable LSRs
     some of which support different ISCs.
   - Each LSR may support more than one ISC at the same time.
   - Such LSRs are known as multi-switching-type-capable LSRs, and
     can be further classified as either "simplex" or "hybrid" nodes
     as defined in Section 4.2.

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   - The MLN may be constructed from any combination of single-
     switching-type-capable LSRs and multi-switching-type-capable

   Since GMPLS provides a comprehensive framework for the control of
   different switching capabilities, a single GMPLS instance may be
   used to control the MLN/MRN. This enables rapid service
   provisioning and efficient traffic engineering across all switching
   capabilities. In such networks, TE Links are consolidated into a
   single Traffic Engineering Database (TED). Since this TED contains
   the information relative to all the different regions and layers
   existing in the network, a path across multiple regions or layers
   can be computed using this TED. Thus optimization of network
   resources can be achieved across the whole MLN/MRN.

   Consider, for example, a MRN consisting of packet- switch capable
   routers and TDM cross-connects. Assume that a packet Label Switched
   Path (LSP) is routed between source and destination packet-switch
   capable routers, and that the LSP can be routed across the PSC-
   region (i.e., utilizing only resources of the packet region
   topology). If the performance objective for the packet LSP is not
   satisfied, new TE links may be created between the packet-switch
   capable routers across the TDM-region (for example, VC-12 links)
   and the LSP can be routed over those TE links. Furthermore, even if
   the LSP can be successfully established across the PSC-region, TDM
   hierarchical LSPs across the TDM region between the packet-switch
   capable routers may be established and used if doing so is
   necessary to meet the operator's objectives for network resources
   availability (e.g., link bandwidth). The same considerations hold
   when VC4 LSPs are provisioned to provide extra flexibility for the
   VC12 and/or VC11 layers in an MLN.

   Sections 3 and 4 of this document provide further background
   information of the concepts and motivation behind multi-region and
   multi-layer networks. Section 5 presents detailed requirements for
   protocols used to implement such networks.


   Early sections of this document describe the motivations and
   reasoning that require the development and deployment of MRN/MLN.
   Later sections of this document set out the required features that
   the GMPLS control plane must offer to support MRN/MLN. There is no
   intention to specify solution- specific and/or protocol elements in
   this document. The applicability of existing GMPLS protocols and
   any protocol extensions to the MRN/MLN is addressed in separate
   documents [MRN-EVAL].

   This document covers the elements of a single GMPLS control plane
   instance controlling multiple layers within a given TE domain. A

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   control plane instance can serve one, two or more layers. Other
   possible approaches such as having multiple control plane instances
   serving disjoint sets of layers are outside the scope of this
   document. It is most probable that such a MLN or MRN would be
   operated by a single Service Provider, but this document does not
   exclude the possibility of two layers (or regions) being under
   different administrative control (for example, by different Service
   Providers that share a single control plane instance) where the
   administrative domains are prepared to share a limited amount of

   For such TE domain to interoperate with edge nodes/domains
   supporting non-GMPLS interfaces (such as those defined by other
   SDOs), an interworking function may be needed. Location and
   specification of this function are outside the scope of this
   document (because interworking aspects are strictly under the
   responsibility of the interworking function).

   This document assumes that the interconnection of adjacent MRN/MLN
   TE domains makes use of [RFC4726] when their edges also support
   inter- domain GMPLS RSVP-TE extensions.

2. Conventions Used in this Document

   Although this is not a protocol specification, the key words "MUST",
   NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" are used in this
   document to highlight requirements, and are to be interpreted as
   described in RFC 2119 [RFC2119].

2.1.List of Acronyms

   ERO: Explicit Route Object
   FA: Forwarding Adjacency
   FA-LSP: Forwarding Adjacency Label Switched Path
   FSC: Fiber Switching Capable
   ISC: Interface Switching Capability
   ISCD: Interface Switching Capability Descriptor
   L2SC: Layer-2 Switching Capable
   LSC: Lambda Switching Capable
   LSP: Label Switched Path
   LSR: Label Switching Router
   MLN: Multi-Layer Network
   MRN: Multi-Region Network
   PSC: Packet Switching Capable
   SRLG: Shared Risk Ling Group
   TDM: Time-Division Switch Capable
   TE: Traffic Engineering
   TED: Traffic Engineering Database
   VNT: Virtual Network Topology

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3. Positioning

   A multi-region network (MRN) is always a multi-layer network (MLN)
   since the network devices on region boundaries bring together
   different ISCs. A MLN, however, is not necessarily a MRN since
   multiple layers could be fully contained within a single region.
   For example, VC12, VC4, and VC4-4c are different layers of the TDM

3.1. Data Plane Layers and Control Plane Regions

   A data plane layer is a collection of network resources capable of
   terminating and/or switching data traffic of a particular format
   [RFC4397]. These resources can be used for establishing LSPs for
   traffic delivery. For example, VC-11 and VC4-64c represent two
   different layers.

   From the control plane viewpoint, an LSP region is defined as a set
   of one or more data plane layers that share the same type of
   switching technology, that is, the same switching type. For example,
   VC-11, VC-4, and VC-4-7v layers are part of the same TDM region.
   The regions that are currently defined are: PSC, L2SC, TDM, LSC,
   and FSC. Hence, an LSP region is a technology domain (identified by
   the ISC type) for which data plane resources (i.e., data links) are
   represented into the control plane as an aggregate of TE
   information associated with a set of links (i.e., TE links). For
   example VC-11 and VC4-64c capable TE links are part of the same TDM
   region. Multiple layers can thus exist in a single region network.

   Note also that the region may produce a distinction within the
   control plane. Layers of the same region share the same switching
   technology and, therefore, use the same set of technology-specific
   signaling objects and technology-specific value setting of TE link
   attributes within the control plane, but layers from different
   regions may use different technology-specific objects and TE
   attribute values. This means that it may not be possible to simply
   forward the signaling message between LSR hosting different
   switching technologies because change in some of the signaling
   objects (for example, the traffic parameters) when crossing a
   region boundary even if a single control plane instance is used to
   manage the whole MRN. We may solve this issue by using triggered
   signaling (see Section 4.3.1).

3.2. Service Layer Networks

   A service provider's network may be divided into different service
   layers. The customer's network is considered from the provider's
   perspective as the highest service layer. It interfaces to the
   highest service layer of the service provider's network.
   Connectivity across the highest service layer of the service

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   provider's network may be provided with support from successively
   lower service layers. Service layers are realized via a hierarchy
   of network layers located generally in several regions and commonly
   arranged according to the switching capabilities of network devices.

   For instance some customers purchase Layer 1 (i.e., transport)
   services from the service provider, some Layer 2 (e.g., ATM), while
   others purchase Layer 3 (IP/MPLS) services. The service provider
   realizes the services by a stack of network layers located within
   one or more network regions. The network layers are commonly
   arranged according to the switching capabilities of the devices in
   the networks. Thus, a customer network may be provided on top of
   the GMPLS-based multi-region/multi-layer network. For example, a
   Layer 1 service (realized via the network layers of TDM, and/or LSC,
   and/or FSC regions) may support a Layer 2 network (realized via ATM
   VP/VC) which may itself support a Layer 3 network (IP/MPLS region).
   The supported data plane relationship is a data plane client-server
   relationship where the lower layer provides a service for the
   higher layer using the data links realized in the lower layer.

   Services provided by a GMPLS-based multi-region/multi-layer network
   are referred to as "Multi-region/Multi-layer network services". For
   example, legacy IP and IP/MPLS networks can be supported on top of
   multi-region/multi-layer networks. It has to be emphasized that
   delivery of such diverse services is a strong motivator for the
   deployment of multi-region/multi-layer networks.

   A customer network may be provided on top of a server GMPLS-based
   MRN/MLN which is operated by a service provider. For example, a
   pure IP and/or an IP/MPLS network can be provided on top of GMPLS-
   based packet over optical networks [RFC5146]. The relationship
   between the networks is a client/server relationship and, such
   services are referred to as "MRN/MLN services". In this case, the
   customer network may form part of the MRN/MLN, or may be partially
   separated, for example to maintain separate routing information but
   retain common signaling.

3.3. Vertical and Horizontal Interaction and Integration

   Vertical interaction is defined as the collaborative mechanisms
   within a network element that is capable of supporting more than
   one layer or region and of realizing the client/server
   relationships between the layers or regions. Protocol exchanges
   between two network controllers managing different regions or
   layers are also a vertical interaction. Integration of these
   interactions as part of the control plane is referred to as
   vertical integration. Thus, this refers to the collaborative
   mechanisms within a single control plane instance driving multiple
   network layers part of the same region or not. Such a concept is
   useful in order to construct a framework that facilitates efficient

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   network resource usage and rapid service provisioning in carrier
   networks that are based on multiple layers, switching technologies,
   or ISCs.

   Horizontal interaction is defined as the protocol exchange between
   network controllers that manage transport nodes within a given
   layer or region. For instance, the control plane interaction
   between two TDM network elements switching at OC-48 is an example
   of horizontal interaction. GMPLS protocol operations handle
   horizontal interactions within the same routing area. The case
   where the interaction takes place across a domain boundary, such as
   between two routing areas within the same network layer, is
   evaluated as part of the inter- domain work [RFC4726], and is
   referred to as horizontal integration. Thus, horizontal integration
   refers to the collaborative mechanisms between network partitions
   and/or administrative divisions such as routing areas or autonomous

   This distinction needs further clarification when administrative
   domains match layer/region boundaries. Horizontal interaction is
   extended to cover such cases. For example, the collaborative
   mechanisms in place between two lambda switching capable areas
   relate to horizontal integration. On the other hand, the
   collaborative mechanisms in place between a packet switching
   capable (e.g., IP/MPLS) domain and a separate time division
   switching capable (e.g., VC4 SDH) domain over which it operates are
   part of the horizontal integration while it can also be seen as a
   first step towards vertical integration.


   The applicability of GMPLS to multiple switching technologies
   provides a unified control and management approach for both LSP
   provisioning and recovery. Indeed, one of the main motivations for
   unifying the capabilities and operations of the GMPLS control plane
   is the desire to support multi-LSP-region [RFC4206] routing and
   Traffic Engineering (TE) capabilities. For instance, this enables
   effective network resource utilization of both the Packet/Layer2
   LSP regions and the Time Division Multiplexing (TDM) or Lambda LSP
   regions in high capacity networks.

   The rationales for GMPLS controlled multi-layer/multi-region
   networks are summarized below:

   - The maintenance of multiple instances of the control plane on
     devices hosting more than one switching capability not only
     increases the complexity of their interactions but also increases
     the total amount of processing individual instances would handle.

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   - The unification of the addressing spaces helps in avoiding
     multiple identifiers for the same object (a link, for instance,
     or more generally, any network resource). On the other hand such
     aggregation does not impact the separation between the control
     plane and the data plane.

   - By maintaining a single routing protocol instance and a single TE
     database per LSR, a unified control plane model removes the
     requirement to maintain a dedicated routing topology per layer
     and therefore does not mandate a full mesh of routing adjacencies
     as is the case with overlaid control planes.

   - The collaboration between technology layers where the control
     channel is associated with the data channel (e.g. packet/framed
     data planes) and technology layers where the control channel is
     not directly associated with the data channel (SONET/SDH, G.709,
     etc.) is facilitated by the capability within GMPLS to associate
     in-band control plane signaling to the IP terminating interfaces
     of the control plane.

   - Resource management and policies to be applied at the edges of
     such a MRN/MLN is made more simple (fewer control to management
     interactions) and more scalable (through the use of aggregated

   - Multi-region/multi-layer traffic engineering is facilitated as
     TE-links from distinct regions/layers are stored within the same
     TE Database.

4. Key Concepts of GMPLS-Based MLNs and MRNs

   A network comprising transport nodes with multiple data plane
   layers of either the same ISC or different ISCs, controlled by a
   single GMPLS control plane instance, is called a Multi-Layer
   Network (MLN). A sub-set of MLNs consists of networks supporting
   LSPs of different switching technologies (ISCs). A network
   supporting more than one switching technology is called a Multi-
   Region Network (MRN).

4.1. Interface Switching Capability

   The Interface Switching Capability (ISC) is introduced in GMPLS to
   support various kinds of switching technology in a unified way
   [RFC4202]. An ISC is identified via a switching type.

   A switching type (also referred to as the switching capability
   type) describes the ability of a node to forward data of a
   particular data plane technology, and uniquely identifies a network
   region. The following ISC types (and, hence, regions) are defined:
   PSC, L2SC, TDM, LSC, and FSC. Each end of a data link (more

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   precisely, each interface connecting a data link to a node) in a
   GMPLS network is associated with an ISC.

   The ISC value is advertised as a part of the Interface Switching
   Capability Descriptor (ISCD) attribute (sub-TLV) of a TE link end
   associated with a particular link interface [RFC4202]. Apart from
   the ISC, the ISCD contains information including the encoding type,
   the bandwidth granularity, and the unreserved bandwidth on each of
   eight priorities at which LSPs can be established. The ISCD does
   not "identify" network layers, it uniquely characterizes
   information associated to one or more network layers.

   TE link end advertisements may contain multiple ISCDs. This can be
   interpreted as advertising a multi-layer (or multi-switching-
   capable) TE link end. That is, the TE link end (and therefore the
   TE link) is present in multiple layers.

4.2. Multiple Interface Switching Capabilities

   In an MLN, network elements may be single-switching-type-capable or
   multi-switching-type-capable nodes. Single-switching-type-capable
   nodes advertise the same ISC value as part of their ISCD sub-TLV(s)
   to describe the termination capabilities of each of their TE
   Link(s). This case is described in [RFC4202].

   Multi-switching-type-capable LSRs are classified as "simplex" or
   "hybrid" nodes. Simplex and hybrid nodes are categorized according
   to the way they advertise these multiple ISCs:

   - A simplex node can terminate data links with different switching
     capabilities where each data link is connected to the node by a
     separate link interface. So, it advertises several TE Links each
     with a single ISC value carried in its ISCD sub-TLV (following
     the rules defined in [RFC4206]). For example, an LSR with PSC and
     TDM links each of which is connected to the LSR   via a separate

   - A hybrid node can terminate data links with different switching
     capabilities where the data links are connected to the node by
     the same interface. So, it advertises a single TE Link
     containing more than one ISCD each with a different ISC value.
     For example, a node may terminate PSC and TDM data links and
     interconnect those external data links via internal links. The
     external interfaces connected to the node have both PSC and TDM

   Additionally, TE link advertisements issued by a simplex or a
   hybrid node may need to provide information about the node's
   internal adjustment capacity between the switching technologies
   supported. The term "adjustment" capacity refers to the property of

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   an hybrid node to interconnect different switching capabilities it
   provides through its external interfaces.. This information allows
   path computation to select an end- to-end multi-layer or multi-
   region path that includes links of different switching capabilities
   that are joined by LSRs that can adapt the signal between the links.

4.2.1.Networks with Multi-Switching-Type-Capable Hybrid Nodes

   This type of network contains at least one hybrid node, zero or
   more simplex nodes, and a set of single-switching-type-capable

   Figure 1 shows an example hybrid node. The hybrid node has two
   switching elements (matrices), which support, for instance, TDM and
   PSC switching respectively. The node terminates a PSC and a TDM
   link (Link1 and Link2 respectively). It also has an internal link
   connecting the two switching elements.

   The two switching elements are internally interconnected in such a
   way that it is possible to terminate some of the resources of, say,
   Link2 and provide adjustment for PSC traffic received/sent over the
   PSC interface (#b). This situation is modeled in GMPLS by
   connecting the local end of Link2 to the TDM switching element via
   an additional interface realizing the termination/adjustment
   function. There are two possible ways to set up PSC LSPs through
   the hybrid node. Available resource advertisement (i.e., Unreserved
   and Min/Max LSP Bandwidth) should cover both of these methods.

                         : Network element           :
                         :            --------       :
                         :           |  PSC   |      :
             Link1 -------------<->--|#a      |      :
                         :           |        |      :
                         :  +--<->---|#b      |      :
                         :  |         --------       :
                         :  |        ----------      :
             TDM         :  +--<->--|#c  TDM   |     :
              +PSC       :          |          |     :
             Link2 ------------<->--|#d        |     :
                         :           ----------      :

                              Figure 1. Hybrid node.

4.3. Integrated Traffic Engineering (TE) and Resource Control

   In GMPLS-based multi-region/multi-layer networks, TE Links may be
   consolidated into a single Traffic Engineering Database (TED) for
   use by the single control plane instance. Since this TED contains

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   the information relative to all the layers of all regions in the
   network, a path across multiple layers (possibly crossing multiple
   regions) can be computed using the information in this TED. Thus,
   optimization of network resources across the multiple layers of the
   same region and across multiple regions can be achieved.

   These concepts allow for the operation of one network layer over
   the topology (that is, TE links) provided by other network layers
   (for example, the use of a lower layer LSC LSP carrying PSC LSPs).
   In turn, a greater degree of control and inter-working can be
   achieved, including (but not limited too):

   - Dynamic establishment of Forwarding Adjacency (FA) LSPs
     [RFC4206] (see Sections 4.3.2 and 4.3.3).

   - Provisioning of end-to-end LSPs with dynamic triggering of FA

   Note that in a multi-layer/multi-region network that includes
   multi- switching-type-capable nodes, an explicit route used to
   establish an end-to-end LSP can specify nodes that belong to
   different layers or regions. In this case, a mechanism to control
   the dynamic creation of FA-LSPs may be required (see Sections 4.3.2
   and 4.3.3).

   There is a full spectrum of options to control how FA-LSPs are
   dynamically established. The process can be subject to the control
   of a policy, which may be set by a management component, and which
   may require that the management plane is consulted at the time that
   the FA-LSP is established. Alternatively, the FA-LSP can be
   established at the request of the control plane without any
   management control.

4.3.1. Triggered Signaling

   When an LSP crosses the boundary from an upper to a lower layer, it
   may be nested into a lower layer FA-LSP that crosses the lower
   layer. From a signaling perspective, there are two alternatives to
   establish the lower layer FA-LSP: static (pre-provisioned) and
   dynamic (triggered).  A pre-provisioned FA-LSP may be initiated
   either by the operator or automatically using features like TE
   auto-mesh [RFC4972]. If such a lower layer LSP does not already
   exist, the LSP may be established dynamically. Such a mechanism is
   referred to as "triggered signaling".

4.3.2. FA-LSPs

   Once an LSP is created across a layer from one layer border node to
   another, it can be used as a data link in an upper layer.

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   Furthermore, it can be advertised as a TE-link, allowing other
   nodes to consider the LSP as a TE link for their path computation
   [RFC4206]. An LSP created either statically or dynamically by one
   instance of the control plane and advertised as a TE link into the
   same instance of the control plane is called a Forwarding Adjacency
   LSP (FA-LSP). The FA-LSP is advertised as a TE link, and that TE
   link is called a Forwarding Adjacency (FA). An FA has the special
   characteristic of not requiring a routing adjacency (peering)
   between its end points yet still guaranteeing control plane
   connectivity between the FA-LSP end points based on a signaling
   adjacency. An FA is a useful and powerful tool for improving the
   scalability of GMPLS Traffic Engineering (TE) capable networks
   since multiple higher layer LSPs may be nested (aggregated) over a
   single FA-LSP.

   The aggregation of LSPs enables the creation of a vertical (nested)
   LSP Hierarchy. A set of FA-LSPs across or within a lower layer can
   be used during path selection by a higher layer LSP. Likewise, the
   higher layer LSPs may be carried over dynamic data links realized
   via LSPs (just as they are carried over any "regular" static data
   links). This process requires the nesting of LSPs through a
   hierarchical process [RFC4206]. The TED contains a set of LSP
   advertisements from different layers that are identified by the
   ISCD contained within the TE link advertisement associated with the
   LSP [RFC4202].

   If a lower layer LSP is not advertised as an FA, it can still be
   used to carry higher layer LSPs across the lower layer. For example,
   if the LSP is set up using triggered signaling, it will be used to
   carry the higher layer LSP that caused the trigger. Further, the
   lower layer remains available for use by other higher layer LSPs
   arriving at the boundary.

   Under some circumstances it may be useful to control the
   advertisement of LSPs as FAs during the signaling establishment of
   the LSPs [DYN-HIER].

4.3.3. Virtual Network Topology (VNT)

   A set of one or more of lower-layer LSPs provides information for
   efficient path handling in upper-layer(s) of the MLN, or, in other
   words, provides a virtual network topology (VNT) to the upper-
   layers. For instance, a set of LSPs, each of which is supported by
   an LSC LSP, provides a virtual network topology to the layers of a
   PSC region, assuming that the PSC region is connected to the LSC
   region. Note that a single lower-layer LSP is a special case of the
   VNT. The virtual network topology is configured by setting up or
   tearing down the lower layer LSPs. By using GMPLS signaling and
   routing protocols, the virtual network topology can be adapted to
   traffic demands.

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   A lower-layer LSP appears as a TE-link in the VNT. Whether the
   diversely-routed lower-layer LSPs are used or not, the routes of
   lower-layer LSPs are hidden from the upper layer in the VNT. Thus,
   the VNT simplifies the upper-layer routing and traffic engineering
   decisions by hiding the routes taken by the lower-layer LSPs.
   However, hiding the routes of the lower-layer LSPs may lose
   important information that is needed to make the higher-layer LSPs
   reliable. For instance, the routing and traffic engineering in the
   IP/MPLS layer does not usually consider how the IP/MPLS TE links
   are formed from optical paths that are routed in the fiber layer.
   Two optical paths may share the same fiber link in the lower-layer
   and therefore they may both fail if the fiber link is cut. Thus the
   shared risk properties of the TE links in the VNT must be made
   available to the higher layer during path computation. Further, the
   topology of the VNT should be designed so that any single fiber cut
   does not bisect the VNT. These issues are addressed later in this

   Reconfiguration of the virtual network topology may be triggered by
   traffic demand changes, topology configuration changes, signaling
   requests from the upper layer, and network failures. For instance,
   by reconfiguring the virtual network topology according to the
   traffic demand between source and destination node pairs, network
   performance factors, such as maximum link utilization and residual
   capacity of the network, can be optimized. Reconfiguration is
   performed by computing the new VNT from the traffic demand matrix
   and optionally from the current VNT. Exact details are outside the
   scope of this document. However, this method may be tailored
   according to the service provider's policy regarding network
   performance and quality of service (delay, loss/disruption,
   utilization, residual capacity, reliability).

5. Requirements

5.1. Handling Single-Switching and Multi-Switching-Type-Capable Nodes

   The MRN/MLN can consist of single-switching-type-capable and multi-
   switching-type-capable nodes. The path computation mechanism in the
   MLN should be able to compute paths consisting of any combination
   of such nodes.

   Both single-switching-type-capable and multi-switching-type-capable
   (simplex or hybrid) nodes could play the role of layer boundary.
   MRN/MLN Path computation should handle TE topologies built of any
   combination of nodes.

5.2. Advertisement of the Available Adjustment Resource

   A hybrid node should maintain resources on its internal links (the
   links required for vertical (layer) integration). Likewise, path

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   computation elements should be prepared to use the availability of
   termination/ adjustment resources as a constraint in MRN/MLN path
   computations to reduce the higher layer LSP setup blocking
   probability caused by the lack of necessary termination/adjustment
   resources in the lower layer(s).

   The advertisement of the adjustment capability to terminate LSPs of
   lower-region and forward traffic in the upper-region is REQUIRED,
   as it provides critical information when performing multi-region
   path computation.

   The path computation mechanism should cover the case where the
   upper-layer links which are directly connected to upper-layer
   switching element and the ones which are connected through internal
   links between upper-layer element and lower-layer element coexist
   (see Section 4.2.1).

5.3. Scalability

   The MRN/MLN relies on unified routing and traffic engineering

   - Unified routing model: By maintaining a single routing protocol
     instance and a single TE database per LSR, a unified control
     plane model removes the requirement to maintain a dedicated
     routing topology per layer, and therefore does not mandate a full
     mesh of routing adjacencies per layer.

   - Unified TE model: The TED in each LSR is populated with TE-links
     from all layers of all regions (TE link interfaces on multiple-
     switching-capability LSRs can be advertised with multiple ISCDs).
     This may lead to an increase in the amount of information that
     has to be flooded and stored within the network.

   Furthermore, path computation times, which may be of great
   importance during restoration, will depend on the size of the TED.

   Thus MRN/MLN routing mechanisms MUST be designed to scale well with
   an increase of any of the following:

   - Number of nodes
   - Number of TE-links (including FA-LSPs)
   - Number of LSPs  - Number of regions and layers
   - Number of ISCDs per TE-link.

   Further, design of the routing protocols MUST NOT prevent TE
   information filtering based on ISCDs. The path computation
   mechanism and the signaling protocol SHOULD be able to operate on
   partial TE information.

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   Since TE Links can advertise multiple Interface Switching
   Capabilities (ISCs), the number of links can be limited (by
   combination) by using specific topological maps referred to as VNTs
   (Virtual Network Topologies). The introduction of virtual
   topological maps leads us to consider the concept of emulation of
   data plane overlays.

5.4. Stability

   Path computation is dependent on the network topology and
   associated link state. The path computation stability of an upper
   layer may be impaired if the VNT changes frequently and/or if the
   status and TE parameters (the TE metric, for instance) of links in
   the VNT changes frequently. In this context, robustness of the VNT
   is defined as the capability to smooth changes that may occur and
   avoid their propagation into higher layers. Changes to the VNT may
   be caused by the creation, deletion, or modification of LSPs.

   Protocol mechanisms MUST be provided to enable creation, deletion,
   and modification of LSPs triggered through operational actions.
   Protocol mechanisms SHOULD be provided to enable similar functions
   triggered by adjacent layers. Protocol mechanisms MAY be provided
   to enable similar functions to adapt to the environment changes
   such as traffic demand changes, topology changes, and network
   failures. Routing robustness should be traded with adaptability of
   those changes.

5.5. Disruption Minimization

   When reconfiguring the VNT according to a change in traffic demand,
   the upper-layer LSP might be disrupted. Such disruption to the
   upper layers must be minimized.

   When residual resource decreases to a certain level, some lower
   layer LSPs may be released according to local or network policies.
   There is a trade-off between minimizing the amount of resource
   reserved in the lower layer and disrupting higher layer traffic
   (i.e. moving the traffic to other TE-LSPs so that some LSPs can be
   released). Such traffic disruption may be allowed, but MUST be
   under the control of policy that can be configured by the operator.
   Any repositioning of traffic MUST be as non-disruptive as possible
   (for example, using make-before-break).

5.6. LSP Attribute Inheritance

   TE-Link parameters should be inherited from the parameters of the
   LSP that provides the TE-link, and so from the TE-links in the
   lower layer that are traversed by the LSP.

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   These include:

   - Interface Switching Capability
   - TE metric
   - Maximum LSP bandwidth per priority level
   - Unreserved bandwidth for all priority levels
   - Maximum Reservable bandwidth
   - Protection attribute
   - Minimum LSP bandwidth (depending on the Switching Capability)
   - SRLG

   Inheritance rules must be applied based on specific policies.
   Particular attention should be given to the inheritance of TE
   metric (which may be other than a strict sum of the metrics of the
   component TE links at the lower layer), protection attributes, and

   As described earlier, hiding the routes of the lower-layer LSPs may
   lose important information necessary to make LSPs in the higher
   layer network reliable. SRLGs may be used to identify which lower-
   layer LSPs share the same failure risk so that the potential risk
   of the VNT becoming disjoint can be minimized, and so that resource
   disjoint protection paths can be set up in the higher layer. How to
   inherit the SRLG information from the lower layer to the upper
   layer needs more discussion and is out of scope of this document.

5.7. Computing Paths With and Without Nested Signaling

   Path computation can take into account LSP region and layer
   boundaries when computing a path for an LSP. Path computation may
   restrict the path taken by an LSP to only the links whose interface
   switching capability is PSC. For example, suppose that a TDM-LSP is
   routed over the topology composed of TE links of the same TDM layer.
   In calculating the path for the LSP, the TED may be filtered to
   include only links where both end include requested LSP switching
   type. In this way hierarchical routing is done by using a TED
   filtered with respect to switching capability (that is, with
   respect to particular layer).

   If triggered signaling is allowed, the path computation mechanism
   may produce a route containing multiple layers/regions. The path is
   computed over the multiple layers/regions even if the path is not
   "connected" in the same layer as the endpoints of the path exist.
   Note that here we assume that triggered signaling will be invoked
   to make the path "connected", when the upper-layer signaling
   request arrives at the boundary node.

   The upper-layer signaling request MAY contain an ERO (Explicit
   Route Object) that includes only hops in the upper layer, in which
   case the boundary node is responsible for triggered creation of the

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   lower-layer FA-LSP using a path of its choice, or for the selection
   of any available lower layer LSP as a data link for the higher
   layer. This mechanism is appropriate for environments where the TED
   is filtered in the higher layer, where separate routing instances
   are used per layer, or where administrative policies prevent the
   higher layer from specifying paths through the lower layer.

   Obviously, if the lower layer LSP has been advertised as a TE link
   (virtual or real) into the higher layer, then the higher layer
   signaling request MAY contain the TE link identifier and so
   indicate the lower layer resources to be used. But in this case,
   the path of the lower layer LSP can be dynamically changed by the
   lower layer at any time.

   Alternatively, the upper-layer signaling request MAY contain an ERO
   specifying the lower layer FA-LSP route. In this case, the boundary
   node MAY decide whether it should use the path contained in the
   strict ERO or re-compute the path within the lower-layer.

   Even in the case that the lower-layer FA-LSPs are already
   established, a signaling request may also be encoded as a loose ERO.
   In this situation, it is up to the boundary node to decide whether
   it should create a new lower-layer FA-LSP or it should use an
   existing lower-layer FA-LSPs.

   The lower-layer FA-LSP can be advertised just as an FA-LSP in the
   upper-layer or an IGP adjacency can be brought up on the lower-
   layer FA-LSP.

5.8. LSP Resource Utilization

   Resource usage in all layers should be optimized as a whole (i.e.,
   across all layers), in a coordinated manner, (i.e., taking all
   layers into account). The number of lower-layer LSPs carrying
   upper-layer LSPs should be minimized (note that multiple LSPs may
   be used for load balancing). Lower-layer LSPs that could have their
   traffic re-routed onto other LSPs are unnecessary and should be

5.8.1. FA-LSP Release and Setup

   If there is low traffic demand, some FA-LSPs that do not carry any
   higher-layer LSP may be released so that lower-layer resources are
   released and can be assigned to other uses. Note that if a small
   fraction of the available bandwidth of an FA-LSP is still in use,
   the nested LSPs can also be re-routed to other FA-LSPs (optionally
   using the make-before-break technique) to completely free up the
   FA-LSP. Alternatively, unused FA-LSPs may be retained for future
   use. Release or retention of underutilized FA-LSPs is a policy

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   As part of the re-optimization process, the solution MUST allow
   rerouting of an FA-LSP while keeping interface identifiers of
   corresponding TE links unchanged. Further, this process MUST be
   possible while the FA-LSP is carrying traffic (higher layer LSPs)
   with minimal disruption to the traffic.

   Additional FA-LSPs may also be created based on policy, which might
   consider residual resources and the change of traffic demand across
   the region. By creating the new FA-LSPs, the network performance
   such as maximum residual capacity may increase.

   As the number of FA-LSPs grows, the residual resource may decrease.
   In this case, re-optimization of FA-LSPs may be invoked according
   to policy.

   Any solution MUST include measures to protect against network
   destabilization caused by the rapid setup and teardown of LSPs as
   traffic demand varies near a threshold.

   Signaling of lower-layer LSPs SHOULD include a mechanism to rapidly
   advertise the LSP as a TE link and to coordinate into which routing
   instances the TE link should be advertised.

5.8.2. Virtual TE-Links

   It may be considered disadvantageous to fully instantiate (i.e.
   pre- provision) the set of lower layer LSPs that provide the VNT
   since this might reserve bandwidth that could be used for other
   LSPs in the absence of upper-layer traffic.

   However, in order to allow path computation of upper-layer LSPs
   across the lower-layer, the lower-layer LSPs may be advertised into
   the upper-layer as though they had been fully established, but
   without actually establishing them. Such TE links that represent
   the possibility of an underlying LSP are termed "virtual TE-links."
   It is an implementation choice at a layer boundary node whether to
   create real or virtual TE-links, and the choice if available in an
   implementation MUST be under the control of operator policy. Note
   that there is no requirement to support the creation of virtual TE-
   links, since real TE-links (with established LSPs) may be used, and
   even if there are no TE-links (virtual or real) advertised to the
   higher layer, it is possible to route a higher layer LSP into a
   lower layer on the assumptions that proper hierarchical LSPs in the
   lower layer will be dynamically created (triggered) as needed.

   If an upper-layer LSP that makes use of a virtual TE-Link is set up,
   the underlying LSP MUST be immediately signaled in the lower layer.

   If virtual TE-Links are used in place of pre-established LSPs, the
   TE-links across the upper-layer can remain stable using pre-

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   computed paths while wastage of bandwidth within the lower-layer
   and unnecessary reservation of adaptation resource at the border
   nodes can be avoided.

   The solution SHOULD provide operations to facilitate the build-up
   of such virtual TE-links, taking into account the (forecast)
   traffic demand and available resource in the lower-layer.

   Virtual TE-links can be added, removed or modified dynamically (by
   changing their capacity) according to the change of the (forecast)
   traffic demand and the available resource in the lower-layer. It
   MUST be possible to add, remove, and modify virtual TE-links in a
   dynamic way.

   Any solution MUST include measures to protect against network
   destabilization caused by the rapid changes in the virtual network
   topology as traffic demand varies near a threshold.

   The concept of the VNT can be extended to allow the virtual TE-
   links to form part of the VNT. The combination of the fully
   provisioned TE-links and the virtual TE-links defines the VNT
   provided by the lower layer. The VNT can be changed by setting up
   and/or tearing down virtual TE links as well as by modifying real
   links (i.e., the fully provisioned LSPs). How to design the VNT and
   how to manage it are out of scope of this document.

   In some situations, selective advertisement of the preferred
   connectivity among a set of border nodes between layers may be
   appropriate. Further decreasing the number of advertisement of the
   virtual connectivity can be achieved by abstracting the topology
   (between border nodes) using models similar to those detailed in

5.9. Verification of the LSPs

   When a lower layer LSP is established for use as a data link by a
   higher layer, the LSP may be verified for correct connectivity and
   data integrity before it is made available for use. Such mechanisms
   are data technology-specific and are beyond the scope of this
   document, but the GMPLS protocols SHOULD provide mechanisms for the
   coordination of data link verification.

5.10. Management

   A MRN/MLN requires management capabilities. Operators need to have
   the same level of control and management for switches and links in
   the network that they would have in a single layer or single region

   We can consider two different operational models: (1) Per-layer

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   management entities, (2) Cross-layer management entities.

   Regarding per-layer management entities, it is possible for the MLN
   to be managed entirely as separate layers although that somewhat
   defeats the objective of defining a single multi-layer network. In
   this case, separate management systems would be operated for each
   layer, and those systems would be unaware of the fact that the layers
   were closely coupled in the control plane. In such a deployment, as
   LSPs were automatically set up as the result of control plane
   requests from other layers (for example, triggered signaling), the
   management applications would need to register the creation of the
   new LSPs and the depletion of network resources. Emphasis would be
   placed on the layer boundary nodes to report the activity to the
   management applications.

   A more likely scenario is to apply a closer coupling of layer
   management systems with cross-layer management entities. This might
   be achieved through a unified management system capable of operating
   multiple layers, or by a meta-management system that coordinates the
   operation of separate management systems each responsible for
   individual layers. The former case might only be possible with the
   development of new management systems, while the latter is feasible
   through the coordination of existing network management tools.

   Note that when a layer boundary also forms an administrative boundary
   it is highly unlikely that there will be unified multi-layer
   management. In this case, the layers will be separately managed by
   the separate administrative entities, but there may be some "leakage"
   of information between the administrations in order to facilitate the
   operation of the MLN. For example, the management system in the lower
   layer network might automatically issue reports on resource
   availability (coincident with TE routing information), and alarm

   This discussion comes close to an examination of how a VNT might be
   managed and operated. As noted in Section 5.8, issues of how to
   design and manage a VNT are out of scope for this document, but it
   should be understood, that the VNT is a client layer construct built
   from server layer resources. This means that the operation of a VNT
   is a collaborative activity between layers. This activity is possible
   even if the layers are from separate administrations, but in this
   case the activity may also have commercial implications.

   MIB modules exist for the modeling and management of GMPLS networks
   [RFC4802], [RFC4803]. Some deployments of GMPLS networks may choose
   to use MIB modules to operate individual network layers. In these
   cases, operators may desire to coordinate layers through a further
   MIB module that could be developed. Multi-layer protocol solutions
   (that is solutions where a single control plane instance operates in
   more than one layer) SHOULD be manageable through MIB modules. A

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   further MIB module to coordinate multiple network layers with this
   control plane MIB module may be produced.

   OAM tools are important to the successful deployment of all networks.

   OAM requirements for GMPLS networks are described in [GMPLS-OAM].
   That document points out that protocol solutions for individual
   network layers should include mechanisms for OAM or to make use of
   OAM features inherent in the physical media of the layers. Further
   discussion of individual layer OAM is out of scope of this document.

   When operating OAM in a MLN, consideration must be given to how to
   provide OAM for end-to-end LSPs that cross domain boundaries and how
   to coordinate errors and alarms detected in a server layer that need
   to be reported to the client layer. These operational choices MUST be
   left open to the service provider and so MLN protocol solutions MUST
   include the following features:

   - Within the context and technology capabilities of the highest
     technology layer of an LSP (i.e., the technology layer of the first
     hop), it MUST be possible to enable end-to-end OAM on a MLN LSP.
     This function appears to the ingress LSP as normal LSP-based OAM
     [GMPLS-OAM], but at layer boundaries, depending on the technique
     used to span the lower layers, client layer OAM operations may need
     to mapped to server layer OAM operations. Most such requirements
     are highly dependent on the OAM facilities of the data plane
     technologies of client and server layers. However, control plane
     mechanisms used in the client layer per [GMPLS-OAM] MUST map and
     enable OAM in the server layer.

   - OAM operation enabled per [GMPLS-OAM] in a client layer for an LSP
     MUST operate for that LSP along its entire length. This means that
     if an LSP crosses a domain of a lower layer technology, the client
     layer OAM operation must operate seamlessly within the client layer
     at both ends of the client layer LSP.

   - OAM function operating within a server layer MUST be controllable
     from the client layer such that the server layer LSP(s) that
     support a client layer LSP have OAM enabled at the request of the
     client layer. Such control SHOULD be subject to policy at the layer
     boundary just as automatic provisioning and LSP requests to the
     server layer are subject to policy.

   - The status including errors and alarms applicable to a server layer
     LSP MUST be available to the client layer. This information SHOULD
     be configurable to be automatically notified to the client layer at
     the layer boundary and SHOULD be subject to policy so that the
     server layer may filter or hide information supplied to the client
     layer. Furthermore, the client layer SHOULD be able to select to
     not receive any or all such information.

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   Note that the interface between layers lies within network nodes and
   is, therefore, not necessarily the subject of a protocol
   specification. Implementations MAY use standardized techniques (such
   as MIB modules) to convey status information (such as errors and
   alarms) between layers, but that is out of scope for this document.

6. Security Considerations

   The MLN/MRN architecture does not introduce any new security
   requirements over the general GMPLS architecture described in
   [RFC3945]. Additional security considerations form MPLS and GMPLS
   networks are described in [MPLS-SEC].

   However, where the separate layers of a MLN/MRN network are
   operated as different administrative domains, additional security
   considerations may be given to the mechanisms for allowing inter-
   layer LSP setup, for triggering lower-layer LSPs, or for VNT
   management. Similarly, consideration may be given to the amount of
   information shared between administrative domains, and the trade-
   off between multi-layer TE and confidentiality of information
   belonging to each administrative domain.

   It is expected that solution documents will include a full analysis
   of the security issues that any protocol extensions introduce.

7. IANA Considerations

   This informational document makes no requests to IANA for action.

8. Acknowledgements

   The authors would like to thank Adrian Farrel and the participants
   of ITU-T Study Group 15 Question 14 for their careful review. The
   authors would like to thank the IESG review team for rigorous review:
   special thanks to Tim Polk, Miguel Garcia, Jari Arkko, Dan Romascanu,
   and Dave Ward.

9. References

9.1. Normative Reference

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

   [RFC3945]  E. Mannie (Editor), "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4202]  Kompella, K., and Rekhter, Y., "Routing Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)," RFC4202, October 2005.

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   [RFC4206]  Kompella, K., and Rekhter, Y., "Label Switched Paths
              (LSP) Hierarchy with Generalized Multi-Protocol Label
              Switching (GMPLS) Traffic Engineering (TE)," RFC4206,
              Oct. 2005.

   [RFC4397]  Bryskin, I., and Farrel, A., "A Lexicography for the
              Interpretation of Generalized Multiprotocol Label
              Switching (GMPLS) Terminology within the Context of the
              ITU-T's Automatically Switched Optical Network (ASON)
              Architecture", RFC 4397, February 2006.

   [RFC4726]  Farrel, A., Vasseur, JP., and Ayyangar, A., "A
              Framework for Inter-Domain Multiprotocol Label
              Switching Traffic Engineering", RFC 4726, November 2006.

9.2. Informative References

   [DYN-HIER] Shiomoto, K., Rabbat, R., Ayyangar, A., Farrel, A.
              and Ali, Z., "Procedures for Dynamically Signaled
              Hierarchical Label Switched Paths", draft-ietf-ccamp-
              lsp-hierarchy-bis, work in progress.

   [MRN-EVAL] Le Roux, J.L., Brungard, D., Oki, E., Papadimitriou,
              D., Shiomoto, K., Vigoureux, M., "Evaluation of
              Existing GMPLS Protocols Against Multi-Layer and
              Multi-Region Network (MLN/MRN) Requirements", draft-
              ietf-ccamp-gmpls-mln-eval, work in progress.

   [RFC5146]  K. Kumaki (Editor), "Interworking Requirements to
              Support Operation of MPLS-TE over GMPLS Networks",
              RFC 5146, March 2008.

   [MPLS-SEC] Fang, L., et al., "Security Framework for MPLS and
              GMPLS Networks", draft-ietf-mpls-mpls-and-gmpls-
              security-framework, work in progress.

   [RFC4802]  Nadeau, T., Ed. and A. Farrel, Ed., "Generalized
              Multiprotocol Label Switching (GMPLS) Traffic
              Engineering Management Information Base", RFC 4802,
              February 2007.

   [RFC4803]  Nadeau, T., Ed. and A. Farrel, Ed., "Generalized
              Multiprotocol Label Switching (GMPLS) Label Switching
              Router (LSR) Management Information Base", RFC 4803,
              February 2007.

   [RFC4847]  T. Takeda (Editor), " Framework and Requirements for
              Layer 1 Virtual Private Networks", RFC 4847, April 2007.

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                draft-ietf-ccamp-gmpls-mln-reqs-11.txt          May 2008

   [RFC4972]  Vasseur, JP., Le Roux, JL., et al., "Routing
              Extensions for Discovery of Multiprotocol (MPLS)
              Label Switch Router (LSR) Traffic Engineering (TE)
              Mesh Membership", RFC 4972, July 2007.

   [GMPLS-OAM] Nadeau, T., Otani, T. Brungard, D., and Farrel, A., "OAM
              Requirements for Generalized Multi-Protocol Label
              Switching (GMPLS) Networks", draft-ietf-ccamp-gmpls-oam-
              requirements, work in progress.

10. Authors' Addresses

   Kohei Shiomoto
   NTT Network Service Systems Laboratories
   3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan

   Dimitri Papadimitriou
   Copernicuslaan 50,
   B-2018 Antwerpen, Belgium
   Phone : +32 3 240 8491

   Jean-Louis Le Roux
   France Telecom R&D,
   Av Pierre Marzin,
   22300 Lannion, France

   Martin Vigoureux
   Route de Nozay, 91461 Marcoussis cedex, France
   Phone: +33 (0)1 69 63 18 52

   Deborah Brungard
   Rm. D1-3C22 - 200
   S. Laurel Ave., Middletown, NJ 07748, USA
   Phone: +1 732 420 1573

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                draft-ietf-ccamp-gmpls-mln-reqs-11.txt          May 2008

11. Contributors' Addresses

   Eiji Oki
   NTT Network Service Systems Laboratories
   3-9-11 Midori-cho, Musashino-shi,
   Tokyo 180-8585,
   Phone: +81 422 59 3441

   Ichiro Inoue
   NTT Network Service Systems Laboratories
   3-9-11 Midori-cho,
   Tokyo 180-8585,
   Phone: +81 422 59 3441

   Emmanuel Dotaro
   Route de Nozay,
   91461 Marcoussis cedex,
   Phone : +33 1 6963 4723

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   this standard.  Please address the information to the IETF at ietf-

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                draft-ietf-ccamp-gmpls-mln-reqs-11.txt          May 2008

13. Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on

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