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Network Working Group K. Shiomoto, Ed. Request for Comments: 5145 NTT Category: Informational March 2008

              Framework for MPLS-TE to GMPLS Migration

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.


 The migration from Multiprotocol Label Switching (MPLS) Traffic
 Engineering (TE) to Generalized MPLS (GMPLS) is the process of
 evolving an MPLS-TE control plane to a GMPLS control plane.  An
 appropriate migration strategy will be selected based on various
 factors including the service provider's network deployment plan,
 customer demand, and operational policy.
 This document presents several migration models and strategies for
 migrating from MPLS-TE to GMPLS.  In the course of migration, MPLS-TE
 and GMPLS devices, or networks, may coexist that may require
 interworking between MPLS-TE and GMPLS protocols.  Aspects of the
 required interworking are discussed as it will influence the choice
 of a migration strategy.  This framework document provides a
 migration toolkit to aid the operator in selection of an appropriate
 This framework document also lists a set of solutions that may aid in
 interworking, and highlights a set of potential issues.

Shiomoto Informational [Page 1] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

Table of Contents

 1. Introduction ....................................................3
 2. Conventions Used in This Document ...............................3
 3. Motivations for Migration .......................................4
 4. MPLS to GMPLS Migration Models ..................................5
    4.1. Island Model ...............................................5
         4.1.1. Balanced Islands ....................................6
         4.1.2. Unbalanced Islands ..................................6
    4.2. Integrated Model ...........................................7
    4.3. Phased Model ...............................................8
 5. Migration Strategies and Toolkit ................................8
    5.1. Migration Toolkit ..........................................9
         5.1.1. Layered Networks ....................................9
         5.1.2. Routing Interworking ...............................11
         5.1.3. Signaling Interworking .............................12
         5.1.4. Path Computation Element ...........................13
 6. Manageability Considerations ...................................13
    6.1. Control of Function and Policy ............................13
    6.2. Information and Data Models ...............................14
    6.3. Liveness Detection and Monitoring .........................14
    6.4. Verifying Correct Operation ...............................14
    6.5. Requirements on Other Protocols and Functional
         Components ................................................14
    6.6. Impact on Network Operation ...............................15
    6.7. Other Considerations ......................................15
 7. Security Considerations ........................................15
 8. Acknowledgements ...............................................16
 9. References .....................................................16
    9.1. Normative References ......................................16
    9.2. Informative References ....................................17
 10. Contributors' Addresses .......................................17

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1. Introduction

 Multiprotocol Label Switching Traffic Engineering (MPLS-TE) to
 Generalized MPLS (GMPLS) migration is the process of evolving an
 MPLS-TE-based control plane to a GMPLS-based control plane.  The
 network under consideration for migration is, therefore, a
 packet-switching network.
 There are several motivations for such migration, mainly the desire
 to take advantage of new features and functions added to the GMPLS
 protocols, which are not present in MPLS-TE for packet networks.
 Additionally, before migrating a packet-switching network from
 MPLS-TE to GMPLS, one may choose to first migrate a lower-layer
 network with no control plane (e.g., controlled by a management
 plane) to using a GMPLS control plane.  This may lead to the desire
 for MPLS-TE/GMPLS (transport network) interworking to provide
 enhanced TE support and facilitate the later migration of the
 packet-switching network.
 Although an appropriate migration strategy will be selected based on
 various factors including the service provider's network deployment
 plan, customer demand, deployed network equipments, operational
 policy, etc., the transition mechanisms used should also provide
 consistent operation of newly introduced GMPLS networks, while
 minimizing the impact on the operation of existing MPLS-TE networks.
 This document describes several migration strategies and the
 interworking scenarios that arise during migration.  It also examines
 the implications for network deployments and for protocol usage.  As
 the GMPLS signaling and routing protocols are different from the
 MPLS-TE control protocols, interworking mechanisms between MPLS-TE
 and GMPLS networks, or network elements, may be needed to compensate
 for the differences.
 Note that MPLS-TE and GMPLS protocols can coexist as "ships in the
 night" without any interworking issues.

2. Conventions Used in This Document

 This is not a requirements document, nevertheless the key words
 "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document
 are to be interpreted as described in RFC 2119 [RFC2119] in order to
 clarify the recommendations that are made.
 In the rest of this document, the term "GMPLS" includes both packet
 switching capable (PSC) and non-PSC.  Otherwise, the term "PSC GMPLS"
 or "non-PSC GMPLS" is used explicitly.

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 In general, the term "MPLS" is used to indicate MPLS traffic
 engineering (MPLS-TE) only ([RFC3209], [RFC3630], and [RFC3784]) and
 excludes other MPLS protocols, such as the Label Distribution
 Protocol (LDP).  TE functionalities of MPLS could be migrated to
 GMPLS, but non-TE functionalities could not.  If non-TE MPLS is
 intended, it is indicated explicitly.
 The reader is assumed to be familiar with the terminology introduced
 in [RFC3945].

3. Motivations for Migration

 Motivations for migration will vary for different service providers.
 This section is presented to provide background so that the migration
 discussions may be seen in context.  Sections 4 and 5 provide
 examples to illustrate the migration models and processes.
 Migration of an MPLS-capable Label Switching Router (LSR) to include
 GMPLS capabilities may be performed for one or more reasons,
 including, not exhaustively:
 o  To add all GMPLS PSC features to an existing MPLS network (upgrade
    MPLS LSRs).
 o  To add specific GMPLS PSC features and operate them within an MPLS
    network (e.g., [RFC4872] and [RFC4873]).
 o  To integrate a new GMPLS PSC network with an existing MPLS network
    (without upgrading any of the MPLS LSRs).
 o  To allow existing MPLS LSRs to interoperate with new non-MPLS LSRs
    supporting only GMPLS PSC and/or non-PSC features.
 o  To integrate multiple control networks, e.g., managed by separate
    administrative organizations, and which independently utilize MPLS
    or GMPLS.
 o  To build integrated PSC and non-PSC networks.  The non-PSC
    networks are controlled by GMPLS.
 The objective of migration from MPLS to GMPLS is that all LSRs, and
 the entire network, support GMPLS protocols.  During this process,
 various interim situations may exist, giving rise to the interworking
 situations described in this document.  The interim situations may
 exist for considerable periods of time, but the ultimate objective is
 not to preserve these situations.  For the purposes of this document,
 they should be considered as temporary and transitory.

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4. MPLS to GMPLS Migration Models

 Three reference migration models are described below.  Multiple
 migration models may coexist in the same network.

4.1. Island Model

 In the island model, "islands" of network nodes operating one
 protocol exist within a "sea" of nodes using the other protocol.
 For example, consider an island of GMPLS-capable nodes (PSC) that is
 introduced into a legacy MPLS network.  Such an island might be
 composed of newly added GMPLS nodes, or it might arise from the
 upgrade of existing nodes that previously operated MPLS protocols.
 The opposite is also quite possible.  That is, there is a possibility
 that an island happens to be MPLS-capable within a GMPLS sea.  Such a
 situation might arise in the later stages of migration, when all but
 a few islands of MPLS-capable nodes have been upgraded to GMPLS.
 It is also possible that a lower-layer, manually-provisioned network
 (for example, a Time Division Multiplexing (TDM) network) is
 constructed under an MPLS PSC network.  During the process of
 migrating both networks to GMPLS, the lower-layer network might be
 migrated first.  This would appear as a GMPLS island within an MPLS
 Lastly, it is possible to consider individual nodes as islands.  That
 is, it would be possible to upgrade or insert an individual
 GMPLS-capable node within an MPLS network, and to treat that GMPLS
 node as an island.
 Over time, collections of MPLS devices are replaced or upgraded to
 create new GMPLS islands or to extend existing ones, and distinct
 GMPLS islands may be joined together until the whole network is
 From a migration/interworking point of view, we need to examine how
 these islands are positioned and how Label Switched Paths (LSPs)
 connect between the islands.
 Four categories of interworking scenarios are considered: (1)
 GMPLS-MPLS.  In case 1, the interworking behavior is examined based
 on whether the GMPLS islands are PSC or non-PSC.

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 Figure 1 shows an example of the island model for MPLS-GMPLS-MPLS
 interworking.  The model consists of a transit GMPLS island in an
 MPLS sea.  The nodes at the boundary of the GMPLS island (G1, G2, G5,
 and G6) are referred to as "island border nodes".  If the GMPLS
 island was non-PSC, all nodes except the island border nodes in the
 GMPLS-based transit island (G3 and G4) would be non-PSC devices,
 i.e., optical equipment (TDM, Lambda Switch Capable (LSC), and Fiber
 Switch Capable (FSC)).
 .................  ..........................  ..................
 :      MPLS      :  :          GMPLS         :  :     MPLS       :
 :+---+  +---+   +----+         +---+        +----+   +---+  +---+:
 :|R1 |__|R11|___| G1 |_________|G3 |________| G5 |___|R31|__|R3 |:
 :+---+  +---+   +----+         +-+-+        +----+   +---+  +---+:
 :      ________/ :  :  _______/  |   _____ / :  :  ________/     :
 :     /          :  : /          |  /        :  : /              :
 :+---+  +---+   +----+         +-+-+        +----+   +---+  +---+:
 :|R2 |__|R21|___| G2 |_________|G4 |________| G6 |___|R41|__|R4 |:
 :+---+  +---+   +----+         +---+        +----+   +---+  +---+:
 :................:  :........................:  :................:
                                e2e LSP
                Figure 1: Example of the island model
                  for MPLS-GMPLS-MPLS interworking

4.1.1. Balanced Islands

 In the MPLS-GMPLS-MPLS and GMPLS-MPLS-GMPLS cases, LSPs start and end
 using the same protocols.  Possible strategies include:
  1. tunneling the signaling across the island network using LSP nesting

or stitching [RFC5150] (the latter is only for GMPLS-PSC)

  1. protocol interworking or mapping (both are only for GMPLS-PSC)

4.1.2. Unbalanced Islands

 As previously discussed, there are two island interworking models
 that support bordering islands.  GMPLS(PSC)-MPLS and MPLS-GMPLS(PSC)
 island cases are likely to arise where the migration strategy is not
 based on a core infrastructure, but has edge nodes (ingress or
 egress) located in islands of different capabilities.
 In this case, an LSP starts or ends in a GMPLS (PSC) island and
 correspondingly ends or starts in an MPLS island.  This mode of
 operation can only be addressed using protocol interworking or

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 mapping.  Figure 2 shows the reference model for this migration
 scenario.  Head-end and tail-end LSRs are in distinct control plane
 ............................  .............................
 :            MPLS          :  :       GMPLS (PSC)         :
 :+---+        +---+       +----+        +---+        +---+:
 :|R1 |________|R11|_______| G1 |________|G3 |________|G5 |:
 :+---+        +---+       +----+        +-+-+        +---+:
 :      ______/  |   _____/ :  :  ______/  |   ______/     :
 :     /         |  /       :  : /         |  /            :
 :+---+        +---+       +----+        +-+-+        +---+:
 :|R2 |________|R21|_______| G2 |________|G4 |________|G6 |:
 :+---+        +---+       +----+        +---+        +---+:
 :..........................:  :...........................:
                           e2e LSP
            Figure 2: GMPLS-MPLS interworking model
 It is important to underline that this scenario is also impacted by
 the directionality of the LSP, and the direction in which the LSP is

4.2. Integrated Model

 The second migration model involves a more integrated migration
 strategy.  New devices that are capable of operating both MPLS and
 GMPLS protocols are introduced into the MPLS network.
 In the integrated model, there are two types of nodes present during
  1. those that support MPLS only (legacy nodes); and
  1. those that support MPLS and GMPLS.
 In this model, as existing MPLS devices are upgraded to support both
 MPLS and GMPLS, the network continues to operate with an MPLS control
 plane, but some LSRs are also capable of operating with a GMPLS
 control plane.  So, LSPs are provisioned using MPLS protocols where
 one end point of a service is a legacy MPLS node and/or where the
 selected path between end points traverses a legacy node that is not
 GMPLS-capable.  But where the service can be provided using only
 GMPLS-capable nodes [RFC5073], it may be routed accordingly and can
 achieve a higher level of functionality by utilizing GMPLS features.

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 Once all devices in the network are GMPLS-capable, the MPLS-specific
 protocol elements may be turned off, and no new devices need to
 support these protocol elements.
 In this model, the questions to be addressed concern the coexistence
 of the two protocol sets within the network.  Actual interworking is
 not a concern.

4.3. Phased Model

 The phased model introduces GMPLS features and protocol elements into
 an MPLS network one by one.  For example, some objects or sub-objects
 (such as the Explicit Route Object (ERO) label sub-object, [RFC3473])
 might be introduced into the signaling used by LSRs that are
 otherwise MPLS-capable.  This would produce a kind of hybrid LSR.
 This approach may appear simpler to implement as one is able to
 quickly and easily pick up new key functions without needing to
 upgrade the whole protocol implementation.  It is most likely to be
 used where there is a desire to rapidly implement a particular
 function within a network without the necessity to install and test
 the full GMPLS function.
 Interoperability concerns though are exacerbated by this migration
 model, unless all LSRs in the network are updated simultaneously and
 there is a clear understanding of which subset of features are to be
 included in the hybrid LSRs.  Interworking between a hybrid LSR and
 an unchanged MPLS LSR would put the hybrid LSR in the role of a GMPLS
 LSR, as described in the previous sections, and puts the unchanged
 LSR in the role of an MPLS LSR.  The potential for different hybrids
 within the network will complicate matters considerably.  This model
 is, therefore, only appropriate for use when the set of new features
 to be deployed is well known and limited, and where there is a clear
 understanding of and agreement on this set of features by the network
 operators of the ISP(s) involved as well as all vendors whose
 equipment will be involved in the migration.

5. Migration Strategies and Toolkit

 An appropriate migration strategy is selected by a network operator
 based on factors including the service provider's network deployment
 plan, customer demand, existing network equipment, operational
 policy, support from its vendors, etc.
 For PSC networks, the migration strategy involves the selection
 between the models described in the previous section.  The choice
 will depend upon the final objective (full GMPLS capability, partial

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 upgrade to include specific GMPLS features, or no change to existing
 IP/MPLS networks), and upon the immediate objectives (full, phased,
 or staged upgrade).
 For PSC networks serviced by non-PSC networks, two basic migration
 strategies can be considered.  In the first strategy, the non-PSC
 network is made GMPLS-capable, first, and then the PSC network is
 migrated to GMPLS.  This might arise when, in order to expand the
 network capacity, GMPLS-based non-PSC sub-networks are introduced
 into the legacy MPLS-based networks.  Subsequently, the legacy
 MPLS-based PSC network is migrated to be GMPLS-capable, as described
 in the previous paragraph.  Finally, the entire network, including
 both PSC and non-PSC nodes, may be controlled by GMPLS.
 The second strategy is to migrate the PSC network to GMPLS first, and
 then enable GMPLS within the non-PSC network.  The PSC network is
 migrated as described before, and when the entire PSC network is
 completely converted to GMPLS, GMPLS-based non-PSC devices and
 networks may be introduced without any issues of interworking between
 These migration strategies and the migration models described in the
 previous section are not necessarily mutually exclusive.  Mixtures of
 all strategies and models could be applied.  The migration models and
 strategies selected will give rise to one or more of the interworking
 cases described in the following section.

5.1. Migration Toolkit

 As described in the previous sections, an essential part of a
 migration and deployment strategy is how the MPLS and GMPLS or hybrid
 LSRs interwork.  This section sets out some of the alternatives for
 achieving interworking between MPLS and GMPLS, and it identifies some
 of the issues that need to be addressed.  This document does not
 describe solutions to these issues.
 Note that it is possible to consider upgrading the routing and
 signaling capabilities of LSRs from MPLS to GMPLS separately.

5.1.1. Layered Networks

 In the balanced island model, LSP tunnels [RFC4206] are a solution to
 carry the end-to-end LSPs across islands of incompatible nodes.
 Network layering is often used to separate domains of different data
 plane technology.  It can also be used to separate domains of
 different control plane technology (such as MPLS and GMPLS
 protocols), and the solutions developed for multiple data plane

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 technologies can be usefully applied to this situation [RFC3945],
 [RFC4206], and [RFC4726].  [MLN-REQ] gives a discussion of the
 requirements for multi-layered networks.
 The GMPLS architecture [RFC3945] identifies three architectural
 models for supporting multi-layer GMPLS networks, and these models
 may be applied to the separation of MPLS and GMPLS control plane
  1. In the peer model, both MPLS and GMPLS nodes run the same routing

instance, and routing advertisements from within islands of one

   level of protocol support are distributed to the whole network.
   This is achievable only, as described in Section 5.1.2, either by
   direct distribution or by mapping of parameters.
   Signaling in the peer model may result in contiguous LSPs, stitched
   LSPs [RFC5150] (only for GMPLS PSC), or nested LSPs.  If the
   network islands are non-PSC, then the techniques of [MLN-REQ] may
   be applied, and these techniques may be extrapolated to networks
   where all nodes are PSC, but where there is a difference in
   signaling protocols.
  1. The overlay model preserves strict separation of routing

information between network layers. This is suitable for the

   balanced island model, and there is no requirement to handle
   routing interworking.  Even though the overlay model preserves
   separation of signaling information between network layers, there
   may be some interaction in signaling between network layers.
   The overlay model requires the establishment of control plane
   connectivity for the higher layer across the lower layer.
  1. The augmented model allows limited routing exchange from the

lower-layer network to the higher-layer network. Generally

   speaking, this assumes that the border nodes provide some form of
   filtering, mapping, or aggregation of routing information
   advertised from the lower-layer network.  This architectural model
   can also be used for balanced island model migrations.  Signaling
   interworking is required as described for the peer model.
  1. The border peer architecture model is defined in [RFC5146]. This

is a modification of the augmented model where the layer border

   routers have visibility into both layers, but no routing
   information is otherwise exchanged between routing protocol
   instances.  This architectural model is particularly suited to the
   MPLS-GMPLS-MPLS island model for PSC and non-PSC GMPLS islands.
   Signaling interworking is required as described for the peer model.

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5.1.2. Routing Interworking

 Migration strategies may necessitate some interworking between MPLS
 and GMPLS routing protocols.  GMPLS extends the TE information
 advertised by the IGPs to include non-PSC information and extended
 PSC information.  Because the GMPLS information is provided as
 additional TLVs that are carried along with the MPLS information,
 MPLS LSRs are able to "see" all GMPLS LSRs as though they were MPLS
 PSC LSRs.  They will also see other GMPLS information, but will
 ignore it, flooding it transparently across the MPLS network for use
 by other GMPLS LSRs.
  1. Routing separation is achieved in the overlay and border peer

models. This is convenient since only the border nodes need to be

   aware of the different protocol variants, and no mapping is
   required.  It is suitable to the MPLS-GMPLS-MPLS and
   GMPLS-MPLS-GMPLS island migration models.
  1. Direct distribution involves the flooding of MPLS routing

information into a GMPLS network, and GMPLS routing information

   into an MPLS network.  The border nodes make no attempt to filter
   the information.  This mode of operation relies on the fact that
   MPLS routers will ignore, but continue to flood, GMPLS routing
   information that they do not understand.  The presence of
   additional GMPLS routing information will not interfere with the
   way that MPLS LSRs select routes.  Although this is not a problem
   in a PSC-only network, it could cause problems in a peer
   architecture network that includes non-PSC nodes, as the MPLS nodes
   are not capable of determining the switching types of the other
   LSRs and will attempt to signal end-to-end LSPs assuming all LSRs
   to be PSC.  This fact would require island border nodes to take
   triggered action to set up tunnels across islands of different
   switching capabilities.
   GMPLS LSRs might be impacted by the absence of GMPLS-specific
   information in advertisements initiated by MPLS LSRs.  Specific
   procedures might be required to ensure consistent behavior by GMPLS
   nodes.  If this issue is addressed, then direct distribution can be
   used in all migration models (except the overlay and border peer
   architectural models where the problem does not arise).
  1. Protocol mapping converts routing advertisements so that they can

be received in one protocol and transmitted in the other. For

   example, a GMPLS routing advertisement could have all of its
   GMPLS-specific information removed and could be flooded as an MPLS
   advertisement.  This mode of interworking would require careful
   standardization of the correct behavior especially where an MPLS
   advertisement requires default values of GMPLS-specific fields to

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   be generated before the advertisement can be flooded further.
   There is also considerable risk of confusion in closely meshed
   networks where many LSRs have MPLS- and GMPLS-capable interfaces.
   This option for routing interworking during migration is NOT
   RECOMMENDED for any migration model.  Note that converting
   GMPLS-specific sub-TLVs to MPLS-specific ones but not stripping the
   GMPLS-specific ones is considered a variant of the proposed
   solution in the previous bullet (unknown sub-TLVs should be ignored
   [RFC3630] but must continue to be flooded).
  1. Ships in the night refers to a mode of operation where both MPLS

and GMPLS routing protocol variants are operated in the same

   network at the same time as separate routing protocol instances.
   The two instances are independent and are used to create routing
   adjacencies between LSRs of the same type.  This mode of operation
   may be appropriate to the integrated migration model.

5.1.3. Signaling Interworking

 Signaling protocols are used to establish LSPs and are the principal
 concern for interworking during migration.  Issues of compatibility
 arise because of differences in the encodings and codepoints used by
 MPLS and GMPLS signaling, but also because of differences in
 functionality provided by MPLS and GMPLS.
  1. Tunneling and stitching [RFC5150] (GMPLS-PSC case) mechanisms

provide the potential to avoid direct protocol interworking during

   migration in the island model because protocol elements are
   transported transparently across migration islands without being
   inspected.  However, care may be needed to achieve functional
   mapping in these modes of operation since one set of features may
   need to be supported across a network designed to support a
   different set of features.  In general, this is easily achieved for
   the MPLS-GMPLS-MPLS model, but may be hard to achieve in the
   GMPLS-MPLS-GMPLS model, for example, when end-to-end bidirectional
   LSPs are requested, since the MPLS island does not support
   bidirectional LSPs.
   Note that tunneling and stitching are not available in unbalanced
   island models because in these cases, the LSP end points use
   different protocols.
  1. Protocol mapping is the conversion of signaling messages between

MPLS and GMPLS. This mechanism requires careful documentation of

   the protocol fields and how they are mapped.  This is relatively
   straightforward in the MPLS-GMPLS unbalanced island model for LSPs
   signaled in the MPLS-GMPLS direction.  However, it may be more
   complex for LSPs signaled in the opposite direction, and this will

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   lead to considerable complications for providing GMPLS services
   over the MPLS island and for terminating those services at an
   egress LSR that is not GMPLS-capable.  Further, in balanced island
   models, and in particular where there are multiple small
   (individual node) islands, the repeated conversion of signaling
   parameters may lead to loss of information (and functionality) or
  1. Ships in the night could be used in the integrated migration model

to allow MPLS-capable LSRs to establish LSPs using MPLS signaling

   protocols and GMPLS LSRs to establish LSPs using GMPLS signaling
   protocols.  LSRs that can handle both sets of protocols could work
   with both types of LSRs, and no conversion of protocols would be

5.1.4. Path Computation Element

 The Path Computation Element (PCE) [RFC4655] may provide an
 additional tool to aid MPLS to GMPLS migration.  If a layered network
 approach (Section 5.1.1) is used, PCEs may be used to facilitate the
 computation of paths for LSPs in the different layers [PCE-INT].

6. Manageability Considerations

 Attention should be given during migration planning to how the
 network will be managed during and after migration.  For example,
 will the LSRs of different protocol capabilities be managed
 separately or as one management domain? For example, in the Island
 Model, it is possible to consider managing islands of one capability
 separately from the surrounding sea.  In the case of islands that
 have different switching capabilities, it is possible that the
 islands already have separate management in place before the
 migration: the resultant migrated network may seek to merge the
 management or to preserve the separation.

6.1. Control of Function and Policy

 The most critical control functionality to be applied is at the
 moment of changeover between different levels of protocol support.
 Such a change may be made without service halt or during a period of
 network maintenance.
 Where island boundaries exist, it must be possible to manage the
 relationships between protocols and to indicate which interfaces
 support which protocols on a border LSR.  Further, island borders are
 a natural place to apply policy, and management should allow
 configuration of such policies.

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6.2. Information and Data Models

 No special information or data models are required to support
 migration, but note that migration in the control plane implies
 migration from MPLS management tools to GMPLS management tools.
 During migration, therefore, it may be necessary for LSRs and
 management applications to support both MPLS and GMPLS management
 The GMPLS MIB modules are designed to allow support of the MPLS
 protocols, and they are built on the MPLS MIB modules through
 extensions and augmentations.  This may make it possible to migrate
 management applications ahead of the LSRs that they manage.

6.3. Liveness Detection and Monitoring

 Migration will not impose additional issues for Operations,
 Administration, and Management (OAM) above those that already exist
 for inter-domain OAM and for OAM across multiple switching
 Note, however, that if a flat PSC MPLS network is migrated using the
 island model, and is treated as a layered network using tunnels to
 connect across GMPLS islands, then requirements for a multi-layer OAM
 technique may be introduced into what was previously defined in the
 flat OAM problem-space.  The OAM framework of MPLS/GMPLS interworking
 will need further consideration.

6.4. Verifying Correct Operation

 The concerns for verifying correct operation (and in particular,
 correct connectivity) are the same as for liveness detection and
 monitoring.  Specifically, the process of migration may introduce
 tunneling or stitching [RFC5150] into what was previously a flat

6.5. Requirements on Other Protocols and Functional Components

 No particular requirements are introduced on other protocols.  As it
 has been observed, the management components may need to migrate in
 step with the control plane components, but this does not impact the
 management protocols, just the data that they carry.
 It should also be observed that providing signaling and routing
 connectivity across a migration island in support of a layered
 architecture may require the use of protocol tunnels (such as Generic

Shiomoto Informational [Page 14] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

 Routing Encapsulation (GRE)) between island border nodes.  Such
 tunnels may impose additional configuration requirements at the
 border nodes.

6.6. Impact on Network Operation

 The process of migration is likely to have significant impact on
 network operation while migration is in progress.  The main objective
 of migration planning should be to reduce the impact on network
 operation and on the services perceived by the network users.
 To this end, planners should consider reducing the number of
 migration steps that they perform and minimizing the number of
 migration islands that are created.
 A network manager may prefer the island model especially when
 migration will extend over a significant operational period because
 it allows the different network islands to be administered as
 separate management domains.  This is particularly the case in the
 overlay, augmented network and border peer models where the details
 of the protocol islands remain hidden from the surrounding LSRs.

6.7. Other Considerations

 A migration strategy may also imply moving an MPLS state to a GMPLS
 state for an in-service LSP.  This may arise once all of the LSRs
 along the path of the LSP have been updated to be both MPLS- and
 GMPLS-capable.  Signaling mechanisms to achieve the replacement of an
 MPLS LSP with a GMPLS LSP without disrupting traffic exist through
 make-before-break procedures [RFC3209] and [RFC3473], and should be
 carefully managed under operator control.

7. Security Considerations

 Security and confidentiality is often applied (and attacked) at
 administrative boundaries.  Some of the models described in this
 document introduce such boundaries, for example, between MPLS and
 GMPLS islands.  These boundaries offer the possibility of applying or
 modifying the security as when crossing an IGP area or Autonomous
 System (AS) boundary, even though these island boundaries might lie
 within an IGP area or AS.
 No changes are proposed to the security procedures built into MPLS
 and GMPLS signaling and routing.  GMPLS signaling and routing inherit
 their security mechanisms from MPLS signaling and routing without any
 changes.  Hence, there will be no additional issues with security in
 interworking scenarios.  Further, since the MPLS and GMPLS signaling
 and routing security is provided on a hop-by-hop basis, and since all

Shiomoto Informational [Page 15] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

 signaling and routing exchanges described in this document for use
 between any pair of LSRs are based on either MPLS or GMPLS, there are
 no changes necessary to the security procedures.

8. Acknowledgements

 The authors are grateful to Daisaku Shimazaki for discussion during
 the initial work on this document.  The authors are grateful to Dean
 Cheng and Adrian Farrel for their valuable comments.

9. References

9.1. Normative References

 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
           and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
           Tunnels", RFC 3209, December 2001.
 [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
           Switching (GMPLS) Signaling Resource ReserVation Protocol-
           Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
           January 2003.
 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
           (TE) Extensions to OSPF Version 2", RFC 3630, September
 [RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
           System (IS-IS) Extensions for Traffic Engineering (TE)",
           RFC 3784, June 2004.
 [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
           Switching (GMPLS) Architecture", RFC 3945, October 2004.
 [RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou, Ed.,
           "RSVP-TE Extensions in Support of End-to-End Generalized
           Multi-Protocol Label Switching (GMPLS) Recovery", RFC 4872,
           May 2007.
 [RFC4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
           "GMPLS Segment Recovery", RFC 4873, May 2007.
 [RFC5073] Vasseur, J., Ed., and J. Le Roux, Ed., "IGP Routing
           Protocol Extensions for Discovery of Traffic Engineering
           Node Capabilities", RFC 5073, December 2007.

Shiomoto Informational [Page 16] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

9.2. Informative References

 [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
           Hierarchy with Generalized Multi-Protocol Label Switching
           (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation
           Element (PCE)-Based Architecture", RFC 4655, August 2006.
 [RFC4726] Farrel, A., Vasseur, J.-P., and A. Ayyangar, "A Framework
           for Inter-Domain Multiprotocol Label Switching Traffic
           Engineering", RFC 4726, November 2006.
 [RFC5150] Ayyangar, A., Kompella, A., Vasseur, JP., and A. Farrel,
           "Label Switched Path Stitching with Generalized
           Multiprotocol Label Switching Traffic Engineering", RFC
           5150, February 2008.
 [RFC5146] Kumaki, K., Ed., "Interworking Requirements to Support
           Operation of MPLS-TE over GMPLS Networks", RFC 5146, March
 [MLN-REQ] Shiomoto, K., Papadimitriou, D., Le Roux, J.L., Vigoureux,
           M., and D. Brungard, "Requirements for GMPLS-Based Multi-
           Region and Multi-Layer Networks (MRN/MLN)", Work in
           Progress, January 2008.
 [PCE-INT] Oki, E., Le Roux , J-L., and A. Farrel, "Framework for
           PCE-Based Inter-Layer MPLS and GMPLS Traffic Engineering,"
           Work in Progress, January 2008.

10. Contributors' Addresses

 Dimitri Papadimitriou
 Francis Wellensplein 1,
 B-2018 Antwerpen, Belgium
 Phone: +32 3 240 8491
 Jean-Louis Le Roux
 France Telecom
 av Pierre Marzin 22300
 Lannion, France
 Phone: +33 2 96 05 30 20

Shiomoto Informational [Page 17] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

 Deborah Brungard
 Rm. D1-3C22 - 200 S. Laurel Ave.
 Middletown, NJ 07748, USA
 Phone: +1 732 420 1573
 Zafar Ali
 Cisco Systems, Inc.
 Kenji Kumaki
 KDDI Corporation
 Garden Air Tower
 Iidabashi, Chiyoda-ku,
 Tokyo 102-8460, JAPAN
 Phone: +81-3-6678-3103
 Eiji Oki
 Midori 3-9-11
 Musashino, Tokyo 180-8585, Japan
 Phone: +81 422 59 3441
 Ichiro Inoue
 Midori 3-9-11
 Musashino, Tokyo 180-8585, Japan
 Phone: +81 422 59 3441
 Tomohiro Otani
 KDDI Laboratories

Editor's Address

 Kohei Shiomoto
 Midori 3-9-11
 Musashino, Tokyo 180-8585, Japan
 Phone: +81 422 59 4402

Shiomoto Informational [Page 18] RFC 5145 Framework for MPLS-TE to GMPLS Migration March 2008

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Shiomoto Informational [Page 19]

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