Network Working Group
   Internet Draft                                      Kenji Kumaki, Ed
   Proposed Category: Informational                    KDDI Corporation
   Expires: June, 2007                                   Tomohiro Otani
                                                          KDDI R&D Labs
                                                        Shuichi Okamoto
                                                      Kazuhiro Fujihara
                                                         Yuichi Ikejiri
                                                         December, 2006

   Interworking Requirements to Support operation of MPLS-TE over GMPLS


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Copyright Notice

   Copyright (C) The Internet Society (2006).

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   This document describes a framework and Service Provider requirements
   for operating Multiprotocol Label Switching (MPLS) traffic
   engineering (TE) networks over Generalized MPLS (GMPLS) networks.

   Operation of an MPLS-TE network as a client network to a GMPLS
   network has enhanced operational capabilities than provided by a co-
   existent protocol model (ships in the night).

   The GMPLS network may be a packet or a non-packet network, and may
   itself be a multi-layer network supporting both packet and non-packet
   technologies. A MPLS-TE Label Switched Path (LSP) originates and
   terminates on an MPLS Label Switching Router (LSR). The GMPLS network
   provides transparent transport for the end-to-end MPLS-TE LSP.

   Specification of solutions is out of scope for this document.

Conventions used in this document

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

Table of Contents

   1. Introduction...................................................3
   2. Reference model................................................4
   3. Detailed Requirements..........................................5
      3.1 End-to-End Signaling.......................................5
      3.2 Triggered Establishment of GMPLS LSPs......................5
      3.3 Diverse Paths for End-to-End MPLS-TE LSPs..................5
      3.4 Advertisement of MPLS-TE Information via the GMPLS Network.5
      3.5 Selective Advertisement of MPLS-TE Information via a Border
      3.6 Interworking of MPLS-TE and GMPLS protection...............6
      3.7 Independent Failure Recovery and Reoptimization............6
      3.8 Complexity and Risks.......................................6
      3.9 Scalability consideration..................................6
      3.10 Performance Consideration.................................7
      3.11 Management Considerations.................................7
   4. Security Considerations........................................7
   5. Recommended Solution Architecture..............................7
      5.1 Use of Contiguous, Hierarchical, and Stitched LSPs.........8
      5.2 MPLS-TE Control Plane Connectivity.........................8
      5.3 Fast Reroute Protection....................................8
   6. IANA Considerations............................................9
   7. Normative References...........................................9

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   8. Informative References........................................10
   9. Acknowledgments...............................................10
   10.Author's Addresses............................................10

1. Introduction

   Multiprotocol Label Switching traffic engineering (MPLS-TE) networks
   are often deployed over transport networks such that the transport
   networks provide connectivity between the Label Switching Routers
   (LSRs) in the MPLS-TE network. Increasingly, these transport networks
   are operated using a Generalized Multiprotocol Label Switching
   (GMPLS) control plane and label Switched Paths (LSPs) in the GMPLS
   network provide connectivity in the MPLS-TE network.

   Generalized Multiprotocol Label Switching (GMPLS) protocols were
   developed as extensions to Multiprotocol Label Switching traffic
   engineering (MPLS-TE) protocols. MPLS-TE is limited to the control of
   packet switching networks, but GMPLS can also control sub-packet
   technologies at layers one and two.

   The GMPLS network may be managed by an operator as a separate network
   (as it was when it was under management plane control before the use
   of GMPLS as a control plane), but optimizations of management and
   operation may be achieved by coordinating the use of the MPLS-TE and
   GMPLS networks and operating the two networks with a close
   client/server relationship.

   GMPLS LSP setup may triggered by the signaling of MPLS-TE LSPs in the
   MPLS-TE network so that the GMPLS network is reactive to the needs of
   the MPLS-TE network. The triggering process can be under the control
   of operator policies without needing direct intervention by an

   The client/server configuration just described can also apply in
   migration scenarios for MPLS-TE packet switching networks that are
   being migrated to be under GMPLS control. [MIGRATE] describes a
   migration scenario called the Island Model. In this scenario, groups
   of nodes (islands) are migrated from the MPLS-TE protocols to the
   GMPLS protocols and operate entirely surrounded by MPLS-TE nodes (the
   sea). This scenario can be effectively managed as a client/server
   network relationship using the framework described in this document.

   In order to correctly manage the dynamic interaction between the MPLS
   and GMPLS networks, it is necessary to understand the operational
   requirements and the control that the operator can impose. Although
   this problem is very similar to the multi-layer networks described in
   [MLN], it must be noted that those networks operate GMPLS protocols
   in both the client and server networks which facilitates smoother

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   interworking. Where the client network uses MPLS-TE protocols over
   the GMPLS server network there is a need to study the interworking of
   the two protocol sets.

   This document examines the protocol requirements for protocol
   interworking to operate an MPLS-TE network as a client network over a
   GMPLS server network, and provides a framework for such operations.

2. Reference model

   The reference model used in this document is shown in Figure 1. It
   can easily be seen that the interworking between MPLS-TE and GMPLS
   protocols must occur on a node and not on a link. Nodes on the
   interface between the MPLS-TE and GMPLS networks must be responsible
   for handling both protocol sets and for providing any protocol
   interworking that is required. We call these nodes Border Routers.

       --------------    -------------------------    --------------
      | MPLS Client  |  |   GMPLS Server Network  |  |  MPLS Client |
      |   Network    |  |                         |  |    Network   |
      |              |  |                         |  |              |
      |     ----   --+--+--    -----   -----    --+--+--   ----     |
      |    |    | |        |  |     | |     |  |        | |    |    |
      |    |MPLS|_| Border |__|GMPLS|_|GMPLS|__| Border |_|MPLS|    |
      |    |LSR | | Router |  | LSR | | LSR |  | Router | |LSR |    |
      |    |    | |        |  |     | |     |  |        | |    |    |
      |     ----   --+--+--    -----   -----    --+--+--   ----     |
      |              |  |                         |  |              |
      |              |  |                         |  |              |
       --------------    -------------------------    --------------

             |         |         GMPLS LSP         |         |
             |         |<------------------------->|         |
             |                                               |
                           End-to-End MPLS-TE LSP

              Figure 1. Reference model of MPLS-TE/GMPLS interworking

   MPLS-TE network connectivity is provided through a GMPLS LSP which is
   created between Border Routers. End-to-end connectivity between MPLS
   LSRs in the client MPLS-TE networks is provided by an MPLS-TE LSP
   that is carried across the MPLS-TE network by the GMPLS LSP using
   hierarchical LSP techniques [RFC4206], LSP stitching segments
   [STITCH] or a contiguous LSP. LSP stitching segments and contiguous

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   LSPs are only available where the GMPLS network is a packet switching
3. Detailed Requirements

   This section describes detailed requirements for MPLS-TE/GMPLS
   interworking in support of the reference model shown in figure 1.

3.1 End-to-End Signaling

   The solution MUST be able to preserve MPLS signaling information
   signaled within the MPLS-TE client network at the start of the MPLS-
   TE LSP, and deliver it on the other side of the GMPLS server network
   for use within the MPLS-TE client network at the end of the MPLS-TE
   LSP. This may require protocol mapping (and re-mapping), protocol
   tunneling, or the use of remote protocol adjacencies.

3.2 Triggered Establishment of GMPLS LSPs

   The solution MUST provide the ability to establish end-to-end MPLS-
   TE LSPs over a GMPLS server network. It SHOULD be possible for GMPLS
   LSPs across the core network to be set up between Border Routers
   triggered by the signaling of MPLS-TE LSPs in the client network.
   GMPLS LSPs MAY also be pre-established as the result of management
   plane control.

3.3 Diverse Paths for End-to-End MPLS-TE LSPs

   The solution SHOULD provide the ability to establish end-to-end
   MPLS-TE LSPs having diverse paths for protection of the LSP traffic.
   This means that MPLS-TE LSPs SHOULD be kept diverse both within the
   client MPLS-TE network and as they cross the server GMPLS network.
   This means that there SHOULD be a mechanism to request the provision
   of diverse GMPLS LSPs between a pair of Border Routers to provide
   protection of the GMPLS span, but also that there SHOULD be a way to
   keep GMPLS LSPs between different Border Routers disjoint.

3.4 Advertisement of MPLS-TE Information via the GMPLS Network

   The solution SHOULD provide the ability to advertise of TE
   information from MPLS-TE client networks across the GMPLS server
   The advertisement of TE information from within an MPLS-TE client
   network to all LSRs in the client network enables a head end LSR to
   compute an optimal path for an LSP to a tail end LSR that is reached
   over the GMPLS server network.
   Where there is more than one client MPLS-TE network, the TE
   information from separate MPLS-TE networks MUST be kept private,
   confidential and secure.

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3.5 Selective Advertisement of MPLS-TE Information via a Border Node

   The solution SHOULD provide the ability to distribute TE reachability
   information from the GMPLS server network to MPLS-TE networks
   selectively. This information is useful for the LSRs in the MPLS-TE
   networks to compute paths that cross the GMPLS server network and to
   select the correct Border Routers to provide connectivity.

   The solution MUST NOT distribute TE information from within a non-PSC
   GMPLS server network to any client MPLS-TE network as that
   information may cause confusion and selection of inappropriate paths.

3.6 Interworking of MPLS-TE and GMPLS protection

   If an MPLS-TE LSPs is protected using MPLS Fast Reroute (FRR)
   [RFC4090], then similar PROTECTION MUST be provided over the GMPLS
   island. Operator and policy controls SHOULD be made available at the
   Border Router to determine how suitable protection is provided in the
   GMPLS island.

3.7 Independent Failure Recovery and Reoptimization

   The solution SHOULD provide failure recovery and reoptimization in
   the GMPLS server network without impacting MPLS-TE client network and
   vice versa. That is, it SHOULD be possible to recover from a fault
   within the GMPLS island or to reoptimize the path across the GMPLS
   island without requiring signaling activity within the MPLS-TE client
   network. Similarly, it SHOULD be possible to perform recovery or
   reoptimization within the MPLS-TE client network without requiring
   signaling activity within the GMPLS server networks.

   In case that failure in the GMPLS server network can not be repaired
   transparently, some kind of notification of the failure SHOULD be
   transmitted to MPLS-TE network.

3.8 Complexity and Risks

   The solution SHOULD NOT introduce unnecessary complexity to the
   current operating network to such a degree that it would affect the
   stability and diminish the benefits of deploying such a solution in
   service provider networks.

3.9 Scalability consideration

   The solution MUST scale well with consideration to at least the
   following considerations.

   - The number of GMPLS-capable nodes (i.e., the size of the GMPLS
   server network).

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   - The number of MPLS-TE-capable nodes (i.e., the size of the MPLS-TE
   client network).
   - The number of MPLS-TE client networks.
   - The number of GMPLS LSPs.
   - The number of MPLS-TE LSPs.

3.10 Performance Consideration

   The solution SHOULD be evaluated with regard to the following

   - Failure and restoration time.
   - Impact and scalability of the control plane due to added
   - Impact and scalability of the data/forwarding plane due to added

3.11 Management Considerations

   Manageability of deployment of an MPLS-TE client network over GMPLS
   server network MUST addresses the following considerations.

   - Need for coordination of MIB modules used for control plane
   management and monitoring in the client and server networks.
   - Need for diagnostic tools that can discover and isolate faults
   across the border between the MPLS-TE client and GMPLS server

4. Security Considerations

   We will write security considerations in next version.

5. Recommended Solution Architecture

   The recommended solution architecture to meet the requirements set
   out in the previous sections is known as the Border Peer Model. This
   architecture is a variant of the Augmented Model described in
   [RFC3945]. The remainder of this document presents an overview of
   this architecture. Details of protocol solutions are described in

   In the Augmented Model, routing information from the lower layer
   (server) network is filtered at the interface to the higher layer
   (client) network and is distributed within the higher layer network.
   In the Border Peer Model, the interface between the client and server
   networks is the Border Router. This router has visibility of the
   routing information in the server network yet also participates as a
   peer in the client network. However, the Border Router does not
   distribute server routing information into the client network.

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   The Border Peer Model may also be contrasted with the Overlay Model
   [RFC3945]. In this model there is a protocol request/response
   interface (the user network interface - UNI) between the client and
   server networks. [RFC4208] shows how this interface may be supported
   by GMPLS protocols operated between client edge and server edge
   routers while retaining the routing information within the server
   network. The Border Peer Model can be viewed as placing the UNI
   within the Border Router thus giving the Border Router peer
   capabilities in both the client and server network.

5.1 Use of Contiguous, Hierarchical, and Stitched LSPs

   All three LSP types MAY be supported in the Border Peer Model, but
   contiguous LSPs are the hardest to support because they require
   protocol mapping between the MPLS-TE client network and the GMPLS
   server network. Such protocol mapping can currently be achieved since
   MPLS-TE signaling protocols are a subset of GMPLS, but this mechanism
   is not future-proofed.

   Contiguous and stitched LSPs can only be supported where the GMPLS
   server network has the same switching type (that is, packet
   switching) as the MPLS-TE network. Requirements for independent
   failure recovery within the GMPLS island require the use of loose
   path reoptimization techniques [LOOSE-REOPT] and end-to-end make-
   before-break [RFC3209] which will not provide rapid recovery.

   For these reasons, the use of hierarchical LSPs across the server
   network is RECOMMENDED for the Border Peer Model, but see the
   discussion of Fast Reroute protection in section 5.3.

5.2 MPLS-TE Control Plane Connectivity

   Control plane connectivity between MPLS-TE LSRs connected by a GMPLS
   island in the Border Peer Model MAY be provided by the control
   channels of the GMPLS network. If this is done, a tunneling mechanism
   (such as GRE [RFC2784]) SHOULD be used to ensure that MPLS-TE
   information is not consumed by the GMPLS LSRs. But care is required
   to avoid swamping the control plane of the GMPLS network with MPLS-TE
   control plane (particularly routing) messages.

   In order to ensure scalability, control plane messages for the MPLS-
   TE client network MAY be carried between Border Routers in a single
   hop MPLS-TE LSP routed through the data plane of the GMPLS server

5.3 Fast Reroute Protection

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   If the GMPLS network is packet switching, Fast Reroute protection can
   be offered on all hops of a contiguous LSP. If the GMPLS network is
   packet switching then all hops of a hierarchical GMPLS LSP or GMPLS
   stitching segment can be protected using Fast Reroute. If the end-to-
   end MPLS-TE LSP requests Fast Reroute protection, the GMPLS packet
   switching network SHOULD provide such protection.

   However, note that it is not possible to provide FRR node protection
   of the upstream Border Router without careful consideration of
   available paths, and protection of the downstream Border Router is
   not possible where hierarchical LSPs or stitching segments are used.

   Note further that Fast Reroute is not available in non-packet
   technologies. However, other protection techniques are supported by
   GMPLS for non-packet networks and are likely to provide similar
   levels of protection.

   The limitations of FRR need careful consideration by the operator and
   may lead to the decision to provide end-to-end protection for the

6. IANA Considerations

   This requirement document makes no requests for IANA action.

7. 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.

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

   [RFC4090] Pan, P., Swallow, G. and A. Atlas, "Fast Reroute
             Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005.

   [RFC4206] Kompella, K., and Rekhter, Y., "Label Switched Paths (LSP)
             Hierarchy with Generalized Multi-Protocol Label Switching
             (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.

   [RFC4208] Swallow, G., et al., "Generalized Multiprotocol Label
             Switching (GMPLS) User-Network Interface (UNI): Resource
             ReserVation Protocol-Traffic Engineering (RSVP-TE) Support
             for the Overlay Model", RFC 4208, October 2005.

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        draft-ietf-ccamp-mpls-gmpls-interwork-reqts-00 December 2006

   [STITCH]  Ayyangar, A., Vasseur, JP. "Label Switched Path Stitching
             with Generalized MPLS Traffic Engineering", draft-ietf-
             ccamp-lsp-stitching, work in progress.

8. Informative References

   [RFC2784] Farinacci, D., et al., "Generic Routing Encapsulation
             (GRE)", RFC 2784, March 2000.

   [BORDER-PEER] Kumaki, K. et al. "Operational, Deployment and
                 Interworking Considerations for GMPLS", draft-kumaki-
                 ccamp-mpls-gmpls-interworking, work in progress.

   [LOOSE-REOPT] Vasseur, JP., Ikejiri, Y., and Zhang, R.,
                 "Reoptimization of Multiprotocol Label Switching
                 (MPLS) Traffic Engineering (TE) loosely routed Label
                 Switch Path (LSP)", draft-ietf-ccamp-loose-path-reopt,
                 work in progress.

   [MIGRATE] Shiomoto, K., et al., "Framework for MPLS-TE to GMPLS
             migration", draft-ietf-ccamp-mpls-gmpls-interwork-fmwk,
             work in progress.

   [MLN] Shiomoto, K., Papadimitriou, D., Le Roux, J.L., Vigoureux, M.,
        Brungard, D., "Requirements for GMPLS-based multi-region and
        multi-layer networks (MRN/MLN)", draft-ietf-ccamp-gmpls-mln-
        reqs, work in progress.

9. Acknowledgments

   The author would like to express the thanks to Raymond Zhang, Adrian
   Farrel, and Deborah Brungard for their helpful and useful comments
   and feedback.

10.Author's Addresses

   Kenji Kumaki (Editor)
   KDDI Corporation
   Garden Air Tower
   Iidabashi, Chiyoda-ku,
   Tokyo 102-8460, JAPAN

   Tomohiro Otani
   KDDI R&D Laboratories, Inc.
   2-1-15 Ohara Kamifukuoka     Phone:  +81-49-278-7357
   Saitama, 356-8502. Japan     Email:

   Shuichi Okamoto

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   NICT JGN II Tsukuba Reserach Center
   1-8-1, Otemachi Chiyoda-ku,   Phone : +81-3-5200-2117
   Tokyo, 100-0004, Japan     E-mail

   Kazuhiro Fujihara
   NTT Communications Corporation
   Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku
   Tokyo 163-1421, Japan

   Yuichi Ikejiri
   NTT Communications Corporation
   Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku
   Tokyo 163-1421, Japan

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