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Versions: 00

Network Working Group                                         P. Francis
Internet-Draft                                                   MPI-SWS
Intended status: Informational                                     X. Xu
Expires: November 24, 2009                                        Huawei
                                                            May 23, 2009


                  MPLS Tunnels for Virtual Aggregation
                     draft-ietf-grow-va-mpls-00.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   Copyright (c) 2009 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

   The document "FIB Suppression with Virtual Aggregation"
   [I-D.francis-intra-va] describes how FIB size may be reduced.  The



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   latest revision of that draft refers generically to tunnels, and
   leaves it to other documents to define the usage and signaling
   methods for specific tunnel types.  This document provides those
   definitions for MPLS Label Switched Paths (LSP), without tag
   stacking.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . . . 3
     1.2.  Changes from Previous Versions  . . . . . . . . . . . . . . 3
   2.  Tunneling Requirements  . . . . . . . . . . . . . . . . . . . . 3
   3.  Tunneling Specification for MPLS  . . . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 5

































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1.  Introduction

   This document specifies how to use and signal the tunnels required by
   [I-D.francis-intra-va], "FIB Suppression with Virtual Aggregation",
   for MPLS.  This document is limited to MPLS without tag stacking.
   This document adopts the terminology of [I-D.francis-intra-va].  This
   document covers the behavior for both VA routers and legacy routers.

1.1.  Requirements notation

   The key words "must", "must NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2.  Changes from Previous Versions

   This document was previously published as
   draft-francis-va-tunnels-mpls-00.  No substantive changes were made
   from that revision.


2.  Tunneling Requirements

   According to [I-D.francis-intra-va], VA has the following tunnel-
   related requirements.  The requirement numbers here (R1 - R5) are
   cited by [I-D.francis-intra-va].

   R1:    Legacy routers and APRs must be able to detunnel packets
      addressed to themselves at their BGP NEXT_HOP address.  They must
      be able to signal the tunnel information needed by other routers
      to initiate these tunneled packets.
   R2:    Border VA routers must be able to detunnel packets targeted to
      neighboring remote ASBRs.  They must be able to forward these
      packets to the targeted remote ASBR without doing a FIB lookup.
      They must be able to signal the tunnel information needed by other
      routers to initiate these tunneled packets.
   R3:    VA routers must be able to initiate tunneled packets targeted
      to any BGP NEXT_HOP address (i.e. those for APRs, legacy routers,
      or remote ASBRs).
   R4:    Legacy routers may optionally be able to initiate tunneled
      packets targeted to any BGP NEXT_HOP address (i.e. those for APRs,
      legacy routers, or remote ASBRs).  The MPLS tunnels defined in
      this document allow this capability.
   R5:    All routers must be able to forward all tunneled packets.







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3.  Tunneling Specification for MPLS

   VA utilizes a straight-forward application of MPLS.  The tunnels are
   MPLS Label Switched Paths (LSP), and are signaled using either the
   Label Distribution Protocol (LDP) [RFC5036].  (Note that usage of
   RSVP-TE [RFC3209] to signal these tunnels, in particular the
   scalability of configuring so many tunnels, is for further study.)
   All routers (VA and legacy alike) must run LDP, as required by R5.  A
   legacy router that cannot run LDP and initiate LSPs terminating at
   itself cannot participate in a VA domain.

   Requirements R1 and R2 require that routers initiate tunnels.  This
   is done by importing the full BGP NEXT_HOP address (/32 if IPv4, /128
   if IPv6) into the IGP (i.e.  OSPF [RFC2328]), and initiating
   Downstream Unsolicited tunnels to all IGP neighbors with the full BGP
   NEXT_HOP address as the Forwarding Equivalence Class (FEC).

   Note that in the case of requirement R2, the BGP NEXT_HOP address is
   that of the remote ASBR, not that of the router that is initiating
   the LSP (i.e. the local ASBR VA router).  Strictly speaking, this is
   non-standard behavior---normally it is the router owning the FEC
   address that initiates signaling.  Nevertheless routers can employ
   existing Penultimate Hop Popping (PHP) mechanisms in the data plane
   for forwarding packets to remote ASBRs.

   Requirements R3 and R4 should naturally be satisfied through normal
   MPLS usage.  In other words, the LSP to the BGP NEXT_HOP address
   should automatically be the preferred method to routing the packet
   towards the BGP NEXT_HOP address.


4.  IANA Considerations

   There are no IANA considerations.


5.  Security Considerations

   Because this document describes a (near) standard application of
   intra-domain MPLS, there are no new security considerations beyond
   those already described in [I-D.francis-intra-va].


6.  Normative References

   [I-D.francis-intra-va]
              Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and
              L. Zhang, "FIB Suppression with Virtual Aggregation",



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              draft-francis-intra-va-01 (work in progress), April 2009.

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

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [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.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.


Authors' Addresses

   Paul Francis
   Max Planck Institute for Software Systems
   Gottlieb-Daimler-Strasse
   Kaiserslautern  67633
   Germany

   Email: francis@mpi-sws.org


   Xiaohu Xu
   Huawei Technologies
   No.3 Xinxi Rd., Shang-Di Information Industry Base, Hai-Dian District
   Beijing, Beijing  100085
   P.R.China

   Phone: +86 10 82836073
   Email: xuxh@huawei.com

















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