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Versions: (draft-vasseur-mpls-number-0-bw-te-lsps) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5330

Networking Working Group                                JP. Vasseur, Ed.
Internet-Draft                                        Cisco Systems, Inc
Intended status: Standards Track                       Matthew. R. Meyer
Expires: March 5, 2009                                   Global Crossing
                                                               K. Kumaki
                                                        KDDI Corporation
                                                   Alberto. Tempia Bonda
                                                          Telecom Italia
                                                       September 1, 2008


 A Link-Type sub-TLV to convey the number of Traffic Engineering Label
  Switched Paths signalled with zero reserved bandwidth across a link
                 draft-ietf-mpls-number-0-bw-te-lsps-12

Status of this Memo

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Abstract

   Several Link-type sub-Type-Lenght-Values (sub-TLVs) have been defined
   for Open Shortest Path First (OSPF) and Intermediate System to
   Intermediate System (IS-IS) in the context of Multiprotocol Label
   Switching (MPLS) Traffic Engineering (TE) in order to advertise some
   link characteristics such as the available bandwidth, traffic
   engineering metric, administrative group and so on.  By making



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   statistical assumptions about the aggregated traffic carried onto a
   set of TE Label Switched Paths (LSPs) signalled with zero bandwith
   (referred to as unconstrained TE LSP in this document), and with the
   knowledge of the number of unconstrained TE LSPs signalled across a
   link, algorithms can be designed to load balance (existing or newly
   configured) unconstrained TE LSP across a set of equal cost paths.
   This requires knowledge of the number of unconstrained TE LSPs
   signalled across a link.  This document specifies a new Link-type
   Traffic Engineering sub-TLV used to advertise the number of
   unconstrained TE LSP(s) signalled across a link.

Requirements Language

   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 RFC 2119 [RFC2119].



































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Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Protocol extensions  . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  IS-IS  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Elements of procedure  . . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8
   Intellectual Property and Copyright Statements . . . . . . . . . . 10



































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1.  Terminology

   Terminology used in this document

   CSPF: Constrained Shortest Path First

   IGP : Interior Gateway Protocol

   LSA: Link State Advertisement

   LSP: Link State Packet

   MPLS: Multiprotocol Label Switching

   LSR: Label Switching Router

   SRLG: Shared Risk Link Group

   TE LSP: Traffic Engineering Label Switched Path

   Unconstrained TE LSP: A TE LSP signalled with a bandwidth equal to 0


2.  Introduction

   It is not uncommon to deploy MPLS Traffic Engineering for the sake of
   fast recovery relying on a local protection recovery mechanism such
   as MPLS TE Fast Reroute (see [RFC4090]).  In this case, a deployment
   model consists of deploying a full mesh of TE LSPs signalled with
   zero bandwidth (also referred to as unconstrained TE LSP in this
   document) between a set of LSRs (Label Switching Routers) and
   protecting these TE LSPs against link, SRLG (Shared Risk Link Group)
   and/or node failures with pre-established backup tunnels.  The
   traffic routed onto such unconstrained TE LSPs simply follows the IGP
   shortest path (since the TE LSP computed by the path computation
   algorithm (e.g.  CSPF) will be no different than the IGP (Interior
   Gateway Protocol) shortest path should the TE metric be equal to the
   IGP metric) but is protected with MPLS TE Fast Reroute.

   When a reoptimization process is triggered for an existing TE LSP,
   the decision on whether to reroute that TE LSP onto a different path
   is governed by the discovery of a lower cost path satisfying the
   constraints (other metrics such that the percentage of reserved
   bandwidth or the number of hops can also be used).  Unfortunately,
   metrics such as the path cost or the number of hops may be
   ineffective in various circumstances: for example, in the case of a
   symmetrical network with ECMPs (Equal Cost Multi-Paths), if the
   network operator uses unconstrained TE LSP, this may lead to a poorly



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   load balanced traffic: indeed, several paths between a source and a
   destination of a TE LSP may exist that have the same cost and the
   reservable amount of bandwidth along each path cannot be used as a
   tie-breaker.

   By making statistical assumptions about the aggregated traffic
   carried by a set of TE LSPs signalled with no bandwidth requirement
   (referred to as unconstrained TE LSPs in this document), algorithms
   can be designed to load balance (existing or newly configured)
   unconstrained TE Label Switched Paths (LSPs) across a set of equal
   cost paths.  This requires knowledge of the number of unconstrained
   Traffic Engineering Label Switched Paths (TE LSPs) signalled across
   each link.

   Note that the specification of load balancing algorithms is outside
   the scope of this document and is referred to for the sake of
   illustration of the motivation for gathering such information.

   Furthermore, the knowledge of the number of unconstrained TE LSPs
   signalled across each link can be used for other purposes, for
   example to evaluate the number of affected unconstrained TE LSPs in
   case of a link failure.

   A set of Link-type sub-TLVs have been defined for OSPF and IS-IS (see
   [RFC3630] and [I-D.ietf-isis-te-bis]) in the context of MPLS Traffic
   Engineering in order to advertise various link characteristics such
   as the available bandwidth, traffic engineering metric,
   administrative group and so on.  As currently defined in [RFC3630]
   and [I-D.ietf-isis-te-bis] the information related to the number of
   unconstrained TE LSP(s) is not available.  This document specifies a
   new Link-type Traffic Engineering sub-TLV used to indicate the number
   of unconstrained TE LSPs signalled across a link.

   Unconstrained TE LSPs that are configured and provisioned through a
   management system MAY be omitted from the count that is reported.


3.  Protocol extensions

   Two Unconstrained TE LSP count sub-TLVs are defined that specify the
   number of TE LSPs signalled with zero bandwidth across a link.

3.1.  IS-IS

   The IS-IS Unconstrained TE LSP Count Sub-TLV is OPTIONAL and MUST NOT
   appear more than once within the extended IS reachability TLV (type
   22) specified in [I-D.ietf-isis-te-bis] or the MT Intermediate
   Systems TLV (type 222) specified in [RFC5120].  If a second instance



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   of the Unconstrained TE LSP Count sub-TLV is present, the receiving
   system MUST only process the first instance of the sub-TLV.

   The IS-IS Unconstrained TE LSP Count Sub-TLV format is defined below:

   Type (1 octet): To be assigned by IANA (suggested value = 23)

   Length (1 octet): 2

   Value (2 octets): number of unconstrained TE LSP(s) signalled across
   the link.

3.2.  OSPF

   The OSPF Unconstrained TE LSP Count TLV is OPTIONAL and MUST NOT
   appear more than once within the Link TLV (Type 2) that is itself
   carried within the Traffic Engineering LSA specified in [RFC3630] or
   the OSPFv3 Intra-Area-TE LSA (function code 10) defined in
   [I-D.ietf-ospf-ospfv3-traffic].  If a second instance of the
   Unconstrained TE LSP Count sub-TLV is present, the receiving system
   MUST only process the first instance of the sub-TLV.

   The OSPF Unconstrained TE LSP Count Sub-TLV format is defined below:

   Type (2 octets): To be assigned by IANA (suggested value = 23)

   Length (2 octets): 4

   Value (4 octets): number of unconstrained TE LSP(s) signalled across
   the link.


4.  Elements of procedure

   The absence of the Unconstrained TE LSP Count (sub-)TLV SHOULD be
   interpreted as an absence of information about the link.

   Similarly to other MPLS Traffic Engineering link characteristics,
   LSA/LSP origination trigger mechanisms are outside the scope of this
   document.  Care must be given to not trigger the systematic flooding
   of a new IS-IS LSP or OSPF LSA with a too high granularity in case of
   change of the number of unconstrained TE LSPs.


5.  IANA Considerations

   IANA has defined a sub-registry for the sub-TLVs carried in the IS-IS
   TLV 22.  IANA is requested to assign a new TLV code-point for the



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   Unconstrained TE LSP Count sub-TLV carried within the TLV 22.

   Suggested Value  TLV Name                               Reference

        23          Unconstrained TE LSP Count (sub-)TLV   This document


   IANA has defined a sub-registry for the sub-TLVs carried in an OSPF
   TE Link TLV (type 2).  IANA is requested to assign a new sub-TLV
   code-point for the Unconstrained TE LSP Count sub-TLV carried within
   the TE Link TLV.

   Suggested Value  TLV Name                               Reference

        23          Unconstrained TE LSP Count (sub-)TLV   This document



6.  Security Considerations

   The function described in this document does not create any new
   security issues for the OSPF and the IS-IS protocols.  Security
   considerations are covered in [RFC2328] and [RFC5340] for the base
   OSPF protocol and in [RFC1195] and [I-D.ietf-isis-rfc3567bis] for
   IS-IS.

   A security framework for MPLS and Generalized MPLS can be found in
   [I-D.ietf-mpls-mpls-and-gmpls-security-framework].


7.  Acknowledgements

   The authors would like to thank Jean-Louis Le Roux, Adrian Farrel,
   Daniel King, Acee Lindem, Lou Berger, Attila Takacs, Pasi Eronen,
   Russ Housley, Tim Folk and Loa Anderson for their useful inputs.


8.  References

8.1.  Normative References

   [I-D.ietf-isis-rfc3567bis]
              Li, T. and R. Atkinson, "Intermediate System to
              Intermediate System (IS-IS) Cryptographic
              Authentication", draft-ietf-isis-rfc3567bis-03 (work in
              progress), July 2008.

   [I-D.ietf-isis-te-bis]



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              Li, T. and H. Smit, "IS-IS extensions for Traffic
              Engineering", draft-ietf-isis-te-bis-00 (work in
              progress), April 2008.

   [I-D.ietf-ospf-ospfv3-traffic]
              Ishiguro, K., Manral, V., Davey, A., and A. Lindem,
              "Traffic Engineering Extensions to OSPF version 3",
              draft-ietf-ospf-ospfv3-traffic-13 (work in progress),
              June 2008.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [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.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              September 2003.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.

8.2.  Informative References

   [I-D.ietf-mpls-mpls-and-gmpls-security-framework]
              Fang, L. and M. Behringer, "Security Framework for MPLS
              and GMPLS Networks",
              draft-ietf-mpls-mpls-and-gmpls-security-framework-03 (work
              in progress), July 2008.

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

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120, February 2008.











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Authors' Addresses

   JP Vasseur (editor)
   Cisco Systems, Inc
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   Email: jpv@cisco.com


   Matthew R. Meyer
   Global Crossing
   3133 Indian Valley Tr.
   Howell, MI  48855
   USA

   Email: mrminc@gmail.com


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

   Email: ke-kumaki@kddi.com


   Alberto Tempia Bonda
   Telecom Italia
   via G. Reiss Romoli 274
   Torino,   10148
   ITALIA

   Email: alberto.tempiabonda@telecomitalia.it















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