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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
Expires: December 22, 2006                             Matthew. R. Meyer
                                                         Global Crossing
                                                               K. Kumaki
                                                        KDDI Corporation
                                                   Alberto. Tempia Bonda
                                                          Telecom Italia
                                                           June 20, 2006


 A Link-Type sub-TLV to convey the number of Traffic Engineering Label
                  Switch Paths signalled across a link
                 draft-ietf-mpls-number-0-bw-te-lsps-02

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   Several Link-type sub-TLVs have been defined for OSPF and ISIS in the
   context of MPLS Traffic Engineering in order to advertise some link



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   characteristics such as the available bandwidth, traffic engineering
   metric, administrative group and so on.  There are various
   circumstances (for example in order to load balance unconstrained TE
   Label Switched Path (LSP) across a set of equal cost paths) where it
   would be useful to also advertise the number of unconstrained Traffic
   Engineering Label Switched Path(s) (TE LSP) 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].


Table of Contents

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


















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1.  Introduction

   A set of Link-type sub-TLVs have been defined for OSPF and ISIS (see
   [I-D.ietf-isis-te-bis] and [RFC3630]) 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.  There are various circumstances
   (detailed below) where it would be useful to also advertise the
   number of unconstrained Traffic Engineering Label Switch Path(s) (TE
   LSP).

   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 unconstrained TE LSPs
   between a set of LSRs and protect these TE LSPs with pre-established
   backup tunnels against link, SRLG and/or node failures.  The traffic
   routed onto such unconstrained TE LSP simply follows the IGP shortest
   path but is protected with MPLS TE Fast Reroute.

   With MPLS Traffic Engineering a usual rerouting criteria is the
   discovery of a better path for a TE LSP where a better path is
   defined as a path with a lower cost according to a specific metric;
   other metric such that the percentage of reserved bandwidth or the
   number of hops can also be used.  Unfortunately, for instance in the
   presence of ECMPs (Equal Cost Multi-Paths) in symmetrical networks
   when unconstrained TE LSP are used, such metrics are usually
   ineffective and may lead to poorly load balanced traffic.  If the
   number of unconstrained TE LSPs traversing each link in the network
   is known, various algorithms can be designed so as to efficiently
   load balance the traffic carried onto such unconstrained TE LSPs.  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
   LSP signalled across a link.

   Note that the specification of load balancing algorithms is outside
   of the scope of this document and merely listed 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 (e.g.
   management, ...).


2.  Terminology




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   Terminology used in this document

   LSA: Link State Advertisement.

   LSP: Link State Packet.

   LSR: Label Switching Router.

   TE LSP: Traffic Engineering Label Switched Path.

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


3.  Protocol extensions

   A new Sub-TLV named NB-O-BW-LSP is defined that specifies the number
   of unconstrained TE LSPs signalled across a link.

3.1.  IS-IS

   The NB-0-BW-LSP sub-TLV is OPTIONAL and MUST appear at most once
   within the extended IS reachability TLV (type 22) specified in
   [I-D.ietf-isis-te-bis].

   The IS-IS NB-0-BW-LSP sub-TLV format is defined below:

   Type (1 octet): To be assigned by IANA (suggested value = 19)

   Length (1 octet): 4

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

3.2.  OSPF

   The NB-0-BW-LSP sub-TLV is OPTIONAL and MUST appear at most once
   within the Link TLV (Type 2) that is itself carried within the
   Traffic Engineering LSA specified in [RFC3630].

   The OSPF NB-0-BW-LSP sub-TLV format is defined below:

   Type (2 octets): To be assigned by IANA (suggested value = 19)

   Length (2 octets): 4

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




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4.  Elements of procedure

   An implementation may decide to implement a dual-thresholds mechanism
   to govern the origination of updated OSPF LSA or ISIS LSP.  Similarly
   to other MPLS Traffic Engineering link characteristics, LSA/LSP
   origination trigger mechanisms are outside of the scope of this
   document.


5.  IANA Considerations

   IANA will assign a new code point for the newly defined IS-IS sub-TLV
   (NB-0-BW-LSP) carried within the TLV 22 (suggested value =19)

   IANA will assign a new code point for the newly defined OSPF sub-TLV
   (NB-0-BW-LSP) carried within the Link TLV (Type 2) of the Traffic
   Engineering LSA (suggested value=19).


6.  Security Considerations

   This document raises no new security issues for IS-IS and OSPF.


7.  Acknowledgements

   The authors would like to thank Jean-Louis Le Roux for his useful
   inputs.


8.  References

8.1.  Normative References

   [I-D.ietf-isis-te-bis]
              Li, T. and H. Smit, "IS-IS extensions for Traffic
              Engineering", draft-ietf-isis-te-bis-00 (work in
              progress), September 2005.

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

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






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8.2.  Informative References

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














































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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: mrm@gblx.net


   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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   Internet Society.




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