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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: November 16, 2006                                  May 15, 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-00

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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 convery some link
   characteristics such as the available bandwidth, traffic enginering
   metric, adminstrative group and so on.  There are various
   circumstances where it would be useful to also know the number of
   unconstrained Traffic Engineering Label Switched Path(s) (TE LSP).
   This document specifies a new Link-type Traffic Engineering sub-TLV
   used to advertise the number of unconstrained TE LSP(s) signalled



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   across a specific 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.  ISIS  . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     3.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Elements of procedure . . . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 7


























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1.  Introduction

   Several 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 enginering metric, adminstrative
   group and so on.  There are various circumstances where it would be
   useful to also know 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 with MPLS TE Fast Reroute (see [RFC4090]).  In this
   case, a common deployment model consists of deploying a full mesh of
   unconstrained TE LSPs between a set of LSRs and protect these TE LSPs
   thanks to pre-established backup tunnels against link, SRLG and/or
   node failures.

   When a set of unconstrained TE LSPs is deployed, various algorithms
   can be designed so as efficiently load balance the traffic carried by
   such unconstrained TE LSPs provided that the number of unconstrained
   TE LSPs traversing each link in the network is known.  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.
   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, ...).

   This document specifies a new Link-type Traffic Engineering sub-TLV
   used to indicate the number of unconstrained TE LSP signalled across
   a specific link.


2.  Terminology

   Terminology used in this document LSR: Label Switch Router.

   TE LSP: MPLS Traffic Engineering Label Switched Path.

   Backup tunnel: the TE LSP that is used to backup up one of the many
   TE LSPs in many-to-one backup (as defined in [FAST-REROUTE]).

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





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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.  ISIS

   The NB-0-BW-LSP TLV is OPTIONAL and MUST appear at most once within
   the extended IS reachability TLV (type 22) specified in [ISIS-TE].
   The NB-0-BW-LSP consists of:

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

   Length (1 octet): 4

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

3.2.  OSPF

   The NB-0-BW-LSP 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 [OSPF-TE].  The NB-0-BW-LSP consists of:

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

   Length (2 octets): 4

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


4.  Elements of procedure

   An implementation may decide to implement a dual-thresholds mechanism
   so as to trigger the origination of an updated OSPF LSA or ISIS LSP.
   Similalry 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 ISIS 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



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   Engineering LSA (suggested value=19).


6.  Security Considerations

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


7.  Acknowledgements

   The author would want to thank Kenji Kumaki, Alberto Tempia, Jean-
   Louis Le Roux and Matt Meyer for their 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.

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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Author's Address

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

   Email: jpv@cisco.com










































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   Internet Society.




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