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Network Working Group                                   JP. Vasseur, Ed.Request for Comments: 5330                            Cisco Systems, IncCategory: Standards Track                                      M.  Meyer                                                                      BT                                                               K. Kumaki                                                           KDDI R&D Labs                                                                A. Bonda                                                          Telecom Italia                                                            October 2008A Link-Type sub-TLV to Convey the Number ofTraffic Engineering Label Switched Paths Signalled withZero Reserved Bandwidth across a LinkStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   Several Link-type sub-Type-Length-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   statistical assumptions about the aggregated traffic carried onto a   set of TE Label Switched Paths (LSPs) signalled with zero bandwidth   (referred to as "unconstrained TE LSP" in this document), 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 LSPs   signalled across a link.Vasseur, et al.             Standards Track                     [Page 1]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008Table of Contents1. Introduction ....................................................22. Terminology .....................................................32.1. Requirements Language ......................................43. Protocol Extensions .............................................43.1. IS-IS ......................................................43.2. OSPF .......................................................44. Elements of Procedure ...........................................55. IANA Considerations .............................................56. Security Considerations .........................................57. Acknowledgements ................................................68. References ......................................................68.1. Normative References .......................................68.2. Informative References .....................................61.  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, but is protected with MPLS TE Fast Reroute.  This is   because 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.   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 as 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   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.Vasseur, et al.             Standards Track                     [Page 2]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008   By making statistical assumptions about the aggregated traffic   carried by a set of unconstrained TE LSPs, algorithms can be designed   to load balance (existing or newly configured) unconstrained TE LSPs   across a set of equal cost paths.  This requires knowledge of the   number of unconstrained 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 [RFC5305]) 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 [RFC5305],   the information related to the number of unconstrained TE LSPs 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.2.  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 PathVasseur, et al.             Standards Track                     [Page 3]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008   Unconstrained TE LSP: A TE LSP signalled with a bandwidth equal to 02.1.  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 inRFC 2119 [RFC2119].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 [RFC5305] or the Multi-Topology (MT) Intermediate   Systems TLV (type 222) specified in [RFC5120].  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 IS-IS Unconstrained TE LSP Count sub-TLV format is defined below:   Type (1 octet): 23   Length (1 octet): 2   Value (2 octets): number of unconstrained TE LSPs signalled across   the link.3.2.  OSPF   The OSPF Unconstrained TE LSP Count sub-TLV is OPTIONAL and MUST NOT   appear more than once within the Link TLV (Type 2) that is itself   carried within either the Traffic Engineering LSA specified in   [RFC3630] or the OSPFv3 Intra-Area-TE LSA (function code 10) defined   in [RFC5329].  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.Vasseur, et al.             Standards Track                     [Page 4]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008   The OSPF Unconstrained TE LSP Count sub-TLV format is defined below:   Type (2 octets): 23   Length (2 octets): 4   Value (4 octets): number of unconstrained TE LSPs 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.   Similar 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 in 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 and has assigned a new TLV codepoint for the Unconstrained TE   LSP Count sub-TLV carried within the TLV 22.   Value       TLV Name                               Reference   23          Unconstrained TE LSP Count (sub-)TLVRFC 5330   IANA has defined a sub-registry for the sub-TLVs carried in an OSPF   TE Link TLV (type 2) and has assigned a new sub-TLV codepoint for the   Unconstrained TE LSP Count sub-TLV carried within the TE Link TLV.   Value       TLV Name                               Reference   23          Unconstrained TE LSP Count (sub-)TLVRFC 53306.  Security Considerations   The function described in this document does not create any new   security issues for the OSPF and IS-IS protocols.  Security   considerations are covered in [RFC2328] and [RFC5340] for the base   OSPF protocol and in [RFC1195] and [RFC5304] for IS-IS.   A security framework for MPLS and Generalized MPLS can be found in   [G/MPLS].Vasseur, et al.             Standards Track                     [Page 5]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 20087.  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 Polk, and Loa Anderson for their useful inputs.8.  References8.1.  Normative References   [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.   [RFC5304]  Li, T. and R. Atkinson, "Intermediate System to              Intermediate System (IS-IS) Cryptographic Authentication",RFC 5304, October 2008.   [RFC5305]  Li, T. and H. Smit, "IS-IS extensions for Traffic              Engineering",RFC 5305, October 2008.   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,              "Traffic Engineering Extensions to OSPF Version 3",RFC5329, September 2008.   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF              for IPv6",RFC 5340, July 2008.8.2.  Informative References   [G/MPLS]   Fang, L., Ed., "Security Framework for MPLS and GMPLS              Networks", Work In Progress, July 2008.   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "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.Vasseur, et al.             Standards Track                     [Page 6]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008Authors' Addresses   JP Vasseur (editor)   Cisco Systems, Inc   1414 Massachusetts Avenue   Boxborough, MA  01719   USA   EMail: jpv@cisco.com   Matthew R. Meyer   BT   Boston, MA   USA   EMail: matthew.meyer@bt.com   Kenji Kumaki   KDDI R&D Laboratories, Inc.   2-1-15 Ohara Fujimino   Saitama 356-8502, JAPAN   EMail: ke-kumaki@kddi.com   Alberto Tempia Bonda   Telecom Italia   via G. Reiss Romoli 274   Torino,  10148   ITALIA   EMail: alberto.tempiabonda@telecomitalia.itVasseur, et al.             Standards Track                     [Page 7]

RFC 5330            Sub-TLV for Unconstrained TE LSP        October 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Vasseur, et al.             Standards Track                     [Page 8]