Network Working Group JP. Vasseur, Ed. Request for Comments: 4971 N. Shen, Ed. Category: Standards Track Cisco Systems, Inc. R. Aggarwal, Ed. Juniper Networks July 2007 Intermediate System to Intermediate System (IS-IS) Extensions for Advertising Router Information Status 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. Copyright Notice Copyright (C) The IETF Trust (2007).
AbstractThis document defines a new optional Intermediate System to Intermediate System (IS-IS) TLV named CAPABILITY, formed of multiple sub-TLVs, which allows a router to announce its capabilities within an IS-IS level or the entire routing domain. 1. Introduction ....................................................2 1.1. Conventions Used in This Document ..........................2 2. IS-IS Router CAPABILITY TLV .....................................3 3. Elements of Procedure ...........................................4 4. Interoperability with Routers Not Supporting the Capability TLV ..................................................5 5. Security Considerations .........................................6 6. IANA Considerations .............................................6 7. Acknowledgment ..................................................6 8. References ......................................................6 8.1. Normative References .......................................6 8.2. Informative References .....................................8
IS-IS] [IS-IS-IP] routers to learn the capabilities of the other routers of their IS-IS level, area, or routing domain. For the sake of illustration, three examples related to MPLS Traffic Engineering (TE) are described here: 1. Mesh-group: the setting up of a mesh of TE Label Switched Paths (LSPs) [IS-IS-TE] requires some significant configuration effort. [AUTOMESH] proposes an auto-discovery mechanism whereby every Label Switching Router (LSR) of a mesh advertises its mesh-group membership by means of IS-IS extensions. 2. Point to Multipoint TE LSP (P2MP LSP). A specific sub-TLV ([TE-NODE-CAP]) allows an LSR to advertise its Point To Multipoint capabilities ([P2MP] and [P2MP-REQS]). 3. Inter-area traffic engineering: Advertisement of the IPv4 and/or the IPv6 Traffic Engineering Router IDs. The use of IS-IS for Path Computation Element (PCE) discovery may also be considered and will be discussed in the PCE WG. The capabilities mentioned above require the specification of new sub-TLVs carried within the CAPABILITY TLV defined in this document. Note that the examples above are provided for the sake of illustration. This document proposes a generic capability advertising mechanism that is not limited to MPLS Traffic Engineering. This document defines a new optional IS-IS TLV named CAPABILITY, formed of multiple sub-TLVs, which allows a router to announce its capabilities within an IS-IS level or the entire routing domain. The applications mentioned above require the specification of new sub- TLVs carried within the CAPABILITY TLV defined in this document. Definition of these sub-TLVs is outside the scope of this document. RFC-2119].
RFC 3784 [IS-IS-TE]. TYPE: 242 LENGTH: from 5 to 255 VALUE: Router ID (4 octets) Flags (1 octet) Set of optional sub-TLVs (0-250 octets) Flags 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ | Reserved |D|S| +-+-+-+-+-+-+-+-+ Currently two bit flags are defined. S bit (0x01): If the S bit is set(1), the IS-IS Router CAPABILITY TLV MUST be flooded across the entire routing domain. If the S bit is not set(0), the TLV MUST NOT be leaked between levels. This bit MUST NOT be altered during the TLV leaking. D bit (0x02): When the IS-IS Router CAPABILITY TLV is leaked from level-2 to level-1, the D bit MUST be set. Otherwise, this bit MUST be clear. IS-IS Router capability TLVs with the D bit set MUST NOT be leaked from level-1 to level-2. This is to prevent TLV looping. The Router CAPABILITY TLV is OPTIONAL. As specified in Section 3, more than one Router CAPABILITY TLV from the same source MAY be present. This document does not specify how an application may use the Router Capability TLV and such specification is outside the scope of this document.
In IS-IS, the atomic unit of the update process is a TLV -- or more precisely, in the case of TLVs that allow multiple entries to appear in the value field (e.g., IS-neighbors), the atomic unit is an entry in the value field of a TLV. If an update to an entry in a TLV is advertised in an LSP fragment different from the LSP fragment associated with the old advertisement, the possibility exists that other systems can temporarily have either 0 copies of a particular advertisement or 2 copies of a particular advertisement, depending on the order in which new copies of the LSP fragment that had the old advertisement and the fragment that has the new advertisement arrive at other systems. Wherever possible, an implementation SHOULD advertise the update to a capabilities TLV in the same LSP fragment as the advertisement that it replaces. Where this is not possible, the two affected LSP fragments should be flooded as an atomic action. Systems that receive an update to an existing capability TLV can minimize the potential disruption associated with the update by employing a holddown time prior to processing the update so as to allow for the receipt of multiple LSP fragments associated with the same update prior to beginning processing. Where a receiving system has two copies of a capabilities TLV from the same system that have different settings for a given attribute, the procedure used to choose which copy shall be used is undefined.
RFC-3567] or [IS-IS-HMAC], should be applied if there is high risk resulting from modification of capability information. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [IS-IS] "Intermediate System to Intermediate System Intra- Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service (ISO 8473)", ISO 10589. [RFC-3567] Li, T. and R. Atkinson, "Intermediate System to Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567, July 2003. [IS-IS-IP] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990. [IS-IS-TE] Smit, H. and T. Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004.
[AUTOMESH] Vasseur, JP., Ed., Le Roux, JL., Ed., Yasukawa, S., Previdi, S., Psenak, P., and P. Mabbey, "Routing extensions for Discovery of Multiprotocol (MPLS) Label Switch Router (LSR) Traffic Engineering (TE) Mesh Membership", RFC 4972, July 2007. [TE-NODE-CAP] Vasseur, JP., Ed., and J.L. Le Roux, "Routing Extensions for Discovery of Traffic Engineering Node Capabilities", Work in Progress, April 2007. [P2MP] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S. Yasukawa, Ed., "Extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for Point-to- Multipoint TE Label Switched Paths (LSPs)", RFC 4875, May 2007. [P2MP-REQS] Yasukawa, S., Ed., "Signaling Requirements for Point- to-Multipoint Traffic-Engineered MPLS Label Switched Paths (LSPs)", RFC 4461, April 2006. [IS-IS-HMAC] Bhatia, M., Ed. and V. Manral, Ed., "IS-IS Generic Cryptographic Authentication", Work in Progress, May 2007.
Mike Shand Cisco Systems 250 Longwater Avenue, Reading, Berkshire, RG2 6GB UK EMail: email@example.com Les Ginsberg Cisco Systems 510 McCarthy Blvd. Milpitas, Ca. 95035 USA EMail: firstname.lastname@example.org Acee Lindem Redback Networks 102 Carric Bend Court Cary, NC 27519 USA EMail: email@example.com Naiming Shen Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA EMail: firstname.lastname@example.org Rahul Aggarwal Juniper Networks 1194 N. Mathilda Avenue San Jose, CA 94089 USA EMail: email@example.com Scott Shaffer EMail: firstname.lastname@example.org
Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 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 in BCP 78 and BCP 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 at http://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 email@example.com. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.