ISIS Internet Draft Jean-Philippe Vasseur Stefano Previdi Mike Shand Cisco Systems Document: draft-vasseur-isis-caps-00.txt Expires: August 2004 February 2004 IS-IS extensions for advertising router capabilities draft-vasseur-isis-caps-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [i]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document defines a new optional IS-IS TLV named CAPABILITY TLV, formed of multiple sub-TLVs, which allows a router to announce its capabilities within an IS-IS level or the entire routing domain. Conventions used in this document 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 [ii]. Vasseur et al. Expires û August 2004 [Page 1] draft-vasseur-isis-caps-00.txt February 2004 Table of Contents 1. Introduction...................................................2 2. IS-IS CAPABILITY TLV...........................................2 2.1 IS-IS CAP-SCOPE sub-TLV....................................3 2.2 IS-IS router-ID sub-TLV....................................3 3. Element of procedure...........................................4 4. Interoperability with routers not supporting the capability TLV.4 5. Security considerations........................................4 6. Intellectual Property Considerations...........................4 7. References.....................................................5 Normative references..............................................5 Informative references............................................5 8. Author's Addresses.............................................6 1. Introduction There are several situations where it is useful for the IS-IS routers to learn the capabilities of the other routers of their IS-IS level, area or routing domain. Some applications are described in [IS-IS-TE- CAP] but for the sake of illustration, one can briefly describes three of them related to MPLS Traffic Engineering. - Path Computation Element (PCE) discovery: in several situations, the Traffic Engineering Label Switched (TE LSP) path is computed by a Label Switch Router (LSR) it is not the head-end for (e.g an ABR or an ASBR respectively in the context of inter-area and inter-AS MPLS TE ([INTER-AREA-AS]). In such a case, having the ability to discover the capability of an router to act as a PCE is extremely useful in term of ease of operation, capacity to react to PCE failure, load sharing between a set of PCEs, etc - Mesh-group: the setting up of a mesh of TE LSPs requires some significant configuration effort. [IS-IS-TE-CAP] proposes an auto- discovery mechanism whereby every LSR of a mesh advertises its mesh-group membership by means of IS-IS extensions. - Point to Multi-point TE LSP (P2MP LSP). A specific sub-TLV ([IS- IS-TE]) allows an LSR to advertise its capabilities to be a ôbranch nodeö of a P2MP TE LSP (see [P2MP] and [P2MP-req]). The capability mentioned above lead to the specification of specific 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 advertisement mechanism not limited to MPLS Traffic Engineering. 2. IS-IS CAPABILITY TLV Vasseur et al. Expires û August 2004 [Page 2] draft-vasseur-isis-caps-00.txt February 2004 The IS-IS TLV is composed of 1 octet for the type, 1 octet specifying the TLV length and a variable length value field. CODE: To be assigned by IANA LENGTH: Variable (1 octet) VALUE: set of sub-TLVs The CAPABILITY TLV is OPTIONAL. As specified in section 3, more than one CAPABILITY TLVs may be present. The CAPABILITY TLV MUST be inserted in fragment 0 in case of a fragmented IS-IS LSP. A CAPABILITY TLV inserted in non-0 LSP fragment MUST be ignored. 2.1 IS-IS CAP-SCOPE sub-TLV The CAP-SCOPE sub-TLV is mandatory and MUST be included in the CAPABILITY TLV. It MUST also always be the first sub-TLV. Furthermore, a router MUST include exactly one CAP-SCOPE TLV. A router receiving a CAPABILITY TLV not starting with the CAP-SCOPE sub-TLV MUST IGNORE the CAPABILITY TLV and continue processing the IS-IS LSP. CODE: 1 LENGTH: 1 VALUE: +-+-+-+-+-+-+-+-+ |S|U| | +-+-+-+-+-+-+-+-+ S bit: when set, the IS-IS CAPABILITY TLV MUST be flooded across the entire routing domain; hence, according to the element of procedure defined in section 3, the CAPABILITY TLV MUST be leaked between IS-IS levels or multiple areas of the same IS-IS level by L1L2 routers that support the CAPABILITY TLV. U bit: the U bit MUST be set each time the CAPABILITY TLV is leaked into another IS-IS level or another area of the same IS-IS level. When set, the U bit MUST not be changed by any other router. 2.2 IS-IS router-ID sub-TLV The router-ID sub-TLV is mandatory and MUST be included in the CAPABILITY TLV. It MUST immediately follow the CAP-SCOPE TLV. Furthermore, a router MUST include exactly one router-ID TLV. CODE: 2 LENGTH: 4 VALUE: unsigned 32 bit number representing the router-ID. Vasseur et al. Expires û August 2004 [Page 3] draft-vasseur-isis-caps-00.txt February 2004 3. Element of procedure In case of capabilities with different scopes, a router MUST include two CAPABILITY TLVs, each TLV carrying the set of sub-TLVs with the same flooding scope. For instance, if a router advertises two capabilities C1 and C2 respectively with a area/level scope and routing domain scope, C1 and C2 being specified by their respective sub-TLV, the router MUST include two CAPABILITY TLVs: - One CAPABILITY TLV with one CAP-SCOPE sub-TLV (S flag set), the ROUTER-ID sub-TLV, followed by the sub-TLV relative to C1. This CAPABILITY TLV MUST be leaked into other IS-IS levels or areas or the same level after having set the U bit of the CAP-SCOPE sub-TLV. Other sub-TLVs MUST be unchanged during the leaking procedure. - One CAPABILITY TLV with one CAP-SCOPE sub-TLV (S flag set), the ROUTER-ID sub-TLV, followed by the sub-TLV relative to C2. Such a CAPABILITY TLV MUST not be leaked into other level or areas of the same level. A router receiving a CAPABILITY TLV carrying a CAP-SCOPE sub-TLV with the S flag and the U flag set MUST NOT leak the CAPABILITY TLV into another ISIS level or areas. This prevents TLV looping. 4. Interoperability with routers not supporting the capability TLV. There is no interoperability issue as a router non-supporting the capability TLV MUST just silently ignore the TLV(s). If just a subset of the sub-TLVs carried within the capability TLV are supported, then the non-supported sub-TLV MUST be silently ignored. 5. Security considerations No new security issues are raised in this document. 6. Intellectual Property Considerations The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 Vasseur et al. Expires û August 2004 [Page 4] draft-vasseur-isis-caps-00.txt February 2004 proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this document. For more information consult the online list of claimed rights. 7. References Normative references [RFC] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels," RFC 2119. [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. [IS-IS-IP] Callon, R., RFC 1195, "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990. [ISIS-TE] Li, T., Smit, H., "IS-IS extensions for Traffic Engineering", draft-ietf-isis-traffic-04.txt (work in progress) Informative references [IS-IS-TE-CAP] JP Vasseur, S. Previdi, JL. Le Roux, ôIS-IS MPLS Traffic Engineering capabilitiesö, draft-vasseur-ccamp-isis-te-caps- 00.txt, work in progress. [P2MP] S. Yasukawa et al. ½ Extended RSVP TE for point-to-multipoint LSP tunnelsö, draft-yasukawa-mpls-rsvp-p2mp-03.txt, work in progress. [P2MP-reqs] S. Yasukawa et al. ½ Requirements for point to multipoint extension to RSVP ©, draft-ietf-mpls-p2mp-requirement-01.txt, work in progress. [INTER-AREA-AS] Vasseur and Ayyangar, ôInter-area and Inter-AS MPLS Traffic Engineeringö, draft-vasseur-ayyangar-inter-area-AS-TE-00.txt, work in progress. Vasseur et al. Expires û August 2004 [Page 5] draft-vasseur-isis-caps-00.txt February 2004 8. Author's Addresses Jean-Philippe Vasseur CISCO Systems, Inc. 300 Beaver Brook Boxborough, MA 01719 USA Email: jpv@cisco.com Stefano Previdi CISCO Systems, Inc. Via Del Serafico 200 00142 - Roma ITALY Email: sprevidi@cisco.com Mike Shand Cisco Systems 250 Longwater Avenue, Reading, Berkshire, RG2 6GB UK Phone: +44 208 824 8690 Email: mshand@cisco.com Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. 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