Network Working Group Sina Mirtorabi Internet Draft Abhay Roy Document: draft-mirtorabi-ospfv3-tag-01.txt Cisco Systems Expiration Date: March 2005 September 2004 Route tags in OSPFv3 draft-mirtorabi-ospfv3-tag-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "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 describes a mechanism to carry a route tag in OSPFv3. Currently only external LSA can carry a tag. This document propose a method to carry tags for intra and inter area prefixes. 1. Introduction [Ref 1] defines tag for OSPFv2 and the usage of it carried with a prefix. This document propose a solution for OSPFv3 [Ref 2] by defining new LSA's to carry tag. The new LSA's will not carry any prefix to duplicate the generation of prefix within the domain but Mirtorabi, Roy [Page 1] Internet Draft Route tags in OSPFv3 September 2004 simply associate a tag with list of Link State IDs corresponding to LSA's that carry prefixes. 2. Intra-area-tag-LSA We define a new LSA called intra-area-tag-LSA to carry tag within an OSPFv3 area. The flooding scope of the LSA is area wide and the Unknown bit (U bit) is set. LSA function code LS Type Description ---------------------------------------------------- 12 0xA00C Intra-area-tag-LSA 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age |1|0|1| 12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LSA body | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The contents of LSA is constructed as sets of tag block defines as follows: Mirtorabi, Roy [Page 2] Internet Draft Route tags in OSPFv3 September 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Rsrv |E| Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rsrv Reserved field, it should be set to 0 and ignored in reception E bit Extended tag bit, when is set the tag will be defined as a 64 bit value, otherwise it is defined as 32 bit value Length The length of the tag block excluding the first four byte (Rsrv+ E + length field) Tag A configurable value set by the user Link State ID Link state ID of the intra-area-prefix-lsa that carries prefixes to be tagged Note that a given Link State ID corresponds to the fragment of intra-area-prefix-lsa which contains prefixes which have a common tag (see section 3). 3. Generation of intra-area-tag-LSA When a router is configured to tag its intra-area prefix, it MUST originate intra-area-prefix-LSA in such a way that all prefixes within a fragment have the same tag value. This is needed since Tag LSA associate a tag to a LSA identified by its Link State ID which may carry many prefixes. A router configured to tag intra-area prefixes, generates Mirtorabi, Roy [Page 3] Internet Draft Route tags in OSPFv3 September 2004 intra-area-tag-LSA corresponding to Link State IDs advertised in its intra-area-prefix-LSA. Note that intra-area-tag-LSA should be regenerated only when there is a change in tag value or the Link State ID list has changed. In other words if intra-area-prefix-lsa is regenerated due to a change of metric or prefix reachability, there is no need to regenerate intra-area-tag-LSA. 4. Multi-access link consideration In a multi-access link, Designated Router (DR) is in charge of generating intra-area-prefix-lsa on behalf of the link. In order to tag prefixes on the multi-access link the designated router SHOULD be tag capable and the tag needs to be configured on the DR/BDR. Note that the DR will have to generate multiple intra-area-prefix-lsas such that all prefixes within a fragment have the same tag value. DR will also generate intra-area-tag-LSA corresponding to Link State IDs advertised in it's intra-area-prefix-lsa. 5. Inter-area-tag-LSA We define a new lsa called Inter-area-tag-LSA to carry tag between OSPFv3 areas. The flooding scope of the LSA is area wide and the Unknown bit (U bit) is set. This LSA is generated by ABRs. LSA function code LS Type Description ---------------------------------------------------- 13 0xA00D Inter-area-Tag-LSA Mirtorabi, Roy [Page 4] Internet Draft Route tags in OSPFv3 September 2004 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age |1|0|1| 13 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LSA body | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The contents of LSA is constructed as sets of tag block defines as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Rsrv |E| Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link State ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rsrv Reserved field, it should be set to 0 and ignored in reception E bit Extended tag bit, when is set the tag will be defined as a 64 bit value, otherwise it is defined as 32 bit value Length The length of the tag block excluding the first four byte (Rsrv + E + length field) Mirtorabi, Roy [Page 5] Internet Draft Route tags in OSPFv3 September 2004 Tag A configurable value set by the user Link State ID Link state ID of the Inter-area-prefix-lsa that carries the prefix to be tagged Note that each Link State ID correspond to a unique prefix in Inter-area-prefix-lsa, however each tag block could carry a list of Link State ID. 6. Generation of Inter-area-tag-LSA An ABR that generates inter-area-prefix-LSA is in charge of tagging inter-area prefixes. This is done by generating inter-area-tag-LSA that corresponds to inter-area-prefix-LSA Link State IDs generated by the ABR. The same rule for processing and generating inter-area-prefix-LSA applies to processing and generating Inter-area-tag-LSA. 7. Backward compatibility This document does not introduce any backward compatibility issues. The new LSA is simply ignored by non-capable routers. 8. Deployment consideration Tag capable router could be introduced gradually without any interoperability problem. It should be noted that in order to tag inter-area prefixes, the ABRs need to be tag capable so that the tags can be propagated through multiple areas. 9. Security Considerations The technique described in this document does not introduce any new security issues into OSPFv3. 10. References [Ref1] Dec, Psenak, Sturgess, "A Proposal for a Tag Value field in OSPF", draft-dec-ospf-tags-00.txt [Ref2] R. Coltun, D. Ferguson and J. Moy, "OSPF for IPv6", RFC 2740, December 1999. Mirtorabi, Roy [Page 6]