Network Working Group A. Lindem, Ed. Internet-Draft P. Psenak Intended status: Standards Track Cisco Systems Expires: January 24, 2019 July 23, 2018 Extensions to OSPF for Advertising Prefix/Link Administrative Tags draft-acee-lsr-ospf-admin-tags-00.txt Abstract It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be able to associate tags with prefixes and links. Previously, OSPFv2 and OSPFv3 were relegated to a single tag for AS External and Not-So- Stubby-Area (NSSA) prefixes. With the flexible encodings provided by OSPFv2 Prefix/Link Attribute Advertisement and OSPFv3 Extended LSAs, multiple administrative tags may advertised for all types of prefixes and links. These administrative tags can be used for many applications including route redistribution policy, selective prefix prioritization, selective IP Fast-ReRoute (IPFRR) prefix protection, and many others. The ISIS protocol supports a similar mechanism that is described in RFC 5130. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 24, 2019. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. Lindem & Psenak Expires January 24, 2019 [Page 1] Internet-Draft OSPF Administrative Tags July 2018 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 2. 32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . . . 3 3. Administrative Tag Applicability . . . . . . . . . . . . . . 4 4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5 4.1. Equal-Cost Multipath Applicability . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. 64-Bit Administrative Tag Sub-TLV . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction It is useful for routers in an OSPFv2 [OSPF] or OSPFv3 [OSPF] routing domain to be able to associate tags with prefixes and links. Previously, OSPFv3 and OSPFv3 were relegated to a single tag for AS External and Not-So-Stubby-Area (NSSA) prefixes. With the flexible encodings provided by OSPFv2 Prefix/Link Attribute Advertisement ([OSPFV2-PREFIX-LINK]) and OSPFv3 Extended LSA ([OSPFV3-EXTENDED-LSA]), multiple administrative tags may be advertised for all types of prefixes and links. These administrative tags can be used many applications including (but not limited to): 1. Controlling which routes are redistributed into other protocols for readvertisement. 2. Prioritizing selected prefixes for faster convergence and installation in the forwarding plane. 3. Identifying selected prefixes for Loop-Free Alternative (LFA) protection. Lindem & Psenak Expires January 24, 2019 [Page 2] Internet-Draft OSPF Administrative Tags July 2018 Throughout this document, OSPF is used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is specific to one version of the OSPF protocol. The ISIS protocol supports a similar mechanism that is described in RFC 5130 [ISIS-ADMIN-TAGS]. 1.1. Requirements notation 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-KEYWORDS]. 2. 32-Bit Administrative Tag Sub-TLV This document creates a new Administrative Tag Sub-TLV for OSPFv2 and OSPFv3. This Sub-TLV specifies one or more 32-bit unsigned integers that may be associated with an OSPF advertised prefix or OSPF Link. The precise usage of these tags is beyond the scope of this document. The format of this Sub-TLV is the same as the format used by the Traffic Engineering Extensions to OSPF [TE]. The LSA payload consists of one or more nested Type/Length/Value (TLV) triplets. The format of each TLV is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ TLV Format The Length field defines the length of the value portion in octets (thus a TLV with no value portion would have a length of 0). The TLV is padded to 4-octet alignment; padding is not included in the length field (so a 3-octet value would have a length of 3, but the total size of the TLV would be 8 octets). The format of the 32-bit Administrative Tag TLV is as follows: Lindem & Psenak Expires January 24, 2019 [Page 3] Internet-Draft OSPF Administrative Tags July 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | First 32-bit Administrative Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | o | o | o | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last 32-bit Administrative Tag | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type A 16-bit field set to TBD. The value MAY be different depending upon the IANA registry from which it is allocated. Length A 16-bit field that indicates the length of the value portion in octets and will be a multiple of 4 octets dependent on the number of administrative tags advertised. If the sub-TLV is specified, at least one administrative tag must be advertised. Value A variable length list of one or more administrative tags. 32-bit Administrative Tag Sub-TLV This sub-TLV will carry one or more 32-bit unsigned integer values that will be used as administrative tags. 3. Administrative Tag Applicability The administrative tag TLV specified herein will be valid as a sub- TLV of the following TLVs specified in [OSPFV2-PREFIX-LINK]: 1. Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA 2. Extended Link TLV advertised in the OSPFv2 Extended Prefix LSA The administrative tag TLV specified herein will be valid as a sub- TLV of the following TLVs specified in [OSPFV3-EXTENDED-LSA]: 1. Router-Link TLV advertised in the E-Router-LSA 2. Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA Lindem & Psenak Expires January 24, 2019 [Page 4] Internet-Draft OSPF Administrative Tags July 2018 3. Intra-Area-Prefix TLV advertised in the E-Link-LSA and the E- Intra-Area-LSA 4. External-Prefix TLV advertised in the E-AS-External-LSA and the E-NSSA-LSA 4. Protocol Operation An OSPF router supporting this specification MUST propagate administrative tags when acting as an Area Border Router and originating summary advertisements into other areas. Similarly, an OSPF router supporting this specification and acting as an ABR for a Not-So-Stubby Area (NSSA) MUST propagate tags when translating NSSA routes to AS External advertisements [NSSA]. The number of tags supported MAY limit the number of tags that are propagated. When propagating multiple tags, the order of the the tags must be preserved. For configured area ranges, NSSA ranges, and configurated summarization of redistributed routes, tags from component routes SHOULD NOT be propagated to the summary. Implementations SHOULD provide a mechanism to configure tags for area ranges, NSSA ranges, and redistributed route summaries. An OSPF router supporting this specification MUST be able to advertise and interpret one 32-bit tag for prefixes and links. An OSPF router supporting this specification MAY be able to advertise and propagate multiple 32-bit tags. The maximum tags that an implementation supports is a local matter depending upon supported applications using the prefix or link tags. When a single tag is advertised for AS External or NSSA LSA prefix, the existing tag in OSPFv2 and OSPFv3 AS-External-LSA and NSSA-LSA encodings SHOULD be utilized. This will facilitate backward compatibilty with implementations that do not support this specification. 4.1. Equal-Cost Multipath Applicability When multiple LSAs contribute to an OSPF route, it is possible that these LSAs will all have different tags. In this situation, the OSPF router MUST associate the tags from one of the LSAs contributing a path and, if the implementation supports multiple tags, MAY associate tags for multiple contributing LSAs up to the maximum number of tags supported. Lindem & Psenak Expires January 24, 2019 [Page 5] Internet-Draft OSPF Administrative Tags July 2018 5. Security Considerations This document describes both a generic mechanism for advertising administrative tags for OSPF prefixes and links. The administrative tags are generally less critical than the topology information currently advertised by the base OSPF protocol. The security considerations for the generic mechanism are dependent on the future application and, as such, should be described as additional capabilities are proposed for advertisement. Security considerations for the base OSPF protocol are covered in [OSPF] and [OSPFV3]. 6. IANA Considerations The following values should be allocated from the OSPF Extended Prefix TLV Sub-TLV Registry [OSPFV2-PREFIX-LINK]: o TBD - 32-bit Administrative Tag TLV The following values should be allocated from the OSPF Extended Link TLV Sub-TLV Registry [OSPFV2-PREFIX-LINK]: o TBD - 32-bit Administrative Tag TLV The following values should be allocated from the OSPFv3 Extended-LSA Sub-TLV Registry [OSPFV3-EXTENDED-LSA]: o TBD - 32-bit Administrative Tag TLV 7. Acknowledgments The authors of RFC 5130 are acknowledged since this document draws upon both the ISIS specification and deployment experience. Thanks to Donnie Savage for his comments and questions. The RFC text was produced using Marshall Rose's xml2rfc tool. 8. References 8.1. Normative References [OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [OSPFV2-PREFIX-LINK] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, November 2015. Lindem & Psenak Expires January 24, 2019 [Page 6] Internet-Draft OSPF Administrative Tags July 2018 [OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, July 2008. [OSPFV3-EXTENDED-LSA] Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 LSA Extendibility", RFC 8362, April 2018. [RFC-KEYWORDS] Bradner, S., "Key words for use in RFC's to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [TE] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering Extensions to OSPF", RFC 3630, September 2003. 8.2. Informative References [ISIS-ADMIN-TAGS] Previdi, S., Shand, M., and C. Martin, "A Policy Control Mechanism in IS-IS Using Administrative Tags", RFC 5130, February 2008. [NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", RFC 3101, January 2003. Appendix A. 64-Bit Administrative Tag Sub-TLV The definition of the 64-bit tag was considered but discard given that there is no strong requirement or use case. The specification is included here for information. This sub-TLV will carry one or more 64-bit unsigned integer values that will be used as administrative tags. The format of the 64-bit Administrative Tag TLV is as follows: Lindem & Psenak Expires January 24, 2019 [Page 7] Internet-Draft OSPF Administrative Tags July 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | First 64-bit Administrative Tag | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | o | o | o | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Last 64-bit Administrative Tag | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type A 16-bit field set to TBD. The value MAY be different depending upon the registry from which it is allocated. Length A 16-bit field that indicates the length of the value portion in octets and will be a multiple of 8 octets dependent on the number of administrative tags advertised. If the sub-TLV is specified, at least one administrative tag must be advertised. Value A variable length list of one or more 64-bit administrative tags. 64-bit Administrative Tag TLV Authors' Addresses Acee Lindem (editor) Cisco Systems 301 Midenhall Way Cary, NC 27513 USA Email: acee@cisco.com Lindem & Psenak Expires January 24, 2019 [Page 8] Internet-Draft OSPF Administrative Tags July 2018 Peter Psenak Cisco Systems Apollo Business Center Mlynske nivy 43 Bratislava, 821 09 Slovakia Email: ppsenak@cisco.com Lindem & Psenak Expires January 24, 2019 [Page 9]