LSR R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 23 January 2024 P. Psenak K. Talaulikar Cisco Systems 22 July 2023 Updates to Anycast Property advertisement for OSPFv2 draft-chen-lsr-anycast-flag-04 Abstract Both SR-MPLS prefixes-SID and IPv4 prefix may be configured as anycast and as such the same value can be advertised by multiple routers. It is useful for other routers to know that the advertisement is for an anycast identifier. Each prefix is advertised along with an 8-bit field of capabilities,by using the flag flield in the OSPFv2 Extended Prefix TLV [RFC7684], but the definition of anycast flag to identify the prefix as anycast has not yet been defined. This document updates [RFC7684], by defining a new flag in the OSPFv2 Extended Prefix TLV Flags [RFC7684] to advertise the anycast property. 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 https://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 23 January 2024. Chen, et al. Expires 23 January 2024 [Page 1] Internet-Draft Anycast Property advertisement July 2023 Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Updates to Anycast Property advertisement for OSPFv2 . . . . 3 3. Updates to Anycast Property advertisement for BGP-LS . . . . 4 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5.1. OSPFv2 Extended Prefix TLV Flags Registry . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. Normative References . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction Both SR-MPLS prefixes-SID and IPv4 prefix may be configured as anycast and as such the same value can be advertised by multiple routers. It is useful for other routers to know that the advertisement is for an anycast identifier. [RFC7684] defines OSPFv2 Opaque LSAs based on Type-Length-Value (TLV) tuples that can be used to associate additional attributes with prefixes or links. The OSPFv2 Extended Prefix TLV that is contained in the OSPFv2 Extended Prefix Opaque LSA is used to advertise additional attributes associated with the prefix, but the definition of anycast flag to identify the prefix as anycast has not yet been defined. This document updates [RFC7684], by defining a new flag in the OSPFv2 Extended Prefix TLV Flags [RFC7684] to advertise the anycast property. Chen, et al. Expires 23 January 2024 [Page 2] Internet-Draft Anycast Property advertisement July 2023 1.1. 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 in RFC 2119 [RFC2119]. 2. Updates to Anycast Property advertisement for OSPFv2 The prefix may be configured as anycast and it is useful for other routers to know that the advertisement is for an anycast identifier. [RFC7684] defines one-octet field contains flags applicable to the prefix, and it has been defines the below flags: +=======+=============+===========+ | Value | Description | Reference | +=======+=============+===========+ | 0x80 | A | [RFC7684] | +-------+-------------+-----------+ | 0x40 | N | [RFC7684] | +-------+-------------+-----------+ | 0x02 | E-Flag | [RFC9089] | +-------+-------------+-----------+ Table 1: OSPFv2 Extended Prefix TLV Flags A new bit in OSPFv2 Extended Prefix TLV Flags[RFC7684] is defined to advertise the anycast property: Value: TBD Description:Anycast (AC-Flag) When the prefix is configured as anycast, the AC-Flag SHOULD be set. Otherwise, this flag MUST be clear. The AC-Flag and the N-bit MUST NOT both be set. If both N-flag and AC-Flag are set, the receiving routers MUST ignore the N-flag. The AC-Flag MUST be preserved when re-advertising the prefix across areas. The same prefix can be advertised by multiple routers, and that if at least one of them sets the An-Flag in its advertisement, the prefix SHOULD be considered as anycast. Chen, et al. Expires 23 January 2024 [Page 3] Internet-Draft Anycast Property advertisement July 2023 3. Updates to Anycast Property advertisement for BGP-LS [RFC9085] defines the Prefix Attribute Flags TLV carries IPv4 prefix attribute flags information, and the Flags field of this TLV is interpreted according to OSPFv2 [RFC7684]. This section extends the interpretation of the Flags field of the Prefix Attribute Flags TLV. Flags: * OSPFv2 flags correspond to the Flags field of the OSPFv2 Extended Prefix TLV defined in [RFC7684] and extended in this draft. 4. Acknowledgements TBD. 5. IANA Considerations This document requests allocation for the following registry. 5.1. OSPFv2 Extended Prefix TLV Flags Registry This document adds a new bit in the "OSPFv2 Extended Prefix TLV Flags"registry: AC-Flag (Anycast Flag). 6. Security Considerations Procedures and protocol extensions defined in this document do not affect the OSPFv2 security model. See the "Security Considerations"section of [RFC7684] for a discussion of OSPFv2 security. 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . Chen, et al. Expires 23 January 2024 [Page 4] Internet-Draft Anycast Property advertisement July 2023 [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler, H., and M. Chen, "Border Gateway Protocol - Link State (BGP-LS) Extensions for Segment Routing", RFC 9085, DOI 10.17487/RFC9085, August 2021, . [RFC9089] Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., and M. Bocci, "Signaling Entropy Label Capability and Entropy Readable Label Depth Using OSPF", RFC 9089, DOI 10.17487/RFC9089, August 2021, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Detao Zhao ZTE Corporation Nanjing China Email: zhao.detao@zte.com.cn Peter Psenak Cisco Systems Slovakia Email: ppsenak@cisco.com Ketan Talaulikar Cisco Systems India Email: ketan.ietf@gmail.com Chen, et al. Expires 23 January 2024 [Page 5]