Internet DRAFT - draft-chen-lsr-anycast-flag

draft-chen-lsr-anycast-flag







LSR                                                              R. Chen
Internet-Draft                                                   D. Zhao
Intended status: Standards Track                         ZTE Corporation
Expires: 28 July 2024                                          P. Psenak
                                                           K. Talaulikar
                                                           Cisco Systems
                                                         25 January 2024


          Updates to Anycast Property advertisement for OSPFv2
                     draft-chen-lsr-anycast-flag-05

Abstract

   Both SR-MPLS prefix-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 28 July 2024.







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Copyright Notice

   Copyright (c) 2024 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.  Use-cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Updates to Anycast Property advertisement for OSPFv2  . . . .   3
   4.  Updates to Anycast Property advertisement for BGP-LS  . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  OSPFv2 Extended Prefix TLV Flags Registry . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Both SR-MPLS prefix-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.





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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.  Use-case

   In the absence of the N-flag, the node specific prefixes need to be
   identified from the anycast prefixs.  A prefix that is advertised by
   a single node and without an AC-flag MUST be considered node
   specific.

3.  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.





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   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 AC-Flag in its advertisement, the prefix
   SHOULD be considered as anycast.

   A prefix that is advertised by a single node and without an AC-flag
   MUST be considered node specific prefix.

4.  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.

5.  Acknowledgements

   TBD.

6.  IANA Considerations

   This document requests allocation for the following registry.

6.1.  OSPFv2 Extended Prefix TLV Flags Registry

   This document adds a new bit in the "OSPFv2 Extended Prefix TLV
   Flags"registry:

   AC-Flag (Anycast Flag).

7.  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.

8.  Normative References






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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [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, <https://www.rfc-editor.org/info/rfc7684>.

   [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, <https://www.rfc-editor.org/info/rfc8362>.

   [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,
              <https://www.rfc-editor.org/info/rfc9085>.

   [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,
              <https://www.rfc-editor.org/info/rfc9089>.

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






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   Peter Psenak
   Cisco Systems
   Slovakia
   Email: ppsenak@cisco.com


   Ketan Talaulikar
   Cisco Systems
   India
   Email: ketan.ietf@gmail.com









































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