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Validity of SR Policy Candidate Path
draft-chen-idr-bgp-sr-policy-cp-validity-02

Document Type Active Internet-Draft (individual)
Authors Ran Chen , Detao Zhao , Ketan Talaulikar , Yisong Liu , Changwang Lin
Last updated 2024-03-01
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draft-chen-idr-bgp-sr-policy-cp-validity-02
Inter-Domain Routing                                             R. Chen
Internet-Draft                                                   D. Zhao
Intended status: Standards Track                         ZTE Corporation
Expires: 2 September 2024                                  K. Talaulikar
                                                     Cisco Systems, Inc.
                                                                  Y. Liu
                                                            China Mobile
                                                            L. Changwang
                                                    New H3C Technologies
                                                            1 March 2024

                  Validity of SR Policy Candidate Path
              draft-chen-idr-bgp-sr-policy-cp-validity-02

Abstract

   This document defines extensions to BGP to distribute the validity
   control parameters of a candidate path for an SR Policy.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 2 September 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 . . . . . . . . . . . . . . . . . .   2
   2.  Carrying CP Validity Sub-TLV in BGP . . . . . . . . . . . . .   3
   3.  CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . .   3
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   SR Policy architecture are specified in [RFC9256].  An SR Policy
   comprises one or more candidate paths (CP) of which at a given time
   one and only one may be active (i.e., installed in forwarding and
   usable for steering of traffic).  Each CP in turn may have one or
   more SID-List of which one or more may be active; when multiple SID-
   List are active then traffic is load balanced over them.

   [I-D.chen-spring-sr-policy-cp-validity]supplemented candidate path
   validity criterion in [RFC9256].  It defines three validity control
   parameters under candidate Path to control the validity judgment of
   candidate Path.

   This document defines extensions to BGP to distribute the validity
   control parameters of a candidate path for an SR Policy.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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2.  Carrying CP Validity Sub-TLV in BGP

   As defined in [I-D.ietf-idr-segment-routing-te-policy], a new SAFI is
   defined (the SR Policy SAFI with codepoint 73) as well as a new NLRI.
   The NLRI contains the SR Policy candidate path and, according to
   [I-D.ietf-idr-segment-routing-te-policy], the content of the SR
   Policy Candidate Path is encoded in the Tunnel Encapsulation
   Attribute defined in [RFC9012] using a new Tunnel-Type called SR
   Policy Type with codepoint 15.  This document defines CP Validity
   Sub-TLV to carry the validity control parameters of a candidate path.

   The new SR Policy encoding structure with CP Validity Sub-TLV is
   expressed as below:

      SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
         Attributes:
            Tunnel Encaps Attribute (23)
               Tunnel Type: SR Policy (15)
                   Binding SID
                   SRv6 Binding SID
                   Preference
                   Priority
                   Policy Name
                   Policy Candidate Path Name
                   Explicit NULL Label Policy (ENLP)
                   CP Validity Sub-TLV
                   Segment List
                       Weight
                       Segment
                       Segment
                       ...
                   ...

                                  Figure 1

3.  CP Validity Sub-TLV

   The format of the CP Validity Sub-TLV is defined 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Type       |    Length     | valid SL count|    Reserved   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                     valid SL weight                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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                                  Figure 2

   where:

   Type: to be assigned by IANA.

   Length: the total length of the value field not including Type and
   Length fields.

   valid SL count´╝Ü1-octet field which indicates the minimum number of
   valid segment Lists under the active candidate path.  When the number
   of valid segment Lists under candidate path is greater than or equal
   to this field, the candidate path is considered valid. 0 indicates no
   requirement for SL count.  0xff indicates that the candidate path is
   considered valid only if all the segment Lists are valid.

   valid SL weight: 4-octet field which indicates the minimum value of
   the sum of the weights of the valid segment List under the active
   candidate Path.  When the sum of the weights of the valid segment
   Lists under the candidate path is greater than or equal to this
   field, the candidate Path is considered valid. 0 indicates no
   requirement for weight.0xffffffff indicates that the candidate path
   is considered valid only if all the segment Lists are valid.

4.  Operations

   The document does not bring new operation beyond the description of
   operations defined in [I-D.ietf-idr-segment-routing-te-policy].  The
   existing operations defined in
   [I-D.ietf-idr-segment-routing-te-policy] can apply to this document
   directly.

   Typically, but not limit to, the SR policies carrying the validity
   control parameters of the candidate path are configured by a
   controller.

   After configuration, the SR policies carrying the validity control
   parameters of the candidate path will be advertised by BGP update
   messages.  The operation of advertisement is the same as defined in
   [I-D.ietf-idr-segment-routing-te-policy], as well as the reception.

5.  IANA Considerations

   This document defines a new sub-TLV in the registry "BGP Tunnel
   Encapsulation Attribute sub-TLVs" to be assigned by IANA:

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      Value   Description               Reference
     ------- ------------------------- --------------
       TBD    CP Validity Sub-TLV       This document

                                  Figure 3

6.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the security considerations discussed in
   [I-D.ietf-idr-segment-routing-te-policy].

7.  Acknowledgements

   TBD.

8.  Normative References

   [I-D.chen-spring-sr-policy-cp-validity]
              Chen, R., Zhao, D., and C. Lin, "Validity of SR Policy
              Candidate Path", Work in Progress, Internet-Draft, draft-
              chen-spring-sr-policy-cp-validity-01, 19 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-chen-spring-
              sr-policy-cp-validity-01>.

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
              D. Jain, "Advertising Segment Routing Policies in BGP",
              Work in Progress, Internet-Draft, draft-ietf-idr-segment-
              routing-te-policy-26, 23 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              segment-routing-te-policy-26>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC9256]  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
              A., and P. Mattes, "Segment Routing Policy Architecture",
              RFC 9256, DOI 10.17487/RFC9256, July 2022,
              <https://www.rfc-editor.org/info/rfc9256>.

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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

   Ketan Talaulikar
   Cisco Systems, Inc.
   Email: ketant.ietf@gmail.com

   Yisong Liu
   China Mobile
   Beijing
   China
   Email: liuyisong@chinamobile.com

   Changwang Lin
   New H3C Technologies
   Beijing
   China
   Email: linchangwang.04414@h3c.com

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