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Advertisement of Candidate Path Validity Control Parameters using BGP-LS
draft-chen-idr-bgp-ls-sr-policy-cp-validity-01

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-ls-sr-policy-cp-validity-01
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

Advertisement of Candidate Path Validity Control Parameters using BGP-LS
             draft-chen-idr-bgp-ls-sr-policy-cp-validity-01

Abstract

   This document describes a mechanism to collect the configuration and
   states of SR policies carrying the validity control parameters of the
   candidate path by using BGP Link-State (BGP-LS) updates.  Such
   information can be used by external components for path computation,
   re-optimization, service placement, etc.

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 2 September 2024.

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.

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   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.  Carrying CP Validity Sub-TLV in BGP-LS  . . . . . . . . . . .   3
   3.  CP Validity Sub-TLV . . . . . . . . . . . . . . . . . . . . .   3
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   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.

   In many network scenarios, the configuration and state of each TE
   Policy is required by a controller which allows the network operator
   to optimize several functions and operations through the use of a
   controller aware of both topology and state information
   [I-D.ietf-idr-te-lsp-distribution].

   Based on the mechanism defined in [I-D.ietf-idr-te-lsp-distribution],
   this document defines extensions to BGP-LS to distribute the validity
   control parameters of a candidate path for an SR Policy.

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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.

2.  Carrying CP Validity Sub-TLV in BGP-LS

   In order to collect configuration and states of SR policies carrying
   the validity control parameters of the candidate path, this document
   defines a new SR Policy state TLV which enable the headend to report
   the validity control parameters of a candidate path.

   This TLV is carried in the optional non-transitive BGP Attribute
   "LINK_STATE Attribute" defined in [RFC7752] associated with the SR
   Policy CP NLRI type.

   This TLV is optional and only one this TLV is advertised for a given
   CP.  If multiple TLVs are present, then the first one is considered
   valid and the rest are ignored as describe in
   [I-D.ietf-idr-bgp-ls-sr-policy].

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                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 1

   where:

   Type: to be assigned by IANA.

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

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   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 quantity.  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 operations procedures of [RFC7752] can apply to this document.
   Typically, but not limit to, the SR policies carrying the validity
   control parameters of the candidate path can be distributed by the
   ingress node.

5.  IANA Considerations

   IANA maintains a registry called "Border Gateway Protocol - Link
   State (BGP-LS) Parameters" with a sub-registry called "Node Anchor,
   Link Descriptor and Link Attribute TLVs".  The following TLV
   codepoints are suggested (for early allocation by IANA):

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

                                  Figure 2

6.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the BGP security model.  See the "Security
   Considerations"section of [RFC4271] for a discussion of BGP security.
   Security considerations for acquiring and distributing BGP-LS
   information are discussed in [RFC7752].

7.  Acknowledgements

   TBD.

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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-bgp-ls-sr-policy]
              Previdi, S., Talaulikar, K., Dong, J., Gredler, H., and J.
              Tantsura, "Advertisement of Segment Routing Policies using
              BGP Link-State", Work in Progress, Internet-Draft, draft-
              ietf-idr-bgp-ls-sr-policy-03, 5 November 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
              ls-sr-policy-03>.

   [I-D.ietf-idr-te-lsp-distribution]
              Previdi, S., Talaulikar, K., Dong, J., Chen, M., Gredler,
              H., and J. Tantsura, "Distribution of Traffic Engineering
              (TE) Policies and State using BGP-LS", Work in Progress,
              Internet-Draft, draft-ietf-idr-te-lsp-distribution-19, 24
              January 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-idr-te-lsp-distribution-19>.

   [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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [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>.

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   [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>.

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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