Skip to main content

Signaling Composite Candidate Path of SR Policy using BGP-LS
draft-li-idr-bgpls-sr-policy-composite-path-02

Document Type Active Internet-Draft (individual)
Authors Hao Li , Mengxiao Chen , Changwang Lin, Jiang Wenying , Weiqiang Cheng
Last updated 2022-03-06
Stream (None)
Intended RFC status (None)
Formats plain text html xml htmlized pdfized bibtex
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date (None)
Responsible AD (None)
Send notices to (None)
draft-li-idr-bgpls-sr-policy-composite-path-02
Network Working Group                                              H. Li
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                  C. Lin
Expires: 8 September 2022                           New H3C Technologies
                                                                W. Jiang
                                                                W. Cheng
                                                            China Mobile
                                                            7 March 2022

      Signaling Composite Candidate Path of SR Policy using BGP-LS
             draft-li-idr-bgpls-sr-policy-composite-path-02

Abstract

   Segment Routing is a source routing paradigm that explicitly
   indicates the forwarding path for packets at the ingress node.  An SR
   Policy is associated with one or more candidate paths, and each
   candidate path is either dynamic, explicit or composite.  This
   document specifies the extensions to BGP Link State (BGP-LS) to carry
   composite candidate path information in the advertisement of 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
   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 8 September 2022.

Copyright Notice

   Copyright (c) 2022 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.

Li, et al.              Expires 8 September 2022                [Page 1]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BGP-LS Extensions for Composite Candidate Path  . . . . . . .   3
     3.1.  Constituent SR Policy TLV . . . . . . . . . . . . . . . .   3
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   As described in [RFC7752], BGP Link State (BGP-LS) provides a
   mechanism by which link-state and TE information can be collected
   from networks and shared with external components using the BGP
   routing protocol.

   Segment routing (SR) [RFC8402] is a source routing paradigm that
   explicitly indicates the forwarding path for packets at the ingress
   node.  The ingress node steers packets into a specific path according
   to the Segment Routing Policy (SR Policy) as defined in
   [I-D.ietf-spring-segment-routing-policy].

   An SR Policy is associated with one or more candidate paths.  A
   composite candidate path acts as a container for grouping of SR
   Policies.  As described in section 2.2 in
   [I-D.ietf-spring-segment-routing-policy], the composite candidate
   path construct enables combination of SR Policies, each with explicit
   candidate paths and/or dynamic candidate paths with potentially
   different optimization objectives and constraints, for a load-
   balanced steering of packet flows over its constituent SR Policies.

   [I-D.jiang-spring-sr-policy-group-use-cases] describes some use cases
   for SR policy group composite candidate path.

Li, et al.              Expires 8 September 2022                [Page 2]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   [I-D.ietf-idr-te-lsp-distribution] describes a mechanism to collect
   the SR policy information that is locally available in a node and
   advertise it into BGP-LS updates.  This document extends it to
   provide some extra information to carry composite candidate path
   information in the BGP-LS advertisement.

2.  Terminology

   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.

3.  BGP-LS Extensions for Composite Candidate Path

   [RFC7752] defines the BGP-LS NLRI that can be a Node NLRI, a Link
   NLRI or a Prefix NLRI.  The corresponding BGP-LS attribute is a Node
   Attribute, a Link Attribute or a Prefix Attribute.
   [I-D.ietf-idr-te-lsp-distribution] describes a mechanism to collect
   the SR Policy information that is locally available in a node and
   advertise it into BGP Link State (BGP-LS) updates.  This section
   defines a new sub-TLV which is carried in the optional non-transitive
   BGP Attribute "LINK_STATE Attribute" defined in [RFC7752].

3.1.  Constituent SR Policy TLV

   Segment Routing Policy (SR Policy) architecture is specified in
   [I-D.ietf-spring-segment-routing-policy].  A SR Policy can comprise
   of one or more candidate paths, and each candidate path is either
   dynamic, explicit or composite.  A composite candidate path can
   comprise of one or more constituent SR policies.  The endpoints of
   the constituent SR Policies and the parent SR Policy MUST be
   identical, and the colors of each of the constituent SR Policies and
   the parent SR Policy MUST be different.

   The Constituent SR Policy TLV is used to report the constituent SR
   policy(s) of a composite candidate path.  The TLV has following
   format:

Li, et al.              Expires 8 September 2022                [Page 3]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   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            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            RESERVED                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Color                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Weight                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sub-TLVs (variable)                     //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   *  Type: to be assigned by IANA.

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

   *  Reserved: 32 bits reserved and MUST be set to 0 on transmission
      and MUST be ignored on receipt.

   *  Color: 4 octets that indicates the color of the constituent SR
      Policy.

   *  Weight: 4 octet field that indicates the weight associated with
      the SID-List for weighted load-balancing.  Refer Section 2.2 and
      2.11 of [I-D.ietf-spring-segment-routing-policy].

   *  Sub-TLVs: no sub-TLV is currently defined.

4.  Operations

   The document does not bring new operation beyond the description of
   operations defined in [RFC7752] and
   [I-D.ietf-idr-te-lsp-distribution].  The existing operations defined
   in [RFC7752] and [I-D.ietf-idr-te-lsp-distribution] can apply to this
   document directly.

   Typically but not limit to, the BGP-LS messages carring composite
   candidate path information along with the SR policy are distributed
   to a controller.

Li, et al.              Expires 8 September 2022                [Page 4]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   After configuration, the composite candidate path information will be
   advertised by BGP update messages.  The operation of advertisement is
   the same as defined in [RFC7752] and
   [I-D.ietf-idr-te-lsp-distribution], as well as the receiption.

5.  Security Considerations

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

6.  IANA Considerations

   This document defines a new TLV in the BGP-LS Link Descriptor and
   Attribute TLVs:

   +=======+===========================+===============+
   | Value | Description               | Reference     |
   +=======+===========================+===============+
   | TBA   | Constituent SR Policy TLV | This document |
   +-------+---------------------------+---------------+

                          Table 1

7.  References

7.1.  Normative References

   [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-16, 22
              October 2021, <http://www.ietf.org/internet-drafts/draft-
              ietf-idr-te-lsp-distribution-16.txt>.

   [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>.

Li, et al.              Expires 8 September 2022                [Page 5]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

7.2.  Informative References

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", Work in
              Progress, Internet-Draft, draft-ietf-spring-segment-
              routing-policy-19, 5 March 2022, <http://www.ietf.org/
              internet-drafts/draft-ietf-spring-segment-routing-policy-
              19.txt>.

   [I-D.jiang-spring-sr-policy-group-use-cases]
              Jiang, W., Cheng, W., Lin, C., and Y. Qiu, "Segment
              Routing Policy Architecture", Work in Progress, Internet-
              Draft, draft-jiang-spring-sr-policy-group-use-cases-00, 7
              March 2022, <http://www.ietf.org/internet-drafts/draft-
              jiang-spring-sr-policy-group-use-cases-00.txt>.

   [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>.

Authors' Addresses

   Hao Li
   New H3C Technologies
   Email: lihao@h3c.com

   Mengxiao Chen
   New H3C Technologies
   Email: chen.mengxiao@h3c.com

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

   Wenying Jiang
   China Mobile
   Email: jiangwenying@chinamobile.com

Li, et al.              Expires 8 September 2022                [Page 6]
Internet-Draft  Signal SR Policy Composite Path in BGP-L      March 2022

   Weiqiang Cheng
   China Mobile
   Email: chengweiqiang@chinamobile.com

Li, et al.              Expires 8 September 2022                [Page 7]