BGP SR Policy Extensions for Network Resource Partition
draft-ietf-idr-sr-policy-nrp-09

IDR Working Group                                                J. Dong
Internet-Draft                                                     Z. Hu
Intended status: Standards Track                     Huawei Technologies
Expires: 20 November 2026                                        R. Pang
                                                            China Unicom
                                                             19 May 2026

        BGP SR Policy Extensions for Network Resource Partition
                    draft-ietf-idr-sr-policy-nrp-09

Abstract

   Segment Routing (SR) Policy is a set of candidate paths, each
   consisting of one or more segment lists and the associated
   information.  The header of a packet steered in an SR Policy is
   augmented with an ordered list of segments associated with that SR
   Policy.  A Network Resource Partition (NRP) is a subset of network
   resources allocated in the underlay network which can be used to
   support one or a group of RFC 9543 network slice services.

   In networks where there are multiple NRPs, an SR Policy may be
   associated with a particular NRP.  The association between SR Policy
   and NRP needs to be specified, so that for service traffic which is
   steered into the SR Policy, the header of the packets can be
   augmented with the information associated with the NRP.  An SR Policy
   candidate path can be distributed using BGP SR Policy.  This document
   defines the extensions to BGP SR policy to specify the NRP which the
   SR Policy candidate path is associated with.

Status of This Memo

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   This Internet-Draft will expire on 20 November 2026.

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Copyright Notice

   Copyright (c) 2026 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
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  NRP Identifier of SR Policy . . . . . . . . . . . . . . . . .   3
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Operational Considerations  . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The concept of Segment Routing (SR) policy is defined in [RFC9256].
   An SR Policy is a set of candidate paths, each consisting of one or
   more segment lists.  The headend of an SR Policy may learn multiple
   candidate paths for an SR Policy.  The header of a packet steered in
   an SR Policy is augmented with an ordered list of segments associated
   with that SR Policy.  The BGP extensions to distribute SR Policy
   candidate paths are defined in [RFC9830].

   [RFC9543] discusses the general framework, components, and interfaces
   for requesting and operating network slices using IETF technologies.
   It also introduces the concept of Network Resource Partition (NRP),
   which is a subset of the resources and associated policies in the
   underlay network.  The network slices defined in [RFC9543] can be
   realized by mapping one or more connectivity constructs to an NRP.
   [RFC9732] describes the framework and the candidate component
   technologies for providing NRP-based enhanced VPN services based on

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   VPN and Traffic Engineering (TE) technologies.  Enhanced VPN can be
   used for the realization of network slice services defined in
   [RFC9543].

   As described in [I-D.ietf-teas-nrp-scalability], one scalable data
   plane approach to support network slicing is to carry a dedicated NRP
   selector ID in the data packet to identify the NRP the packet belongs
   to, so that the packet can be processed and forwarded using the
   subset of network resources allocated to the NRP.

   In networks where there are multiple NRPs, an SR Policy may be
   associated with a particular NRP.  [I-D.ietf-spring-sr-policy-nrp]
   describes the association of candidate paths with NRPs under the SR
   Policy architecture.  This document defines the extensions to BGP to
   specify the control plane NRP ID [I-D.ietf-teas-ns-ip-mpls] that is
   associated with an SR Policy candidate path.  The control plane NRP
   ID is linked to the NRP identifier used in data plane (denoted as NRP
   Selector ID).

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.  NRP Identifier of SR Policy

   In order to specify the NRP the candidate path of SR policy is
   associated with, a new sub-TLV called "NRP ID" sub-TLV is defined in
   the BGP Tunnel Encapsulation Attribute [RFC9012].  The NRP ID sub-TLV
   can be carried in the BGP Tunnel Encapsulation Attribute with the
   tunnel type set to SR Policy.  The use of the NRP ID sub-TLV in other
   tunnel types is outside the scope of this document.

   The NRP sub-TLV has the following format:

       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      |     Flags     |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         NRP ID (4 octets)                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 1. NRP ID Sub-TLV

   where:

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   *  Type: 123 (assigned by IANA)

   *  Length: 6 octets.

   *  Flags: 1-octet flag field.  None is defined at this stage.  The
      flags MUST be set to zero on transmission and MUST be ignored on
      receipt.

   *  Reserved: 1 octet of reserved bits.  It MUST be set to zero on
      transmission and MUST be ignored on receipt.

   *  NRP ID: A 32-bit domain significant identifier which is used to
      identify an NRP in the control plane [I-D.ietf-teas-ns-ip-mpls].
      The values of 0 and 0xFFFFFFFF are reserved.

   The encoding structure of BGP SR Policy with the NRP ID 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)
                      NRP ID
                      Segment List
                          Weight
                          Segment
                          Segment
                          ...
                      ...
                Figure 2. SR Policy Encoding with NRP ID sub-TLV

   The NRP ID sub-TLV is optional and MUST NOT appear more than once for
   one SR Policy candidate path.

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3.  Procedures

   When a candidate path of SR Policy is instantiated within an NRP, and
   a network-wide data plane NRP Selector ID is used for identifying the
   resources of the NRP, the originating node of SR Policy MUST include
   the NRP ID sub-TLV in the BGP Tunnel Encapsulation Attribute of the
   BGP SR Policy.  The setting of other fields and attributes in BGP SR
   Policy follows the mechanism as defined in [RFC9830].

   On reception of an SR Policy NLRI with NRP ID sub-TLV in the BGP
   Tunnel Encapsulation Attribute , a BGP speaker determines if it is
   valid and usable according to the rules defined in Section 4.2 of
   [RFC9830].

   The selected best routes of the SR Policy SAFI is passed on to the SR
   Policy Module (SRPM) for further processing as described in
   Section 4.2.2 of [RFC9830].

   Although the proposed mechanism allows different candidate paths in
   one SR policy to be associated with different NRPs, in normal network
   scenarios it is considered that the association between an SR Policy
   and NRP is consistent, in such case all candidate paths of one SR
   policy SHOULD be associated with the same NRP.

4.  Error Handling

   The error handling of the BGP Update messages for BGP SR Policy SAFI
   with the NRP extensions defined in this document follows the
   procedures in section 5 of [RFC9830].

   The NRP ID sub-TLV is considered malformed if its format does not
   match the above description.  If the NRP ID sub-TLV appears more than
   once, or its format is considered malformed, the associated BGP SR
   Policy NLRI is considered malformed and the "treat-as-withdraw"
   strategy of [RFC7606] MUST be applied.

5.  Operational Considerations

   The mechanism specified in this document adds additional information
   to the signaling of SR Policy candidate paths in BGP.  As the number
   of NRP increases, the number of SR Policies may also increase.  When
   SR Policies are associated with different NRPs, the amount of control
   plane information exchanged between the network controller and the
   headend nodes for provisioning SR Policy would increase.  However,
   since the SR Policy candidate paths distributed using BGP are only
   installed by the corresponding headend nodes, the impacts to the BGP
   control plane are considered acceptable.

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6.  Security Considerations

   The security considerations of BGP [RFC4271] and BGP SR Policy
   [RFC9830] apply to this document.

   The security considerations of SR Policy [RFC9256] and SR Policy NRP
   extensions [I-D.ietf-spring-sr-policy-nrp] apply to this document.

7.  IANA Considerations

   IANA has assigned the sub-TLV type as defined in Section 2 from "BGP
   Tunnel Encapsulation Attribute sub-TLVs" registry in the "Border
   Gateway Protocol (BGP) Tunnel Encapsulation" registry group.

             Value     Description                     Reference
             ----------------------------------------------------
              123        NRP ID                       This document

8.  Acknowledgments

   The authors would like to thank Guoqi Xu, Lei Bao, Haibo Wang,
   Shunwan Zhuang and Susan Hares for their review and discussion of
   this document.

9.  References

9.1.  Normative References

   [I-D.ietf-teas-ns-ip-mpls]
              Saad, T., Beeram, V. P., Dong, J., Halpern, J. M., and S.
              Peng, "Realizing Network Slices in IP/MPLS Networks", Work
              in Progress, Internet-Draft, draft-ietf-teas-ns-ip-mpls-
              07, 28 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-ns-
              ip-mpls-07>.

   [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>.

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   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

   [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>.

   [RFC9012]  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", RFC 9012,
              DOI 10.17487/RFC9012, April 2021,
              <https://www.rfc-editor.org/info/rfc9012>.

   [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>.

   [RFC9543]  Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S.,
              Makhijani, K., Contreras, L., and J. Tantsura, "A
              Framework for Network Slices in Networks Built from IETF
              Technologies", RFC 9543, DOI 10.17487/RFC9543, March 2024,
              <https://www.rfc-editor.org/info/rfc9543>.

   [RFC9830]  Previdi, S., Filsfils, C., Talaulikar, K., Ed., Mattes,
              P., and D. Jain, "Advertising Segment Routing Policies in
              BGP", RFC 9830, DOI 10.17487/RFC9830, September 2025,
              <https://www.rfc-editor.org/info/rfc9830>.

9.2.  Informative References

   [I-D.ietf-spring-sr-policy-nrp]
              Yue, Chen, R., Dong, J., Lin, C., and J. Wenying, "Segment
              Routing Policy Extension for Network Resource Partition",
              Work in Progress, Internet-Draft, draft-ietf-spring-sr-
              policy-nrp-00, 3 March 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              sr-policy-nrp-00>.

   [I-D.ietf-teas-nrp-scalability]
              Dong, J., Li, Z., Gong, L., Yang, G., and G. S. Mishra,
              "Scalability Considerations for Network Resource
              Partition", Work in Progress, Internet-Draft, draft-ietf-
              teas-nrp-scalability-09, 11 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              nrp-scalability-09>.

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   [RFC9732]  Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for NRP-Based Enhanced Virtual Private
              Networks", RFC 9732, DOI 10.17487/RFC9732, March 2025,
              <https://www.rfc-editor.org/info/rfc9732>.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Email: jie.dong@huawei.com

   Zhibo Hu
   Huawei Technologies
   Email: huzhibo@huawei.com

   Ran Pang
   China Unicom
   Email: pangran@chinaunicom.cn

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