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BGP Colorful Prefix Routing (CPR) for SRv6 based Services
draft-wang-idr-cpr-02

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Haibo Wang , Jie Dong , Jingrong Xie , Xinjun Chen
Last updated 2023-07-10 (Latest revision 2023-03-25)
Replaced by draft-ietf-idr-cpr
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draft-wang-idr-cpr-02
Interdomain Routing Working Group                                H. Wang
Internet-Draft                                                   J. Dong
Intended status: Informational                                    J. Xie
Expires: 11 January 2024                                         X. Chen
                                                     Huawei Technologies
                                                            10 July 2023

       BGP Colorful Prefix Routing (CPR) for SRv6 based Services
                         draft-wang-idr-cpr-02

Abstract

   This document describes a mechanism to advertise different IPv6
   prefixes which are associated with different color attributes to
   establish end-to-end intent-aware paths for SRv6 services.  Such IPv6
   prefixes are called "Colorful Prefixes", and this mechanism is called
   Colorful Prefix Routing (CPR).  In SRv6 networks, the colorful
   prefixes are the SRv6 locators associated with different intent.
   SRv6 services (e.g.  SRv6 VPN services) with specific intent could be
   assigned with SRv6 SIDs under the corresponding SRv6 locators, which
   are advertised as colorful prefixes.  This allows the SRv6 service
   traffic to be steered into end-to-end intent-aware paths simply based
   on the longest prefix matching of SRv6 Service SIDs to the colorful
   prefixes.  In data plane, dedicated tranport label or SID for the
   inter-domain path is not needed, thus the encapsulation efficiency
   could be optimized.  The existing IPv6 Address Family could be used
   for the advertisement of IPv6 colorful prefixes, thus this mechanism
   is easy to interoperate and can be deployed incrementally in multi-
   domain networks.

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 11 January 2024.

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Copyright Notice

   Copyright (c) 2023 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
   2.  BGP CPR . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Colorful Prefix Allocation  . . . . . . . . . . . . . . .   4
     2.2.  Colorful Prefix Advertisement . . . . . . . . . . . . . .   4
     2.3.  CPR to Intra-domain Path Resolution . . . . . . . . . . .   5
     2.4.  SRv6 Service Route Advertisement  . . . . . . . . . . . .   6
     2.5.  SRv6 Service Steering . . . . . . . . . . . . . . . . . .   6
   3.  Encapsulation and Forwarding Processes  . . . . . . . . . . .   6
     3.1.  CPR over SRv6 Intra-Domain Paths  . . . . . . . . . . . .   7
     3.2.  CPR over MPLS Intra-Domain Paths  . . . . . . . . . . . .   7
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   With the trend of using one common network to carry multiple types of
   services, each service type can have different requirements on the
   network.  Such requirements are usually considered as the "intent" of
   the service or customer, and is represented as an abstract notion
   called "color".

   In network scenarios where the services are delivered across multiple
   network domains, there is need to provide the services with different
   end-to-end paths to meet the intent.
   [I-D.hr-spring-intentaware-routing-using-color] describes the problem
   statements and requirements for inter-domain intent-aware routing.

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   The inter-domain path can be established using either MPLS or IP data
   plane.  In MPLS based networks, the traditional inter-domain approach
   is to establish an end-to-end LSP based on the BGP-LU mechanisms as
   defined in [RFC8277].  Each domain or area border node needs to
   perform label swapping for the end-to-end BGP-LU LSP, and encapsulate
   the label stack which are used for the intra-domain LSP within the
   subsequent network domain or area.

   While in IP based networks, the IP reachability information can be
   advertised to network nodes in different domains using BGP, so that
   all the domain or area border nodes have the routes to the IP
   prefixes of the destination node in other domains.  With the
   introduction of SRv6 [RFC8986], services are assigned with SRv6
   Service SIDs [RFC9252], which are routable in the network according
   to its SRv6 locator prefix.  Thus the inter-domain path can be
   established simply based on the inter-domain prefix routes, and the
   BGP-LU inter-domain LSP mechanism is not necessary for IPv6 and SRv6
   based networks.

   This document describes a mechanism to advertise different IPv6
   prefixes which are associated with different color attributes to
   establish end-to-end intent-aware paths for SRv6 services.  Such IPv6
   prefixes are called "Colorful Prefixes", and this mechanism is called
   Colorful Prefix Routing (CPR).  In SRv6 networks, the colorful
   prefixes are the SRv6 locators associated with different intent.
   SRv6 services (e.g.  SRv6 VPN services) with specific intent could be
   assigned with SRv6 SIDs under the corresponding SRv6 locators, which
   are advertised as colorful prefixes.  This allows the SRv6 service
   traffic to be steered into end-to-end intent-aware paths simply based
   on the longest prefix matching of SRv6 Service SIDs to the colorful
   prefixes.  In data plane, the dedicated tranport label or SID for the
   inter-domain path is not needed, thus the encapsulation efficiency
   could be optimized.  The existing IPv6 Address Family could be used
   for the advertisement of IPv6 colorful prefixes, which makes this
   mechanism easy to interoperate and can be deployed incrementally in
   multi-domain networks.

2.  BGP CPR

   This section describes the BGP CPR mechanisms.  More specifically,
   section 2.1 describes the allocation of the IPv6 colorful prefixes,
   section 2.2 describes the advertisement of colorful prefixes in BGP,
   section 2.3 describes the resolution of CPR routes to the intra-
   domain paths, and section 2.4 describes the steering of SRv6 services
   to CPR routes.

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2.1.  Colorful Prefix Allocation

   In SRv6 networks, an SRv6 locator needs to be allocated for each
   node.  In order to distinguish N different intent, a PE node needs to
   be allocated with N SRv6 locators, each of which is associated a
   different intent.  This can be achieved by splitting the base SRv6
   locator of the node into N sub-locators, and these sub-locators are
   called colorful locators.

   For example, node PE2 is allocated with the base SRv6 Locator
   2001:db8:aaaa:1::/64.  In order to provide 16 different intent, this
   base SRv6 Locator is split into 16 sub-locators from
   2001:db8:aaaa:1:0000::/68 to 2001:db8:aaaa:1:F000::/68, each of these
   sub-locators is associated with a different intent, such as low-
   delay, high-bandwidth, etc.

2.2.  Colorful Prefix Advertisement

   After the allocation of colorful prefixes on a PE node, routes to
   these colorful prefixes need to be advertised both in the local
   domain and also to other domains using BGP, so that the SRv6 services
   routes could be resolved using the corresponding CPR route.

   In a multi-domain IPv6 network, the IPv6 unicast Address Family/
   Subsequent Address Family (AFI/SAFI = 2/1) [RFC2545] is used for the
   advertisement of the colorful prefix routes.  The color extended
   community [RFC9012] is carried with the colorful prefix route.  The
   procedure of colorful prefix advertisement is described using an
   example with the following topology:

      Color Domain:           Color Domain:           Color Domain:
      C11, C12,...            C21, C22,...            C31, C32,...
     +--------------+        +--------------+        +-------------+
     |              |        |              |        |             |
     |        [ASBR11]---[ASBR21]      [ASBR23]---[ASBR31]         |
 --[PE1] [P1]       |  X     |    [P2]      |   X    |     [P3]  [PE3]--
     |        [ASBR12]---[ASBR22]      [ASBR24]---[ASBR32]         |
     |              |        |              |        |             |
     +--------------+        +--------------+        +-------------+
           AS1                     AS2                     AS3

  Colorful Prefixes of PE3:
  Low delay: 2001:db8:aaaa:1:1000::/68
  high bandwidth: 2001:db8:aaaa:1:2000::/68
  ...
        Figure 1. Example Topology for CPR Route Illustration

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   Assume PE3 is provisioned with two different colorful prefixes CLP-1
   and CLP-2 for two different intent such as "low-delay" and "high-
   bandwidth" respectively.  Note that in different network domains, the
   color representing the same intent may be different.  In this
   example, the color used for "low-delay" in AS1, AS2 and AS3 are C11,
   C21 and C31 respectively, and the color used for "high-bandwidth" in
   AS1, AS2 and AS3 are C12, C22 and C32 respectively.

   *  PE3 originates BGP IPv6 unicast (AFI/SAFI=2/1) route for the
      colorful prefixes PE3:CL1:: and PE3:CL2::. Each route should carry
      the corresponding color extended community C31 or C32.  PE3 also
      advertises a route for the base SRv6 Locator prefix PE3:BL, and
      there is no color extended community carried with this route.

   *  ASBR31 and ASBR32 receive the CPR routes of PE3, and advertise the
      CPR routes further to ASBR23 and ASBR24 with next-hop set to
      itself.

   *  ASBR23 and ASBR24 receive the CPR routes of PE3.  As the color-to-
      intent mapping in AS2 is different from AS3, the color in the
      received CPR routes are changed to the corresponding color in AS2,
      e.g.  C21 and C22.  ASBR23 and ASBR 24 advertise the CPR routes
      further in AS2 with the next-hop set to itself.

   *  The behavior of ASBR21 and ASBR22 are similar to the behavior of
      ASBR31 and ASBR32.

   *  The behavior of ASBR11 and ASBR12 are similar to behavior of
      ASBR31 and ASBR32.  The color in the received CPR routes are
      changed to the corresponding color in AS1, e.g.  C11 and C12.

   In network scenarios where some of the intermediate network domains
   are MPLS based, the CPR routes may still be advertised using the IPv6
   unicast address family (AFI/SAFI=2/1) in the MPLS-based intermediate
   domains, and at the MPLS domain border nodes, some route resolution
   policy could be used to make the CPR routes resolved to intra-domain
   intent-aware MPLS LSPs.  Another possible mechanism is to use the
   IPv6 LU address family (AFI/SAFI=2/4) to advertise the CPR routes in
   the MPLS domains, the detailed procedure is described in
   Section 7.1.2.1 of [I-D.agrawal-spring-srv6-mpls-interworking].

2.3.  CPR to Intra-domain Path Resolution

   A domain border node which receives a CPR route can resolve the CPR
   route to an intra-domain color-aware path based on the tupple (N, C),
   where N is the next-hop of the CPR route, and C is the color extended
   community of the CPR route.  The intra-domain color-aware path could
   be built with any of the following mechanisms:

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   *  SRv6 or SR-MPLS Policy

   *  SRv6 or SR-MPLS Flex-Algo

   *  RSVP-TE

   For example, PE1 receives a CPR route to PE3:CL1 with color C31 and
   next-hop ASBR11, it can resolve the CPR routes to an intra-domain
   SRv6 Policy based on the tupple (ASBR11, C31).

   The intra-domain path resolution scheme could be based on any
   existing tunnel resolution policy, and new tunnel resolution
   mechanisms could be introduced if needed.

2.4.  SRv6 Service Route Advertisement

   For an SRv6 service which is associated with a specific intent, the
   SRv6 Service SID could be allocated under the corresponding colorful
   locator prefix.  For example, on PE3 in the example topology, an SRv6
   VPN service with the low delay intent can be allocated with the SRv6
   End.DT4 SID 2001:db8:aaaa:1:1000::0100, where
   2001:db8:aaaa:1:1000::/68 is the SRv6 colorful prefix for low delay
   service.

   The SRv6 service routes are advertised using the mechanism defined in
   [RFC9252], the SRv6 Service SID is carried using the BGP Prefix-SID
   attribute [RFC8669].  The inter-domain VPN Option C is used, which
   means the next-hop of the SRv6 service route is set to the
   originating PE and not changed.  Since the intent of the service is
   embedded in the SRv6 service SID, the SRv6 service route does not
   need to carry the color extended community.

2.5.  SRv6 Service Steering

   With the CPR routing mechanism, the ingress PE node which receives
   the SRv6 service routes follows the behavior of SRv6 best-effort
   forwarding.  The SRv6 service SID carried in the service route is
   used as the destination address in the outer IPv6 header encapsulated
   to the service packet.  If the corresponding CPR route has been
   received and installed, longest prefix matching of SRv6 service SIDs
   to the colorful prefixes is performed, then the intra-domain color-
   aware paths in each network domain which the CPR route is resolved to
   are used for forwarding the SRv6 service traffic.

3.  Encapsulation and Forwarding Processes

   This section describes the encapsulation and forwarding process of
   data packets which are matched with the corresponding CPR route.

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3.1.  CPR over SRv6 Intra-Domain Paths

   Following is an illustration of the packet encapsulation and
   forwarding process of CPR over SRv6 Policy.  The abstract
   representation of IPv6 and SRH in section 6 of [RFC8754] is used.

   PE3 is provisioned with a colorful prefix PE3:C1 for "low-delay".

   In AS1, the SRv6 Policy for (ASBR11, C11) is represented with SID
   list (P1, BR11).

   In AS2, the SRv6 Policy for (ASBR23, C21) is represented with the SID
   list (P2, BR23).

   In AS3, the SRv6 Policy for (PE3, C31) is represented with the SID
   list (P3, PE3).

   For packets which belong to an SRv6 VPN service associated with the
   SRv6 Service SID PE3:CL1.DT, the packet encapsulation and forwarding
   process is shown as below:

   PE1 ->P1  : (PE1, P1)(PE3:CL1.DT, BR11; SL=2)(C-pkt)
   P1  ->BR11: (PE1, BR11)(PE3:CL1.DT, BR11; SL=1)(C-pkt)
   BR11->BR21: (PE1, PE3:CL1.DT)(C-pkt)
   BR21->P2  : (PE1, P2)(PE3:CL1.DT, BR23; SL=2)(C-pkt)
   P2  ->BR23: (PE1, BR23)(PE3:CL1.DT, BR23; SL=1)(C-pkt)
   BR23->BR31: (PE1, PE3:CL1.DT)(C-pkt)
   BR31->P3  : (PE1, P3)(PE3:CL1.DT, PE3; SL=2)(C-pkt)
   P3  ->PE3 : (PE1, PE3)(PE3:CL1.DT, PE3; SL=1)(C-pkt)

   In some network domains, SRv6 Flex-Algo may be used to provide intent
   aware intra-domain path.  The encapsulation is similar to the case
   with SRv6 Policy.

3.2.  CPR over MPLS Intra-Domain Paths

   In network scenarios where some of the network domains use MPLS based
   data plane, the CPR route can be resolved over a color-aware intra-
   domain MPLS LSP.  Such intra-domain MPLS LSP may be established using
   SR-MPLS Policy, SR-MPLS Flex-Algo or RSVP-TE.

   The encapsulation and forwarding of SRv6 service packets over an
   intra-domain MPLS LSP is based on the MPLS mechanisms as defined in
   [RFC3031] [RFC3032] and [RFC8660].

   In AS1, the SR-MPLS Policy for (ASBR11, C11) is represented with
   Label-stack (P1, BR11).

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   In AS2, the SR-MPLS Flex-Algo for (ASBR23, C21) is represented with
   Label-stack (BR23).

   In AS3, the SR-MPLS Policy for (PE3, C31) is represented with Label-
   stack (P3, PE3).

   For packets which belong to an SRv6 VPN service associated with the
   SRv6 Service SID PE3:CL1.DT, the packet encapsulation and forwarding
   process is shown as below:

   PE1 ->P1  : Label-stack (P1, BR11) (PE1, PE3:CL1.DT)(C-pkt)
   P1  ->BR11:     Label-stack (BR11) (PE1, PE3:CL1.DT)(C-pkt)
   BR11->BR21:                        (PE1, PE3:CL1.DT)(C-pkt)
   BR21->P2  :     Label-stack (BR23) (PE1, PE3:CL1.DT)(C-pkt)
   P2  ->BR23:     Label-stack (BR23) (PE1, PE3:CL1.DT)(C-pkt)
   BR23->BR31:                        (PE1, PE3:CL1.DT)(C-pkt)
   BR31->P3  :  Label-stack (P3, PE3) (PE1, PE3:CL1.DT)(C-pkt)
   P3  ->PE3 :      Label-stack (PE3) (PE1, PE3:CL1.DT)(C-pkt)

4.  Operational Considerations

   When the colorful prefixes are assigned as the sub-locators of the
   node's base SRv6 locator, the IPv6 unicast route of the base locator
   prefix is the covering prefix of all the colorful locator prefixes.
   To make sure the colorful locator prefixes can be distributed to the
   ingress PE nodes along the border nodes, it is required that route
   aggregation be disabled for IPv6 unicast routes which carries the
   color extended community.

   All the border nodes and the ingress PE nodes needs to install the
   colorful locator prefixes into the RIB and FIB.  For transit domains
   which support the CPR mechanism, the border nodes can use the tupple
   (N, C) to resolve the CPR routes to intent-aware intra-domain paths.
   For transit domains which do not support the CPR mechanism, the
   border nodes would ignore the color extended community and resolve
   the CPR routes over a best effort intra-domain path to the next-hop
   N, while the CPR route will be advertised further to the downstream
   domains with only the next-hop changed to itself.  This allows the
   CPR routes to be resolved to intent-aware intra-domain paths in any
   network domains which support the CPR mechanism, while can fall back
   to resolve over best-effort intra-domain path in the legacy network
   domains.

   In this document, IPv6 Unicast address family is used for the
   advertisement of IPv6 colorful prefixes.  The primary advantage of
   this approach is the improved interoperability with legacy networks
   that lack support for intent-aware paths, and the facilitation of
   incremental deployment of intent-aware routing mechanisms.  One

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   potential concern arises regarding the necessity of separating
   colorful prefixes from public IPv6 unicast routes.  While as the IP
   prefixes and SRv6 locators of network infrastructure are usually
   advertised as part of the IP unicast routes, and appropriate filters
   are configured at the boundaries of network administration, this is
   not considered to be a significant issue.  [I-D.ietf-idr-bgp-car]
   proposes new BGP CAR NLRIs for the advertisement of color-aware
   routes and colorful prefixes, which allows to separate the colorful
   prefixes and IPv6 unicast service routes using different BGP SAFIs,
   while loosing some interoperability benefits.

   The mechanism described in this document uses color-aware serivce
   SIDs to steer SRv6 based services to intent-aware paths.  Normally
   one service SID is allocated for a service (e.g.  VRF) which is
   associated with a specific intent.  In some special scenarios,
   multiple service SIDs may need to be allocated for different intents
   associated with the service.  [I-D.ietf-idr-bgp-car] and
   [I-D.ietf-idr-bgp-ct] describes another mechanism, in which the SRv6
   service SIDs are not directly associated with the intent, while
   additional transport SRv6 SIDs are required for steering traffic to
   the inter-domain intent-aware paths, and an SRv6 operation similar to
   MPLS label swapping is needed on the border nodes of network domains.

5.  IANA Considerations

   This document makes no request of IANA.

6.  Security Considerations

   The mechanism described in this document provide an approach for
   inter-domain intent-aware routing based on existing BGP protocol
   mechanisms.  It does not introduces any additional security
   considerations than those described in [RFC4271] and [RFC4272].

7.  Acknowledgements

   The authors would like to thank Shunwan Zhuang and Zhibo Hu for the
   review and discussion.

8.  References

8.1.  Normative References

   [RFC2545]  Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
              Extensions for IPv6 Inter-Domain Routing", RFC 2545,
              DOI 10.17487/RFC2545, March 1999,
              <https://www.rfc-editor.org/info/rfc2545>.

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   [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>.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <https://www.rfc-editor.org/info/rfc4272>.

   [RFC8669]  Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
              A., and H. Gredler, "Segment Routing Prefix Segment
              Identifier Extensions for BGP", RFC 8669,
              DOI 10.17487/RFC8669, December 2019,
              <https://www.rfc-editor.org/info/rfc8669>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/info/rfc8986>.

   [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>.

   [RFC9252]  Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
              B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
              Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
              DOI 10.17487/RFC9252, July 2022,
              <https://www.rfc-editor.org/info/rfc9252>.

8.2.  Informative References

   [I-D.agrawal-spring-srv6-mpls-interworking]
              Agrawal, S., Ali, Z., Filsfils, C., Voyer, D., Dawra, G.,
              and Z. Li, "SRv6 and MPLS interworking", Work in Progress,
              Internet-Draft, draft-agrawal-spring-srv6-mpls-
              interworking-11, 13 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-agrawal-
              spring-srv6-mpls-interworking-11>.

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   [I-D.hr-spring-intentaware-routing-using-color]
              Hegde, S., Rao, D., Sangli, S. R., Agrawal, S., Filsfils,
              C., Talaulikar, K., Patel, K., Uttaro, J., Decraene, B.,
              Bogdanov, A., Jalil, L., Alston, A., Xu, X., Gulko, A.,
              Khaddam, M., Contreras, L. M., Steinberg, D., Guichard,
              J., Henderickx, W., and Co-authors, "Problem statement for
              Inter-domain Intent-aware Routing using Color", Work in
              Progress, Internet-Draft, draft-hr-spring-intentaware-
              routing-using-color-01, 14 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-hr-spring-
              intentaware-routing-using-color-01>.

   [I-D.ietf-idr-bgp-car]
              Rao, D., Agrawal, S., and Co-authors, "BGP Color-Aware
              Routing (CAR)", Work in Progress, Internet-Draft, draft-
              ietf-idr-bgp-car-02, 6 July 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
              car-02>.

   [I-D.ietf-idr-bgp-ct]
              Vairavakkalai, K. and N. Venkataraman, "BGP Classful
              Transport Planes", Work in Progress, Internet-Draft,
              draft-ietf-idr-bgp-ct-11, 5 July 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
              ct-11>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <https://www.rfc-editor.org/info/rfc3032>.

   [RFC8277]  Rosen, E., "Using BGP to Bind MPLS Labels to Address
              Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
              <https://www.rfc-editor.org/info/rfc8277>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

Authors' Addresses

Wang, et al.             Expires 11 January 2024               [Page 11]
Internet-Draft          BGP CPR for SRv6 Service               July 2023

   Haibo Wang
   Huawei Technologies
   China
   Email: rainsword.wang@huawei.com

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

   Jingrong Xie
   Huawei Technologies
   China
   Email: xiejingrong@huawei.com

   Xinjun Chen
   Huawei Technologies
   China
   Email: ifocus.chen@huawei.com

Wang, et al.             Expires 11 January 2024               [Page 12]