Skip to main content

A Framework for Constructing Service Function Chaining Systems Based on Segment Routing
draft-li-spring-sr-sfc-control-plane-framework-10

Document Type Active Internet-Draft (individual)
Authors Yuanyang Yin , Cheng Li , Ahmed El Sawaf , Hongyi Huang , Zhenbin Li
Last updated 2024-03-01
RFC stream (None)
Intended RFC status (None)
Formats
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-spring-sr-sfc-control-plane-framework-10
SPRING Working Group                                              Y. Yin
Internet-Draft                                             China Telecom
Intended status: Informational                                     C. Li
Expires: 2 September 2024                            Huawei Technologies
                                                                A. Sawaf
                                                   Saudi Telecom Company
                                                                H. Huang
                                                                   Z. Li
                                                     Huawei Technologies
                                                            1 March 2024

A Framework for Constructing Service Function Chaining Systems Based on
                            Segment Routing
           draft-li-spring-sr-sfc-control-plane-framework-10

Abstract

   Segment Routing (SR) introduces a versatile methodology for defining
   end-to-end network paths by encoding sequences of topological sub-
   paths, known as "segments".  This architecture can be deployed over
   both MPLS and IPv6 data planes, offering a flexible routing solution.

   Service Function Chaining (SFC) supports the establishment of
   composite services through an ordered sequence of Service Functions
   (SFs) that are applied to packets or frames based on initial
   classification.  SFC's implementation can utilize various underlying
   technologies, including the Network Service Header (NSH) and SR, to
   facilitate the creation and management of service chains.

   This document presents a comprehensive control framework for
   developing SFC architectures using Segment Routing.  It explores
   control plane solutions for the distribution of service function
   instance routes and service function paths, as well as techniques for
   directing packets into specific service function chains.  The
   discussion encompasses both theoretical foundations and practical
   considerations for integrating SR into SFC deployments.

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/.

Yin, et al.             Expires 2 September 2024                [Page 1]
Internet-Draft         SR based SFC Control Plane             March 2024

   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.
   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Overview of SR Based SFC Control Plane  . . . . . . . . . . .   4
   3.  Stateless SR Based SFC  . . . . . . . . . . . . . . . . . . .   6
     3.1.  Service Function Instance Route Distribution  . . . . . .   7
     3.2.  Service Function Path Route Distribution  . . . . . . . .   7
     3.3.  Steer Packets into SFC  . . . . . . . . . . . . . . . . .   8
   4.  Stateful SR Based SFC . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Service Function Route Distribution . . . . . . . . . . .   8
     4.2.  Service Function Path Route Distribution  . . . . . . . .   8
     4.3.  Steer Packets into SFC  . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   9
   References  . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     Normative References  . . . . . . . . . . . . . . . . . . . . .   9
     Informative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

Yin, et al.             Expires 2 September 2024                [Page 2]
Internet-Draft         SR based SFC Control Plane             March 2024

1.  Introduction

   Segment Routing (SR), as defined in [RFC8402], introduces a source
   routing paradigm that assigns a specific forwarding path for packets
   at the ingress node via an ordered list of directives, known as
   segments.  SR's implementation varies with the underlying data plane:
   SR-MPLS [RFC8660] for MPLS and SRv6 [RFC8754] for IPv6.

   Service Function Chaining (SFC), outlined in [RFC7665], facilitates
   the assembly of composite services through a sequenced application of
   Service Functions (SF) on packets or frames, triggered by
   classification processes.

   Network Service Header (NSH) [RFC8300] provides a basis for SFC,
   enabling a "stateful SFC" by necessitating nodes along the Service
   Function Path (SFP) to maintain specific SFC states, such as mappings
   between the Service Path Identifier (SPI) and Service Index (SI) for
   subsequent forwarding actions.  [RFC9015] introduces the use of BGP
   as a control plane mechanism for SFC architectures utilizing NSH and
   MPLS.  It proposes a new BGP address family, the SFC AFI/SAFI,
   comprising two route types: Service Function Instance Route (SFIR)
   and Service Function Path Route (SFPR), facilitating the construction
   of NSH or MPLS-based SFCs with SFIR and SFPR data.

   Alternatively, SFC can leverage SR for instantiation, where the SR
   source node explicitly embeds the forwarding path into packets.  In
   SR-based SFC, an SFC is denoted by a SID list from the source SR
   node, potentially linked with service details (e.g., Deep Packet
   Inspection, DPI), obviating the need for maintaining per-SFC state
   along the SFP, hence termed "stateless SFC."

   To deploy SR-based SFC, this document explores several mechanisms,
   including the distribution of SFIR and SFPR, as well as packet
   steering into an SFP.  The review aims to establish a comprehensive
   framework for constructing an SFC system utilizing Segment Routing.

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.

1.2.  Terminology

   MPLS: Multiprotocol Label Switching.

Yin, et al.             Expires 2 September 2024                [Page 3]
Internet-Draft         SR based SFC Control Plane             March 2024

   SID: Segment Identifier.

   SR: Segment Routing.

   SR-MPLS: Segment Routing with MPLS data plane.

   SRH: Segment Routing Header.

   SFIR: Service Function Instance Route

   SFPR: Service Function Path Route

   Further, this document makes use of the terms defined in [RFC7665]
   and [I-D.ietf-spring-sr-service-programming].

2.  Overview of SR Based SFC Control Plane

   As per [RFC7665], the architecture of SFC consists of classifiers,
   Service Function Forwarders (SFFs), Service Functions (SFs) and SFC
   Proxies.  This is illustrated in Figure 1.

                                       +-----+         +-----+   +-----+
                                       |     |         | SFC |   |     |
                                       | SF1 |         |Proxy|---| SF2 |
                                       +-----+         +-----+   +-----+
                                          |               |
     +--------------+                     |               |
     |   Service    |       SFC        +------+        +------+
     |Classification|  Encapsulation   | SFF1 |        | SFF2 |
 --->|   Function   |+---------------->|      |--------|      |------->
     |              |                  |      |        |      |
     +--------------+                  +------+        +------+

          SFC-enabled Domain

                       Figure 1. SFC Architecture

   In order to construct an SFC, SFIR and SFPR should be distributed to
   classifiers and SFFs.  Also, the rules of steering packets into
   specific SFPs should be configured at the classifier.  [RFC9015].

   In SR, a source node can explicitly indicate the forwarding path for
   packets by inserting an ordered list of instructions.  These packet
   steering policies, known as SR policy, can be installed by a central
   controller via BGP [I-D.ietf-idr-sr-policy-safi] or other mechanisms.

Yin, et al.             Expires 2 September 2024                [Page 4]
Internet-Draft         SR based SFC Control Plane             March 2024

   When SFC is constructed based on SR, SFPR and packet steering rules
   can be installed by SR policy at the ingress node, which plays the
   role of classifier in the SFC architecture.  In other words, SFPR
   does not need to be distributed to all the nodes along the SFP.  The
   architecture of SR based SFC is illustrated in Figure 2.

         +-----+                       +-----+         +-----+   +-----+
         |     |                       |     |         | SR  |   |     |
         |SR-C |                       | SF1 |         |Proxy|---| SF2 |
         +-----+                       +-----+         +-----+   +-----+
            |                             |               |
            |                             |               |
     +--------------+                  +------+        +------+
     |              |   SFC Encap/SR   | SFF1/|        | SFF2/|
 --->|CF/SR ingress |+---------------->|  SR  |--------|  SR  |------->
     |              |                  |      |        |      |
     +--------------+                  +------+        +------+

          SFC-enabled Domain

                     Figure 2. SR based SFC architecture.

   *  CF/SR ingress: an SR ingress node plays the role of Classifier in
      the SFC architecture, and it connects to an SR controller, where
      the SR policies originate.

   *  SR-C: SR Controller (SR-C) is connected to the SR ingress node,
      and may be attached to any node in the network.  SR-C is capable
      of discovering topology, and calculating constrained paths for
      SFCs.

   *  SFF/SR nodes: the SFF component in SFC architecture, which enables
      SR to steer packets to SFs.

   *  SFn: Service Functions, can be SR-aware or SR-unaware.  If an SF
      is SR-unaware then SR proxy is needed.

   *  SR proxy: A proxy between SFF/SR nodes and SR-unaware SF.

   There are two solutions to encode SFC in the SR data plane.
   [I-D.ietf-spring-sr-service-programming] defines data plane
   functionality required to implement service segments and achieve
   service programming in SR-enabled MPLS and IP networks.  It can be
   termed "Stateless SFC" since no per-SFC state is maintained on the SR
   nodes along the SFP.

Yin, et al.             Expires 2 September 2024                [Page 5]
Internet-Draft         SR based SFC Control Plane             March 2024

   The second solution can be termed "Stateful SFC" [RFC9491], since it
   still maintains per-SFC state on nodes.  [RFC9491]describes two modes
   of operation:

   *  NSH-based SFC with SR-based transport tunnel: SR is used as the
      transport tunnel to route packets between classifier and SFF or
      SFFs.  Service plane routing relies on NSH.

   *  SR-based SFC with Integrated NSH Service Plane: The SFP is encoded
      within the SR segment-list, while the NSH only maintains the
      service plane context information, which will be used at NSH-aware
      SFs, and at SFFs as a pointer to cache SR segment-lists.

   In order to support these data plane encodings, control plane
   mechanisms are required.  The existing control plane mechanisms are
   shown in Table 1.

             +===================+========+======+==========+
             | SR based SFC      | SFIR   | SFPR | Steering |
             |                   |        |      | policy   |
             +===================+========+======+==========+
             | Stateless         | BGP    | BGP  | BGP      |
             |                   | BGP-LS | PCEP | PCEP     |
             |                   | IGP    |      |          |
             +-------------------+--------+------+----------+
             | NSH-based SFC     | BGP    | BGP  | BGP      |
             | with SR-based     |        | PCEP |          |
             | transport tunnel  |        |      |          |
             +-------------------+--------+------+----------+
             | SR-based SFC with | BGP    | BGP  | BGP      |
             | Integrated NSH    | BGP-LS | PCEP | PCEP     |
             | Service Plane     | IGP    |      |          |
             +-------------------+--------+------+----------+

              Table 1: SR based SFC Control Plane Solutions

3.  Stateless SR Based SFC

   As describe in [I-D.ietf-spring-sr-service-programming], service
   instances are associated with a segment, called a service SID.  These
   service SIDs are leveraged as part of a SID-list to steer packets
   through the corresponding services

Yin, et al.             Expires 2 September 2024                [Page 6]
Internet-Draft         SR based SFC Control Plane             March 2024

3.1.  Service Function Instance Route Distribution

   To associate a segment with a service, service information, such as
   Service Function Type (SFT), should be included in segment
   distribution.  [I-D.dawra-idr-bgp-ls-sr-service-segments] specifies
   the extensions to BGP-LS for discovery and advertisement of service
   segments to enable setup of service programming paths using Segment
   Routing.  [I-D.dawra-idr-bgp-ls-sr-service-segments] extends SRv6
   Node SID TLV [RFC9514] and SR-MPLS SID/ Label TLV [RFC9085] to
   associate the Service SID Value with Service-related Information
   using Service Chaining Sub-TLV.  The Service Chaining Sub-TLV
   contains information of Service SID value, Function Identifier
   (Static Proxy, Dynamic Proxy, Shared Memory Proxy, Masquerading
   Proxy, SR Aware Service Etc.), Service Type (DPI, Firewall,
   Classifier, LB etc.), Traffic Type (IPv4 OR IPv6 OR Ethernet) and
   Opaque Data (such as brand and version, other extra information).
   This extension works for both SR- MPLS and SRv6.

   [RFC9015] proposes a BGP-based SFC control plane solution, and it
   works for SR-MPLS as well.  Service function instance route
   distribution can use SFIR in SFC AFI/SAFI.  SFPR and steering rules
   for the classifier can be distributed by SR policy, which is defined
   in [I-D.ietf-idr-sr-policy-safi].  BGP control plane of SRv6-based
   SFC still needs to be defined.

   IGP extensions are proposed by [I-D.xu-lsr-isis-service-function-adv]
   and [I-D.xu-lsr-ospf-service-function-adv].  In IS-IS solution, SFFs
   within the SFC domain need to advertise each SF they are offering by
   using a new sub-TLV of the IS-IS Router CAPABILITY TLV [RFC7981].
   This new sub-TLV is called Service Function sub-TLV, and it can
   appear multiple times within a given IS-IS Router CAPABILITY TLV or
   when more than one SF needs to be advertised.  OSPF extensions are
   similar, and use the OSPF Router Information (RI) Opaque LSA
   [RFC7770] to carry Service Function sub-TLV.

   However, due to IGP flooding issues, IGP extensions are not very
   appropriate, and the drafts have expired for a long time.

3.2.  Service Function Path Route Distribution

   With SR, the SFPR does not need to be distributed to nodes along the
   SFP but only to the ingress node.  SFPR and steering rules for the
   classifier can be distributed by SR policy.  The BGP extension is
   defined in [I-D.ietf-idr-sr-policy-safi].  The PCEP extension is
   defined in [I-D.ietf-pce-segment-routing-policy-cp].

Yin, et al.             Expires 2 September 2024                [Page 7]
Internet-Draft         SR based SFC Control Plane             March 2024

3.3.  Steer Packets into SFC

   In SR, packet steering rules are learned through SR policy.  Thus,
   there is no need to install other rules in the classifier, which is
   the SR source node.

4.  Stateful SR Based SFC

   "Stateful SFC" [RFC9491] proposes two modes of SR based SFC:

   *  NSH-based SFC with SR-based transport tunnel

   *  SR-based SFC with Integrated NSH Service Plane

4.1.  Service Function Route Distribution

   For NSH-based SFC with SR-based transport tunnel, service information
   is maintained by NSH while SR is only used for transport between
   SFFs, so [RFC9015] can be used for this mode.

   To indicate NSH, an SFF label [RFC8596] should be inserted as the
   last label in the label stack in SR-MPLS.  The control plane of SFF
   is also described in [RFC9015].  For choosing/configuring SR as the
   transport tunnel, BGP route of SFF's BGP Tunnel Encapsulation
   Attribute Type should be "SR TE Policy Type"
   [I-D.ietf-idr-sr-policy-safi].  For SR-based SFC with Integrated NSH
   Service Plane, there is no control plane solution as yet defined.

4.2.  Service Function Path Route Distribution

   Same as SFIR distribution, SFPR BGP distribution in NSH-based SFC
   with SR-based transport tunnel is identical to the mechanism defined
   in [RFC9015].  PCEP extension for SFPR distribution can reuse the NSH
   based SFC extension defined in [I-D.wu-pce-traffic-steering-sfc].
   For SR-based SFC with Integrated NSH Service Plane, control plane
   solution is to be added in other documents.

4.3.  Steer Packets into SFC

   For NSH-based SFC with SR-based transport tunnel, it is the same with
   the NSH based SFC.  The Classifier is responsible for determining to
   which packet flow a packet belongs (usually by inspecting the packet
   header), imposing an NSH, and initializing the NSH with the SPI of
   the selected SFP and the SI of its first hop [RFC9015].  For SR-based
   SFC with Integrated NSH Service Plane, control plane solution is to
   be added in other document.

Yin, et al.             Expires 2 September 2024                [Page 8]
Internet-Draft         SR based SFC Control Plane             March 2024

5.  IANA Considerations

   This document does not require any IANA actions.

6.  Security Considerations

   This document does not introduce additional security requirements and
   mechanisms.

Acknowledgements

   Many thanks for Ruizhao Hu's valuable comments and help.

References

Normative References

   [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/rfc/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/rfc/rfc8174>.

Informative References

   [I-D.dawra-idr-bgp-ls-sr-service-segments]
              Dawra, G., Filsfils, C., Talaulikar, K., Clad, F.,
              Bernier, D., Uttaro, J., Decraene, B., Elmalky, H., Xu,
              X., Guichard, J., and C. Li, "BGP-LS Advertisement of
              Segment Routing Service Segments", Work in Progress,
              Internet-Draft, draft-dawra-idr-bgp-ls-sr-service-
              segments-06, 17 August 2021,
              <https://datatracker.ietf.org/doc/html/draft-dawra-idr-
              bgp-ls-sr-service-segments-06>.

   [I-D.ietf-idr-sr-policy-safi]
              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-sr-
              policy-safi-00, 4 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
              policy-safi-00>.

Yin, et al.             Expires 2 September 2024                [Page 9]
Internet-Draft         SR based SFC Control Plane             March 2024

   [I-D.ietf-pce-segment-routing-policy-cp]
              Koldychev, M., Sivabalan, S., Barth, C., Peng, S., and H.
              Bidgoli, "PCEP Extensions for SR Policy Candidate Paths",
              Work in Progress, Internet-Draft, draft-ietf-pce-segment-
              routing-policy-cp-14, 9 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
              segment-routing-policy-cp-14>.

   [I-D.ietf-spring-sr-service-programming]
              Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C.,
              Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and
              S. Salsano, "Service Programming with Segment Routing",
              Work in Progress, Internet-Draft, draft-ietf-spring-sr-
              service-programming-09, 20 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              sr-service-programming-09>.

   [I-D.wu-pce-traffic-steering-sfc]
              Wu, Q., Dhody, D., Boucadair, M., Jacquenet, C., and J.
              Tantsura, "PCEP Extensions for Service Function Chaining
              (SFC)", Work in Progress, Internet-Draft, draft-wu-pce-
              traffic-steering-sfc-12, 30 June 2017,
              <https://datatracker.ietf.org/doc/html/draft-wu-pce-
              traffic-steering-sfc-12>.

   [I-D.xu-lsr-isis-service-function-adv]
              Xu, X., Huang, H., Shah, H. C., and L. M. Contreras,
              "Advertising Service Functions Using IS-IS", Work in
              Progress, Internet-Draft, draft-xu-lsr-isis-service-
              function-adv-00, 9 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-xu-lsr-isis-
              service-function-adv-00>.

   [I-D.xu-lsr-ospf-service-function-adv]
              Xu, X., Huang, H., Shah, H. C., and L. M. Contreras,
              "Advertising Service Functions Using OSPF", Work in
              Progress, Internet-Draft, draft-xu-lsr-ospf-service-
              function-adv-00, 9 March 2023,
              <https://datatracker.ietf.org/doc/html/draft-xu-lsr-ospf-
              service-function-adv-00>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/rfc/rfc7665>.

Yin, et al.             Expires 2 September 2024               [Page 10]
Internet-Draft         SR based SFC Control Plane             March 2024

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/rfc/rfc7770>.

   [RFC7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/rfc/rfc7981>.

   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,
              <https://www.rfc-editor.org/rfc/rfc8300>.

   [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/rfc/rfc8402>.

   [RFC8596]  Malis, A., Bryant, S., Halpern, J., and W. Henderickx,
              "MPLS Transport Encapsulation for the Service Function
              Chaining (SFC) Network Service Header (NSH)", RFC 8596,
              DOI 10.17487/RFC8596, June 2019,
              <https://www.rfc-editor.org/rfc/rfc8596>.

   [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/rfc/rfc8660>.

   [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/rfc/rfc8754>.

   [RFC9015]  Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L.
              Jalil, "BGP Control Plane for the Network Service Header
              in Service Function Chaining", RFC 9015,
              DOI 10.17487/RFC9015, June 2021,
              <https://www.rfc-editor.org/rfc/rfc9015>.

   [RFC9085]  Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
              H., and M. Chen, "Border Gateway Protocol - Link State
              (BGP-LS) Extensions for Segment Routing", RFC 9085,
              DOI 10.17487/RFC9085, August 2021,
              <https://www.rfc-editor.org/rfc/rfc9085>.

Yin, et al.             Expires 2 September 2024               [Page 11]
Internet-Draft         SR based SFC Control Plane             March 2024

   [RFC9491]  Guichard, J., Ed. and J. Tantsura, Ed., "Integration of
              the Network Service Header (NSH) and Segment Routing for
              Service Function Chaining (SFC)", RFC 9491,
              DOI 10.17487/RFC9491, November 2023,
              <https://www.rfc-editor.org/rfc/rfc9491>.

   [RFC9514]  Dawra, G., Filsfils, C., Talaulikar, K., Ed., Chen, M.,
              Bernier, D., and B. Decraene, "Border Gateway Protocol -
              Link State (BGP-LS) Extensions for Segment Routing over
              IPv6 (SRv6)", RFC 9514, DOI 10.17487/RFC9514, December
              2023, <https://www.rfc-editor.org/rfc/rfc9514>.

Authors' Addresses

   Yuanyang Yin
   China Telecom
   Guangzhou
   China
   Email: yinyuany@chinatelecom.cn

   Cheng Li
   Huawei Technologies
   Email: c.l@huawei.com

   Ahmed El Sawaf
   Saudi Telecom Company
   Riyadh
   Saudi Arabia
   Email: aelsawaf.c@stc.com.sa

   Hongyi Huang
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing
   100095
   China
   Email: hongyi.huang@huawei.com

   Zhenbin Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Rd.
   Beijing
   100095
   China

Yin, et al.             Expires 2 September 2024               [Page 12]
Internet-Draft         SR based SFC Control Plane             March 2024

   Email: lizhenbin@huawei.com

Yin, et al.             Expires 2 September 2024               [Page 13]