Introducing Resource Awareness to SR Segments
draft-ietf-spring-resource-aware-segments-17

SPRING Working Group                                             J. Dong
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                             T. Miyasaka
Expires: 23 July 2026                                   KDDI Corporation
                                                                  Y. Zhu
                                                           China Telecom
                                                                  F. Qin
                                                                   Z. Li
                                                            China Mobile
                                                         19 January 2026

             Introducing Resource Awareness to SR Segments
              draft-ietf-spring-resource-aware-segments-17

Abstract

   This document describes a mechanism to allocate network resources to
   one or a set of Segment Routing Identifiers (SIDs).  Such SIDs are
   referred to as resource-aware SIDs.  The resource-aware SIDs retain
   their original forwarding semantics, with the additional semantics to
   identify the set of network resources available for the packet
   processing and forwarding action.  The proposed mechanism is
   applicable to both segment routing with MPLS data plane (SR-MPLS) and
   segment routing with IPv6 data plane (SRv6).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on 23 July 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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.  Segments with Resource Awareness  . . . . . . . . . . . . . .   4
     2.1.  SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  SRv6  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Control Plane Considerations  . . . . . . . . . . . . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Huawei Technologies . . . . . . . . . . . . . . . . . . .  10
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  12
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     10.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   The Segment Routing (SR) Architecture [RFC8402] specifies a mechanism
   to steer packets through an ordered list of segments.  A segment is
   referred to by its Segment Identifier (SID).  With SR, explicit
   source routing can be achieved without introducing per-path state
   into the network.  The base SR specifications do not have the
   capability of identifying or reserving a set of network resources.
   Although a centralized controller can have a global view of network
   state and can provision different services using different SR paths,
   in data packet forwarding it still relies on the DiffServ QoS
   mechanism [RFC2474] [RFC2475] to provide coarse-grained traffic
   differentiation in the network.  While such a mechanism may be
   sufficient for some types of services, other may require a set of
   dedicated network resources to achieve resource isolation in the same
   network.  Also note the number of such services could be larger than
   the number of traffic classes available with DiffServ QoS.

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   Without needing to define new SID types, this document extends the SR
   paradigm by associating SIDs with network resource attributes, so
   that network resources can be allocated to one or a set of SIDs.
   Such SIDs are referred to as resource-aware SIDs.  These resource-
   aware SIDs retain their original functionality, with the additional
   semantics of identifying the set of network resources available for
   the packet processing action.  Typical types of network resources
   include link bandwidth, buffers, and queues that are associated with
   class of service, scheduling weights or time cycles, and it is also
   possible to associate SR SIDs with other types of resources (e.g.,
   the processing and storage resources).  For a particular SR segment,
   multiple resource-aware SIDs can be allocated, each of which
   represents a subset of network resources allocated in the network to
   meet the requirements of one or a group of customers or services.
   Each subset of the network resources may be associated with one or
   multiple resource-aware SIDs.  The allocation of network resources to
   segments can be done either via local configuration or via a
   centralized controller.  Other approaches are possible such as use of
   a control plane signaling protocol, but they are out of the scope of
   this document.

   An SR Policy that requires dedicated network resources can be
   composed of a list of resource-aware SIDs.  This can be useful for
   service which requires dedicated network resources along the SR path.
   In addition, a subset of the network topology and resources
   (considered as a "virtual network") can be represented by a group of
   resource-aware SIDs that meet the connectivity and resource goals.
   The resources associated with each segment of the virtual network can
   be the same or different.  The proposed mechanism is applicable to SR
   with both MPLS data plane (SR-MPLS) and IPv6 data plane (SRv6).  The
   reader is expected to be familiar with the terminology in [RFC8402],
   [RFC8660] and [RFC8986].

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.

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2.  Segments with Resource Awareness

   In the Segment Routing architecture [RFC8402], several types of
   segments are defined to represent either topological or service
   instructions.  A topological segment can be a node segment or an
   adjacency segment.  A service segment may be associated with specific
   service functions for service chaining purpose.  This document
   introduces additional resource semantics to the existing types of
   SIDs.  A resource-aware SID retains its original functionality, with
   the additional semantics of identifying a set of network resources
   allocated in the network for the packet processing action.  A
   resource-aware SID is considered local resource-aware if the
   associated network resource is allocated on a specific node in the
   network.  A resource-aware SID is considered global resource-aware if
   the associated network resource is allocated on multiple nodes in the
   network.  A local resource-aware SIDs may be allocated with a
   dedicated set of network resources, while for global resource-aware
   SIDs, a common set of network resources may be allocated to a group
   of resource-aware SIDs.

   This section describes the mechanisms of using resource-aware SR SIDs
   to indicate the network resource information associated with the SR
   paths or virtual networks based on the two SR data plane
   instantiations: SR-MPLS and SRv6.  The mechanisms to identify the
   forwarding path or network topology with SIDs as defined in [RFC8402]
   do not change.  Aligning with the SR architecture, the control plane
   for resource-aware segments can be centralized, distributed, or
   hybrid.  When resource-aware segments are associated with a virtual
   network, the control plane for distributing the resource-aware SIDs
   and the associated topology or Flexible-Algorithm can be based on
   [RFC4915], [RFC5120] and [RFC9350].

2.1.  SR-MPLS

   The MPLS instantiation of Segment Routing is specified in [RFC8660].
   [RFC8402] specifies several type of SIDs, including the an IGP
   Adjacency Segment (Adj-SID), the IGP-Prefix Segment (Prefix-SID), and
   the IGP-Node Segment (Node-SID).  It also introduces the BGP Peer
   Adjacency Segment (PeerAdj SID).  These type of SIDs can be reused to
   represent both the topological instructions and the set of network
   resources allocated for packet processing following the instructions.

   A resource-aware Adj-SID is a local resource-aware segment, it
   represents a subset of the network resources (e.g., bandwidth, buffer
   and queuing resources) on a given link, thus each resource-aware Adj-
   SID is associated with a subset of the link's traffic engineering
   (TE) capabilities and resources (known as TE attributes [RFC2702]).

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   For one IGP link, multiple resource-aware Adj-SIDs can be assigned,
   each of which is associated with a subset of the link resources
   allocated on the link.  For one inter-domain link, multiple BGP
   PeerAdj SIDs may be assigned, each of which is associated with a
   subset of the link resources allocated on the inter-domain link.  The
   resource-aware Adj-SIDs may be associated with a specific network
   topology and/or algorithm, so that it is used only for resource-aware
   SR paths computed within the topology and/or algorithm.

   Note this per-segment resource allocation complies with the SR
   paradigm, which avoids introducing per-path state into the network.
   Several approaches can be used to partition and reserve the link
   resources, such as [FLEXE], logical sub-interfaces with reserved
   bandwidth, dedicated queues, etc.  The detailed mechanism of link
   resource partitioning is out of scope of this document.

   A resource-aware prefix-SID is a global resource-aware segment, it is
   associated with a network topology and/or algorithm which the
   attached node participates in.  In addition, a resource-aware prefix-
   SID is allocated with a set of network resources (e.g., bandwidth,
   buffer and queuing resources) on all the nodes and links
   participating in the associated topology and/or algorithm.  Such set
   of network resources can be used for forwarding packets which are
   encapsulated with this resource-aware prefix-SID, along the paths
   computed in the associated topology and/or algorithm.

   Although it is possible that each resource-aware prefix-SID is
   allocated with a set of dedicated resources on every node and link in
   the associated topology and/or algorithm, the overhead of per-prefix
   resource reservation is usually considered unacceptable in both
   control plane signaling and data plane states, and it is likely some
   of the allocated resources will be wasted.  It is RECOMMENDED that a
   common set of network resources be allocated by the network nodes and
   links participating in the topology and/or algorithm, and this common
   set of network resources is associated with a group of resource-aware
   Prefix-SIDs.  Such a common set of network resources constitutes a
   resource group.  For a given <topology, algorithm> tuple, there can
   be one or multiple resource groups.  This way, a group of resource-
   aware prefix-SIDs which are associated with the same <topology,
   algorithm> tuple can share the set of network resources in a resource
   group.  The association between the SR SIDs and a resource group can
   be provisioned using the management plane or a control plane.

   The recommendation above helps to reduce the dynamics in per-prefix
   resource allocation and adjustment, so that the network resource can
   be allocated based on planning and does not have to rely on dynamic
   signaling.  When the set of nodes and links that participate in a
   <topology, algorithm> tuple changes, the set of network resources

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   allocated on specific nodes and links may need to be adjusted.  When
   the set of network resources are locally configured on the network
   links, this means that the resources allocated to resource-aware Adj-
   SIDs on those links may have to be adjusted, and new TE attributes
   for the associated adj-SIDs re-advertised.

   For one IGP prefix, multiple resource-aware prefix-SIDs can be
   allocated.  Each resource-aware prefix-SID may be associated with a
   unique <topology, algorithm> tuple, in this case different <topology,
   algorithm> tuples can be used to distinguish the resource-aware
   prefix-SIDs of the same prefix.  In another case, for one IGP prefix,
   multiple resource-aware prefix-SIDs may be associated with the same
   <topology, algorithm> tuple but different resource groups, then an
   additional control plane distinguisher needs to be introduced to
   distinguish different resource-aware prefix-SIDs associated with the
   same <topology, algorithm> but different resource groups.  The first
   approach is simpler and does not require extensions to control plane
   protocols, while there can be scalability concerns when the number of
   resource groups is large, as it would require a large number of
   topologies or Flex-Algorithms.  The second approach is more scalable,
   while it requires additional extensions to the control plane
   protocols.  The exact control plane extensions are out of the scope
   of this document.

   A group of resource-aware Adj-SID and resource-aware Prefix-SIDs can
   be used to construct the SID lists of an SR Policy, which can be used
   to steer the traffic to be forwarded along the explicit paths (either
   strict or loose) and processed using the set of network resources
   identified by the resource-aware SIDs.

   In SR-MPLS packet forwarding, each resource-aware Adj-SID identifies
   both the next-hop of the node and the set of resources used for
   packet processing on the outgoing interface.  Each resource-aware
   Prefix-SID identifies the path to the node which the prefix is
   attached to, and the set of network resources used for packet
   forwarding on the transit nodes along the path.  The transit nodes
   use the resource-aware Prefix-SIDs to determine the next-hop of the
   packet and the set of associated local resources, then forward the
   packet to the next-hop using the set of local resources.

   When the set of network resources allocated on the egress node also
   needs to be determined, it is RECOMMENDED that Penultimate Hop
   Popping (PHP) [RFC3031] be disabled, otherwise the inner service
   label needs to be used to infer the set of resources to be used for
   packet processing on the egress node of the SR path.

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   This mechanism requires the allocation of additional prefix-SIDs or
   adj-SIDs to identify different sets of network resources.  As the
   number of resource groups increases, the number of SIDs would
   increase accordingly, while it should be noted that there is still no
   per-path state introduced into the network.

2.2.  SRv6

   [RFC8986] defines the SRv6 SID format (LOC:FUNCT:ARG) and the base
   set of SRv6 behaviors bound to the SRv6 SIDs.  When the LOC (Locator)
   part of the SRv6 SIDs is routable, it leads to the node which
   instantiates the SID.

   The approach of introducing resource-awareness to SRv6 is by firstly
   making the SRv6 Locators resource-aware.  For one SRv6 node, multiple
   resource-aware SRv6 Locators can be assigned.  A resource-aware
   Locator is associated with a network topology and/or algorithm in
   which the originating node participates, as well as a set of network
   resources (e.g., bandwidth, buffer, and queueing resources) on each
   node and the attached links participating in the same topology and/or
   algorithm.  Then resource-aware SRv6 SIDs are allocated using the
   resource-aware SRv6 Locator as the prefix.  The set of network
   resources allocated to the resource-aware SRv6 Locator are used in
   forwarding packets in which the resource-aware SRv6 SIDs are encoded
   as the destination IPv6 address.

   Similar to the approach used with resource-aware prefix-SIDs in SR-
   MPLS, it is RECOMMENDED that a common set of network resources are
   allocated by the network nodes and links participating in a topology
   and/or algorithm, and this resource group is associated with a group
   of resource-aware Locators of the same topology and/or algorithm.

   For one IGP link, multiple resource-aware SRv6 End.X SIDs can be
   allocated to identify different set of link resources allocated on
   the link.  Each resource-aware End.X SID MUST use a resource-aware
   locator as its prefix.  SRv6 SIDs for other types of behaviors MAY
   also be assigned as resource-aware SIDs, which can identify the set
   of network resources allocated by the node for executing the
   behavior.

   A group of resource-aware SRv6 SIDs can be used to construct the SID
   lists of an SR Policy, which can be used to steer the traffic to be
   forwarded along the explicit paths (either strict or loose), and be
   processed using the set of network resources identified by the
   resource-aware SRv6 Locators and SIDs.

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   In SRv6 packet forwarding, the transit nodes uses the resource-aware
   Locator of the SRv6 SID carried in the destination IPv6 address field
   to determine the next-hop of the packet, and the associated set of
   network resources, then the packet is forwarded to the next-hop using
   the set of local resources in the resource group.  On the segment
   endpoint nodes, the resource-aware End.X SID identifies both the
   next-hop and the set of resources used for packet processing on the
   outgoing interface of the node which instantiates the SID.

   This mechanism requires the allocation of additional SRv6 Locators
   and SIDs to identify different set of network resources.  As the
   number of resource groups increases, the number of SRv6 Locators and
   SIDs would increase accordingly, while it should be noted that there
   is still no per-path state introduced into the network.

3.  Control Plane Considerations

   The mechanism described in this document assumes the use of a
   centralized controller to collect the information about the network
   (configuration, state, routing databases, etc.) as well as the
   service information (traffic matrix, performance statistics, etc.)
   for the planning of network resources based on the service
   requirements.  The centralized controller can also be used to
   instruct the network nodes to allocate the network resources and
   associate the resources to resource-aware SIDs.  The resource-aware
   SIDs can be either explicitly provisioned by the controller, or can
   be dynamically allocated by network nodes.  The distributed control
   plane is complementary to the centralized controller.  When the
   resource-aware SIDs are locally configured or dynamically allocated,
   a distributed control plane can be used for the collection and
   distribution of the resource-aware SIDs among network nodes, together
   with the set of associated local network resource information.  Then
   some of the network nodes can distribute the collected information to
   the centralized controller.  The mechanisms as defined in
   [RFC8665][RFC8667] [RFC9085] [RFC9352] [RFC9513] and [RFC9514] can be
   reused with possible extensions to improve the efficiency and
   scalability.  The details are out of the scope of this document.

   The support for a resource group and the information to associate
   packets to it MUST be aligned among the network nodes in that
   resource group, so as to ensure that packets are processed
   consistently within a resource group.  This task can be accomplished
   via local configuration or via a centralized controller.  Other
   approaches may be possible.

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   To indicate the support for a given resource group, a node needs to
   advertise the identifier of the resource group, the associated
   topology and algorithm, the resource-aware SIDs and potentially a set
   of TE attributes representing the resources allocated to it.

   The controller is also responsible for the centralized computation
   and optimization of the SR paths taking the topology, algorithm and
   network resource constraints into consideration.  The interaction
   between the controller and the network nodes can be based on Netconf/
   YANG [RFC6241] [RFC7950] [I-D.ietf-spring-sr-policy-yang], BGP SR
   Policy [RFC9830] or PCEP [RFC8664] [RFC9603].  In some scenarios,
   extensions to some of these protocols may be needed to improve the
   efficiency and scalability of the control plane, which are out of the
   scope of this document.  Distributed computation of resource-aware SR
   paths is also possible, the topology, algorithm and/or resource
   constraints needs to be taken into consideration by network nodes.
   The distributed control plane may be based on [RFC4915], [RFC5120],
   [RFC9350] with necessary extensions.

   When a network node is instructed to associate a SID with specific
   resources, its actions will depend on the operational mechanisms of
   the network.  In some cases the association between SIDs and
   resources is configured on the individual network nodes, and the
   control plane (e.g.  IGP) is used to distribute the SID information
   and the allocated resource information to the controller and the
   ingress nodes for TE constraint-based path computation.  In network
   cases with SR and other TE mechanisms (such as RSVP-TE) co-existing
   in the network, the IGP advertisements of available resources may
   need to be updated to indicate that there has been a change to the
   available resources resulting from the instantiation of a new
   resource-aware SID, it is suggested such updates would be rate-
   limited.  In still other cases the association between SIDs and
   network resources is provisioned by the central controller which is
   responsible for all TE management, then the distributed control plane
   does not need to take any additional action.

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

5.  Implementation Status

   This section is to be removed before publishing as an RFC.

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   RFC-Editor: Please clean up the references cited by this section
   before publication.

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in [RFC7942].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.

   According to [RFC7942], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

   This section is provided in compliance with the SPRING working group
   policies ([SPRING-WG-POLICIES]).

5.1.  Huawei Technologies

   Huawei Technologies reported the following implementations of the
   resource-aware segments (Section 2).  The resource-aware segments are
   used to build SR based Network Resource Partitions (NRPs) and
   resource guaranteed SR Policies.

   *  Huawei ATN9XX, CX600 routers.

   *  Huawei NE40E, NE8000, NE5000E routers.

   At the time of this report, all the implementations listed above are
   in production and follow the specification in the latest version of
   this document, including all the "MUST" and "SHOULD" clauses for the
   resource-aware segments.

   This report was last updated on August 28, 2025.

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6.  Operational Considerations

   Resource-aware segments can coexist with the existing SR segments.
   Network operators may introduce resource-aware segments into a
   portion of their SR networks to support services which require
   guaranteed network resources (e.g. bandwidth).  The use of either
   base SR segments or resource-aware SR segments for specific service
   is based on operators' local policy.

   Resource-aware segments require to introduce additional SR-MPLS SIDs
   or SRv6 Locators/SIDs for different subsets of network resources.
   This would increase the amount of SR SIDs to be managed, and would
   also increase the amount of state to be maintained by network nodes.
   Althougth with the SR paradigmn, per-path state can be avoided in the
   network, operators need to be aware of the additional cost of
   introducing resource-aware segments, and provide careful planning of
   the resource groups, so that the resource-aware segments can meet the
   service requirements without introducing unacceptable complexity to
   network operation and management.

7.  Security Considerations

   The security considerations of segment routing and SRv6 in [RFC8402]
   [RFC8660] [RFC8754], [RFC8986] and [I-D.ietf-spring-srv6-security]
   are applicable to this document.

   The resource-aware SIDs may be used for provisioning of SR paths or
   virtual networks to carry traffic with specific SLA requirements
   (such as latency).  By disrupting the SLA of such traffic an attack
   can be directly targeted at the customer application, or can be
   targeted at the network operator by causing them to violate their
   SLA, triggering commercial consequences.  Dynamic attacks of this
   sort are not something that networks have traditionally guarded
   against, and networking techniques need to be developed to defend
   against this type of attack.  By rigorously policing ingress traffic
   and carefully provisioning network resources provided to such
   services, this type of attack can be prevented.  However care needs
   to be taken when providing shared resources, and when the network
   needs to be reconfigured as part of ongoing maintenance or in
   response to a failure.

   A compromised network node may choose not to allocate the necessary
   resources to a set of resource-aware SIDs, this may result in the
   expected SLA being disrupted due to lack of resource guarantee.

   The details of the underlay network MUST NOT be exposed to third
   parties, to prevent attacks aimed at exploiting shared network
   resources.

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8.  Contributors

   Stewart Bryant
   Email: stewart.bryant@gmail.com

   Francois Clad
   Email: fclad@cisco.com

   Zhenbin Li
   Email: lizhenbin@huawei.com

   Zhibo Hu
   Email: huzhibo@huawei.com

   Joel Halpern
   Email: jmh@joelhalpern.com

9.  Acknowledgements

   The authors would like to thank Mach Chen, Stefano Previdi, Charlie
   Perkins, Bruno Decraene, Loa Andersson, Alexander Vainshtein, John
   Drake and Alvaro Retana for the valuable discussion and suggestions
   to this document.

10.  References

10.1.  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/info/rfc2119>.

   [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>.

   [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>.

   [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>.

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   [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>.

   [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>.

10.2.  Informative References

   [FLEXE]    "Flex Ethernet Implementation Agreement", March 2016,
              <https://www.oiforum.com/wp-content/uploads/2019/01/OIF-
              FLEXE-01.0.pdf>.

   [I-D.ietf-spring-sr-policy-yang]
              Saleh, T., Raza, S. K., Zhuang, S., Matsushima, S., and V.
              P. Beeram, "YANG Data Model for Segment Routing Policy",
              Work in Progress, Internet-Draft, draft-ietf-spring-sr-
              policy-yang-06, 20 October 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              sr-policy-yang-06>.

   [I-D.ietf-spring-srv6-security]
              Buraglio, N., Mizrahi, T., tongtian124, Contreras, L. M.,
              and F. Gont, "Segment Routing IPv6 Security
              Considerations", Work in Progress, Internet-Draft, draft-
              ietf-spring-srv6-security-10, 12 January 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              srv6-security-10>.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

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   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/info/rfc2475>.

   [RFC2702]  Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
              McManus, "Requirements for Traffic Engineering Over MPLS",
              RFC 2702, DOI 10.17487/RFC2702, September 1999,
              <https://www.rfc-editor.org/info/rfc2702>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

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   [RFC8664]  Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
              and J. Hardwick, "Path Computation Element Communication
              Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
              DOI 10.17487/RFC8664, December 2019,
              <https://www.rfc-editor.org/info/rfc8664>.

   [RFC8665]  Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
              H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", RFC 8665,
              DOI 10.17487/RFC8665, December 2019,
              <https://www.rfc-editor.org/info/rfc8665>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

   [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/info/rfc9085>.

   [RFC9086]  Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
              Ray, S., and J. Dong, "Border Gateway Protocol - Link
              State (BGP-LS) Extensions for Segment Routing BGP Egress
              Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
              2021, <https://www.rfc-editor.org/info/rfc9086>.

   [RFC9087]  Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
              and D. Afanasiev, "Segment Routing Centralized BGP Egress
              Peer Engineering", RFC 9087, DOI 10.17487/RFC9087, August
              2021, <https://www.rfc-editor.org/info/rfc9087>.

   [RFC9350]  Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
              and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
              DOI 10.17487/RFC9350, February 2023,
              <https://www.rfc-editor.org/info/rfc9350>.

   [RFC9352]  Psenak, P., Ed., Filsfils, C., Bashandy, A., Decraene, B.,
              and Z. Hu, "IS-IS Extensions to Support Segment Routing
              over the IPv6 Data Plane", RFC 9352, DOI 10.17487/RFC9352,
              February 2023, <https://www.rfc-editor.org/info/rfc9352>.

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   [RFC9513]  Li, Z., Hu, Z., Talaulikar, K., Ed., and P. Psenak,
              "OSPFv3 Extensions for Segment Routing over IPv6 (SRv6)",
              RFC 9513, DOI 10.17487/RFC9513, December 2023,
              <https://www.rfc-editor.org/info/rfc9513>.

   [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/info/rfc9514>.

   [RFC9552]  Talaulikar, K., Ed., "Distribution of Link-State and
              Traffic Engineering Information Using BGP", RFC 9552,
              DOI 10.17487/RFC9552, December 2023,
              <https://www.rfc-editor.org/info/rfc9552>.

   [RFC9603]  Li, C., Ed., Kaladharan, P., Sivabalan, S., Koldychev, M.,
              and Y. Zhu, "Path Computation Element Communication
              Protocol (PCEP) Extensions for IPv6 Segment Routing",
              RFC 9603, DOI 10.17487/RFC9603, July 2024,
              <https://www.rfc-editor.org/info/rfc9603>.

   [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>.

   [SPRING-WG-POLICIES]
              Chairs, S. W. G., "SPRING Working Group Policies", 14
              October 2022,
              <https://wiki.ietf.org/en/group/spring/WG_Policies>.

Authors' Addresses

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

   Takuya Miyasaka
   KDDI Corporation
   Email: ta-miyasaka@kddi.com

   Yongqing Zhu
   China Telecom
   Email: zhuyq8@chinatelecom.cn

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   Fengwei Qin
   China Mobile
   Email: qinfengwei@chinamobile.com

   Zhenqiang Li
   China Mobile
   Email: li_zhenqiang@hotmail.com

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