



PCE                                                               L. Han
Internet-Draft                                              China Mobile
Intended status: Standards Track                                L. Zhang
Expires: 3 September 2026                                         Huawei
                                                                 M. Wang
                                                            China Mobile
                                                                 J. Dong
                                                                  Huawei
                                                                 R. Chen
                                                         ZTE Corporation
                                                            2 March 2026


   Path Computation Element Communication Protocol(PCEP) IPv6 Segment
         Routing Extensions for Inter-Layer Network Programing
         draft-many-pce-srv6-inter-layer-network-programing-01

Abstract

   In some networks, the cross-layer planning and optimization is
   considered more efficient than independent planning and operation of
   the layer-3 and the underlying networks in terms of resource
   utilization and SLA assurance.

   This document extends the PCEP SRv6 for inter-layer network, which
   enable the PCE to instantiate candidate paths comprising both the
   layer-3 network segments and underlay network segments.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 3 September 2026.







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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Object Extensions . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  The ERO Object  . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  The RRO Object  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [RFC5440] describes Path Computation Element Communication Protocol
   (PCEP) for communication between a Path Computation Client (PCC) and
   a PCE or between a pair of PCEs.

   [RFC8231] specifies extensions to PCEP that allow a stateful PCE to
   compute and recommend network paths in compliance with [RFC4657] and
   defines objects and TLVs for MPLS-TE LSPs.  Stateful PCEP extensions
   provide synchronization of LSP state between a PCC and a PCE or
   between a pair of PCEs, delegation of LSP control, reporting of LSP
   state from a PCC to a PCE, and controlling the setup and path routing
   of an LSP from a PCE to a PCC.

   [RFC8281] further extends PCEP, providing a mechanism to dynamically
   initiate LSPs on a PCC based on the requests from a stateful PCE or a
   controller using stateful PCE.





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   [RFC8664] specifies PCEP extensions for supporting an SR-TE LSP for
   the MPLS data plane.  [RFC9603] extends [RFC8664] to support SR for
   the IPv6 data plane.

   As defined in [RFC8402], Segment Routing (SR) architecture allows the
   source node to steer a packet through a path indicated by an ordered
   list of instructions, called "segments".  A segment can represent any
   instruction, topological or service based, and it can have a semantic
   local to an SR node or global within an SR domain.

   Segment Routing over IPv6 (SRv6) [RFC8986] enables a network operator
   or an application to specify a packet processing program by encoding
   a sequence of instructions in the IPv6 packet header.

   Based on [RFC8986], [I-D.ietf-spring-srv6-inter-layer-programming]
   defines a new SRv6 behavior, which can be used for steering packets
   to underlay network connections, so that the packet network layer can
   be integrated with the underlying layers efficiently to provide
   better SLA assurance.

   This document extends the PCEP SRv6 for inter-layer network, which
   enable the PCE to instantiate candidate paths comprising both the
   layer-3 network segments and underlay network segments.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Object Extensions

2.1.  The ERO Object

   As specified in [RFC8664], an SR-TE path consists of one or more SIDs
   where each SID MAY be associated with the identifier that represents
   the node or adjacency corresponding to the SID.  This identifier is
   referred to as the NAI.  An NAI can be represented in various formats
   (e.g., IPv4 address, IPv6 address, etc).

   However, when an SRv6-TE path includes the END.IL SID defined in
   [I-D.ietf-spring-srv6-inter-layer-programming], the existing layer-3
   NAIs are not applicable to the END.IL SID.  Therefore, a new kind of
   NAI is needed for the END.IL SID.





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   [RFC9603] defines the "SRv6-ERO" subobject in the ERO to carry the
   SRv6 SID, the format of it is shown as follows:


   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|   Type=40   |     Length    | NT    |     Flags     |V|T|F|S|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Reserved         |      Endpoint Behavior        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                   SRv6 SID (conditional)                      |
   |                        (128-bit)                              |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                 NAI (variable, conditional)                 //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                  SID Structure (conditional)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1: SRv6-ERO Subobject Format

   The NT field in this subobject indicates the type and format of the
   NAI contained in the object body.  The value 2, 4 and 6 have been
   allocated for indicating different kind of NAI.

   This document request to allocate a new NT value for indicating the
   underlay network connection.

   Value TBD1: the NAI consists of a local IPv6 address, a Remote IPv6
   address, and a underlay tunnel ID.  This is used to identify the
   underlay network tunnel and used with the SRv6 inter-layer SID.

   The NAI associated with the new NT value is shown in the following
   figure:


     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //                Local IPv6 address(16 octets)                //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    //               Remote IPv6 address(16 octets)                //
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Underlay tunnel ID                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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              Figure 2: NAI for Underlay Interface Identifier

   This NAI is specified as a pair of global IPv6 address and an
   Underlay tunnel ID.  It is used to describe an underaly network
   tunnel between two nodes identified by global IPv6 address.  Each
   global IPv6 address is configured on a specific router, so together
   they identify a pair of routers at the end of the tunnel.  The
   underlay tunnel ID is configured by the management system and
   uniquely identifies a underlay network tunnel within the source node.

2.2.  The RRO Object

   A PCC reports an SRv6 path to a PCE by sending a PCRpt message, per
   [RFC8231].  The RRO on this message represents the SID list that was
   applied by the PCC, that is, the actual path taken.  The procedures
   of [RFC8664] with respect to the RRO apply equally to this
   specification without change.

   [RFC9603] defines the SRv6-RRO subobject to carry the SRv6 SID
   applied by the PCC.  The format of the SRv6-RRO subobject is the same
   as that of the SRv6-ERO subobject but without the L flag.

   The extension to the NT field of SRv6-ERO subobject is also
   applicable to the SRv6-RRO subobject.

3.  Procedures

   TBD

4.  Security Considerations

   TBD

5.  IANA Considerations

   This document requests IANA to make the following allocations from
   the PCEP SRv6-ERO NAI Types sub-registry.

    +=======+=========================================+===============+
    | Value | Description                             | Reference     |
    +=======+=========================================+===============+
    | TBD1  | NAI is an underlay interface identifier | This document |
    +-------+-----------------------------------------+---------------+

                                  Table 1

6.  References




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6.1.  Normative References

   [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>.

   [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>.

   [I-D.ietf-spring-srv6-inter-layer-programming]
              Han, L., Dong, J., Wang, M., Chen, R., and Z. Du, "SRv6
              for Inter-Layer Network Programming", Work in Progress,
              Internet-Draft, draft-ietf-spring-srv6-inter-layer-
              programming-01, 27 November 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              srv6-inter-layer-programming-01>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [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>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC4657]  Ash, J., Ed. and J.L. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.



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   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [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>.

   [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>.

Authors' Addresses

   Liuyan Han
   China Mobile
   No.32 XuanWuMen West Street
   Beijing, 100053
   China
   Email: hanliuyan@chinamobile.com


   Li Zhang
   Huawei
   Beiqing Road
   Beijing
   China
   Email: zhangli344@huawei.com


   Minxue Wang
   China Mobile
   No.32 XuanWuMen West Street
   Beijing, 100053
   China
   Email: wangminxue@chinamobile.com


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





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   Ran Chen
   ZTE Corporation
   Nanjing
   China
   Email: chen.ran@zte.com.cn














































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