



PCEP Working Group                                          V. P. Beeram
Internet-Draft                                                       HPE
Intended status: Standards Track                             K. Kompella
Expires: 2 September 2026                               Juniper Networks
                                                                A. Stone
                                                                   Nokia
                                                            1 March 2026


 Path Computation Element Communication Protocol (PCEP) Extensions for
  Multipath Traffic Engineered Directed Acyclic Graph (MPTED) Tunnels
                     draft-beeram-pce-pcep-mpted-01

Abstract

   A Multipath Traffic Engineered Directed Acyclic Graph (MPTED) tunnel
   is a Traffic Engineering (TE) construct that facilitates weighted
   load balancing of unicast traffic across a constrained set of paths
   optimized for a specific objective.

   This document describes the provisioning of an MPTED Tunnel in a TE
   network using Path Computation Element Communication Protocol (PCEP)
   in a stateful PCE model.

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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   This Internet-Draft will expire on 2 September 2026.

Copyright Notice

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






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   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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Modes of Operation  . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  PCC Initiated and PCC Signaled  . . . . . . . . . . . . .   4
     2.2.  PCE Initiated and PCC Signaled  . . . . . . . . . . . . .   5
     2.3.  PCC Initiated and PCE Signaled  . . . . . . . . . . . . .   6
     2.4.  PCE Initiated and PCE Signaled  . . . . . . . . . . . . .   7
   3.  Protocol Extensions . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Capability Negotiation  . . . . . . . . . . . . . . . . .   8
     3.2.  PCC Initiated MPTED Tunnels . . . . . . . . . . . . . . .   8
     3.3.  PCE Initiated MPTED Tunnels . . . . . . . . . . . . . . .   8
     3.4.  Signaling for Junction Management . . . . . . . . . . . .   8
     3.5.  PCEP Messages and Objects . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  Manageability Considerations  . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The notion of a Multipath Traffic Engineering Directed Acyclic Graph
   (MPTED) tunnel is introduced in [I-D.draft-kompella-teas-mpte].  An
   MPTED tunnel is a Traffic Engineering (TE) construct that contains a
   constrained set of paths representing an optimized Directed Acyclic
   Graph (DAG) from one or more ingresses to one or more egresses.  The
   paths that make up an MPTED tunnel traverse a set of junction nodes.
   An MPTED junction refers to the construct associated with the MPTED
   tunnel at each junction node and constitutes a set of previous-hops
   and a set of next-hops over which traffic is load-balanced in a
   weighted fashion.  Provisioning an MPTED tunnel in a TE network
   involves provisioning the control and forwarding plane state



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   associated with the MPTED junction at each junction node.

   [RFC8231] specifies extensions to the Path Computation Element
   Protocol (PCEP) that enable the deployment of a stateful Path
   Computation Element (PCE) model.  These extensions allow a Path
   Computation Client (PCC) to delegate control of the Label Switched
   Paths (LSPs) associated with its TE Tunnels to a stateful
   PCE. [RFC8281] specifies extensions that allow a PCE to instantiate
   and manage PCE-initiated LSPs on a PCC under the stateful PCE
   model. This document describes the extensions to PCEP that would
   enable (a) a PCC to delegate control of the MPTED TE Tunnel to a
   stateful PCE and (b) a PCE to instantiate and manage PCE-initiated
   MPTED Tunnels on a PCC under the stateful PCE model.

   Each MPTED computation request that a PCE caters to carries a set of
   ingress nodes, a set of egress nodes, a set of constraints, and an
   optimization objective.  The computation result for the MPTED
   contains a set of unordered elements called JUNCTIONs. Each ingress,
   transit, and egress node on the DAG is a junction and has a JUNCTION
   element associated with it.  A JUNCTION element contains the
   information necessary to provision a specific junction node in the
   computed DAG.  The onus is on the MPTED tunnel signaling source to
   signal and provision the MPTED junction on each junction node.
   Depending on the type of the MPTED tunnel and the signaling protocol
   used, the signaling source function may reside either on the PCC or
   the PCE.  This document also describes the extensions to PCEP that
   enable the PCE to act as an MPTED tunnel signaling source and manage
   the MPTED junctions on a junction node.

   As discussed in [I-D.draft-kompella-teas-mpte], an MPTED tunnel may
   be realized over a Multiprotocol Label Switching (MPLS) forwarding
   plane or a native Internet Protocol (IP) v4/v6 forwarding plane using
   an appropriate tunnel type.  The focus of this version of the
   document is on discussing how the PCEP protocol is extended to
   facilitate distributed and centralized provisioning of MPTED Tunnels
   over an MPLS forwarding plane in a TE network.

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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1.2.  Terminology

   The reader is expected to be familiar with the terminology used in
   [I-D.draft-kompella-teas-mpte].

2.  Modes of Operation

2.1.  PCC Initiated and PCC Signaled

   In this mode of operation, the PCC is the MPTED tunnel originator and
   the signaling source.  The PCC delegates the control of the MPTED
   tunnel to the PCE.  The PCE computes the MPTED, produces a set of
   JUNCTIONs, and puts the onus on the PCC to signal and provision the
   JUNCTION on each junction node. . After the signaling setup sequence
   is complete, the PCC notifies the PCE of the status of each junction
   in the DAG.  The MPTED tunnel setup is deemed complete on the PCE
   when all junction notifications are received from the PCC.  An
   example of this mode of operation is an MPLS deployment where RSVP
   MPTED tunnels that use signaled label switching originate on an
   ingress node, and the DAG computation is offloaded to the PCE.

                                 +---------+
                           .---->|   PCE   |
                     PCC  /      |         |
                     Init/       |  MPTED  |
                        /        | Computer|
                       /         +---------+
                      |
                      |
                      v
                 +----------+                  +--------+
                 |   PCC    |                  |Junction|
                 |          |    .------------>|  Node  |
                 |  MPTED   |   /  +--------+  +--------+
                 |  Tunnel  |  /   |Junction|
                 |Originator| /.-->|  Node  |
                 |          |//    +--------+
                 |  MPTED   |/                  +--------+
                 |Signaling |------------------>|Junction|
                 |  Source  |\     +--------+   |  Node  |
                 |    |     |\\    |Junction|   +--------+
                 |    v     | \.-->|  Node  |
                 |+--------+|  \   +--------+
                 ||Junction||   \               +--------+
                 ||  Node  ||    .------------->|Junction|
                 |+--------+|                   |  Node  |
                 +----------+                   +--------+




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                  Figure 1: PCC Initiated and PCC Signaled

2.2.  PCE Initiated and PCC Signaled

   In this mode of operation, the PCE serves as the MPTED tunnel
   originator, and the PCC acts as the signaling source.  The PCE
   computes the MPTED and initiates the setup process by providing the
   PCC a list of JUNCTIONs.  The PCC signals and provisions the JUNCTION
   on each junction node.  After the signaling setup sequence is
   complete, the PCC notifies the PCE of the status of each junction in
   the DAG.  The MPTED tunnel setup is deemed complete on the PCE when
   all junction notifications are received from the PCC.  An example of
   this mode of operation is an MPLS deployment where RSVP MPTED
   tunnels, which use signaled label switching, are originated and
   computed by the PCE.

                                 +----------+
                           .---->|   PCE    |
                     PCE  /      |          |
                     Init/       |  MPTED   |
                        /        |  Tunnel  |
                       /         |Originator|
                      |          |          |
                      |          |   MPTED  |
                      |          | Computer |
                      |          +----------+
                      |
                      |                        +--------+
                      v                        |Junction|
                 +----------+    .------------>|  Node  |
                 |          |   /  +--------+  +--------+
                 |   PCC    |  /   |Junction|
                 |          | /.-->|  Node  |
                 |          |//    +--------+
                 |  MPTED   |/                  +--------+
                 |Signaling |------------------>|Junction|
                 |  Source  |\     +--------+   |  Node  |
                 |    |     |\\    |Junction|   +--------+
                 |    v     | \.-->|  Node  |
                 |+--------+|  \   +--------+
                 ||Junction||   \               +--------+
                 ||  Node  ||    .------------->|Junction|
                 |+--------+|                   |  Node  |
                 +----------+                   +--------+

                  Figure 2: PCE Initiated and PCC Signaled





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2.3.  PCC Initiated and PCE Signaled

   In this mode of operation, the PCC serves as the MPTED tunnel
   originator, and the PCE acts as the signaling source.  The PCC
   delegates the control of the MPTED tunnel to the PCE.  The PCE
   computes the MPTED, produces a set of JUNCTIONs, and uses a signaling
   protocol to provision the JUNCTION on each junction node.  PCEP MAY
   be used as the signaling protocol on the PCE for junction management.
   The MPTED tunnel setup is deemed complete on the PCE when junction
   notifications are received from all junction nodes.  An example of
   this mode of operation with PCEP signaling for junction management is
   an MPLS deployment where Segment Routing MPTED tunnels, which use
   static labels, originate on an ingress node and are provisioned in
   the TE network by the PCE.

                                   +---------+
                       .---------->|   PCE   |
                 PCC  /            |         |
                 Init/             |  MPTED  |
                    /              | Computer|
                   /               |         |
                  /                |  MPTED  |
                 /             .---|Signaling|------.
                |             /    |  Source |       \
                |            /     +---------+        \
                v           /      /    |    \         \
           +----------+    /      /     |     \         |
           |   PCC    |   |      /      v      \        v
           |          |   |     /  +---------+  \  +---------+
           |  MPTED   |   |    |   |Junction |   | |Junction |
           |  Tunnel  |   |    |   |  Node   |   | |  Node   |
           |Originator|   |    |   +---------+   | +---------+
           |          |   |    |                 |
           |+--------+|<--'    |                 |
           ||Junction||       +---------+   +---------+
           ||  Node  ||       |Junction |   |Junction |
           |+--------+|       |  Node   |   |  Node   |
           +----------+       +---------+   +---------+

                  Figure 3: PCC Initiated and PCE Signaled











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2.4.  PCE Initiated and PCE Signaled

   In this mode of operation, the PCE serves as the MPTED tunnel
   originator and the signaling source.  The PCE computes the MPTED,
   produces a set of JUNCTIONs, and uses a signaling protocol to
   provision the JUNCTION on each junction node.  PCEP MAY be used as
   the signaling protocol on the PCE for junction management.  The MPTED
   tunnel setup is deemed complete on the PCE when junction
   notifications are received from all junction nodes.  An example of
   this mode of operation with PCEP signaling for junction management is
   an MPLS deployment where Segment Routing MPTED tunnels, which use
   static labels, are originated and provisioned in the TE network by
   the PCE.

                                   +----------+
                          .------->|   PCE    |
                         /         |          |
                        /          |  MPTED   |
                  PCE  /           |  Tunnel  |
                  Init/            |Originator|
                     /             |          |
                    /              |  MPTED   |
                   /               | Computer |
                  /                |          |
                 /                 |  MPTED   |
                |              .---|Signaling |------.
                |             /    |  Source  |       \
                |            /     +----------+        \
                |           /      /    |    \          \
                |          /      /     |     \          |
                |         |      /      v      \         v
                v         |     /  +---------+  \  +---------+
           +----------+   |    |   |Junction |   | |Junction |
           |          |   |    |   |  Node   |   | |  Node   |
           |   PCC    |   |    |   +---------+   | +---------+
           |          |   |    |                 |
           |+--------+|<--'    |                 |
           ||Junction||       +---------+   +---------+
           ||  Node  ||       |Junction |   |Junction |
           |+--------+|       |  Node   |   |  Node   |
           +----------+       +---------+   +---------+

                  Figure 4: PCE Initiated and PCE Signaled

3.  Protocol Extensions






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3.1.  Capability Negotiation

   Depending on the deployment needs and the signaling protocol used for
   junction management, one or more entities can perform the roles of
   (a) MPTED tunnel originator, (b) MPTED computer, and (c) MPTED
   signaling source.  The stakeholders involved in provisioning an MPTED
   tunnel in a stateful PCE model are the PCC, the PCE, and the junction
   nodes.  The capabilities of each stakeholder must be advertised to
   enable the assignment of an appropriate role for each stakeholder
   when originating an MPTED tunnel.

   The extensions to the capability negotiation procedures on the PCE
   and PCC will be discussed in a subsequent version.

3.2.  PCC Initiated MPTED Tunnels

   The protocol procedures to facilitate PCC initiated MPTED tunnels
   will be discussed in a subsequent version.

3.3.  PCE Initiated MPTED Tunnels

   The protocol procedures to facilitate PCE initiated MPTED tunnels
   will be discussed in a subsequent version.

3.4.  Signaling for Junction Management

   The procedures to facilitate junction management using PCEP signaling
   will be discussed in a subsequent version.

3.5.  PCEP Messages and Objects

   The definition of MPTED PCEP messages and objects will be furnished
   in a subsequent revision.

4.  Security Considerations

   The security considerations described in [RFC5440], [RFC8231], and
   [RFC8281] are applicable to this specification.  An unauthorized PCE
   may maliciously influence the paths traversed by traffic flows
   steered onto the MPTED tunnel by manipulating the state on the
   junction nodes.  The procedures described
   in [RFC8253] and [RFC9325] can be used to protect against this
   attack.

5.  Manageability Considerations

   This section will be updated in a subsequent version and will follow
   the advice and guidance of [RFC6123]



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6.  IANA Considerations

   This version of the document has no IANA actions.  The requests for
   appropriate IANA actions will be added in a subsequent version.

7.  References

7.1.  Normative References

   [I-D.draft-kompella-teas-mpte]
              Kompella, K., Jalil, L., Khaddam, M., and A. Smith,
              "Multipath Traffic Engineering", Work in Progress,
              Internet-Draft, draft-kompella-teas-mpte-01, 7 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-kompella-
              teas-mpte-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/rfc/rfc2119>.

   [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/rfc/rfc5440>.

   [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>.

   [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/rfc/rfc8231>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/rfc/rfc8253>.

   [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/rfc/rfc8281>.




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   [RFC9325]  Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/rfc/rfc9325>.

7.2.  Informative References

   [RFC6123]  Farrel, A., "Inclusion of Manageability Sections in Path
              Computation Element (PCE) Working Group Drafts", RFC 6123,
              DOI 10.17487/RFC6123, February 2011,
              <https://www.rfc-editor.org/rfc/rfc6123>.

Acknowledgments

   The authors would like to thank Sudharsana Venkatraman for her input
   from discussions.

   This document was prepared using kramdown.

Contributors

   Chandrasekar Ramachandran
   HPE
   Email: chandrasekar.ramachandran@hpe.com


Authors' Addresses

   Vishnu Pavan Beeram
   HPE
   Email: vishnupavan.ietf@gmail.com


   Kireeti Kompella
   Juniper Networks
   Email: kireeti.ietf@gmail.com


   Andrew Stone
   Nokia
   Email: andrew.stone@nokia.com









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