Path Computation Element Communication Protocol (PCEP) Extensions for Multipath Traffic Engineered Directed Acyclic Graph (MPTED) Tunnels
draft-beeram-pce-pcep-mpted-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Vishnu Pavan Beeram , Kireeti Kompella | ||
| Last updated | 2025-07-07 | ||
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draft-beeram-pce-pcep-mpted-00
PCEP Working Group V. P. Beeram
Internet-Draft K. Kompella
Intended status: Standards Track Juniper Networks
Expires: 8 January 2026 7 July 2025
Path Computation Element Communication Protocol (PCEP) Extensions for
Multipath Traffic Engineered Directed Acyclic Graph (MPTED) Tunnels
draft-beeram-pce-pcep-mpted-00
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
Task Force (IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 8 January 2026.
Copyright Notice
Copyright (c) 2025 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
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extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
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
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
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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.
1.2. Terminology
The reader is expected to be familiar with the terminology used in
[I-D.draft-kompella-teas-mpte].
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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 |
+----------+ +--------+
Figure 1: PCC Initiated and PCC Signaled
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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-00, 3 March 2025,
<https://datatracker.ietf.org/doc/html/draft-kompella-
teas-mpte-00>.
[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
Juniper Networks
Email: csekar@juniper.net
Authors' Addresses
Vishnu Pavan Beeram
Juniper Networks
Email: vbeeram@juniper.net
Kireeti Kompella
Juniper Networks
Email: kireeti.ietf@gmail.com
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