Internet Engineering Task Force (IETF) C. Li
Request for Comments: 9752 H. Zheng
Updates: 7470 Huawei Technologies
Category: Standards Track S. Sivabalan
ISSN: 2070-1721 Ciena
S. Sidor
Z. Ali
Cisco Systems, Inc.
March 2025
Conveying Vendor-Specific Information in the Path Computation Element
Communication Protocol (PCEP) Extensions for Stateful PCE
Abstract
This document specifies extensions to the Path Computation Element
Communication Protocol (PCEP) that enable the inclusion of vendor-
specific information in stateful Path Computation Element (PCE)
operations. These extensions allow vendors to incorporate
proprietary data within PCEP messages, facilitating enhanced network
optimization and functionality in environments requiring vendor-
specific features. The extensions maintain compatibility with
existing PCEP implementations and promote interoperability across
diverse network deployments. RFC 7470 defines a facility to carry
vendor-specific information in stateless PCEP messages. This
document extends this capability for the Stateful stateful PCEP messages.
This document updates RFC 7470 to revise the reference to specify that Enterprise numbers are
managed through the IANA
registry for managing "Private Enterprise Numbers. Numbers (PENs)" registry.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9752.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction
1.1. Requirements Language
1.2. Use of RBNF
2. Procedures for the Vendor Information Object
3. Procedures for the Vendor Information TLV
4. Manageability Considerations
4.1. Control of Function and Policy
4.2. Information and Data Models
4.3. Liveness Detection and Monitoring
4.4. Verifying Correct Operations
4.5. Requirements On Other Protocols
4.6. Impact on Network Operations
5. IANA Considerations
6. Security Considerations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
The Path Computation Element Communication Protocol (PCEP) [RFC5440]
provides mechanisms for a Path Computation Element (PCE) to perform
path computation in response to a Path Computation Client (PCC)
request.
A Stateful stateful PCE is capable of considering, for the purposes of path
computation, not only the network state in terms of links and nodes
(referred to as the Traffic Engineering Database or TED) but also the
status of active services (previously computed paths, and currently
reserved resources, stored in the Label Switched Paths Database (LSP-
DB)). [RFC8051] describes general considerations for a Stateful stateful PCE
deployment and examines its applicability and benefits, as well as
its challenges and limitations through a number of use cases.
[RFC8231] describes a set of extensions to PCEP to provide stateful
control. A Stateful stateful PCE has access to not only the information
carried by the network's Interior Gateway Protocol (IGP), but also
the set of active paths and their reserved resources for its
computations. The additional state allows the PCE to compute
constrained paths while considering individual LSPs and their
interactions. [RFC8281] describes the setup, maintenance, and
teardown of PCE-initiated LSPs under the Stateful stateful PCE model. These
extensions add new messages in PCEP for Stateful stateful PCE.
[RFC7470] defines the Vendor Information object, which can carry
arbitrary, proprietary information, such as vendor-specific
constraints, in stateless PCEP. It also defines the VENDOR-
INFORMATION-TLV, which allows arbitrary information to be embedded
within any existing or future PCEP object that supports TLVs.
While originally designed for stateless PCEP, the Vendor Information
object and VENDOR-INFORMATION-TLV are also useful in the Stateful stateful PCE
model. The VENDOR-INFORMATION-TLV can already be included in any of
the stateful PCEP objects per [RFC7470]. This document further
extends stateful PCEP messages to support the use of the Vendor
Information object.
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. Use of RBNF
The message formats in this document are illustrated using Routing
Backus-Naur Form (RBNF) encoding, as specified in [RFC5511]. The use
of RBNF is illustrative only and may omit certain important details;
the normative specification of messages is found in the descriptive
text. If there is any divergence between the RBNF and the
descriptive text, the descriptive text is considered authoritative.
2. Procedures for the Vendor Information Object
A Path Computation LSP State Report message (also referred to as
PCRpt message; see Section 6.1 of [RFC8231]) is a PCEP message sent
by a PCC to a PCE to report the current state of an LSP. A PCC that
wants to convey proprietary or vendor-specific information or metrics
to a PCE does so by including a Vendor Information object in the
PCRpt message. The contents and format of the object, including the
VENDOR-INFORMATION object and the VENDOR-INFORMATION-TLV, are
described in Section 4 of [RFC7470]. The PCE determines how to
interpret the information in the Vendor Information object by
examining the Enterprise Number it contains.
[RFC7470] stated that:
| Enterprise Numbers are assigned by IANA and managed through an
| IANA registry [RFC2578].
This document updates [RFC7470] and replaces this text with:
| Enterprise Numbers are assigned by IANA and managed through the
| "Private Enterprise Numbers (PENs)" registry as described in
| [RFC9371].
The Vendor Information object is OPTIONAL in a PCRpt message.
Multiple instances of the object MAY be contained in a single PCRpt
message. Different instances of the object MAY have different
Enterprise Numbers.
The format of the PCRpt message (with Section 6.1 of [RFC8231] as the
base) is updated as follows:
<PCRpt Message> ::= <Common Header>
<state-report-list>
Where:
<state-report-list> ::= <state-report>[<state-report-list>]
<state-report> ::= [<SRP>]
<LSP>
<path>
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<path> is defined in [RFC8231].
A Path Computation LSP Update Request message (also referred to as
PCUpd message; see Section 6.2 of [RFC8231]) is a PCEP message sent
by a PCE to a PCC to update the attributes of an LSP. The Vendor
Information object can be included in a PCUpd message to convey
proprietary or vendor-specific information.
The format of the PCUpd message (with (using the format described in
Section 6.2 of [RFC8231] as the base) is updated as follows:
<PCUpd Message> ::= <Common Header>
<update-request-list>
Where:
<update-request-list> ::= <update-request>
[<update-request-list>]
<update-request> ::= <SRP>
<LSP>
<path>
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<path> is defined in [RFC8231].
A Path Computation LSP Initiate Message (also referred to as
PCInitiate message; see Section 5.1 of [RFC8281]) is a PCEP message
sent by a PCE to a PCC to trigger an LSP instantiation or deletion.
The Vendor Information object can be included in a PCInitiate message
to convey proprietary or vendor-specific information.
The format of the PCInitiate message (with (using the format described in
Section 5.1 of [RFC8281] as the base) is updated as follows:
<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
[<PCE-initiated-lsp-list>]
<PCE-initiated-lsp-request> ::=
(<PCE-initiated-lsp-instantiation>|
<PCE-initiated-lsp-deletion>)
<PCE-initiated-lsp-instantiation> ::= <SRP>
<LSP>
[<END-POINTS>]
<ERO>
[<attribute-list>]
[<vendor-info-list>]
Where:
<vendor-info-list> ::= <VENDOR-INFORMATION>
[<vendor-info-list>]
<PCE-initiated-lsp-deletion> and <attribute-list> are as defined in
[RFC8281].
A legacy implementation that does not recognize the Vendor
Information object will act according to the procedures set out in
[RFC8231] and [RFC8281]. An implementation that supports the Vendor
Information object, but receives one carrying an Enterprise Number
that it does not support, MUST ignore the object in the same way as
described in Section 2 of [RFC7470].
3. Procedures for the Vendor Information TLV
The Vendor Information TLV can be used to carry vendor-specific
information that applies to a specific PCEP object by including the
TLV in the object. This includes objects used in Stateful PCE
extensions such as Stateful PCE Request Parameter (SRP) and LSP
objects. All of the procedures are as described in Section 3 of
[RFC7470].
4. Manageability Considerations
All manageability requirements and considerations listed in
[RFC5440], [RFC7470], [RFC8231], and [RFC8281] apply to the PCEP
protocol extensions defined in this document. In addition, the
requirements and considerations listed in this section apply.
4.1. Control of Function and Policy
The requirements for control of function and policy for vendor-
specific information as set out in [RFC7470] continue to apply to
Stateful PCEP extensions specified in this document.
4.2. Information and Data Models
The PCEP YANG module is specified in [PCEP-YANG]. Any standard YANG
module will not include details of vendor-specific information.
However, a standard YANG module could be extended to report the use
of the Vendor Information object or TLV and the Enterprise Numbers
that the objects and TLVs contain.
4.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
4.4. Verifying Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440] and [RFC8231].
4.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
4.6. Impact on Network Operations
Mechanisms defined in [RFC5440] and [RFC8231] also apply to PCEP
extensions defined in this document.
Section 6.6 of [RFC7470] highlights how the presence of additional
vendor-specific information in PCEP messages may congest the
operations and how to detect and handle it. This also applies to
stateful PCEP messages as outlined in Section 2. Specifically, a
PCEP speaker SHOULD NOT include vendor information in stateful PCEP
message if it believes the recipient does not support that
information.
Encoding optimization for the Vendor Information object, for example,
in case the object has the same content encoded for multiple LSPs, is
considered out of the scope of this document and may be proposed in
the future as a separate document applicable to other PCEP objects.
5. IANA Considerations
This document has no IANA actions.
6. Security Considerations
The protocol extensions defined in this document do not change the
nature of PCEP. Therefore, the security considerations set out in
[RFC5440], [RFC7470], [RFC8231], and [RFC8281] apply unchanged.
As per
Per [RFC8231], it is RECOMMENDED that these PCEP extensions only be
activated on authenticated and encrypted sessions across PCEs and
PCCs using Transport Layer Security (TLS) [RFC8253], as per [RFC8253]. See the
recommendations and best current practices for using TLS in RFC 9325
[BCP195].
The use of vendor-specific information as defined in [RFC7470] and in
this document may provide a covert channel that could be misused by
PCEP speaker implementations or by malicious software at PCEP
speakers. While there is limited protection against this, an
operator monitoring the PCEP sessions can detect the use of vendor-
specific information, be aware of the decoding mechanism for this
data, and inspect it accordingly. It is crucial for the operator to
remain vigilant and monitor for any potential misuse of this object.
Appropriate steps need to be taken to prevent the installation of
malicious software at the PCEP speaker by implementing robust
integrity, authentication, and authorization techniques for
installation and updating, which are out of scope of this document.
7. References
7.1. Normative References
[BCP195] Best Current Practice 195,
<https://www.rfc-editor.org/info/bcp195>.
At the time of writing, this BCP comprises the following:
Moriarty, K. and S. Farrell, "Deprecating TLS 1.0 and TLS
1.1", BCP 195, RFC 8996, DOI 10.17487/RFC8996, March 2021,
<https://www.rfc-editor.org/info/rfc8996>.
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/info/rfc9325>.
[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>.
[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>.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511, April
2009, <https://www.rfc-editor.org/info/rfc5511>.
[RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
<https://www.rfc-editor.org/info/rfc7470>.
[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>.
[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>.
[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>.
7.2. Informative References
[PCEP-YANG]
Dhody, D., Ed., Beeram, V. P., Hardwick, J., and J.
Tantsura, "A YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
Internet-Draft, draft-ietf-pce-pcep-yang-30, 26 January
2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
pce-pcep-yang-30>.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578,
DOI 10.17487/RFC2578, April 1999,
<https://www.rfc-editor.org/info/rfc2578>.
[RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
Stateful Path Computation Element (PCE)", RFC 8051,
DOI 10.17487/RFC8051, January 2017,
<https://www.rfc-editor.org/info/rfc8051>.
[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/info/rfc8253>.
[RFC9371] Baber, A. and P. Hoffman, "Registration Procedures for
Private Enterprise Numbers (PENs)", RFC 9371,
DOI 10.17487/RFC9371, March 2023,
<https://www.rfc-editor.org/info/rfc9371>.
Acknowledgments
Thanks to Dhruv Dhody for shepherding the document and for their
significant contributions and suggestions.
Thanks to Adrian Farrel, Avantika, Deb Cooley, Éric Vyncke, Gunter
Van de Velde, John Scudder, Mahendra Singh Negi, Mahesh Jethanandani,
Mike McBride, Murray Kucherawy, Orie Steele, Paul Wouters, Roman
Danyliw, Susan Hares, Swapna K, Udayasree Palle, Warren Kumari,
Wassim Haddad, and Xiao Min for their reviews, comments and
suggestions.
Contributors
Dhruv Dhody
Huawei
India
Email: dhruv.ietf@gmail.com
Mike Koldychev
Ciena
Email: mkoldych@proton.me
Authors' Addresses
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing
100095
China
Email: c.l@huawei.com
Haomian Zheng
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan
Guangdong, 523808
China
Email: zhenghaomian@huawei.com
Siva Sivabalan
Ciena
385 Terry Fox Drive
Kanata Ontario K2K 0L1
Canada
Email: msiva282@gmail.com
Samuel Sidor
Cisco Systems, Inc.
Email: ssidor@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com