RFC 9756 | PCEP IANA Update | March 2025
Dhody & Farrel | Standards Track | [Page]

Stream:
  Internet Engineering Task Force (IETF)
RFC:
  9756
Updates:
  5440, 8231, 8233, 8281, 8623, 8664, 8685, 8697, 8733, 8745, 8779, 8780, 8800, 8934, 9050, 9059, 9168, 9357, 9504, 9603, 9604
Category:
  Standards Track
Published:
  March 2025
ISSN:
  2070-1721
Authors:
  D. Dhody
  Huawei
  A. Farrel
  Old Dog Consulting

# RFC 9756

# Update to the IANA Path Communication Element Protocol (PCEP) Numbers Registration Procedures and the Allowance of Experimental Error Codes

## Abstract

This document updates the registration procedure within the IANA "Path Computation Element Protocol (PCEP) Numbers" registry group. This specification changes some of the registries with Standards Action to IETF Review as defined in RFC 8126 and thus updates RFCs 8231, 8233, 8281, 8623, 8664, 8685, 8697, 8733, 8745, 8779, 8780, 8800, 8934, 9050, 9059, 9168, 9357, 9504, 9603, and 9604.¶

Designating "experimental use" sub-ranges within codepoint registries is often beneficial for protocol experimentation in controlled environments. Although the registries for PCEP messages, objects, and TLV types have sub-ranges assigned for Experimental Use, the registry for PCEP Error-Types and Error-values currently does not. This document updates RFC 5440 by designating a specific range of PCEP Error-Types for Experimental Use.¶

## 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/rfc9756.¶

## 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 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.¶

## 1. Introduction

The IANA "Path Computation Element Protocol (PCEP) Numbers" registry group was populated by several RFCs produced by the Path Computation Element (PCE) Working Group. Most of the registries include IETF Review [RFC8126] as the registration procedure. There are a few registries that use Standards Action. Thus, the values in those registries can be assigned only through the Standards Track or Best Current Practice RFCs in the IETF Stream. This memo changes the policy from Standards Action to IETF Review to allow any type of RFC under the IETF Stream to make the allocation request.¶

Further, in Section 9 of [RFC5440], IANA assigns values to the PCEP parameters. The allocation policy for each of these parameters specified in [RFC5440] is IETF Review [RFC8126]. In consideration of the benefits of conducting experiments with PCEP and the utility of experimental codepoints [RFC3692], codepoint ranges for PCEP messages, objects, and TLV types for Experimental Use [RFC8126] are designated in [RFC8356]. However, protocol experiments may also need to return protocol error messages indicating experiment-specific error cases. It will often be that previously assigned error codes (in the "PCEP-ERROR Object Error Types and Values" registry) can be used to indicate the error cases within an experiment, but there may also be instances where new, experimental error codes are needed. In order to run experiments, it is important that the codepoint values used in the experiments do not collide with existing codepoints or any future allocations. This document updates [RFC5440] by changing the allocation policy for the registry of PCEP Error-Types to mark some of the codepoints as assigned for Experimental Use. As stated in [RFC3692], experiments using these codepoints are not intended to be used in general deployments, and due care must be taken to ensure that two experiments using the same codepoints are not run in the same environment.¶

## 2. Standards Action PCEP Registries Affected

The following table lists the registries under the "Path Computation Element Protocol (PCEP) Numbers" registry group whose registration policies have been changed from Standards Action to IETF Review. The affected registries list this document as an additional reference. Where this change has been applied to a specific range of values within the particular registry, that range is given in the Remarks column.¶

Table 1: PCEP Registries Affected
Registry | RFC | Remarks
--- | --- | ---
BU Object Type Field | [RFC8233] |
LSP Object Flag Field | [RFC8231] |
STATEFUL-PCE-CAPABILITY TLV Flag Field | [RFC8231] |
LSP-ERROR-CODE TLV Error Code Field | [RFC8231] |
SRP Object Flag Field | [RFC8281] |
SR-ERO Flag Field | [RFC8664] |
PATH-SETUP-TYPE-CAPABILITY Sub-TLV Type Indicators | [RFC8664] |
SR Capability Flag Field | [RFC8664] |
WA Object Flag Field | [RFC8780] |
Wavelength Restriction TLV Action Values | [RFC8780] |
Wavelength Allocation TLV Flag Field | [RFC8780] |
S2LS Object Flag Field | [RFC8623] |
H-PCE-CAPABILITY TLV Flag Field | [RFC8685] |
H-PCE-FLAG TLV Flag Field | [RFC8685] |
ASSOCIATION Flag Field | [RFC8697] |
ASSOCIATION Type Field | [RFC8697] |
AUTO-BANDWIDTH-CAPABILITY TLV Flag Field | [RFC8733] |
Path Protection Association Group TLV Flag Field | [RFC8745] |
Generalized Endpoint Types | [RFC8779] | 0-244
GMPLS-CAPABILITY TLV Flag Field | [RFC8779] |
DISJOINTNESS-CONFIGURATION TLV Flag Field | [RFC8800] |
SCHED-PD-LSP-ATTRIBUTE TLV Opt Field | [RFC8934] |
Schedule TLVs Flag Field | [RFC8934] |
FLOWSPEC Object Flag Field | [RFC9168] |
Bidirectional LSP Association Group TLV Flag Field | [RFC9059] |
PCECC-CAPABILITY sub-TLV | [RFC9050] |
CCI Object Flag Field for MPLS Label | [RFC9050] |
TE-PATH-BINDING TLV BT Field | [RFC9604] |
TE-PATH-BINDING TLV Flag Field | [RFC9604] |
LSP-EXTENDED-FLAG TLV Flag Field | [RFC9357] |
LSP Exclusion Subobject Flag Field | [RFC9504] |
SRv6-ERO Flag Field | [RFC9603] |
SRv6 Capability Flag Field | [RFC9603] |

Future registries in the "Path Computation Element Protocol (PCEP) Numbers" registry group should prefer to use IETF Review over Standards Action.¶

## 3. Experimental Error-Types

Per this document, IANA has designated four PCEP Error-Type codepoints (252-255) for Experimental Use.¶

IANA maintains the "PCEP-ERROR Object Error Types and Values" registry under the "Path Computation Element Protocol (PCEP) Numbers" registry group. IANA has changed the assignment policy for the "PCEP-ERROR Object Error Types and Values" registry as follows:¶

Table 2: PCEP-ERROR Object Error Types and Values Registry Assignment Policy
Range | Registration Procedures | Note
--- | --- | ---
0-251 | IETF Review | The IETF Review procedure applies to all Error-values (0-255) for Error-Types in this range.
252-255 | Experimental Use | The Experimental Use policy applies to all Error-values (0-255) for Error-Types in this range.

Furthermore, IANA has added the following entry to the registry:¶

Table 3: PCEP-ERROR Object Error Types and Values Registry
Error-Type | Meaning | Error-value | Reference
--- | --- | --- | ---
252-255 | Reserved for Experimental Use | 0-255: Reserved for Experimental Use | RFC 9756

### 3.1. Advice on Experimentation

An experiment that wishes to return experimental error codes should use one of the experimental Error-Type values as defined in this document. The experiment should agree on, between all participating parties, which Error-Type to use and which Error-values to use within that Error-Type. The experiment will describe what the meanings of those Error-Type/Error-value pairs are. Those Error-Types and Error-values should not be recorded in any public (especially any IETF) documentation. Textual or symbolic names for the Error-Types and Error-values may be used to help keep the documentation clear.¶

If multiple experiments are taking place at the same time using the same implementations, care must be taken to keep the sets of Error-Types/Error-values distinct.¶

Note that there is no scope for experimental Error-values within existing non-experimental Error-Types. This reduces the complexity of the registry and implementations. Experiments should place all experimental Error-values under the chosen experimental Error-Types.¶

If, at some future time, the experiment is declared a success and moved to IETF work targeting publication on the Standards Track, each pair of Error-Types/Error-values will need to be assigned by IANA from the registry. In some cases, this will involve assigning a new Error-Type with its subtended Error-values. In other cases, use may be made of an existing Error-Type with new subtended Error-values being assigned. The resulting change to code in an implementation is as simple as changing the numeric values of the Error-Types and Error-values.¶

### 3.2. Handling of Unknown Experimentation

A PCEP implementation that receives an experimental Error-Type in a PCEP message and does not recognize the Error-Type (i.e., is not part of the experiment) will treat the error as it would treat any other unknown Error-Type (such as from a new protocol extension). An implementation that is notified of a PCEP error will normally close the PCEP session (see [RFC5440]). In general, PCEP implementations are not required to take specific action based on Error-Types but may log the errors for diagnostic purposes.¶

An implementation that is part of an experiment may receive an experimental Error-Type but not recognize the Error-value. This could happen because of any of the following reasons:¶

- a faulty implementation¶

- two implementations not being synchronized with respect to which Error-values to use in the experiment¶

- more than one experiment being run at the same time¶

As with unknown Error-Types, an implementation receiving an unknown Error-value is not expected to do more than log the received error and may close the PCEP session.¶

## 4. IANA Considerations

This memo is entirely about updating the IANA "Path Computation Element Protocol (PCEP) Numbers" registry group.¶

## 5. Security Considerations

This memo does not change the security considerations for any of the updated RFCs. Refer to [RFC5440] and [PCEPS-UPDATES] for further details of the specific security measures applicable to PCEP.¶

[RFC3692] asserts that the existence of experimental codepoints introduces no new security considerations. However, implementations accepting experimental error codepoints need to consider how they parse and process them in case they come, accidentally, from another experiment. Further, an implementation accepting experimental codepoints needs to consider the security aspects of the experimental extensions. [RFC6709] provides various design considerations for protocol extensions (including those designated as experimental).¶

## 6. References

### 6.1. Normative 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>.
[RFC8126]
  Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>.
[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>.
[RFC8233]
  Dhody, D., Wu, Q., Manral, V., Ali, Z., and K. Kumaki, "Extensions to the Path Computation Element Communication Protocol (PCEP) to Compute Service-Aware Label Switched Paths (LSPs)", RFC 8233, DOI 10.17487/RFC8233, September 2017, <https://www.rfc-editor.org/info/rfc8233>.
[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>.
[RFC8356]
  Dhody, D., King, D., and A. Farrel, "Experimental Codepoint Allocation for the Path Computation Element Communication Protocol (PCEP)", RFC 8356, DOI 10.17487/RFC8356, March 2018, <https://www.rfc-editor.org/info/rfc8356>.
[RFC8623]
  Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful Path Computation Element (PCE) Protocol Extensions for Usage with Point-to-Multipoint TE Label Switched Paths (LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019, <https://www.rfc-editor.org/info/rfc8623>.
[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>.
[RFC8685]
  Zhang, F., Zhao, Q., Gonzalez de Dios, O., Casellas, R., and D. King, "Path Computation Element Communication Protocol (PCEP) Extensions for the Hierarchical Path Computation Element (H-PCE) Architecture", RFC 8685, DOI 10.17487/RFC8685, December 2019, <https://www.rfc-editor.org/info/rfc8685>.
[RFC8697]
  Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H., Dhody, D., and Y. Tanaka, "Path Computation Element Communication Protocol (PCEP) Extensions for Establishing Relationships between Sets of Label Switched Paths (LSPs)", RFC 8697, DOI 10.17487/RFC8697, January 2020, <https://www.rfc-editor.org/info/rfc8697>.
[RFC8733]
  Dhody, D., Ed., Gandhi, R., Ed., Palle, U., Singh, R., and L. Fang, "Path Computation Element Communication Protocol (PCEP) Extensions for MPLS-TE Label Switched Path (LSP) Auto-Bandwidth Adjustment with Stateful PCE", RFC 8733, DOI 10.17487/RFC8733, February 2020, <https://www.rfc-editor.org/info/rfc8733>.
[RFC8745]
  Ananthakrishnan, H., Sivabalan, S., Barth, C., Minei, I., and M. Negi, "Path Computation Element Communication Protocol (PCEP) Extensions for Associating Working and Protection Label Switched Paths (LSPs) with Stateful PCE", RFC 8745, DOI 10.17487/RFC8745, March 2020, <https://www.rfc-editor.org/info/rfc8745>.
[RFC8779]
  Margaria, C., Ed., Gonzalez de Dios, O., Ed., and F. Zhang, Ed., "Path Computation Element Communication Protocol (PCEP) Extensions for GMPLS", RFC 8779, DOI 10.17487/RFC8779, July 2020, <https://www.rfc-editor.org/info/rfc8779>.
[RFC8780]
  Lee, Y., Ed. and R. Casellas, Ed., "The Path Computation Element Communication Protocol (PCEP) Extension for Wavelength Switched Optical Network (WSON) Routing and Wavelength Assignment (RWA)", RFC 8780, DOI 10.17487/RFC8780, July 2020, <https://www.rfc-editor.org/info/rfc8780>.
[RFC8800]
  Litkowski, S., Sivabalan, S., Barth, C., and M. Negi, "Path Computation Element Communication Protocol (PCEP) Extension for Label Switched Path (LSP) Diversity Constraint Signaling", RFC 8800, DOI 10.17487/RFC8800, July 2020, <https://www.rfc-editor.org/info/rfc8800>.
[RFC8934]
  Chen, H., Ed., Zhuang, Y., Ed., Wu, Q., and D. Ceccarelli, "PCE Communication Protocol (PCEP) Extensions for Label Switched Path (LSP) Scheduling with Stateful PCE", RFC 8934, DOI 10.17487/RFC8934, October 2020, <https://www.rfc-editor.org/info/rfc8934>.
[RFC9050]
  Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "Path Computation Element Communication Protocol (PCEP) Procedures and Extensions for Using the PCE as a Central Controller (PCECC) of LSPs", RFC 9050, DOI 10.17487/RFC9050, July 2021, <https://www.rfc-editor.org/info/rfc9050>.
[RFC9059]
  Gandhi, R., Ed., Barth, C., and B. Wen, "Path Computation Element Communication Protocol (PCEP) Extensions for Associated Bidirectional Label Switched Paths (LSPs)", RFC 9059, DOI 10.17487/RFC9059, June 2021, <https://www.rfc-editor.org/info/rfc9059>.
[RFC9168]
  Dhody, D., Farrel, A., and Z. Li, "Path Computation Element Communication Protocol (PCEP) Extension for Flow Specification", RFC 9168, DOI 10.17487/RFC9168, January 2022, <https://www.rfc-editor.org/info/rfc9168>.
[RFC9357]
  Xiong, Q., "Label Switched Path (LSP) Object Flag Extension for Stateful PCE", RFC 9357, DOI 10.17487/RFC9357, February 2023, <https://www.rfc-editor.org/info/rfc9357>.
[RFC9504]
  Lee, Y., Zheng, H., Gonzalez de Dios, O., Lopez, V., and Z. Ali, "Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE Usage in GMPLS-Controlled Networks", RFC 9504, DOI 10.17487/RFC9504, December 2023, <https://www.rfc-editor.org/info/rfc9504>.
[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>.
[RFC9604]
  Sivabalan, S., Filsfils, C., Tantsura, J., Previdi, S., and C. Li, Ed., "Carrying Binding Label/SID in PCE-Based Networks", RFC 9604, DOI 10.17487/RFC9604, August 2024, <https://www.rfc-editor.org/info/rfc9604>.

### 6.2. Informative References

[PCEPS-UPDATES]
  Dhody, D., Turner, S., and R. Housley, "Updates for PCEPS: TLS Connection Establishment Restrictions", Work in Progress, Internet-Draft, draft-ietf-pce-pceps-tls13-04, 9 January 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-pce-pceps-tls13-04>.
[RFC3692]
  Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", BCP 82, RFC 3692, DOI 10.17487/RFC3692, January 2004, <https://www.rfc-editor.org/info/rfc3692>.
[RFC6709]
  Carpenter, B., Aboba, B., Ed., and S. Cheshire, "Design Considerations for Protocol Extensions", RFC 6709, DOI 10.17487/RFC6709, September 2012, <https://www.rfc-editor.org/info/rfc6709>.

## Appendix A. Rationale for Updating All Registries with Standards Action

This specification updates all the mentioned registries with the Standards Action policy. The PCE WG considered keeping Standards Action for some registries, such as flag fields with limited bits where the space is tight, but decided against it. The Working Group Last Call and IETF Last Call processes should be enough to handle the case of frivolous experiments taking over the few codepoints. The working group could also create a new protocol field and registry for future use as done in the past (see [RFC9357]).¶

## Appendix B. Consideration of RFC 8356

It is worth noting that [RFC8356] deliberately chose to make experimental codepoints available only in the PCEP messages, objects, and TLV type registries. Appendix A of [RFC8356] gives a brief explanation of why that decision was taken, stating that:¶

> The justification for this decision is that, if an experiment finds that it wants to use a new codepoint in another PCEP sub-registry, it can implement the same function using a new experimental object or TLV instead.¶

While it is true that an experimental implementation could assign an experimental PCEP object and designate it the "experimental errors object", using it to carry arbitrary contents including experimental error codes, such an approach would cause unnecessary divergence in the code. The allowance of experimental Error-Types is a better approach that will more easily enable the migration of successful experiments onto the Standards Track.¶

## Acknowledgements

Thanks to John Scudder for the initial discussion behind this document. Thanks to Ketan Talaulikar, Andrew Stone, Samuel Sidor, Quan Xiong, Cheng Li, and Aijun Wang for the review comments. Thanks to Carlos Pignataro for the OPSDIR review. Thanks to Meral Shirazipour for the GENART review. Thanks to Paul Kyzivat for the ArtArt review. Thanks to Alexey Melnikov for the SECDIR review.¶

## Contributors

## Authors' Addresses