RFC 9863 | PCEP Color | October 2025
Rajagopalan, et al. | Standards Track | [Page]

Stream:
  Internet Engineering Task Force (IETF)
RFC:
  9863
Category:
  Standards Track
Published:
  October 2025
ISSN:
  2070-1721
Authors:
  B. Rajagopalan
  Juniper Networks
  V. Beeram
  Juniper Networks
  S. Peng
  ZTE Corporation
  M. Koldychev
  Ciena Corporation
  G. Mishra
  Verizon Communications Inc.

# RFC 9863

# Path Computation Element Protocol (PCEP) Extension for Color

## Abstract

Color is a 32-bit numerical (unsigned integer) attribute used to associate a Traffic Engineering (TE) tunnel or policy with an intent or objective. For example, a TE Tunnel constructed to deliver low latency services and whose path is optimized for delay can be tagged with a color that represents "low latency." This document specifies extensions to the Path Computation Element Protocol (PCEP) to carry the color attribute.¶

## 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/rfc9863.¶

## 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

A Traffic Engineering (TE) Tunnel [RFC3209] or Segment Routing (SR) policy [RFC9256] can be associated with an intent or objective (e.g., low latency) by tagging it with a color. This color attribute is used as a guiding criterion for mapping services onto the TE Tunnel [RFC9012] or SR Policy [RFC9256]. The term "color" used in this document must not be interpreted as the "thread color" specified in [RFC3063] or the "resource color" (also referred to as "link color") specified in [RFC3630], [RFC5329], [RFC5305], and [RFC7308].¶

[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. [RFC8664] specifies extensions that enable stateful control of SR paths via PCEP.¶

This document introduces extensions to PCEP to allow a color tag to be assigned to any TE path operated under a stateful PCE model (including those set up using RSVP-TE [RFC8408] or Segment Routing [RFC8664]). The only exception where the extensions defined in this document MUST NOT be used to carry the color attribute is for SR paths established using the extensions defined in [RFC9862]. For these SR paths, the associated color is already included as part of the SR Policy identifier encoding.¶

The mechanism employed by the PCC for mapping services onto a TE path associated with a color attribute is outside the scope of this document, as is any other use of the color tag.¶

### 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. Protocol Operation

When the PCEP session is created, a PCEP (PCE/PCC) speaker sends an Open message with an OPEN object that contains the STATEFUL-PCE-CAPABILITY TLV, as defined in [RFC8231]. A STATEFUL-PCE-CAPABILITY TLV Flag (see Section 3.1) is introduced in this document to enable the PCEP speaker to advertise color capability.¶

In PCRpt, PCUpd, and PCInitiate messages, the LSP object [RFC8231] [RFC8281] is a mandatory inclusion and is used to carry information specific to the target LSP. A TLV called the COLOR TLV (see Section 3.2), which MAY be carried in the LSP object, is introduced in this document to carry the color attribute associated with the LSP. Only one COLOR TLV SHOULD be included in the LSP object. If the COLOR TLV appears in the LSP object more than once, only the first occurrence is processed, and any others MUST be ignored.¶

A PCEP speaker that has advertised color capability MUST NOT send COLOR TLV encoded in the LSP object to a PCEP Peer [RFC5440] that has not advertised color capability. A PCEP speaker that advertises both color capability and SR Policy Association [RFC9862] capability MUST NOT send COLOR TLV encoded in the LSP object for SR Paths. The COLOR TLV is ignored if it shows up in the LSP object of a message that carries an ASSOCIATION object of type SR Policy Association [RFC9862]. The color encoded in the SR Policy Association takes precedence in such a scenario.¶

If a PCC is unable to honor a color value passed in a PCUpd or a PCInitiate message, the PCC MUST reject the message and send a PCErr message with Error-Type=19 (Invalid Operation) and Error-value=31 (Invalid color). This is expected behavior in scenarios where a PCC implementation does not support a color value of zero for specific path setup types, and it receives that value in the COLOR TLV of a PCUpd or a PCInitiate message.¶

When LSPs that belong to the same TE Tunnel are within the same Path Protection Association Group [RFC8745], they are all expected to have the same color attached to them. If a PCEP speaker determines inconsistency in the color associated with the LSPs belonging to the same Path Protection Association Group, it MUST reject the message carrying the inconsistent color and send a PCErr message with Error-Type=19 (Invalid Operation) and Error-value=32 (Inconsistent color).¶

## 3. Protocol Extensions

### 3.1. Color Capability

Section 7.1.1 of [RFC8231] defines STATEFUL-PCE-CAPABILITY TLV flags. The following flag is used to indicate if the speaker supports color capability:¶

C-bit (Bit 20):
  A PCE/PCC indicates that it supports the color capability defined in this document by setting this bit.¶

### 3.2. COLOR TLV

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type                      |          Length=4             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Color                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: COLOR TLV

Type:
  67¶
Length:
  4¶
Color:
  4-byte field that carries the actual color value (specified as an unsigned integer). A value of zero is allowed.¶

## 4. Security Considerations

This document defines a TLV for color and a flag for color capability negotiation, which do not add any security concerns beyond those discussed in [RFC5440], [RFC8231], and [RFC8281].¶

An unauthorized PCE may maliciously associate the LSP with an incorrect color. The procedures described in [RFC8253] and [RFC9325] can be used to protect against this attack.¶

## 5. Manageability Considerations

This section follows the advice and guidance of [RFC6123].¶

### 5.1. Control of Function through Configuration and Policy

An implementation supporting this document SHOULD allow the operator to turn on and off the PCEP color capability advertisement (Section 3.1). An implementation supporting this document SHOULD allow the configuration of color assignment to a TE Tunnel or an SR Policy. A PCC MAY have a local policy configuration that specifies how the color tag is used. This policy configuration is outside the scope of this document.¶

### 5.2. Information and Data Models

An implementation supporting this document SHOULD allow the inclusion of color in the data model used to retrieve the operational state of a TE Tunnel or an SR Policy. The YANG model in [YANG-TE] could be used to retrieve the operational state of a TE Tunnel, and the YANG model in [SR-POLICY-YANG] could be used to retrieve the operational state of an SR Policy.¶

### 5.3. Liveness Detection and Monitoring

The extensions defined in this document do not require any additional liveness detection and monitoring support. See [RFC5440] and [RFC5886] for more information.¶

### 5.4. Verifying Correct Operation

The operator MAY retrieve the operational state of TE Paths to verify if they are tagged with the correct intended color.¶

### 5.5. Requirements on Other Protocols

This document places no explicit requirements on other protocols.¶

### 5.6. Impact on Network Operation

The impact on network operations depends on how the color tag is used in the deployment. This is outside the scope of this document.¶

## 6. IANA Considerations

### 6.1. PCEP TLV Type Indicator

IANA has assigned a value in the "PCEP TLV Type Indicators" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group as follows:¶

Table 1
Value | Description | Reference
--- | --- | ---
67 | Color | RFC 9863

### 6.2. STATEFUL-PCE-CAPABILITY TLV Flag Field

IANA has assigned a bit value in the "STATEFUL-PCE-CAPABILITY TLV Flag Field" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group as follows:¶

Table 2
Value | Description | Reference
--- | --- | ---
20 | COLOR-CAPABILITY | RFC 9863

### 6.3. PCEP-Error Object

IANA has assigned two Error-values for Error-Type=19 (Invalid Operation) within the "PCEP-ERROR Object Error Types and Values" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group as follows:¶

Table 3
Error-Type | Meaning | Error-value | Reference
--- | --- | --- | ---
19 | Invalid Operation | 31: Invalid Color | RFC 9863
32: Inconsistent Color | RFC 9863

### 6.4. LSP-ERROR-CODE TLV Error Code Field

A draft version of this document added an error code in the "LSP-ERROR-CODE TLV Error Code Field" registry of the "Path Computation Element Protocol (PCEP) Numbers" registry group, which was also early allocated by the IANA.¶

IANA has marked it as deprecated.¶

Table 4
Value | Meaning | Reference
--- | --- | ---
9 | Deprecated (Unsupported Color) | RFC 9863

## 7. References

### 7.1. Normative References

[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>.
[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>.
[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>.
[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>.
[RFC8408]
  Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. Hardwick, "Conveying Path Setup Type in PCE Communication Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, July 2018, <https://www.rfc-editor.org/info/rfc8408>.
[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>.
[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>.
[RFC9012]
  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder, "The BGP Tunnel Encapsulation Attribute", RFC 9012, DOI 10.17487/RFC9012, April 2021, <https://www.rfc-editor.org/info/rfc9012>.
[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/info/rfc9325>.
[RFC9862]
  Koldychev, M., Sivabalan, S., Sidor, S., Barth, C., Peng, S., and H. Bidgoli, "Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing (SR) Policy Candidate Paths", RFC 9862, DOI 10.17487/RFC9862, October 2025, <https://www.rfc-editor.org/info/rfc9862>.

### 7.2. Informative References

[RFC3063]
  Ohba, Y., Katsube, Y., Rosen, E., and P. Doolan, "MPLS Loop Prevention Mechanism", RFC 3063, DOI 10.17487/RFC3063, February 2001, <https://www.rfc-editor.org/info/rfc3063>.
[RFC3209]
  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, <https://www.rfc-editor.org/info/rfc3209>.
[RFC3630]
  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, <https://www.rfc-editor.org/info/rfc3630>.
[RFC5305]
  Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5329]
  Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed., "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, DOI 10.17487/RFC5329, September 2008, <https://www.rfc-editor.org/info/rfc5329>.
[RFC5886]
  Vasseur, JP., Ed., Le Roux, JL., and Y. Ikejiri, "A Set of Monitoring Tools for Path Computation Element (PCE)-Based Architecture", RFC 5886, DOI 10.17487/RFC5886, June 2010, <https://www.rfc-editor.org/info/rfc5886>.
[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/info/rfc6123>.
[RFC7308]
  Osborne, E., "Extended Administrative Groups in MPLS Traffic Engineering (MPLS-TE)", RFC 7308, DOI 10.17487/RFC7308, July 2014, <https://www.rfc-editor.org/info/rfc7308>.
[RFC9256]
  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", RFC 9256, DOI 10.17487/RFC9256, July 2022, <https://www.rfc-editor.org/info/rfc9256>.
[SR-POLICY-YANG]
  Saleh, T., Raza, S. K., Zhuang, S., Matsushima, S., and V. P. Beeram, "YANG Data Model for Segment Routing Policy", Work in Progress, Internet-Draft, draft-ietf-spring-sr-policy-yang-06, 20 October 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-spring-sr-policy-yang-06>.
[YANG-TE]
  Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I. Bryskin, "A YANG Data Model for Traffic Engineering Tunnels, Label Switched Paths, and Interfaces", Work in Progress, Internet-Draft, draft-ietf-teas-yang-te-39, 17 October 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-teas-yang-te-39>.

## Acknowledgments

The authors would like to thank Kaliraj Vairavakkalai, Colby Barth, Natrajan Venkataraman, Tarek Saad, Dhruv Dhody, Adrian Farrel, Andrew Stone, Diego Achaval, and Narasimha Kommuri for their review and suggestions.¶

## Contributors

The following people have contributed to this document:¶

## Authors' Addresses