PCE Working Group B. Rajagopalan Internet-Draft V. Beeram Intended status: Standards Track Juniper Networks Expires: 21 August 2025 S. Peng ZTE Corporation M. Koldychev Ciena Corporation G. Mishra Verizon Communications Inc. 17 February 2025 Path Computation Element Protocol (PCEP) Extension for Color draft-ietf-pce-pcep-color-11 Abstract Color is a 32-bit numerical (unsigned integer) attribute that is used to associate a Traffic Engineering (TE) tunnel or policy with an intent or objective (e.g., low latency). This document specifies extensions to Path Computation Element Protocol (PCEP) to carry the color attribute. 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 working documents as Internet-Drafts. The list of current Internet- 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 21 August 2025. 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. Rajagopalan, et al. Expires 21 August 2025 [Page 1] Internet-Draft PCEP Color February 2025 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 4 3.1. Color Capability . . . . . . . . . . . . . . . . . . . . 4 3.2. Color TLV . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Manageability Considerations . . . . . . . . . . . . . . . . 5 5.1. Control of Function through Configuration and Policy . . 5 5.2. Information and Data Models . . . . . . . . . . . . . . . 5 5.3. Liveness Detection and Monitoring . . . . . . . . . . . . 5 5.4. Verifying Correct Operation . . . . . . . . . . . . . . . 5 5.5. Requirements on Other Protocols . . . . . . . . . . . . . 6 5.6. Impact on Network Operation . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6.1. PCEP TLV Type Indicator . . . . . . . . . . . . . . . . . 6 6.2. STATEFUL-PCE-CAPABILITY TLV Flag Field . . . . . . . . . 6 6.3. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 6 6.4. LSP-ERROR-CODE TLV Error Code Field . . . . . . . . . . . 7 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 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]. Rajagopalan, et al. Expires 21 August 2025 [Page 2] Internet-Draft PCEP Color February 2025 [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 [I-D.ietf-pce-segment-routing-policy-cp]. 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. Rajagopalan, et al. Expires 21 August 2025 [Page 3] Internet-Draft PCEP Color February 2025 A PCEP speaker that has advertised color capability MUST NOT send Color TLV encoded in the LSP object to a PCEP Peer that has not advertised color capability. A PCEP speaker that advertises both color capability and SR Policy Association capability ([I-D.ietf-pce-segment-routing-policy-cp]) 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 which carries an ASSOCIATION object of type SR Policy Association ([I-D.ietf-pce-segment-routing-policy-cp]). 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=TBD1 (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=TBD2 (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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Rajagopalan, et al. Expires 21 August 2025 [Page 4] Internet-Draft PCEP Color February 2025 Figure 1: Color TLV Type has the value 67. Length carries a value of 4. The 'color' field is 4-bytes long, and carries the actual color value (specified as an unsigned integer). A color 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. 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. Rajagopalan, et al. Expires 21 August 2025 [Page 5] Internet-Draft PCEP Color February 2025 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 This document introduces a value in the "PCEP TLV Type Indicators" sub-registry of the PCEP Numbers registry as follows: Value Description Reference ---------------------------------------------- 67 Color This document Note: The code point specified for the TLV Type Indicator is an early allocation by IANA. 6.2. STATEFUL-PCE-CAPABILITY TLV Flag Field This document introduces a bit value in the "STATEFUL-PCE-CAPABILITY TLV Flag Field" sub-registry of the PCEP Numbers registry as follows: Value Description Reference ---------------------------------------------- 20 COLOR-CAPABILITY This document Note: The code point specified for the STATEFUL-PCE-CAPABILITY TLV Flag is an early allocation by IANA. 6.3. PCEP-Error Object This document introduces 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: Error- Meaning Error-value Reference Type ------------------------------------------------------------------ 19 Invalid Operation TBD1: Invalid Color This document TBD2: Inconsistent Color This document Rajagopalan, et al. Expires 21 August 2025 [Page 6] Internet-Draft PCEP Color February 2025 6.4. LSP-ERROR-CODE TLV Error Code Field An earlier version of this document added an error code in the "LSP- ERROR-CODE TLV Error Code Field" registry of the PCEP Numbers registry group, which was also early allocated by the IANA. IANA is requested to cancel the early allocation made which is not needed anymore. As per the instructions from the chairs, please mark it as deprecated. Value Meaning Reference ------------------------------------------------------ 9 Deprecated (Unsupported Color) This document 7. Implementation Status [Note to the RFC Editor - remove this section before publication, as well as remove the reference to RFC 7942.] This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to [RFC7942], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". At the time of publication of this version, there are no known implementations. Juniper Networks has plans to implement the extensions defined in this document. Rajagopalan, et al. Expires 21 August 2025 [Page 7] Internet-Draft PCEP Color February 2025 8. 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. 9. Contributors The following people have contributed to this document: Quan Xiong ZTE Corporation Email: xiong.quan@zte.com.cn 10. References 10.1. Normative References [I-D.ietf-pce-segment-routing-policy-cp] 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", Work in Progress, Internet-Draft, draft-ietf-pce-segment-routing-policy-cp- 20, 20 January 2025, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Rajagopalan, et al. Expires 21 August 2025 [Page 8] Internet-Draft PCEP Color February 2025 [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, . [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, . [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, . [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, . [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, . [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, . [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, . [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, . 10.2. Informative References Rajagopalan, et al. Expires 21 August 2025 [Page 9] Internet-Draft PCEP Color February 2025 [RFC3063] Ohba, Y., Katsube, Y., Rosen, E., and P. Doolan, "MPLS Loop Prevention Mechanism", RFC 3063, DOI 10.17487/RFC3063, February 2001, . [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, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, . [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, . [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, . [RFC6123] Farrel, A., "Inclusion of Manageability Sections in Path Computation Element (PCE) Working Group Drafts", RFC 6123, DOI 10.17487/RFC6123, February 2011, . [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS Traffic Engineering (MPLS-TE)", RFC 7308, DOI 10.17487/RFC7308, July 2014, . [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", BCP 205, RFC 7942, DOI 10.17487/RFC7942, July 2016, . [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, . Rajagopalan, et al. Expires 21 August 2025 [Page 10] Internet-Draft PCEP Color February 2025 Authors' Addresses Balaji Rajagopalan Juniper Networks Email: balajir@juniper.net Vishnu Pavan Beeram Juniper Networks Email: vbeeram@juniper.net Shaofu Peng ZTE Corporation Email: peng.shaofu@zte.com.cn Mike Koldychev Ciena Corporation Email: mkoldych@proton.me Gyan Mishra Verizon Communications Inc. Email: gyan.s.mishra@verizon.com Rajagopalan, et al. Expires 21 August 2025 [Page 11]