PCE Working Group M. Fizgeer Internet-Draft Ribbon Communications Intended status: Standards Track 11 October 2025 Expires: 14 April 2026 PCE Redundancy Extensions in Path Computation Element Communication Protocol (PCEP) draft-fizgeer-pce-redundancy-extensions-00 Abstract The Path Computation Element Communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to instantiate and manage Label Switched Paths (LSPs) on a Path Computation Client (PCC). A PCE redundance case is very important and has no real solution for many cases, like as active-standby, active-active or not concurrent sessions of PCC with different PCEs. This document proposes extensions to PCEP to allow a PCC and PCEs to support PCE fast and smooth redundancy in case of PCEP session and PCE failure. 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 14 April 2026. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. Fizgeer Expires 14 April 2026 [Page 1] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.1. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . 5 3.2. LSP object . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. DELEGATION-TIMER-EXPIRATION TLV . . . . . . . . . . . . . 5 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Optional extension for take delegation action . . . . . . 6 5. Manageability Considerations . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7.1. STATEFUL-PCE-CAPABILITY TLV Flag . . . . . . . . . . . . 7 7.2. LSP object . . . . . . . . . . . . . . . . . . . . . . . 7 7.3. PCNtf message DELEGATION-TIMER-EXPIRATION TLV . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction PCE redundancy case is very important and complicate scenario, as PCEP protocol doesn't support exchange of session information between PCEs. 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. Fizgeer Expires 14 April 2026 [Page 2] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 2. Terminology This document uses the following terms defined in [RFC5440]: PCC, PCE, PCEP Peer, and PCEP speaker. The base PCEP specification [RFC4655] originally defined the use of the PCE architecture for MPLS and GMPLS networks with LSPs instantiated using the RSVP-TE signaling protocol. Over time, support for additional path setup types, such as SRv6, has been introduced [RFC9603]. The term "LSP" is used extensively in PCEP specifications and, in the context of this document, refers to a Candidate Path within an SR Policy, which may be an SRv6 path (still represented using the LSP Object as specified in [RFC8231]. 3. PCEP Extensions Let's consider simple configuration: +--------+ +--------+ | PCE 1 | | PCE 2 | +--------+ +--------+ | | | | | | +-------------+ | PCC | +-------------+ Figure 1: PCE redundancy Fizgeer Expires 14 April 2026 [Page 3] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 PCE1 PCC PCE2 | | | | Active Session | Active Session | | PCE Init | PCE Init | |------------------>| | | Terminated Session| | | | | | | Start del and state | | | timers | | | | | | Del timer expired | | | | | | Put LSPs (PCE1) as orphan | | |<----------------------------| | | Take delegation LSPs (PCE1) | | |---------------------------->| | | State timer expired | | | (internal) | | | Delete LSPs (PCE1) | Note: PCE2 session can be created/exist in different states after or in parallel with PCE1 session and others. Only in the timeslot between expiration of the deletion timer and the state timer, PCE2 can take delegation. Figure 2: PCE redundancy and take delegation timeslot A PCE1 can instantiate LSPs on a PCC. When session between PCE1 and PCC is terminated, PCC starts delegation and state timers. Once delegation timer is expired, all LSPs are changed to orphan. Once state timer is expired, all LSPs in orphan state are deleted by PCC. PCE2 can take delegation of orphan LSPs only, but doesn't aware about timers of PCE1-PCC session. This document specifies PCEP extensions to handle this situation in different scenarios: Multiple parallel sessions in mode active-standby Multiple parallel sessions in mode active-active Sequential sessions (one session is terminated, then another session is established) Fizgeer Expires 14 April 2026 [Page 4] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 3.1. OPEN Object This document defines one new flag for use in the STATEFUL-PCE- CAPABILITY TLV. 3.1.1. STATEFUL-PCE-CAPABILITY TLV A new flag is proposed for the STATEFUL-PCE-CAPABILITY TLV, originally defined in Section 5.4 of [RFC8231]. * D (DELEGATION-INFO-CAPABILITY): If set, indicates that the PCEP peer supports LSP delegation info. 3.2. LSP object New TLV with address of PCE to which LSP is delegated SHALL be added: 0 1 2 3 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 = 16 | +---------------+----------------------------------------------+ | IPv4 Delegation Address | +--------------------------------------------------------------+ Figure 2: Delegated PCE IPv4 address 0 1 2 3 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 = 52 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + IPv6 Delegation Address + | (16 octets) | + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Delegated PCE IPv6 address PCC SHALL send this TLV for any delegated LSP to all PCEs with active session in PCRpt message. 3.3. DELEGATION-TIMER-EXPIRATION TLV Fizgeer Expires 14 April 2026 [Page 5] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 New NT (notification type) and NV (notification value) are required for PCNtf: New NT - Delegation timeout New NV - TBD New DELEGATION-TIMER-EXPIRATION TLV is required in Notification (PCNtf) Message MUST be used for this new NT: PCE address (was owner) for session with its delegation timer expired. PCC SHALL send this message to all PCEs with active session. 4. Operation After receiving the PCNtf message with new NT, the active PCE SHALL/MAY take delegation for all LSPs that were delegated to this PCE (LSP with this IP delegated address) 4.1. Optional extension for take delegation action Here, maybe, new sub-TLV or new flag in PCInit message will help: get all LSPs were delegated to specific IP (like as PLSP ID = 0 in PCInit with remove flag message means deletion for all PCE initiated LSPs): New flag in PCInit: D take delegation, PLSP ID = 0, New sub-TLV: Address of the last delegation PCE PCC SHALL send list of above LSPs with new delegation address and delegation flag Note: : if there are more than 2 parallel session, the first PCE sent get delegation all, will get it ownership, P CC is responsible to lock other PCEs for it 5. Manageability Considerations All manageability requirements and considerations listed in [RFC5440], [RFC8231], and [RFC9604] apply to the PCEP extensions defined in this document. Fizgeer Expires 14 April 2026 [Page 6] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 A PCE or PCC implementation MAY allow the capability of supporting PCEP extensions introduced in this document to be enabled/disabled as part of the global configuration. An implementation SHOULD allow the operator to view the advertised and received capabilities. 6. Security Considerations The security considerations described in [RFC5440], [RFC8231], and [RFC9604] are applicable to this document. No additional security measures are required. 7. IANA Considerations 7.1. STATEFUL-PCE-CAPABILITY TLV Flag IANA maintains a registry, named "STATEFUL-PCE-CAPABILITY TLV Flag Field", within the "Path Computation Element Protocol (PCEP) Numbers" registry group. IANA is requested to make the following assignment: +======+================================+===============+ | Bit | Description | Reference | +======+================================+===============+ | TBD1 | D (DELEGATION-INFO-CAPABILITY) | This document | +------+--------------------------------+---------------+ Table 1 7.2. LSP object IANA maintains a registry, named "TE-PATH-BINDING TLV Flag Field", within the "Path Computation Element Protocol (PCEP) Numbers" registry group. IANA is requested to make the following assignments: +------+--------------------------------+---------------+ | N | Description | Reference | +------+--------------------------------+---------------+ | TBD2 | IPv4 delegation address | This document | +------+--------------------------------+---------------+ | TBD3 | IPv6 delegation address | This document | +------+--------------------------------+---------------+ Table 2 7.3. PCNtf message DELEGATION-TIMER-EXPIRATION TLV Fizgeer Expires 14 April 2026 [Page 7] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 +------+--------------------------------+---------------+ | N | Description | Reference | +------+--------------------------------+---------------+ | TBD4 | PCE address (was owner) IPv4 | This document | +------+--------------------------------+---------------+ | TBD5 | PCE address (was owner) IPv6 | This document | +------+--------------------------------+---------------+ | TBD6 | Delegation timeoutr | This document | +------+--------------------------------+---------------+ Table 3 8. References 8.1. 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, . [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, . [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, . [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, . [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, . 8.2. Informative References Fizgeer Expires 14 April 2026 [Page 8] Internet-Draft PCE Redundancy Extensions in Path Comput October 2025 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [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, . Appendix A. Acknowledgements Author's Address Marina Fizgeer Ribbon Communication Yagia Kapaim 24 Petah Tikva Israel Email: marina.fizgeer@rbbn.com Fizgeer Expires 14 April 2026 [Page 9]