PCE Redundancy Extensions in Path Computation Element Communication Protocol (PCEP)
draft-fizgeer-pce-redundancy-extensions-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Marina Fizgeer | ||
| Last updated | 2025-10-12 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
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draft-fizgeer-pce-redundancy-extensions-00
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.
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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.
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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.
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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
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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)
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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
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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.
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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
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+------+--------------------------------+---------------+
| 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,
<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>.
[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>.
[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>.
8.2. Informative References
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[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[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>.
Appendix A. Acknowledgements
Author's Address
Marina Fizgeer
Ribbon Communication
Yagia Kapaim 24
Petah Tikva
Israel
Email: marina.fizgeer@rbbn.com
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