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Inter Stateful Path Computation Element (PCE) Communication Procedures.

Document Type Replaced Internet-Draft (pce WG)
Authors Stephane Litkowski , Siva Sivabalan , Cheng Li , Haomian Zheng
Last updated 2021-06-28 (Latest revision 2021-02-22)
Replaces draft-dhody-pce-stateful-pce-lspdb-realtime-sync
Replaced by draft-ietf-pce-state-sync
Stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Expired & archived
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Stream WG state Adopted by a WG
Other - see Comment Log
Document shepherd (None)
IESG IESG state Replaced by draft-ietf-pce-state-sync
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at:


The Path Computation Element Communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform path computation in response to a Path Computation Client (PCC) request. The Stateful PCE extensions allow stateful control of Multi-Protocol Label Switching (MPLS) Traffic Engineering (TE) Label Switched Paths (LSPs) using PCEP. A Path Computation Client (PCC) can synchronize an LSP state information to a Stateful Path Computation Element (PCE). The stateful PCE extension allows a redundancy scenario where a PCC can have redundant PCEP sessions towards multiple PCEs. In such a case, a PCC gives control of a LSP to only a single PCE, and only one PCE is responsible for path computation for this delegated LSP. There are some use cases, where an inter-PCE stateful communication can bring additional resiliency in the design, for instance when some PCC-PCE session fails. The inter-PCE stateful communication may also provide a faster update of the LSP states when such an event occurs. Finally, when, in a redundant PCE scenario, there is a need to compute a set of paths that are part of a group (so there is a dependency between the paths), there may be some cases where the computation of all paths in the group is not handled by the same PCE: this situation is called a split-brain. This split-brain scenario may lead to computation loops between PCEs or suboptimal path computation. This document describes the procedures to allow a stateful communication between PCEs for various use-cases and also the procedures to prevent computations loops.


Stephane Litkowski
Siva Sivabalan
Cheng Li
Haomian Zheng

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)