The Path Computation Element (PCE) provides path computation
functions in support of traffic engineering in Multi-Protocol Label
Switching (MPLS) and Generalized MPLS (GMPLS) networks.
A limited form of statefulness is useful to improve PCE functionality
in situations in which the local TED might not be up to date, or in
the case of concurrent requests where most of the LSPs are computed
before the end of the set-up of the LSPs, when the TED is updated.
The PCC is responsible to setup or not the TE-Path computed by the
PCE. By providing an indication that it intends to use the resources
on the TE-Path a PCC can help the PCE to get a more accurate dynamic
TED view and thus the PCE can avoid suggesting the use of the same
resources for subsequent TE LSPs.
This document proposes an extension to the PCEP protocol to allow the
PCC to indicate to the PCE to block or reserve the resources computed
in a path request of a TE LSP for subsequent requests for a certain
time and can help to reduce the number of crankbacks.