PCUpd Message.
http://tools.ietf.org/html/draft-crabbe-pce-stateful-pce-mpls-te-00
4.2. MPLS-TE specific descriptors for the PCUpd Message
A Path Computation LSP Update Request message (also referred to as
PCUpd message) is a PCEP message sent by a PCE to a PCC to update
attributes of an LSP. A PCUpd message can carry more than one LSP
Update Request. The Message-Type field of the PCEP common header for
the PCUpd message is set to [TBD].
The format of the PCUpd message is defined in
[I-D.ietf-pce-stateful-pce] and included here for easy reference:
::=
Where:
::= []
::=
[]
Where:
::=[]
For MPLS-TE LSPs, the endoding of path descriptor is defined as
follows:
::=
Where:
::=
Where:
::= []
[]
[]
::= []
There is one mandatory object that MUST be included within each LSP
Update Request in the PCUpd message: the LSP object (see
[I-D.ietf-pce-stateful-pce]). If the LSP object is missing, the
receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory
Object missing) and Error-value=[TBD] (LSP object missing).
The LSP Update Request MUST contain a path descriptor for the primary
path, and MAY contain one or more path descriptors for backup paths.
A path descriptor MUST contain an ERO object. A path descriptor MAY
further contain the BANDWIDTH, IRO, and METRIC objects. The ERO,
LSPA, BANDWIDTH, METRIC, and IRO objects are defined in [RFC5440].
Each LSP Update Request results in a separate LSP setup operation at
a PCC. An LSP Update Request MUST contain all LSP parameters that a
PCC wishes to set for the LSP. A PCC MAY set missing parameters from
locally configured defaults. If the LSP specified the Update Request
is already up, it will be re-signaled. The PCC will use make-before-
break whenever possible in the re-signaling operation.
A PCC MUST respond with an LSP State Report to each LSP Update
Request to indicate the resulting state of the LSP in the network. A
PCC MAY respond with multiple LSP State Reports to report LSP setup
progress of a single LSP.
If the rate of PCUpd messages sent to a PCC for the same target LSP
exceeds the rate at which the PCC can signal LSPs into the network,
the PCC MAY perform state compression and only re-signal the last
modification in its queue.
Note that a PCC MUST process all LSP Update Requests - for example,
an LSP Update Request is sent when a PCE returns delegation or puts
an LSP into non-operational state. The protocol relies on TCP for
message-level flow control.
Note also that it's up to the PCE to handle inter-LSP dependencies;
for example, if ordering of LSP set-ups is required, the PCE has to
wait for an LSP State Report for a previous LSP before triggering the
LSP setup of a next LSP.