Path Computation Element
charter-ietf-pce-07

The PCE Working Group is chartered to specify the required protocols 
so as to enable a Path Computation Element (PCE)-based architecture
for the computation of paths for MPLS and GMPLS Point to Point and 
Point to Multi-point Traffic Engineered LSPs.

In this architecture path computation does not necessarily occur on 
the head-end (ingress) LSR, but on some other path computation entity
that may not be physically located on each head-end LSR. The TEAS
Working Group is responsible for defining and extending architectures
for Traffic Engineering (TE) and it is expected that the PCE and TEAS
WGs will work closely together on elements of TE architectures that
utilize PCE.

The PCE WG works on the application of this model within a single
domain or within a group of domains (where a domain is a layer, IGP
area or Autonomous System with limited visibility from the head-end
LSR). At this time, applying this model to large groups of domains such
as the Internet is not thought to be possible, and the PCE WG will not
spend energy on that topic.

The WG specifies the PCE communication Protocol (PCEP) and needed
extensions for communication between Path Computation Clients (PCCs)
and PCEs, and between cooperating PCEs. Security mechanisms such as 
authentication and confidentiality are included.

The WG determines requirements for extensions to existing routing and
signaling protocols in support of the PCE architecture and the 
signaling of inter-domain paths (e.g., RSVP-TE and its GMPLS
variations). Any necessary extensions will be produced in 
collaboration with the Working Groups responsible for the protocols.

The WG also works on the mechanisms to for multi-layer path
computation and PCEP extensions for communication between several
network layers.

The WG defines the required PCEP extensions for Wavelength Switched
Optical Networks (WSON) while keeping consistency with the GMPLS
protocols specified in the CCAMP and TEAS WGs.

Work Items:

- PCEP extensions to support MPLS and GMPLS Traffic Engineered LSP 
  path computation models involving PCEs. This includes the case of
  computing the paths of intra- and inter-domain TE LSPs. Such path
  computation includes the generation of primary, protection and
  recovery paths, as well as computations for (local/global)
  reoptimization and load balancing. Both intra- and inter-domain
  applications are covered.

- In cooperation with the TEAS Working Group, development of PCE-
  based architectures for Traffic Engineering.

- In cooperation with protocol specific Working Group (e.g., MPLS,
  CCAMP), development of LSP signaling (RSVP-TE) extensions required
  to support PCE-based path computation models.

- Specification of PCEP extensions for expressing path computation 
  requests and responses in the various GMPLS-controlled networks, 
  including WSON.

- Definition of PCEP extensions for path computation in multi-layer
  networks.

- Definition of the PCEP extensions used by a stateful PCE for 
  recommending a new path for an existing or new LSP to the PCC/PCE.
  Further protocol extensions must cover the case where receiving 
  PCC/PCE chooses to not follow the recommendation.