Routing is the process of finding a suitable route for conveying data between a source and one or a set of destination. Routing can be subject to a set of constraints, like QoS, policy, or price. Constraint-based path computation is a strategic component of traffic engineering in MPLS and GMPLS networks. It is used to determine the path through the network that traffic should follow, and provides the route for each Label Switched Path (LSP) that is set up.
Path computation has previously been performed either in a management system or at the head-end of each LSP. But path computation in large, multi-domain networks may be very complex and may require more computational power and network information than is usually available at a network element, yet may still need to be more dynamic than can be provided by a management system.
A Path Computation Element (PCE) is defined by the Internet Engineering Task Force (IETF) in RFC 4655 [1], as
An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints
Thus, a PCE is an entity capable of computing complex paths for a single or set of services. A PCE might be a network node, network management station, or dedicated computational platform which is aware of the network resources and has the ability to consider multiple constraints for sophisticated path computation. PCE applications include computing Label Switched Paths for MPLS and GMPLS Traffic Engineering. The various components of the PCE architecture are in the process of being standardized by the IETF's PCE Working Group[2].
PCE represents a modern vision of networks where route computations should more or less be separated from actual packet forwarding.
==External links==??