The Path Computation Element Communication Protocol (PCEP) is a special set of rules that allows a Path Computation Client (PCC) to request path computations from Path Computation Elements (PCEs). The protocol also lets the PCEs return responses.
Path Computation Element (PCE) is a network component, application or node that can compute sophisticated paths through a network by applying computational constraints in real time. Traditionally, network routes are are calculated and managed off-line as part of a network's traffic engineering. In such a scenario, when a new customer comes online, the customer's traffic requirements are evaluated and superimposed on the current network's topology. Defined by IETF RFC 4655, the Path Computation Element (PCE) has a complete picture of flows and paths in the network at the precise moment derived from other Operational Support Software (OSS) programs so it can calculate in real time the optimal path through the network. This path is then used to automatically update router configurations and the traffic engineering database.
The PCE architecture and PCE protocol are defined by the IETF in RFCs 4655 and RFC 5440.