Design and evaluation of a PCEP-based topology discovery protocol for stateful PCE

In this paper, we present a topology discovery protocol for a stateful path computation element (PCE), in which the PCE has an out-of-band control channel to every switch in a unified control. The proposed protocol is an extended version of the PCE communication protocol (PCEP) called the Generalized TOPology (G-TOP) protocol that allows the PCE to automatically construct the network topology as a controller without using a distributed routing protocol. With the G-TOP protocol, the centralized PCE controller proactively extracts neighbor information as well as link status information from switches when it starts. The controller also reactively updates topology changes that arise from the switch when detecting faults or changes in the link state. We implement the proposed protocol, and show that the proposed protocol reduces not only the topology discovery/updating time but also traffic to the controller.