LISP Map Server Reliable Transport

The communication between LISP ETRs and Map-Servers is based on unreliable UDP message exchange coupled with periodic message transmission in order to maintain soft state. The drawback of periodic messaging is the constant load imposed on both the ETR and the Map-Server. New LISP use cases increase the amount of state that needs to be communicated and challenge the scalability of the system when using the UDP exchange. This document introduces the use of a reliable transport for ETR to Map-Server communications in order to eliminate the periodic messaging overhead, while providing reliability, flow-control and endpoint liveness detection.