A periodic state exchange protocol and its verification

Abstract

We present an elegant protocol for reliably transmitting data messages from a sender to a receiver over a highspeed network that may reorder, lose, or corrupt messages. The protocol is based on a new principle that calls for the periodic exchange of state information between the sender and receiver. Our formal definition of the protocol is abstract and does not include explicit timing information such as the rate of sending state information. The abstract definition makes our formal verification of the protocol simple and based solely on well-established concepts: invariants, well-foundedness, and action fairness. We use the formal definition of the protocol and its proof of correctness to deduce the required timing information. In particular, we show that the rate of sending state information is at most (m-1)/2T where m is a measure of the memory size in the sender, and T is an upper bound on the required time for one message to be sent, propagated, and received between the sender and receiver. >