Data link layer: two impossibility results

Abstract : The data link layer in a layered communication network is designed to ensure reliable data transfer over a noisy physical channel. Formal specifications are given for physical channels and data links, in terms of I/O automata. Based on these specifications, two impossibility results are proved. First, no data link protocol can tolerate crashes of the host processors on which the protocol runs. Second, any data link protocol constructed to use an arbitrary non-FIFO physical channel requires unbounded headers. Keywords: Crashing; Volatile memory bounded headers; Communication protocols; Data link layer; Physical layer.