Slide - The Key to Polynomial End-to-End Communication

We consider the basic task of of end-to-end communication in dynamic networks, that is, delivery in finite time of data items generated on-line by a sender, to a receiver, in order and without duplication or omission. A dynamic communication network is one in which links may repeatedly fail and recover. In such a network, though it is impossible to establish a communication path consisting of nonfailed links, reliable communication is possible, if there is no cut of permanently failed links between a sender and receiver. This paper presents the first polynomial complexity end-to-end communication protocol in dynamic networks. In the worst case the protocol sends O(n2m) messages per data item delivered, where n and m are the number of processors and number of links in the network respectively. The centerpiece of our solution is the novel slide protocol, a simple and efficient method for delivering tokens across an unreliable network. Slide is the basis for several self-stabilizing protocols and load-balancing algorithms for dynamic networks that have subsequently appeared in the literature. We use our end-to-end protocol to derive a file-transfer protocol for sufficiently large files. The bit communication complexity of this protocol is O(nD) bits, where D is the size in bits of the file. This file-transfer protocol yields an O(n) amortized message complexity end-to-end protocol. © 1997 Academic Press.