Fifo Channels from Unreliable Channels

Abstract

Fifo, lossy, and LRD connection-less channels were presented in the previous chapter. This chapter presents a distributed program that implements a connection-less fifo channel between two addresses a1 and a2, given an unreliable, i.e., lossy or LRD, connection-less channel connecting the two addresses. Henceforth we omit the “connection-less” qualifier when referring to these channels. The program has a component system at each address, which accepts messages from its local user, transfers them over the unreliable channel to the remote component system, which then delivers them in order to the remote user. Figure 5.1 illustrates the configuration. In computer networking, such a program is referred to as a data transfer protocol [4, 9, 10]. Following this terminology, we refer to the distributed program as DtpDist and the program of each component system as Dtp, where “dtp” is short for data transfer protocol. We refer to the messages exchanged between the dtp users as “data blocks”, and reserve the term “messages” for the messages exchanged between the dtp systems; the former would be sent inside the latter.