Sequencing computation steps in a network

It is sometimes necessary in the course of a distributed computation to arrange that a certain set of operations is carried out in the correct order and the correct number of times (typically once). If several sets of operations are performed on different machines on the network there is no obvious mechanism for enforcing such ordering constraints in a fully distributed way. This lack basically stems from the difficulty of preventing copying and repetition of messages by machines and from the impossibility of constraining externally the actions of machines in response to messages that come into their hands. This paper presents a possible method for ensuring the integrity of sequences of operations on different machines. The technique may be thought of as a means of enabling machines to ensure that requests made of them are valid and timely, not as means of centralized control of services.