An extension to an existing method for building multiphase protocols is presented. One of the limitations of the former method is a stringent restriction on the validity of phases. Consequently, the protocols built by this method must run in a noiseless environment or rely on other protocols for reliable transport. Another restriction is a rigid requirement on the selection of the points that connect different phases. The presented method either minimizes or eliminates the above restrictions. It enables a multiphase protocol to deal with message corruption and loss, and provides a less restrictive way for phase connection. It also maintains the advantages of the existing method in allowing a multiphase protocol to be constructed in an easy and modular way.>

The author describes a method for designing communication protocols which can perform several distinct functions, but are limited to the execution of one function at a time. The construction of such a protocol consists of two steps: (1) developing a component protocol for each function to be included, and (2) integrating the components into the target protocol. The integration involves the resolution of potential component competition and process synchronization problems. A sufficient condition for the safety of the integrated protocol is also discussed. This design method is simple to use and promotes reuse of existing protocols. The construction of two protocols-the call setup phase of a data link control protocol and a portion of the CCITT's X.21 Recommendation-is demonstrated.>

In this paper we present a new methodology for designing reliable communication protocols. This methodology enhances communicating processes with a synchronization mechanism so that they can detect and resolve the errors caused by collisions automatically. The major advantages of this new methodology include: (1) the “state explosion” problem involved in protocol validation is alleviated; and (2) the burden of handling errors due to collisions is removed from the protocol designer. There is a need to verify that this methodology is applicable to arbitrary protocols. In this paper we also discuss the application of a program verification technique to this methodology.