From specification to realization: implementing the express transfer protocol

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Virginia Tech

The research described in this thesis deals with effective protocol specification. The primary question addressed is whether the Express Transfer Protocol (XTP), a "real-time" Transport layer protocol, is sufficiently specified or are there "holes" in its specification? A new protocol evaluation process is formulated and applied to XTP in order to answer this question. The evaluation process combines a detailed analysis of the XTP specification with an attempt to implement parts of the protocol from the specification. Special attention is given to those aspects of the protocol that affect "real-time" naval tactical communications. The detailed analysis of the specification and its effect on the specification revision process are presented. The analysis is described in formal comment papers and electronic mail transmitted to the protocol designer, Dr. Greg Chesson. Elements of the protocol most applicable to tactical communication are selected for implementation. A number of assumptions are made so that an implementation can be built. The design of the prototype implementation and the assumptions made to build it are discussed. Both the hardware and software being used to build the implementation are presented. The protocol evaluation process is found to be appropriate for evaluating XTP. A comparison is made between this technique of protocol evaluation and existing techniques (i.e., simulation, complete implementation, and protocol verification). The principal conclusion of the protocol valuation process is that a number of areas of the XTP Protocol Definition (prior to Revision 3.3) are not sufficiently specified. These areas must be properly specified before a complete implementation can be built. Without a complete specification, the communications support intended for XTP is unlikely to be realized.