Designing Reliable Test Architectures for Communication Protocols

In an external architecture for testing communication protocols, the service provider is an abstraction of the stack of protocols and the public data network interconnecting the lower tester with the implementation under test. In this paper, the effects of a public data network are studied (i.e. the service provider) when testing a protocol implementation's conformity to its speci"cation. The three main characteristics of a service provider are dynamic round trip delay (RTD), message buffering and lossy transmission. It is shown that if proper care is not taken in test architectures and test cases, the dynamic attributes of a service provider may make correct test cases useless. The outline of the paper is as follows. First, the notion of a time server protocol (TSP) in a test architecture to estimate the RTD dynamically in the service provider is introduced. The generalization capability of neural networks is used as the central idea in the dynamic estimation of RTDs from previous actual measurement of delays. Second, the notion of a test architecture's reliability and the properties that a reliable architecture must satisfy are de"ned. A reliable test architecture is obtained by augmenting a basic test architecture with a TSP and a "lter protocol to discard spurious events. Finally, some dif"culties in assigning test verdicts are studied and measures are suggested for overcoming them. Thus, an extended service provider is designed by augmenting the actual service provider with the new components. This work proposes an interface to an extended service provider to conceal the side-effects of the bare service provider.