In protocol conformance testing, there is an important class of errors, namely coordination loss that cannot be anticipated because some source of error is external to both the tester and the implementation under test, (IUT). Furthermore, it is not possible to simulate their occurrence exhaustively in the test environment. Therefore they are very difficult to catch in the testing phase. In this paper we propose use self-stabilization as a design principle of design for testability (DFT) to overcome this testing problem. This will improve the reliability of protocol implementations derived from self-stabilizing protocol specifications. We present a novel algorithm and the corresponding design principles to design self-stabilizing protocols, and give an example of a self-stabilizing protocol.

We propose a superimposition algorithm than can be employed by a substrate to change its behavior according to current conditions or properties of the mobile environment. The algorithm has some interesting features such as it is completely distributed, works on-line, does not generate extra messages, and is based on unstable predicates. The algorithm proposed can be used by multiple local controllers that use information only from the subset of the participating mobile units. This is certainly an advantage over a centralized approach that is likely to be more expensive than distributed decisions since there are delays in the communication and the cost of sending extra messages.

Given an n-nodes network and an assertion G expressing its correctness, it is shown that G can be decomposed into collection of n local assertions and n.(n-1) “communication” assertions. The special case of a 2-nodes network is first examined, and it is shown how the notion of Galois connections in lattice theory is a basic tool for the assertion decomposition. The principles of a communication protocol that allow to maintain the resulting assertions are described. For the n-nodes network it is shown that assertion G induces Galois connections between any two parts of the network. General formulae for the local and communication assertions are found using this fact. It is also shown that the communication assertions do involve only a pair of nodes each one, which makes possible the use of techniques taken from the 2-nodes network for their maintenance. As an application example a distributed algorithm to solve the “2-out-of-3” problem is proposed.