Verification of a Sliding Window Protocol Using IOA and MONA

We show how to use a decision procedure for WS1S (the MONA tool) to give automated correctness proofs of a sliding window protocol under assumptions of unbounded window sizes, buffer sizes, and channel capacities. We also verify a version of the protocol where the window size is fixed. Since our mechanized target logic is WS1S, not the finite structures of traditional model checking, our method employs only two easy reductions outside the decidable framework. Additionally, we formulate invariants that describe the reachable global states, but the bulk of the detailed reasoning is left to the decision procedure. Because the notation of WS1S is too lowlevel to describe complicated protocols at a reasonable level of abstraction, we use a higher level language for the protocol description, and then build a tool that automatically translates this language to the MONA syntax. The higher level language we use is IOA. It is a language for distributed programming and is based on Input/Output Automata. Key-words: automated verification, formal methods, sliding window protocol, MONA, I/O Automata.