Abstract: A finite symbolic representation of the states of an unbounded FIFO queue. Because the representation is protocol verification tools of the type which explore the state space of a protocol may be used to verify protocols which involve unbounded FIFO queues and consequently have an infinite state space. In a preferred embodiment, the finite symbolic representation is used together with a finite state automaton whose states are the global states of the protocol. A symbolic representation of the queue states is associated with each of the global states. State space exploration continues until all new queue states reached are already contained in the states of the finite symbolic representation. Increased processing speed is achieved by employing meta-transitions in the finite state automaton and exploring the meta-transitions from a global state before exploring the ordinary transitions.