A multi-level approach has been proposed for generating test sequences
for the control portion of communication protocols, given the specifi
cation. Test sequences generated using this approach have a high degre
e of fault coverage and the capability to recover from errors. The met
hod does not assume the existence of an error-free reset input to move
a protocol Finite State Machine (FSM) from any state to an initial st
ate, unlike many other methods. The multi-level approach, thus, can be
used to generate test sequences for real-world protocols. The methodo
logy has been used to generate test sequences for a subset of the OSI
Class 4 Transport Protocol and results are presented.