Run-time fault detection of communication protocols is essential because of
faults that occur in the form of coding defects, memory problems and
external disturbances. We propose a signature-based method to detect
run-time faults. A polynomial using the state and event information
as coefficients is used to transform a sequence of states and events into a
number (signature). The static signature corresponding to the correct
execution of the protocol is compared with the run-time signature. This
technique is reliable, fast, and efficient compared to the existing
techniques. The states and events are assigned values such that multiple
paths leading to the same state result in a unique signature. This reduces
the number of run-time comparisons required to verify the correct execution
of the protocol. Fault-detection based on signatures is also much simpler
than observer-based methods. We propose extensions to communication
protocols that facilitate the application of signature-based techniques to
detect run-time faults in communication protocols. In this paper, we
present eXTP4, an extended transport layer protocol that facilitates
run-time fault detection.