Run-time fault detection in communication protocols is essential to detect faults that cannot be detected during the testing phase. 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 more reliable, faster, and efficient compared to 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 comparisons required to verify the correct execution of the protocol. In this paper, we present eXTP4, an extended transport layer protocol that facilitate run-time fault detection