Test derivation methods suitable for interoperability testing of communication protocols were proposed in the literature and applied to the TCP and the ATM protocols. The test cases that were generated by them deal with only the control part of the protocols. However, in real protocol testing, the test cases must manage the data part of them as well. For complete testing, in principle all possible values of the data part must be tested although it is impractical to do so. In this thesis, a method is presented for generating the interoperability test suite for both the data part and the control part with the example of TCP connection establishment. In this process, experimental design techniques from industrial engineering are used to reduce the size of test suite while keeping a well-defined level of test coverage. Experimental design techniques have been used for protocol conformance testing but not for interoperability testing so far. We generate the test suite for the TCP data part by this method and show a possibility that we can test interoperability of protocols with the reduced number of test cased with a well-defined level of test coverage.