conclusive FIGURE 8.1 Compliance testing. © 2009 by Taylor & Francis Group, LLC Compliance and Interoperability Testing of SIP Devices giving information about the capability of a product to work in an Internet Protocol (IP) network according to the standard. Interoperability testing is the next logical step after compliance testing. While compliance testing verifies that system A complies with specification X and that system B also complies with specification X, interoperability testing evaluates a successful communication between systems A and B [7]. In order to perform interoperability testing, all possible system interoperations between the end users, versus the rest of the system, have to be tested (assuming that access to the system is possible only through end user behaviors) [7]. The major steps of the interoperability testing process are illustrated in Figure 8.2: 1. By analyzing the specification, test purposes are defined and an ATS is written. 2. From this ATS, an ETS is implemented. 3. The ETS is executed on a protocol analyzer against two or more SUTs. 4. A TR is generated after execution of ETS. Interoperability testing is like compliance testing: (1) the ATCs and ATSs of both test types appear similar, (2) the processes of implementing the ATS and running the ETS are the same, (3) the results are listed in TR and the verdicts are pass, fail, or inconclusive. The main difference between them is that interoperability testing verifies several SUTs at the same time [8]. 8.1.3 Compliance Versus Interoperability Testing "Compliance" is the ability to operate in the way defined by a standard. Two systems that comply with a standard are likely to have a high degree of interoperability but complete interoperability cannot be guaranteed [9]. Standard Inconclusive FIGURE 8.2 Interoperability testing. © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security Compliance testing Interoperability testing FIGURE 8.3 Compliance versus interoperability differences in practice. Even af