values for the method in the start line and the CSeq header field. Any element receiving this request will respond with a 400 Bad Request. C 2009 by Taylor & Francis Group, LLC Compliance and Interoperability Testing of SIP Devices TP for registration Registrant Registration being listed as an option, the Group test purpose is applicable if the SUT is selection declared as supporting periodic registration and can behave as User Agent. Status PICS: A. 1/1 and A.2/1 Valid behavior SIP_RG_RT_V_001 Status Mandatory RFC 3261 [1] section 10.2. Ensure that the IUT, in order to be registered, sends a REGISTER request Purpose to its registrar, without user name in the Request-URI and with a SIP-URI as request-URI. FIGURE 8.7 Registrant: Test purpose for registration. The last example (Figure 8.11), is an INVITE message that exercises an implementation's parser and application-layer logic. This INVITE request contains a body of unknown type. It is syntactically valid: a parser must not fail when receiving it, a proxy receiving this request would process it just as it would any other INVITE, and an endpoint receiving this request would reject it with a 415 Unsupported Media Type error. 8.3 SIP Testing Tools In order to validate protocol implementations, various test tools are used today by the VoIP developers' community. Moreover, those tools are also used by service providers or technical marketing organizations during product interoperability testing or in order to verify protocol implementation comp- liance statements. This paragraph analyzes some commercially available tools for SIP testing and classifies them on the basis of their main features, in: (1) protocol analyzer tools, (2) simulation tools, and (3) robustness tools. C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security TP for call control Originating endpoint Group selection IUT is an User Agent Status PICS: A.1/1 Call establishment Group IUT can behave as a User Agent client to selection establish a call. Status PICS: A.16/1