.0../via P/2.0/U0 P 192.1 8.129.50 :5060:br anch-z9h G4bk1000 0010.. <sip:23 51110192 .168.129 .165:506 0>;tag-5 tz011000 0009. Message Header in SIP message (sip.msg_hdr), 369 bytes P: 1097 D: FIGURE 8.15 INVITE client transaction: analysis with Wireshark. - the CSeq header method matches "INVITE" and the via header has a protocol name set to SIP, a protocol version set to 2.0 and a branch parameter set to a value beginning with "z9hG4bK". 8.4.4.2 State Machine Transitions and ACK Response Some ETSI TPs want to check the state transition at the receipt of a particular response to INVITE. Following the same Wireshark analysis detailed in Figure 8.15, if the IUT is in the calling state, on receipt of a trying (100 trying) response, enters in the proceeding state. Then, on receipt of one or more ringing (180 ringing) responses the IUT remains in the proceeding state. Consequently, another TP has the purpose to ensure that, on receipt of a success (200 OK) response, the IUT sends an ACK request and enters in the terminated state. Some ETSI TPs have as purpose to ensure IUT behavior at the receipt of 300-699 messages. For example, the IUT when an INVITE client transaction is in the calling state, on receipt of a multiple choices (300 multiple choices) response must send an ACK request with the same Call-ID, From headers and request-URI as in the original INVITE request and the same tag in the to header as in the multiple choices (300 multiple choices) response. Figure 8.16 shows the Wireshark analysis of these specifications. C 2009 by Taylor & Francis Group, LLC Compliance and Interoperability Testing of SIP Devices 300 Multiple Choices.pcap Wireshark Edit View Go Capture Analyze Statistics Help Eiter: Expression. Clear Apply No. Time Source Destination Protocol 71 23.408941 30.30.10.32 30.253.253.71 SIP/SDP Request: INVITE sip:0291970552030.253.253.71:5060, with session 72 23.505211 30.253.253.71 0.30.10.32 Status: 300 Multiple choices 73 23.508858 30.30.10.32 30.253.253.71 SIP Request: CKsip:0291970552030.253 Requ