g sim- ulation, send feedback, and give reports. Performance tools collect, calculate statistics, and output simulation data into log files. The state space analysis tools automatically calculate state space and SCC graph of a model, report state space results and make state space query through CPN ML functions C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security for analysis. The CPN ML language is used in CPN tools for declarations and net inscriptions, which are important for our analysis. 16.3.2 Modeling Methods for SIP From the related work on modeling for SIP through CPN, there are always two ways for SIP modeling, the whole SIP modeling for all-sided test and the simplified SIP modeling for specific interest to the study. 16.3.2.1 Whole SIP Modeling order to test SIP functions and the extensions of SIP, sometimes it has to model the whole complex SIP based on RFCs. As SIP is a transactional protocol, models shown in Figure 16.7 are a top SIP and a top UA based on an INVITE transaction described in RFC 3261. The expanding subnets INVITE-Client and INVITE server of the UA model in Figure 16.7 are shown in Figure 16.8 and Figure 16.9. Modeling of the whole SIP always depends on structures in RFC 3261, such as SIP structure, SIP calling sequence, security mechanisms etc. The model in the paper is based on the layered SIP structure and the INVITE transaction OK200 TU-REQ RES-TU Message Message INVITE CALLING Error INVITE Client CALLING CALLING STATE Error CALLING INVITE @ +4000 Proceeding Timer A CALLING RxERR-CALLING-TxACK Proceeding STATE INVITE +32000 Proceeding CALLING Error Proceeding Timer B Terminated Completed RxERR-PROC-TxACK Terminated OK200 CALLING +32000 Terminated Completed Completed Terminated Timer D Completed RxTEMP STATE STATE Error Proceeding Completed Templxx Terminated RxOK-PROC Re-RxTEMP Terminated Templxx Message OK200 Re-RxERR Error Destroy Receive Message FIGURE 16.8 INVITE client model. © 2009 by Taylor & Francis Group, LLC SIP Modeling and Simulation