s, such as SIP. It provides a cost-effective, scalable, and evolving test automation solution for network equipment manufactures and service providers. Figure 8.13 shows the SPT test logic program (TLP) that is a protocol-specific call flow design diagram. In this case, the TLP is used to simulate a network device using SIP, to generate a call flow (originating endpoint). The TLP consists of a set of states and transitions between states. Users can create and/or edit a TLP with a finite set of states and transition links between the states to define the SIP test logic. The TLP editor allows users to display and modify the characteristics of any selected state (etc., sending SIP messages) in order to realize a specific SIP test. 8.3.3 Robustness Tools Robustness is defined as the degree to which a system operates correctly in the presence of exceptional inputs or stressful environmental conditions [37]. This general class of tools (often referred to as protocol "fuzzers") includes tests designed to flush out problems and vulnerabilities with lower-level SIP stacks and parser mechanisms. The need for SIP-oriented robustness validation is important now, but will be even more important as the proliferation of SIP- based communications grows and malicious VoIP denial of service attacks become more prevalent. C 2009 by Taylor & Francis Group, LLC Compliance and Interoperability Testing of SIP Devices Spirent Protocol Test Platform 3.30 [User:Temp] [Working Directory:C:\ProgramFiles\SpirentluserdatalTemp] Main StateMachine Tools History Window Help Max Call Category Owner Unknown State Tested/Verified Transport Time(Seconds) Start Auto (1) Rcv 401 Authentication Get vanderlD & challenge call hold time from Initial cal testcase data VID CHTFlag Rev100 C*OtherVander Send INVITE Get CipcoCID Cisco (2) Get regularCID Rev.R09,180 Rcv100 Rcv180 (7 CiscoCIDPretix Sip CIDPrefix Rev100 C=G711U B RcvR09960200 Rcv180 Send INVITE 180 Rcvd HTFromTD HTFromDB HTFromTD HTFromDB Reven C-G711A Rev200 Rcv200 (8) Rev100 Auto (4) C=G723 Rcy