alize signaling and voice quality problems in VoIP networks. H.323, H.248, MGCP, SIP, T.38, RTP are the main protocols supported. C 2009 by Taylor & Francis Group, LLC Compliance and Interoperability Testing of SIP Devices 8.3.2 Simulation Tools Simulation tools are used to run a representation of the code in a controlled environment. The advantages of the simulation are that the tests are cheap, quick to assemble, and easy to control and to reproduce. The disadvantages are that simulation tests may differ from real implementations. 8.3.2.1 Sipp Sipp [29] is a GNU Operating System General Public License (GNU GPL) open source software test tool/traffic generator for SIP. It includes a few basic SipStone user agent scenarios (UAC and UAS) and establishes and releases multiple calls with the INVITE and BYE methods. It can also read custom XML scenario files describing from very simple to complex call flows. It fea- tures the dynamic display of statistics about running tests (call rate, round trip delay, and message statistics), periodic CSV statistics dumps, TCP and UDP over multiple sockets or multiplexed with retransmission management and dynamically adjustable call rates. 8.3.2.2 ProLab SIP Test Manager ProLab SIP Test Manager by RADVISION [30] is an advanced testing sys- tem capable of performing essential tests including performance, load, stress, interoperability, and media and protocol compliance. The ProLab SIP Test Manager is a highly scalable, feature-rich testing system that is suitable for use in different stages of the product development cycle. 8.3.2.3 SIP Express Router SIP Express Router (SER) [31] is a high-performance, configurable, free SIP (IETF RFC3261) server. It can act as registrar, proxy, or redirect server. SER features an application-server interface, presence support, SMS gateway, SIM- PLE2Jabber gateway, RADIUS/syslog accounting and authorization, server status monitoring, and FCP security. A Web-based user provisioning, serweb, is also available. 8.3.2.4 Sipbomber Sipbomber [32] is a to