ication Servers SIP can also be used to provide more advanced and rich services. Application servers are those that provide added functionalities. SIP application servers © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security Media Gateway server RTSP/SIP Media SIP+SDP Conferencing session chair member member FIGURE 2.5 Internet conferencing example combining SIP and RTSP. manage incoming requests and run associated specific applications. Services can be customized by the parameters on specific fields of the request, origin information, or other variables. Currently, several initiatives aim at providing advanced mechanisms to implement SIP services. Initiatives within the community of Java develop- ers and in the open source community are highlighted. 2.2.2.1 Java-Based Approach Java for Advanced Intelligent Networks (JAIN) [13] aims at standardizing different APIs that enable the fast development of next generation Java-based communications. SIP has been covered by the JAIN initiative, producing de JAIN-SIP API. This API encapsulates a SIP stack behind some well-defined interfaces. Given the amazing evolution of dynamic Web-services, the SIP commu- nity has also adopted one of the most widespread environments to create and deploy SIP services. It is called the Servlet programming API, specified within the Java Community Process. The next section will describe the JAIN initiative and the SIP Servlet Programming model. The JAIN initiative has defined a set of Java technology APIs that enable the rapid development of next generation Java-based communications prod- ucts and services for the Java platform. Within the JAIN community, JAIN SIP is the part in charge of implement- ing interfaces for the use of the SIP protocol. The JAIN SIP specification provides functionalities from RFC 3261 (SIP) and the RFCs with SIP exten- sions. Some of these features are methods to format the messages, application ability to receive and send messages, analysis ability about incoming mes- sages by a