Formal definition of SIP end systems behavior

The rapid improvement of hardware performance and the constantly growing bandwidth of computers have encouraged the development of communications based on computer networks. The first step in this direction is the definition of a set of protocols that will enable the design and implementation of various multimedia communication services. SIP (session initiation protocol) is a protocol for initiating multimedia conferences, and is a proposed standard, but its behavior is still not formally defined. We give a formal definition of the behavior of SIP end systems in the form of automata that include all features currently supported by SIP. The automata are defined using UML. This greatly simplifies the implementation of SIP systems compatibility between different systems based on SIP, because there are software tools that can translate UML specifications directly into the high-level languages (e.g., C++, Java).