10
Introduction to Detailed Procedures
This part gives a detailed example of Session Initiation Protocol (SIP) and Session Description Protocol (SDP) related procedures in the Internet Protocol Multimedia Subsystem (IMS). Signalling procedures, protocol messages and their elements are described and explained based on an exampleof IMS registration and a subsequent IMS Multimedia Telephony session between two users. Additionally, it will be shown in detail how voice call continuity works.
The reader will see how IMS signalling works and how previously described concepts and architecture are realized at the protocol level. Nevertheless, this part concentrates on the straight forward examples and does not handle error or abnormal procedures in detail.
To give a better understanding of the procedures applied, each chapter of this part is split into several sections which concentrate on different concepts, such as routing, authentication or media negotiation. Each chapter will describe those parts of individual SIP and SDP messages that are necessary for their understanding. An overview section is included in each chapter to give an introduction to the basic operation. At the end of each chapter the related standards and specifications are listed, to allow the interested reader to obtain more detail by reading the base specifications.
10.1 The Example Scenario
This part is based on the assumption that both users are attached to the General Packet Radio Service (GPRS), which is used as ...
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