Design And Implementation Of SIP Stack In Application Server

With the development of technology of mobile telecommunications, The NGN (Next Generation Network) becomes the direction. The NGN adapts the layered structure as service layer, control layer, media transport layer and access layer. In NGN network, AS (Application Server) is a function entity in service layer which provides the executing environment of value-added services, and AS enables third-party application developers to make use of network functionality through an open standardized interface. SIP (Session Initiation Protocol) becomes important call control protocol in NGN. AS uses SIP as its call control protocol, and SIP provides functions of creating, modifying, and terminating sessions with one or more participants in IP networks.Application Server composes of service executing subsystem, resource adaptor subsystem, protocol subsystem, management subsystem and deployment subsystem. The SIP stack is in the resource adaptor subsystem, which provides the SIP functions defining in RFC3261. According of SIP layered architecture, the SIP stack in AS composes of network module, message encoding/decoding module, transaction state management module, dialog state management module and management module.This article illustrates the design and implementation of SIP stack in application server. In chapter one, it introduces the background of the SIP stack in application server recently. In chapter two, it introduces the background of the Next Generation Network and IP Multimedia Subsystem. In IMS, application server provides the facilities of open services executing and managing environment. We compare the open source SIP stack and commercial SIP stack, and research the advantages and disadvantages. And then we analyze the needs of our SIP stack.Chapter three carries out the general design of SIP stack entity in application server. The SIP stack design scheme, including functional view, process view, deployment view, are first explained. Then the designs for the several modules of SIP stack, such as network module, message encoding/decoding module, transaction state management module, dialog state management module and management module are proposed. We describe some key technologies such as thread pool technology, Spring technology, JMX technology, message queen technology and so on. We use the Object Oriented programming model, and considering the SIP extending character. The SIP stack enclosing in JAIN-SIP is provided to application server.In chapter four, we do performance tests based on SIP B2BUA call model, and the test results prove that it can meet the design objects.There are still some problems to solve to make it better. In the end of this thesis paper we give the front-end and back-end architecture to solve these problems and make a prospect for the development of AS.