【作者】 严成安；

【导师】 黄本雄；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2005， 硕士

【摘要】 作为下一代网络的核心技术,软交换提供了一个开放的体系结构,实现了网络和业务的融合,促进了固定电话网、移动网、因特网和广播电视网的统一。融合是下一代网络的必然趋势,解决融合中的网络互通问题尤为重要。IETF 制定的SIP 标准以其简单、灵活等诸多优点已经成为网络中会话控制的核心协议之一,在下一代网络和移动通信领域得到了广泛应用。论文就SIP 在软交换应用中的互通性问题进行分析和研究,从协议的互操作、互通模型设计以及SIP 用户代理的实现三个方面进行论述。首先根据软交换网络的四层结构将网络的互通问题进行分解,分别是接入层不同类型的终端、传输层不同的媒体格式与承载技术、控制层的多种控制信令以及业务层不同的网络资源接入。其中位于控制层面的信令协议适配与互通是会话的基础,论文选用两个比较有代表性的协议H.323 和ISUP,从组网方式、信令消息映射以及呼叫流程等方面,分析了SIP 与它们的互操作。为实现SIP 与PSTN 互通,分析了SIP 协议的扩展机制,并采用了电话号码到域名映射的ENUM 技术解决两种网络间的地址解析问题。接着提出了以抽象的呼叫模型实现多协议互通的方案。智能网呼叫模型具有很好通用性,适合多协议的呼叫控制,对它进行改造增加连接管理模块,可实现呼叫与承载分离的软交换呼叫模型。通过该模型作为中间协议很好的完成了SIP 和其它协议间的互通。达到了软交换系统多协议接入、使网络平滑演进的要求,并减小了解决协议互通问题的工作量。最后,结合具体项目并根据软交换呼叫模型,设计了软交换中的SIP 用户代理模块。给出了设计思想,包括各个功能模块的划分,接口设计,状态机实现以及基本类结构等。实现了与ISUP 等多协议的互通功能,并设计了媒体协商的提供/应答模型。目前,该设计在测试中能够满足现有软交换系统中SIP 协议的基本要求,并具有较好的性能。更多还原

【Abstract】 As a key technology of NGN, Softswitch provides an open network architecture, which realizes the integration of network and service, and leads the unification of PSTN, Mobile Network, Cable Television Network and Internet. Network integration is a trend of NGN, of which the interworking problem needs to be resolved urgently. As one of the session control protocols which has simpleness、flexibility and other characteristics, SIP (session initial protocol) defined by IETF, has been widely used in NGN and Mobile Network. This thesis mainly analyses and studies the interoperability of SIP in Softswitch, which includes interoperation、model of interworking and design of SIP user agent. Firstly, according to four-layer structure of Softswitch network, the interworking problem should be divided into four parts of different kinds of terminals in access layer, media formats and carrying technology in transport layer, many signals in control layer and different service resource in application layer. Among them, signal adaptation and conversion is session foundation, the interworking between SIP and H.323 or ISUP is described, in which network framework, signal mapping and call flow are discussed in detail. In order to realize the interworking between SIP and PSTN network, the SIP extension is introduced and the ENUM is used. Then the problem of address analysis is resolved. Secondly, multi-protocol interworking scheme using call model is put forward. Call model of Softswitch in which call and carry are separate, can be realized using supplement of connecting module and evolvement of IN’s(intelligent network). The interworking of SIP with other protocols can be resolved through call model of Softswitch, which supports access of many protocols and evolvement of network, and reduces hard work for protocols interworking. In the end of this thesis, with the detail research project and according to the Softswitch call model, the design of SIP UA module in Softswitch is given, which includes functions classification, interface design, finite state machine implementation and basic class structures. As a result of the implementation of this design, SIP UA can realize multi-protocol interworking with ISUP and other protocols, and finish the Offer/Answer model of media negotiation. Now the design with high capability meets the requirement of SIP in Softswitch.更多还原