符合28181标准的User Agent

GB/T 28181标准对安全防范视频监控联网系统提出了新的要求，该标准规定了具体的SIP交互流程，并提出了新的扩展. 其中用户代理是SIP设备、SIP客户端等规定实体的重要组成部件. 用户代理的主要任务是不仅要符合标准的SIP流程，还要作为UAC负责发起呼叫，也要作为UAS负责接收呼叫并作响应. 用户代理的研究和设计对视频监控系统是否符合GB/T 28181标准及系统性能有着重要影响. 本文设计了一个符合标准的高效的用户代理，内容主要包括整体结构设计，设计的关键思想，以及如何基于该用户代理构建SIP客户端. 本文设计的用户代理具有高度模块化、低耦合、高效率、易扩展等特点，视频监控系统可以很方便快捷地构建相应的SIP实体.

User Agent Compled with 28181 General

The standard of GB/T 28181 puts forward new requirements to the video security monitoring network system. This standard also provides specific process for SIP interaction and new expansion.The user agent is an important part of SIP equipment, SIP client and other entities. The user agent's main task is not only to meet the standard SIP processes, but also to serve as UAC to initiate a call and receive a call then respond it. The research and design of user agent has important influence on whether or not the video security monitoring network system is in line with the GB/T 28181 standard and system performances. This paper designs a standard and efficient user agent, which includes: the overall structure, key ideas of this design and how to construct SIP client based on user agent. In this paper, the design of user agent has many advantages,such as:highly modular, low coupling and high efficiency.The video security monitoring network system can easily and quickly build the appropriate SIP entity.