GPRS环境下TCP协议的性能分析与改进

【作者】 杜吉荣；

【导师】 陈抗生；

【作者基本信息】 浙江大学 ， 电子科学与技术， 2002， 硕士

【摘要】 TCP协议是Internet协议族的重要组成之一，最初被设计用来在有线网络上为上层应用提供端到端的可靠连接，我们所熟悉的WWW、FTP、EMAIL服务都是以TCP为基础的。随着移动通信的发展，作为向3G过渡的一个中间阶段，建立在GSM系统基础上的GPRS网络将提供数据业务，使用户可以通过移动终端随时随地的接入Internet。 本文详细研究了TCP协议的机理，无线链路的一般特征以及GPRS网络的特性，并分析了它们对TCP性能的影响。在总结了大量文献和仿真结果的基础上，针对GPRS网络中经常发生的链路中断所导致的TCP发送方长时间的延迟问题，提出了一个解决方案—PROBE机制，并在LINUX内核中初步实现。最后给出了本人对TCP协议未来发展趋势的一点展望。 通过在爱立信公司的GPRS仿真环境GATE上的标准测试表明这一方法能够极大的改善TCP协议在恶劣的GPRS环境中的性能，使之能够达到应用的水平，而标准TCP在遇到这类问题时是难以正常运转的。更多还原

【Abstract】 The Transfer Control Protocol(TCP) is one of the most important Internet Protocols, which is initially designed for fixed networks, where the main problem is the congestion. The General Packet Radio Service (GPRS) system will provide an easy adaptation to applications running in the Internet such as WWW, FTP and e-mail. These applications work with the TCP protocol. However, the character is very different between the wireless link in GPRS system and the wireline link in fixed networks, which cause the standard TCP protocol to fail to run.The thesis focuses on how to improve the TCP pefformance over GPRS. After having a deep understanding of the TCP mechanism, the gerenal characters of usual wireless links and the special characters of GPRS networks. Based on many literatures and simulations, a solution using PROBE mechanism is provided to solve the problem, the very long delay by interrupt of wireless link, which is often happened in busy GPRS networks. This solution is implemented using the LINUX kernel. At last a prospect of the future TCP over wireless and wireline mixed networks is shown.The solution has passed the standard tests of GPRS Application Test Environment (GATE) developed by Ericsson. The result is inspirer while the standard TCP cannot run correctly in the severe cases.更多还原