Application Layer Protocol Filtering System Design And Realization

With the rapid development of Internet, new network applications, such as instant messaging, P2P file sharing, online games and so on, are emerging. These new network applications lead to serious network congestion, and cause serious negative impacts on the important business. In addition, enterprise and public institutions, and telecom operators have new needs for network traffic management, such as the prohibition of online chat, P2P download, play games and so on. These demands require filtering of protocols on application layer. Under this background, there is a series of studies on the realization of the protocol filtering system in this dissertation. The primary work is summarized as below:(1) Designing and implementing a subsystem of high-speed data capturing and protocol filtering based on memory mapping technology. Based on the analysis of existing design, the subsystem of high-speed data capturing and protocol filtering based on memory mapping technology is designed. Our system can avoid data copies between the kernel space and user space, improve the transmission speed of data packet and filter information between the kernel and user space, and speed up the system's data processing speed and filtration efficiency.(2) Designing and implementing an application layer protocol filtering system, with the protocol signature database modifiable. The system captures the original IP packet, makes fragment reassembly and transport layer flow analysis, identifies data on the application layer, and records the information of filtering. This system, being sniffer, could be transparent to the network. Also it can be installed on the gateway device. It deals with the network traffic through the collection, analysis, identification and filtering, to meet the design requirements.(3) Designing and implementing a web interface for control and management of application layer protocol filtering system. The apache and PHP are used to construct this subsystem. This system can control and manage the application layer protocol filtering system, facilitating the operations.Test results show that the system's performance has a great improvement, compared with L7-filter. Meanwhile the test result also reflects the advantage of the system architecture.