Design And Implementation Of A VoIP Traffic Detection System Based On DPI Techniques

VoIP (Voice over InternetProtocol) is a hot topic in the field of Internet application, that implements the voice real-time transporting on the Internet. Its basic principle is:The speech data codes are compressed by voice compress algorithm, and then the packages of voice data, using TCP/IP standard are sent to the receiver through the IP network, then sort and join these voice packets in series; after the step of decompression, the speech signal is restored and the purpose transmitting the voice on the internet is implemented.For its low-cost, openness and flexibility, VoIP possesses a major impact to PSTN services which the telecommunication operator run. Especially in IDD and DDD business, it has caused a great loss of business. At the same time, because VoIP yields big profits and national supervision policy issues, there are many illegal VoIP operators now, who hire telecom operators' broadband network to run VoIP voice services, streaming the telecom operators' business income and disrupting the market order. Furthermore, changes of (of technology and networks) made by PC to Phone business, lend the national security and operational control into a blank state, any sudden event, will make us have none ability to ensure transparent and secure communication systems; Finally, there have been a large number of domestic virtual operators, whose business is almost unregulated and do not have any experience for the future management of the business location. Therefore, how to effectively limit the impact on the telecom operator from VoIP and effectively control it at the technical level, it has become a technical issues that the telecom operators have to study.The key of controlling the VoIP traffic effectively is that the VoIP flow of real-time network can be detected out accurately. This paper places emphasis on how to detect the VoIP traffic accurately and efficiently. The main content of this article contains the following several aspects:This paper expounded the principle of VoIP technology, development, and elaborate its advantages and disadvantages;This paper generally presents the method of current flow identification. such as the technology based on DPI and DFI which has been widely used;This paper describes a scheme of traffic identification based on DPI, then designs and implements a Network Flow Inspection System. The system consists of the update of characteristic repository and traffic identification, the software updates of the update of characteristic,custom rule and traffic identification made it easy to be integrated to meet the challenge from the rapidly development of internet. The test results demonstrate that the performance of system is reliable and the recognition rate reaches as high as above 95%. The system is able to identify over dozens of VoIP applications with good stability and availability. It also enjoys excellent expandability. It could be cooperated with other outside system to be applied through a series of API. For example : flow statistic, bandwidth management, flow accounting, content accounting and so on.