Design And Implementation Of Lawful Interception System Based On SIP

In recent years, VoIP has gradually replaced the traditional signaling network, became the main carrier of voice communication network. However, with the continuous expansion of the application range, it also brings a series of security management problems, among which the lawful interception of VoIP is an outstanding issue.To design and implement a solution of LI system based on SIP is the major objective of this paper. As groundwork, the T1.678 LI model designed by ATIS for the VoIP network is introduced, and the function and interfaces of each components are described in this paper.Then the basic concepts and deployment of VoIP network is described briefly, as well as SIP protocol. Basis on the SIP network involving SBC (Session Border Controller), a LI system is designed and implemented.The architecture of this system is based on the T1.678 LI model, which consist of access model (as Access Function), SIP processor (as Mediation Function) and HI message processors (as Delivery Function). The goal of this system is to sufficiently filter out network data, intercept SIP calls and report to monitor center following the T 1.678 standard.First, the design of access model choses external IAP as solution after comparing the intercept requirments, built-in LI model and system efficiency, which is capable of filtering network data efficiently based on target number.Then, by analysising the SBC's working mechanism, a solution for processing SIP messages is proposed to solve the problems about how to analysis SIP messages, how to analysis call senarios and how to intercept voice channel. Then the internal models of the key model-SIP processor are described detailly as well as how it works inside.At last, the structure of T1.678 handover messages and the detailed design and work flow of HI message processors are described detaily, including HI2 processor and H13 processor.The design and implementation of LI system based on SIP would be valuable to the the researches on the lawful interception over VoIP network.