Research And Design Of Distributed Lawful Interception System In VoIP Network

Lawful Interception (LI) is a information security process in which the communications of telecommunication services users are monitored with legal sanction. Conventional lawful interception is fulfilled by deploying interception equipment on fixed channel of switches. Because the route of signal and transaction medial traffic which are carried on IP network is not ascertainable in VoIP network, lawful interception becomes more complicated and difficult. This dissertation focus on the research of lawful interception system in VoIP network on aspects of LI architecture and device deployment strategy and designation in SIP phone network, we hope that can offer reference for telecom services providers to design and unify the interception interface.This dissertation expounded the concept and principle and procedure about lawful interception first. Based on the analysis of ESTI 's LI prototype system, considering the requirement of VoIP, we introduce IPCC 's LI reference model in Soft-switch-based network, and then analyze principle and functions of each module and the interface between TSP network and LEA network of this reference model.We adopt a distributed LI system for VoIP network which fulfill IPCC 's LI reference model. This distributed LI system consists of three-level control device and storage device and a suit of protocol. the distribute LI system employ corresponding deployment strategy according to the terminal type and the amount of subscribers and configuration of VoIP network, dispose compatible amount and suitable type interception device at the appropriate places in VoIP network.At last, after analyzing the architecture of SIP telephone network, we bring forward the deploy scheme of distribute LI system in SIP-based VoIP network. In TSP network, telecom service providers deploy TLD which take responsibility for management of LI and ILD which implement delivery function and BLD which wiretap calls. In LEA network, lawful enforcement agencies deploy LEA interception management server and storage device. Due to SIP phone network has the feature of centralized call control and distributed media handling, the LI system intercept call identity information on the call server and intercept call content on the media access device or network layer access device.