Lawful Interception System

Lawful interception is a kind of action based on the law. As a powerful weapon against crime, lawful interception becomes more and more important. The article, depending on the interception standard of ETSI standard, studies the interception of the wireless telecommunications, VOIP system based on SIP and IP network..Lawful Interception involved intercepted data transmission between the network system, which may include Network Operator, Access Provider and Service Provider, and the Law Enforcement Agency. The ETSI standard defines three interfaces:- HI1 port concerned with warrant information, HI2 port concerned with intercept related information and HI3 for the content of communication.The author had taken part in the development of Telecommunication Monitor System (TMS). In this system, HI1 port and HI2 port data were transferred by TCP/DP, and HI3 port by No.7 signal system. Now, the system has passed test.HI1 port of the packed switched network and that of circuit switched network have the same data structure, also about HI2 port. However, delivery of packetized content of communication (HI3 port) shall not use No.7 signal system but TCP/IP. The article generalized the interception mode of packed switched network, VIOP system based on SIP and IP network from circuit switched network.The VOIP system based on SIP is distributed system. In the proposal interception mode, to gain the intercepted data relates to SIP proxy and gateway, we shall gain signal data from SIP proxy and communication content from gateway. Therefore, it is important that the SIP proxy is in harmony with gateway.The IP-world is a highly structured mixture of communications-transportation and communications-services, with the services being mostly defined so as to be transparent to the communications carrier. Therefore a solution for the requirement for Lawful Interception of IP-traffic is very different from anything experienced to date in the circuit-switched environment. The straightforward way of performing an intercept of this kind of traffic is to go for the internet service provision. That would mean that the order to intercept is issued to the ISP and based on the customer-id of the subject with that ISP. The article puts forward the interception mode by the method of the network connection.