Border gateway function performance requirements for the lawful intercept of voice at IMS architecture

Lawful intercept is a mandatory regulatory service that must be available when delivering voice services over packet-based networks. The carrier should be capable of providing the law-enforcement authorities with logged information about calls originated and terminated by a particular subscriber. Moreover, the carrier should also be able to intercept subscribers’ call-content (e.g., voice conversations). In both cases, the interception should be undetectable by the intercepted subscriber or other callers. Despite the importance of the topic, little effort has been made so far to analyze the performance aspects of lawful intercept in a packet-based network.This paper presents an overall analysis of the performance requirements of the border gateway function at the IMS architecture for lawful call-content interception on an end-to-end packet-based network with only voice packets. In particular, various performance characteristics of the VoIP transmission, like VoIP traffic and VoIP signaling traffic, with an emphasis on the SIP, were investigated in order to determine the margins of the border gateway function's performance requirements where an efficient and undetectable transfer of lawful call-content interception over packet-based networks can be expected.