Abstract: With the wide application of VoIP, how to implement lawful interception rapidly and effectively has become the focus of present research. The characteristics of H.323 network and its protocol were analyzed, and the traffic identification methodology based on H.323，the algorithm of extracting the dynamic conversation and the flow of network interception were expounded in detail. And on such basis, a design of interception model based on H.323 was put forward.

Key words: H.323, Voice over Internet Protocol (VoIP), lawful interception, traffic identification

摘要： 随着VoIP的广泛应用，如何对其实施快捷、有效的合法监听已成为当前研究的热点。对H.323协议网络及其协议自身的特点进行了研究和分析，并对基于H.323的VoIP流量的识别方法、动态会话的提取算法和网络监听流程作了重点阐述，在此基础上，提出了一个基于H.323的VoIP监听模型的设计方案。

关键词: H.323, IP电话技术, 合法监听, 流量识别