- 學位論文
支援網路電話即時監聽機制之分散式架構
Distributed Architecture for Real-Time Lawful Intercept in SIP-based VoIP Systems
摘要
網際網路語音（Voice over IP，簡稱VoIP）服務挾帶低通話成本的優勢，不斷地吸引傳統電話的使用者，包括個人及企業用戶，轉而使用VoIP這項新興的技術。當VoIP步入商業化階段並在市場上開始提供通話服務時，相關的電信法規要求提供電話監聽的機制。目前在傳統公眾電話網路上已有一套運作良好的監聽系統，而VoIP由於聲音的傳送並不像傳統電話需要透過中央交換機，相較之下較不易進行監聽。 近年來所提出的VoIP監聽系統，大都需要修改SIP代理伺服器架構，讓SIP代理伺服器將監聽訊息導向相關的監聽設備以進行監聽。但SIP為一開放的通訊協定，因此任何人都可以自行開發或使用各種廠牌的SIP伺服器；且由於將封包更改傳送路由的方式，容易讓被監聽者察覺。再者，將監聽的內容即時以檔案的型式儲存，會造成其磁碟讀寫的效能問題，在同時需要進行多人監聽時，會形成效能上的瓶頸。 針對上述問題，本論文提出一套VoIP的分散式監聽功能架構。我們將監聽功能佈建在網路基礎設備上，透過在網路設備上交換的封包做分析，建立監聽系統。由於監聽設備分散在各個子網路中，透過自動化回報及訊息交流，達到分散式監聽的目標，並且在執行監聽時由各個監聽設備即時將監聽內容傳至監聽者。因此本論文所提出的架構具有易於部署在不同的環境中，不需修改現有的SIP代理伺服器系統，能夠於通話進行中即時監聽內容等特點。
並列摘要
Due to the low cost and the convenience of Internet, the Voice over Internet Protocol（VoIP）services are also attracting the subscribers of the traditional telephone to turn to use this new technology. For VoIP to be commercialized, it must support Lawful Interception which is required by the Law Enforcement Agency of each country. In contrast to the Public Switched Telephone Network（PSTN）which has a good monitoring system, it is more difficult to develop a monitoring system for VoIP because the sound transmission in VoIP need not go through the central office (CO). Recently, a few VoIP monitoring systems are proposed, but most of them need to revise the SIP proxy server behavior. They rely on the SIP proxy server to modify the SIP message body to conduct the monitoring. However, SIP is an open communication protocol; anyone may develop his/her own SIP server, so the server-based solution of monitoring will not always work. Moreover, because redirecting the packet flow to the monitoring device will change the route, it may be easy for people to detect that their conversation is being monitored. Users may also apply S/MIME to encrypt the contents of the SIP message body to prevent them from being modified by the SIP proxy server. Furthermore, the system stores the audio conversation in files, so the disk I/O will cause significant performance issues. As the requests for more monitoring increase, this will become the performance bottleneck. To conquer the above pitfalls, this thesis proposes a distributed architecture of VoIP monitoring. We will distribute the monitoring equipment in many subnets, and wiretapping can be done by immediately passing the intercepted audio packets to the Law Enforcement Agency. In a word, this thesis proposes an architecture which is easy to deploy in different environments without amending the existing SIP proxy server, and it can support the real-time monitoring of audio conversation easily.
參考文獻
延伸閱讀
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