電信產業在各國的法律規範下，都必須要能提供監聽犯罪者通話的功能，傳統的PSTN和GSM都有一套監聽系統，可以提供給司法單位去監聽傳統電話和行動電話的用戶，所以當網路電話日漸發展和商業化的同時，也會面臨到監聽的問題，但是目前的網路電話仍無法提供此監聽的功能。
因此在論文中我們提出一套監聽系統的架構，此架構能在不影響SIP通訊架構下有效執行監聽功能，而且不造成伺服器的負擔，同時可以做到即時監聽，將被監聽者的通話即時且原音播出，以供檢調單位錄製。
作法上首先建立欲監聽用戶的資料庫，然後利用SIP通訊協定中每通通話的訊息皆會經由Proxy Server的特性，去察看是否是欲監聽用戶的通話，若是就將被監聽者的封包複製一份傳給監聽者，監聽者將收到封包混音播出，以此作法去實作出此套架構，以供發展網路電話的電信業者參考。

Telecommunication industry in national legal norm must be able to provide lawful interception functions of offenders phone. The traditional PSTN and GSM have had such a system that can provide investigating authorities to monitor telephone and mobile phone users. In the meanwhile, IP telephony must provide the same monitor functions. However, the current SIP-based IP telephony is still unable to provide this monitoring function.
In my thesis, I designed and implemented a monitoring system structure over SIP. It can efficiently carry out lawful interception without violating SIP communication. Additionally, it will not cause any overload on server, but will be able to monitor immediately. The recorded data can be played back without any delay and distortion.
A database is built up first for those who are monitored. When SIP dialog begins, SIP proxy inspects whether a call must be monitored. If it is the case of monitoring, a duplicate packet flow is delivered to the monitor. The monitor can playback. I believe this implementation can become a platform for further work in the lawful interception.

第1 章 序論.................................................................................................................8
1.1 節 研究動機....................................................................................................8
1.2 節 論文架構....................................................................................................8
第2 章 網路電話.........................................................................................................9
2.1 節 VOIP 網路電話簡介.................................................................................9
2.1.1 網路電話演進......................................................................................9
2.1.2 VOIP 網路電話優點和缺點..............................................................11
2.2 節 VOIP 網路電話的通訊協定...................................................................12
2.3 節 SIP 通訊協定...........................................................................................14
2.3.1 SIP 的通訊架構..................................................................................15
2.3.2 SIP 的訊息..........................................................................................17
2.3.3 SIP 通訊運作......................................................................................21
2.4 節 SER 簡介.................................................................................................21
第3 章 發展平台.......................................................................................................23
3.1 節 Infineon EASY5120P 簡介.....................................................................23
3.2 節 ADM5120 ................................................................................................23
3.2.1 Memory Interface................................................................................24
3.2.2 SDRAM ..............................................................................................24
3.2.3 FLASH................................................................................................25
3.3 節 VINETIC-x 架構.....................................................................................25
3.3.1 VINETIC-2CPE..................................................................................26
3.4 節 Firmware Architecture .............................................................................27
3.4.1 PCM Module.......................................................................................28
3.4.2 ALM Module ......................................................................................29
3.4.3 CODER Module..................................................................................29
第4 章 相關研究.......................................................................................................31
4.1 節 監聽系統架構設計..................................................................................31
4.1.1 分散式同步截收型監聽系統............................................................31
4.1.2 轉送型監聽系統................................................................................33
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4.2 節 H.323 為基礎的四種監聽方法...............................................................34
4.2.1 在匣道器上監聽................................................................................35
4.2.2 利用Gatekeeper 將被監聽的通話導向監聽設備..........................36
4.2.3 固定路徑監聽....................................................................................39
4.2.4 隨機處理模式監聽............................................................................40
第5 章 SIP 架構的監聽系統設計與實做.................................................................41
5.1 節 監聽系統設計..........................................................................................41
5.2 節 實作方法..................................................................................................44
5.2.1 SER(SIP Express Router)建置...........................................................44
5.2.2 欲監聽用戶資料庫建立....................................................................45
5.2.3 加入監聽訊息....................................................................................45
5.2.4 更新監聽表格....................................................................................48
5.2.5 UA device 監聽模式...........................................................................49
第6 章 結論和未來工作...........................................................................................53

[1] ITU-T Recommendation " H.323, Packet-based Multimedia Communications Systems ", International Telecommunication Union, Nov. 2000.
[2] IETF, Rosenberg, J., et al, " RFC3261: SIP: Session Initiation Protocol ", June 2002.
[3] IETF, Andreasen, F. and B. Foster, " Media Gateway Control Protocol (MGCP)Version 1.0 ", RFC 3435, January 2003.
[4] IETF, H. Schulzrinne, et al, " RFC1889: RTP: A transport Protocol for Real-TimeApplication ", January 1996.
[5] Infineon , " VINETIC-2CPE System Package Release Notes " ,2005
[6] Infineon , " Easy 5120 Hardware Description User's Manual " , 2005
[7] Infineon , " VINETIC-2CPE Preliminary Data Sheet " , 2005
[8] 賈文康,陳文生" 網路電話（VOIP）合法監聽架構之設計 ",第14屆全國資訊安全會議
[9] Milanovic, A.; Srbljic, S.; Raznjevic, I.; Sladden, D.; Matosevic, I.; Skrobo, D.;" Methods for lawful interception in IP telephony networks based on H.323 ",EUROCON 2003. Computer as a Tool. The IEEE Region 8 Volume 1, 22-24 Sept.2003, Page(s):198 - 202 vol.1
[10] ITU-T Recommendation H.225.0. " Call Signaling Protocols And Media StreamPacketization For Packet-Based Multimedia Communication System ",
International Telecommunication Union, November 2000
[11] ITU-T Recommendation H.245. " Control Protocol For Multimedia
Communication ", International Telecommunication Union, July 2001
[12] Handley, M. and V. Jacobson," SDP: Session Description Protocol ", RFC 2327, April 1998.
[13] Chia-Ming Sung; Ching-Cheng Lo; June-Hao Peng; Wen-Nung Tsai; "A study on VoIP Security ", International Computer Symposium, Dec. 2004, Page(s): 1230 -1237
[14] IETF, Fielding, R., et al, " RFC2616: Hypertext Transfer Protocol -- HTTP/1.1 ",June 1999.
[15] SER，http://www.iptel.org/ser/
[16] OSIP，http://www.gnu.org/software/osip/doc/html/
[17] Phpmyadmin，http://www.phpmyadmin.net/home_page/index.php
[18] MYSQL，http://dev.mysql.com/doc/