現今通信產業之蓬勃發展，各式各樣的通信設備推陳出新，常用的通信設備已不再侷限於家用的話機.。透過網際網路，網路電話、軟體電話等都能做到與傳統話機同樣的功能。而這些通訊產品共通的部份就是使用者身份的識別，不管是電話號碼或是URI（Universal Resource Identity）。而ENUM（tElephone Number Mapping）提供一種名稱映對機制來讓電話號碼與網域名稱作轉換及互通的機制，讓電信設備與網際網路整合，相輔相成。
在這篇論文中，我們利用ENUM設計一個具負載平衡的分散式系統。將傳統單一伺服器的流量負擔分散至各伺服器以加強服務的可靠性。面對未來VoIP和傳統PSTN作結合時，在使用者人數增加下，能夠提供更強固的服務品質。

With the rapid growth of communication, various communication equipments get rid of the stale and bring forth the fresh. The frequently used communication device is not limited to domestic telephone any longer. We can achieve the same functionality as traditional telephone by the use of VoIP（Voice over IP）over the Internet. The common fraction of these communication products is the user identity which may be achieved by either a telephone number or an URI (Universal Resource Identity).
In this paper, we implement a distributed system with load balancing. This is achieved by utilization of ENUM. It can distribute the load of the traditional server to several servers to enhance the reliability of services. For the future combination of VoIP and the traditional PSTN, we expect to provide more consistent services while the number of user is increasing.

第1章 序論.................................................................................................................................1
1.1 研究背景.............................................................................................................................1
1.2 研究動機與目的.................................................................................................................1
1.3 研究方法與步驟.................................................................................................................2
1.3.1 研究方法.....................................................................................................................2
1.3.2 研究步驟.....................................................................................................................3
1.4 章節介紹.............................................................................................................................3
第2章 SIP協定及網路電話介紹................................................................................................4
2.1 SIP協定（RFC3261）剖析及VOIP網路電話介紹............................................................4
2.2 SIP 主要元件介紹...............................................................................................................6
2.3 SIP訊息（MESSAGE）及通話流程.....................................................................................8
2.3.1 SIP請求（Request）訊息............................................................................................9
2.3.2 SIP回應（Response）訊息.........................................................................................9
2.3.3 會談描述協定SDP（Session Description Protocol）.............................................10
2.3.4 SIP對話流程..............................................................................................................11
2.4 網路電話硬體架構...........................................................................................................12
2.5 網路電話軟體架構...........................................................................................................17
2.5.1 Web功能及運作流程.................................................................................................19
第3章 相關研究........................................................................................................................23
3.1 ENUM介紹........................................................................................................................23
3.2 ENUM運作方式................................................................................................................25
3.2.1 NAPTR 資源紀錄......................................................................................................25
vi
3.2.2 ENUM服務運作流程.................................................................................................27
第4章 架構與實作....................................................................................................................29
4.1 伺服器端...........................................................................................................................29
4.1.1 OpenSER介紹............................................................................................................30
4.1.2 OpsnSER架構............................................................................................................31
4.1.3 OpenSER SIP訊息路由機制......................................................................................33
4.1.4 OpenSER Modules......................................................................................................34
4.1.5 ENUM module............................................................................................................39
4.1.6 在openser.cfg上設定ENUM......................................................................................43
4.2 客戶端...............................................................................................................................45
第5章 結論................................................................................................................................47

[1] Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[2] Flavio E. Goncalves, “Building Telephony Systems with OpenSER”, March 2007
[3] J. Rosenberg, H. Schulzrinne, G. Camarillo,A. Johnston,J. Peterson,R. Sparks,M. Handley,E. Schooler ”SIP: Session Initiation Protocol”, RFC 3261,June 2002
[4] J Peterson.ENUMservice Registration for Session Initiation Protocol(SIP) Addresses-of-Record[S].IETF,RFC3764,2004.
[5] M. Handley, V. Jacobson, “SDP: Session Description Protocol”, RFC-2327, April 1998
[6] M. Mealling, R. Daniel “The Naming Authority Pointer (NAPTR) DNS Resource Record”, RFC 2915,September 2000
[7] P. Faltstrom “E.164 number and DNS”, RFC 2916 , September 2000
[8] P. Mockapetris, “DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION”, RFC 1035 , November 1987
[9] R Blane. Liaison to “IETF/ISOC on ENUM[S]” RFC3026,2001
[10] R Brandner,L Conroy,R Stastny.IANA Registration for ENUMservice Web and FT[S].IETF,RFC4002,2005.
[11] “ADM-5120 Data Sheet Rev. 1.1”, Infineon Technologies., March 2005
[12] ”Easy 5120 Hardware Description User’s Manual ” , Infineon , 2005
[13] Web Page “ENUM Module”, http://www.openser.org/docs/modules/devel/enum.html
[14] Web Page “OpenSER Documentation”, http://www.openser.org/dokuwiki/doku.php
[15] Web Page ”DNS Configuration”, http://mit.edu/sip/sip.edu/dns.shtml,2003
49
[16] Web Page “The Open Source SIP Server”, http://www.openser.org/
[17] Web Page “SIP/ENUM TRIAL”, http://service.enum.org.tw/
[18] Web Page “Telephone Number Mapping(Enum)”, http://www.ietf.org/html.charters/enum-charter.html
[19] 賈文康, “Session Initiation Protocol(SIP) Methodology Handbook”,March 2006
[20] 王峰，錢華林 “ENUM系統以及解析服務的研究”
[21] Web Page ”台灣SIP/ENUM應用促進會”, http://www.enum.org.tw/seft2/ipox.htm