近年來，VoIP ( Voice over IP )的應用愈受到歡迎，而且愈來愈多的網路研究人員注重於VoIP技術議題。然而，有部分的使用者已經習慣使用傳統的電話號碼，因為他們覺得傳統電信網路仍然比VoIP較為方便。那毫無意義可言的IP 位址，以及冗長的網域名稱，實在是不容易記住。
在本論文中，我們設計與實作一個可以提供ENUM (tElephone NUmber Mapping ) 服務的SIP客戶端系統。透過ENUM (RFC 2916) 技術把電話號碼編碼成E.164號碼。藉由查詢DNS來取得存在於NAPTR (Naming Authority Pointer)記錄之相對應SIP URI (Universal Resource Identifier)。ENUM 服務在傳統電信網路以及VoIP之間扮演了舉足輕重的角色。對使用者來說，他們不會覺得使用習慣有所改變。

VoIP applications become popular in recently years, and more and more network researchers are interested in VoIP issues. However, users are used to using the traditional telephony number to make calls. This is because the telephony number is more convenient than the meaningless IP address and the diffusive domain name in VoIP networks. They are really hard to remember.
In this paper, we discuss the design and implementation of ENUM (tElephone NUmber Mapping) service over a SIP user agent. According to the technology of ENUM (RFC2916), the dialed numbers can be encoded into E.164 numbers. By querying the DNS, we can get the SIP URI (Universal Resource Identifier) which exists in the NAPTR (Naming Authority Pointer) resource records. The ENUM service plays an important role between the traditional telephony networks and the VoIP networks. The users can be unaware of the different operation style in VoIP.

中文摘要 I
ABSTRACT II
目錄 III
圖目錄 V
表目錄 VI
CHAPTER 1 序論 1
CHAPTER 2 網路電話簡介 2
2.1 VOIP相關協定簡介 2
2.2 SIP相關簡介 3
2.2.1 Client 端 4
2.2.2 Server 端 4
2.3 SIP請求訊息 5
2.4 SIP回應訊息 6
CHAPTER 3 相關研究 9
3.1 DNS – NAPTR RECORD 9
3.1.1 何謂 NAPTR(Naming Authority Pointer) record 9
3.1.2 何謂 E.164 編碼 11
3.1.3 利用指令查詢(query) 11
CHAPTER 4 架構和實作 15
4.1 系統架構 15
4.2 SIP UA 18
4.3 RESOLVER SERVER 23
4.3.1 Resolver 23
4.3.2 Parser 29
4.4 加入 ENUM 功能的SIP運作流程 37
CHAPTER 5 總結 41

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