網際網路的快速發展促進了各種新興技術之崛起，其中網路電話(VoIP)的技術不再侷限於語音封包的傳遞，更整合了視訊、語音信箱與多媒體及低費率的優勢。因此，越來越多企業與學校資訊部門紛紛加入網路電話的建置，透過SIP IP-PBX交換機與網路電話閘道器和各家不同的網路電話提供業者界接，更是節省了許多國際電話的費用。
目前市面上的網路電話設備已經非常成熟，早已具備取代傳統電話的能力。但由於網路電話是透過H.323、SIP等IP通訊協定建立連線，使得其通話傳輸建構在不穩定的平台上。然而大部份相關的網路電話管理系統，都只有提供通話記錄及通話存取之管理；當網路電話無法正常提供服務時，並不能得知錯誤的原因。使得網路電話的推廣與存在遭受使用者的質疑。
本論文提出一套錯誤診斷系統來監控以SIP為基礎的網路電話系統，主動式的收集註冊於相同Proxy Server下SIP User Agents撥打電話時彼此間訊息交換的情況，並將這些訊息交換過程轉換成時間限制Petri Net (TCPN, Timing Constraint Petri Net)模型診斷。當系統診斷出錯誤時，藉由SIP標準訂定的錯誤訊息以及走訪TCPN模型所取得的警訊透過比對知識庫找出撥打障礙的原因，最後以E-mail方式將錯誤原因並給予建議解決方法通知網管人員，使其得以在最短時間內修復錯誤以確保使用者通話品質。

Voice over Internet Protocol (VoIP) is not limited to the transmission of voice packets, but integrates video, voice mail, and multimedia, all at a low cost. An increasing number of agencies, enterprises, and schools are designing and deploying IP telephony networks. Session Initiation Protocol Internet Protocol Private Branch Exchanges (SIP IP-PBXs) and Internet Telephony Gateways (ITGs) can connect with other Internet Telephony Service Providers (ITSPs) to take advantage of tremendous savings in long-distance and international calling.
Currently one obstacle to total replacement of Public Switched Telephone Networks (PSTNs) by VoIP is the limited management control over VoIP faults. Since VoIP must often establish connections under uncontrollable conditions, it is necessary VoIP’s protocols (such as H.323 and SIP) to provide network management with detailed information concerning faults. Existing management systems only provide call detail records, dial plan settings, and call access control. Existing systems do not provide efficient and immediate call quality monitoring, which causes users to question the maturity of VoIP technology.
In this paper, we proposed a fault detection system to manage SIP-based VoIP systems. We collected messages exchanged between SIP User Agents (UA) and SIP Servers. When each call was established from the calling UA to the receiving UA, Simple Network Management Protocol (SNMP) transmitted relevant information to our fault detection system. A Timing Constraint Petri Net (TCPN) model monitored calls; when faults were detected, the management system searched the knowledge base, determined an explanation for each fault, and automatically e-mailed the relevant explanation, along with suggested solutions, to management personnel. The system as developed provides timely management of person-to-person calls; we suggest that future research could usefully extend this technology to conference calls.

誌謝 i
摘要 ii
Abstract iii
目錄 v
圖目錄 vii
表目錄 ix
第一章 導論 1
1.1 研究背景 1
1.2 研究動機與目的 3
1.3 系統架構 5
1.4 論文章節概要 6
第二章 相關研究 7
2.1 網路電話服務暨相關管理系統 7
2.2 網路電話監控管理系統 9
2.2.1 傳統式故障偵測與排除 9
2.2.2 主動式故障偵測 11
2.2.3 網路電話上的安全性考量 13
2.3 Petri Net的相關研究 14
2.3.1 Petri Net簡介 15
2.3.2 Petri Net衍生模組 16
第三章 網路電話撥打障礙 18
3.1 SIP-based網路電話介紹 18
3.2 撥打錯誤的分析與探討 23
3.2.1 錯誤的種類 23
3.2.2 錯誤與警訊 29
第四章 研究方法與架構 31
4.1 網路電話錯誤診斷模組 31
4.2 錯誤偵測 32
4.2.1 SIP Call Flow 32
4.2.2 Petri Net 34
4.2.3 Timing Constraint Petri Net 36
4.2.4 TCPN警訊格式 40
4.3 警訊比對與過濾 41
4.3.1 知識庫建置 42
4.3.2 警訊過濾 46
第五章 系統實作 48
5.1 系統架構 48
5.2 系統環境與開發工具 49
5.2.1 資料收集 51
5.2.2 診斷系統實作 52
5.3 系統效能分析 56
5.3.1 網管流量負擔 56
5.3.2 Trap傳送時間的討論 57
5.3.3 系統執行效能 58
5.3.4 討論 58
第六章 結論與未來發展 59
參考文獻 60
附錄 64
附錄A、TCPN Place 64
附錄B、TCPN Translation 66
附錄C、發射週期時間 67

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