近十年來網際網路的發展迅速，網路的應用也隨之擴大，加上最近幾年的VoIP(Voice Over IP)技術的漸趨成熟及未來IP(Internet Protocol)網路上的整合，也開始朝向Voice／Video／Data／Fax／LAN(Local Area Netwrok)的一體化的趨勢，並且與話務帳務系統(Billing system)結合，為新一代的電信服務的機制，僅需利用Internet而不經過公眾電話網路（簡稱PSTN）。除了利用電腦外加軟、硬體外，也有一些廠商提供另一種替代方案，即ITG (Internet Telephone Gateway)；利用閘道Gateway來判別語音訊息或是傳統的網路封包資料，且將電話部分自動轉送到傳統的PSTN上。
「通訊」一直是長久一來人們不斷追逐，努力突破且永遠不會消失淘汰的技術，因應時代潮流傳統的電信市場正是下一波面臨重大挑戰的產業。回想過去近十年的電信技術正以倍數的成長，將傳統的Circuit Switch 轉變為Packet Switch所面臨的將會是整個產業型態的重大轉變，未來電信業者的獲利不再豐盈，也不像目前中華電信一樣獨占市場，所有語音、影像通訊，將透過寬頻網路來取代。
話務帳務系統經由代理人機制的觸發接收到由PSTN所產生的CDR(Ｃall Detail Record)或則是由IP所產生的EDR(Event Detail Record)。經由系統自動觸發後所產生的資料根據系統先前已設定種種的因素而進行運算，例如費率、帳務資料、客戶資料、計費方案等等而產生一個話務帳務的明細資料並自動產生列印檔及自動列印。

The Internet is most popular and is used in the widespread areas such as habitation, school, enterprises, the government and airports. Furthermore, the communication on the Internet is without occupied one line until terminating talking. The VOIP technology of H.323 protocol has transformed into significant technology since 1996. According to the American IDC corporation research report, the VOIP has been used at American and the total time is 1 billion minutes in 1999. The trend of VOIP is to integrate the Voice, Video, Data, Fax, LAN, WAN and Answer Machine with the billing system and becomes very convenient and easy to use at any time and location. Also, the new VOIP technology with intelligent billing system is instead of the traditional technology with the fix and expensive communication fees. 
The billing system receives all of CDR by PSTN or EDR by IP through the agent mechanism when the events interface (agent) is triggered. The Billing Production is according to factors such as the Rating, Billing Data, customer DB and Tariff and Sharing Schemes. After the Billing Production occurs, the Payment Checking, Bill Printing and Bill Delivery are launched at the same time.

Chapter 1 INTRODUCTION	1
1.1 Background	1
1.2 Motivation	3
1.3 Purpose	4
1.4 Thesis Architecture	5
Chapter 2 Related Work	6
2.1 H.323	6
2.1.1 H.323 Components	6
2.1.2 H.323 Zone	9
2.1.3 protocols specified by H.323	10
2.1.3.1 Audio CODEC	11
2.1.3.2 Video CODEC	12
2.1.3.3 H.225 Registration, Admission, and Status	12
2.1.3.4 H.225 Call Signaling	12
2.1.3.5 H.245 Control Signaling	13
2.1.3.6 Real-Time Transport Protocol	13
2.1.3.7 Real-Time Transport Control Protocol	13
2.1.4 H.323 Connection Procedure	14
2.2 Billing	20
2.2.1 Billing Architecture	20
2.2.2 Charging Data	22
2.2.2.1 Call Detail Record (CDR)/Event Detail Record (EDR)	22
2.2.2.2 Internet Protocol Detail Record (IPDR)	23
2.2.3 Charging Models	23
2.3 INTELLIGENT AGENT	29
Chapter 3 SYSTEM ENVIRONMENT	33
3.1 System Architecture	33
3.2 System Procedure	35
3.2.1 Register Mode(RM)	35
3.2.2 Text Mode(TM)	36
3.2.3 Audio Mode(AM)	38
3.2.4 Video Mode(VM)	40
3.2.5 Call Mode(CM)	42
3.3 Billing System	43
Chapter 4 CONCLUSION AND FUTURE WORK	48
4.1 Conclusion	48
4.2 Future Work	50
REFERENCES	51

Figure 1 H.323 Terminals on a Packet Network	6
Figure 2 H.323 Architecture	8
Figure 3 An H.323 Zone	10
Figure 4 H.323 Protocol Diagram	11
Figure 5 H.323 Call Establishment	14
Figure 6 H.323 control signaling flows	16
Figure 7 H.323 media stream and media control flows	18
Figure 8 Call release flows	19
Figure 9 Billing System	20
Figure 10 The diagram of integrated PSTN and VOIP	33
Figure 11 The diagram of implementation	34
Figure 12 Register Mode	35
Figure 13 Text Mode	36
Figure 14 Audio Mode	38
Figure 15 Video Mode	40
Figure 16 Call Mode	42
Figure 17 Billing Architecture	43
Figure 18 The agent communication state diagram	46
Table 1 Charging Model Comparison	28

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