隨著近年來網路快速的發展及頻寬快速的增加，網際網路的即時服務需求在許多網路服務上是必須的，因此網際網路即時服務的傳輸問題就變成一個很重要的議題。目前大多數的應用還是使用TCP 作為通訊協定，但由於TCP 可靠傳輸的特性，以致於TCP 無法符合即時性傳輸的需求，所以必須設計一套新的通訊協定來使用在即時服務的傳輸上。根據需求，我們發現了一套新的open source 的應用層通訊協定 – UDT(UDP-based Data Transfer)，可以透過此通訊協定中提供的部份可靠傳輸的特性，將此通訊協定應用在即時服務的傳輸中，此外，透過此通訊協定composable 特性，可以讓使用者根據需求去調整通訊協定內的參數和設定讓自己的應用達到更好的效能。
本篇論文首先會針對RTP(Real-time Transport Protocol)和UDT 做比較，並說明在本論文實驗環境下不選擇RTP 的原因。而本論文的實驗環境是假設在金融即時服務的環境下測試，以往在此環境下會使用的通訊協定是TCP，所以實驗中會針對TCP 和UDT 的測試結果來做比較和分析，並透過調整參數去測試UDT 在即時服務傳輸環境下的效能，像是資料遺失率…等，希望可以提供使用者在使用UDT 作為即時傳輸服務的通訊協定時的一個參考。

Due to the rapid development of the Internet and the fast expansion of the bandwidth, the requirement of the real-time service for the Internet is necessary. In this way, the problem of the real-time service for the Internet becomes an important issue. Most of the applications still use TCP as the protocol, but due to the reliable property of TCP, TCP can’t fit the requirement of the real-time transfer. So, we need to implement a protocol which we can use on the real-time transfer service.
According to the requirement, we find an open source application layer protocol – UDT (UDP-based Data Transfer). We can implement the application of real-time transfer by using the partial reliable messaging property of the protocol. In addition, user can adjust the parameters or settings of the protocol to make their application get into better performance by using the composable property of the protocol.
In our research, we’ll compare with RTP (Real-time Transport Protocol) and UDT, and also explain the reason why we don’t choose RTP in our research. The
assumption environment of our research is financial real-time service, and the protocol of such applications is TCP. In this way, we’ll analyze and compare the
result of the tests between TCP and UDT. We’ll also adjust the parameters of the protocol to test the performance of the UDT under the environment of the real-time transfer, such as data lose rate, etc.. These results can supply the reference for the users when using UDT as their protocol to implement their real-time applications.

致謝 i
摘要 ii
ABSTRACT iii
目錄 iv
圖目錄 vii
表目錄 ix
1. 序論 1
1.1. 研究背景 1
1.2. 研究動機與目的 2
1.3. 國內外研究現況 2
1.3.1 網路傳輸通訊協定之研究現況 2
1.3.2. 即時傳輸服務相關之研究現況 4
1.3.2.1. RSVP (Resource ReServation Protocol) 5
1.3.2.2. RTP (Real-time Transport Protocol) 6
1.3.2.3. RTCP (Real-time Control Protocol) 8
1.3.2.4. RTSP (Real-Time Streaming Protocol) 8
1.3.3. 尚待研究問題及研究意義 9
1.4. 論文架構 9
2. UDT概論與介紹 11
2.1. UDT背景介紹 11
2.2. UDT特性和功能 12
2.2.1. UDT特性 12
2.2.2. UDT功能 13
2.3. UDT封包定義 13
2.3.1. 資料封包(Data Packets) 13
2.3.2. 控制封包(Control Packets) 15
2.3.3. Sender模組和Receiver模組間的關係 17
2.4. UDT模組和元件 17
2.4.1. 傳送者模組(Sender Module) 18
2.4.2. 接收者模組(Receiver Module) 18
2.4.3. 應用程式介面模組(APIs Module) 19
2.4.4. UDP通道模組(UDP Channel Module) 20
2.4.5. 流量控管模組(Congestion Control Module) 20
2.4.6. UDP Multiplexer 20
2.4.7. 計時器(Timers) 21
2.5. UDT運作流程 21
2.5.1. Client – Server連線模式 22
2.5.2. Peer-to-Peer連線模式 22
2.5.3. 資料的傳送(Data Sending) 22
2.5.4. 資料的接收(Data Receiving) 23
2.6. 壅塞控制(CONGESTION CONTROL) 24
2.6.1. 壅塞控制機制 24
2.6.1.1. 與TCP的壅塞控制機制的差異 26
2.6.2. Noisy Link 26
2.7. UDT COMPOSABLE特性 27
2.8. UDT的部份可靠傳輸模式(PARTIAL RELIABLE MESSAGING MODE) 29
2.8.1. 使用時機 29
2.8.2. 使用方法 29
2.8.3. 重複封包(Duplicate Packets)的出現 30
2.9. UDT使用方式 30
2.9.1. 建立UDT Library 30
2.9.2. 設定UDT Library路徑 31
2.9.3. 建立UDT連線 31
2.9.3.1. Reliable Streaming連線 31
2.9.3.2. Partial Reliable Messaging連線 32
2.10. UDT使用時機 33
3. 研究與實作 34
3.1. 實驗環境介紹 34
3.2. 通訊協定的選擇 34
3.3. 軟體介紹 36
3.4. 實驗介紹與分析 36
3.4.1. 實驗一 36
3.4.1.1. 實驗說明 36
3.4.1.2. 實驗設計 36
3.4.1.3. 實驗環境 37
3.4.1.4. 實驗結果 37
3.4.1.5. 實驗分析 38
3.4.2. 實驗二 39
3.4.2.1. 實驗說明 39
3.4.2.2. 實驗設計 39
3.4.2.3. 實驗環境 40
3.4.2.4. 實驗結果 41
3.4.2.5. 實驗分析 43
3.4.3. 實驗三 43
3.4.3.1. 實驗說明 43
3.4.3.2. 實驗設計 44
3.4.3.3. 實驗環境 45
3.4.3.4. 實驗結果 46
3.4.3.5. 實驗分析 48
3.4.4. 實驗四 49
3.4.4.1. 實驗說明 49
3.4.4.2. 實驗設計 49
3.4.4.3. 實驗環境 50
3.4.4.4. 實驗結果 51
3.4.4.5. 實驗分析 51
4. 結論與未來展望 52
5. 參考文獻 54
附錄 58

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