現今Internet的發展規模是藉著互連異質網路，而不斷地延伸著。由於不同區域通訊系統之頻寬及容量等傳輸資源不同，加上路由器對IP資料包的存轉處理通常只有選徑功能，因此從來源到目的端對端壅塞控制是必須的。在IP之上的傳輸協定即提供此類的機制，如TCP被設計來維持壅塞避免的可靠性傳遞。
然而，對於多媒體串流（multimedia streaming）的應用，TCP的可靠要求卻需要付出很不利於此類應用的代價，有如重送對時間延遲的增加，以及滑動視窗（sliding window）基礎的爆衝（burst）。我們需要有調整速率基礎的傳輸協定，並能支援媒體展現的格式，RTP/RTCP已為此成形，但是多媒體的應用仍有重要研究議題。
兩個顯著的因素包括：較長週期控制的壅塞避免效果？速率控制是否為TCP-friendly？在這篇論文裡，提出根據類似RTP/RTCP的接收端對封包的loss-ratio及jitter-ratio等採樣與使用時間基礎的TCP模型以進行TCP-friendly速率估計。所謂時間基礎模型是指以時間為變數的速率方程式；而現有的封包基礎模型則是以計數封包為變數的方程式。估計的意思是對於Internet上某個固定速率的連線，其接收端能很接近地估計與其競爭的其他TCP連線的平均速率。若有良好的速率估計，這就能成為速率調整與壅塞避免等機制的基礎。
這個研究包括了推導時間基礎的TCP傳輸率模型，在接收端的取樣與分析機制，以及讓UDP固定速率連線在理想及競爭環境下的ns2模擬實驗，結果顯示我們的方式有良好的估計效果。此做法和其他的相關研究的不同點，在於雖然它們有些可以達到TCP-friendly，速率卻不平順，或者不能配合RTCP較長週期控制。另外的不同點則是我們採用創新的模型和參考jitter資訊。

By interconnecting heterogeneous networks, the deployment scale of Internet is continuously expanding. Since distinct local communication systems may have different resources like capacities and bandwidths, and the IP datagrams store-and-forward processing of routers is usually in routing semantics, the end-to-end congestion control on the source and destination is necessary. The transport protocol over IP provides the mechanism. For example, TCP is designed for reliable data delivery with congestion avoidance.
However, for the multimedia streaming applications, the reliability requirement of TCP has some costs which are harmful to this kind of applications. These costs are, for example, the un-necessary delay to retransmit data, and the packets burst of sliding window-based scheme. Thus, it is necessary to have an alternative transport protocol using rate-based scheme and supporting the multimedia presentation profiles. RTP/RTCP suite is designed for these purposes, but there still are the critical research issues for multimedia streaming applications.
Two significant factors are the performance of longer periodic control, and the friendliness to TCP on the rate adjustment. To satisfy these two criteria, this dissertation proposes a rate estimation scheme based on the packets loss ratio and jitter ratio sampling at the RTP/RTCP-like receiver and using the time-based TCP model. The ‘time-based’ model is a rate equation of time variables, while the existing model, says ‘packet-based’, is another equation of the variable of packets count. The meaning of the rate estimation is that for one connection of a particular sending rate, the receiver can closely estimate the average transmission rate of other TCP traffic flows in competition. If the rate estimation performs well, it can be the basis of rate adjustment and congestion avoidance.
This research contains the inferring of the time-based TCP model, the functionalities for sampling and analysis at receiver, and ns-2 simulation of fixed sending rate UDP under ideal and competition environments. The results show that this approach conducts good estimation. The time-based proposal addresses the drawbacks of existing proposals that even with TCP friendliness, their sending rates are not smooth, or they are not suitable for RTCP long periodic control. Other differences are the innovative model for TCP and the consideration of jitter information.

[BB01] D. Bansal and H. Balakrishnan, “Binomial Congestion Control Algorithms”, in Proc. of IEEE Infocom, Apr. 2001
[BDS96] I. Busse, B. Deffner, H. Schulzrinne, “Dynamic QoS Control of Multimedia Applications based on RTP”, in Journal of Computer Communications, Elsevier Science, Jan. 1996
[CJ89] D. Chiu and R. Jain, "Analysis of the Increase/Decrease Algorithms for Congestion Avoidance in Computer Networks", in Journal of Computer Networks and ISDN, Jun. 1989
[FF95] K. Fall and S, Floyd, “Comparisons of Tahoe, Reno, and Sack TCP”, Technical Report, Lawrence Berkeley National Laboratory, Dec. 1995
[FF99] S. Floyd and K. Fall, “Promoting the Use of End-to-End Congestion Control in the Internet”, IEEE/ACM Transactions on Networking, Aug. 1999
[FHPW00] S. Floyd, M. Handley, J. Padhye, and J. Widmer, “Equation-Based Congestion Control for Unicast Applications”, in Proc. ACM SIGCOMM Symposium on Communications Architectures and Protocols, Aug. 2000
[FJ91] S. Floyd and V. Jacobson, “On Traffic Effects in Packet-Switched Gateways”, ACM SIGCOMM Computer Communication Review, Apr. 1991
[JGMB01] S. Jin, L. Guo, I. Matta, and A. Bestavros, “TCP-Friendly SIMD Congestion Control and Its Convergence Behavior”, Technical Report, Boston University, May 2001
[JRC97] R. Jain, K. Ramakrishnan, D-M. Chiu, “Congestion Avoidance in Computer Networks with a Connectionless Network Layer”, Technical Report, Digital Equipment Corporation, Jun. 1997
[Kes97] S. Keshav, “An Engineering Approach to Computer Networking”, pages 39-40, Book, Addison-Wesley Publishing Company, 1997
[MF97] J. Mahdavi and S. Floyd. “TCP-friendly unicast rate-based flow control”, Technical note sent to IRTF end2end-interest mailing list, Jun. 1997
[MSMO97] M. Mathis, J. Semke, J. Mahdavi, and T. Ott, “The Macroscopic Behavior of the TCP Congestion Avoidance Algorithm”, ACM SIGCOMM Computer Communication Review, Jul. 1997
[NS] “Network Simulator – ns (version 2)”, development through the VINT project at LBNL, Xerox PARC, UCB, and USC/ISI”, URL: http://www.isi.edu/nsnam/ns/index.html
[PD00] L. Paterson and B. Davie, “Computer Networks: A Systems approach”, pages 684, 649, Book, Morgan Kaufmann Publishers, 2000
[PFTK98] J. Padhye, V. Firoiu, D. Towsley, and J. Kurose. “Modeling TCP Throughput: A Simple Model and its Empirical Validation”, in Proc. ACM SIGCOMM Symposium on Communications Architectures and Protocols, Aug. 1998
[PKTK99] J. Padhye, J Kurose, D. Towsley, and R. Koodli, “A Model Based TCP-Friendly Rate Control Protocol”, in Proc. International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV), Jun. 1999
[RHE99] R. Rejaie, M. Handley, D. Estrin. “RAP: An End-to-end Rate-based Congestion Control Mechanism for Realtime Streams in the Internet”, in Proc. IEEE Infocom, Mar. 1999
[ROY00] I. Rhee, V. Ozdemir, and Y. Yi, “TEAR: TCP emulation at receivers – flow control for multimedia streaming”, Technical Report (draft), North Carolina State University, Apr. 2000
[SCFJ01] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, “RTP: A Transport Protocol for Real-Time Applications”, Internet Draft: draft-ietf-avt-rtp-new-11.txt, IETF AVT Working Group, Nov. 2001
[SS98] D. Sisalem and H. Schulzrinne, “The Loss-Delay Based Adjustment Algorithm: A TCP-Friendly Adaptation Scheme”, in Proc. International Workshop on Network and Operating Systems Support for Digital Audio and Video (NOSSDAV), Jul. 1998
[SS00] D. Sisalem and H. Schulzrinne, “The Direct Adjustment Algorithm: A TCP-Friendly Adaptation Scheme”, in Proc. Quality of Future Internet Services Workshop, Sep. 2000
[SW00] D. Sisalem and A. Wolisz. “LDA+: A TCP-Friendly Adaptation Scheme for Multimedia Communication”, in Proc. IEEE International Conference on Multimedia and Expo (ICME), Jul. 2000
[TXW01] J. Tian, S. Xiangzhi, W. Wenjun, “The Effect on the Inter-fairness of TCP and TFRC by the phase of TCP traffics”, in Proc. IEEE International Conference on Computer Networks and Mobile Computing, Oct. 2001
[WDM01] J. Widmer, R. Denda, and M. Mauve, “A Survey on TCP-Friendly Congestion Control”, in IEEE Network Magazine, May/Jun. 2001
[YL00] Y. R. Yang and S. S. Lam, “General AIMD Congestion Control”, in Proc. IEEE International Conference on Network Protocols (ICNP), Nov. 2000
[YKL00] Y. R. Yang, M. S. Kim, and S. S. Lam, “Transient Behaviors of TCP-friendly Congestion Control Protocols”, Technical Report, University of Texas at Austin, Jul. 2000