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Project Overview

This project aims to verify and analyze the TFRC congestion control protocol, conduct experiments to check for any shortcomings, study the loss model, and develop optimizations for TFRC. A comparison of TCP, TFRC, and UDP will also be done to understand the importance of loss as a network metric.

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Project Overview

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  1. Project Overview • Study of Tfrc • Verification, Analysis and Development Verification : Experiments. Analysis : Check for short comings if any. Study of loss model. Development : Use of Tfrc within our environment (optimizations if any) . Comparison of TCP, TFRC and UDP to understand the concept of loss and its importance as a network metric. -Mayukh, clemson university

  2. Tfrc • What is it? An equation based congestion control protocol designed to compete ‘fairly’ with TCP under varying network environments. TCP friendly : A flow that in steady state uses no more bandwidth than a conformant TCP running under comparable conditions Why does it need to be friendly ? Majority of flows are TCP flows (Reno, SACK). Any new protocol that is developed needs to keep this in mind. Tfrc is not intended to replace TCP , just complement it. Why do we need it ? Ideal for unicast streaming multimedia (there is a version of Tfrc now intended for multicast services, but that is outside the scope of this project). Any applications that require a smooth and controlled sending rate. -Mayukh, clemson university

  3. Tfrc (contd ..) • How does it work ? Uses a throughput equation to calculate the sending rate. The receiver sends feedback reports to the server. A typical feedback message has an estimation of the loss event rate (p) and the receiving rate. (X_recv). The control equation is a function of p and Round trip time R. See RFC 3448 for protocol specs. (yes its an RFC now !) Points of interest : The throughput equation used Calculation of the loss event rate. (Use of Full Averaged Loss Interval method) -Mayukh, clemson university

  4. Results There has been a lot of interesting work done on TFRC. Extensive experiments under various conditions have been conducted , below is a gist of the results. 1> Tfrc does compete fairly with TCP : This was one of the primary design objectives and it has been shown under varying conditions that Tfrc is indeed TCP friendly. 2> It has a smooth sending rate. The purpose was to make Tfrc respond more gently to congestion events (rather than cutting sending rate in half for a single packet loss like Tcp) 3> Responds slowly to congestion events. A fallout of making Tfrc generate a consistent smooth sending rate. See 1> “Modeling TCP throughput : A simple Model and its Empirical Validation ‘ 2> “Equation based congestion control for Unicast Applications “ for more details. -Mayukh, clemson university

  5. My stuff this sem. • What am I supposed to do ?? Build on the code. Get it operational in our lab. Conduct Experiments. Study the loss rate. Objective 1 : Verify that what we have maps to the ICIR code and to the protocol specs. Method : Our Tfrc Vs ICIR Tfrc Vs Tcp. Using the network emulator in our lab run a series of tests comparing performance of our Tfrc versus the rest. (Its important we have a correct version of Tfrc before we proceed!!) -Mayukh, clemson university

  6. My stuff 2 .. Objective 2 : Once we have a confirmed running version of Tfrc, we are free to conduct various other interesting experiments. Make certain that the code has been integrated into the metricTool completely. Simulated network environments : Im hoping to use Ns. Use of SURGE. To observe the behavior of Tfrc in a ‘simulated internet’ (multiple users, short lived tcp flows etc. ) -Mayukh, clemson university

  7. My stuff 3… • Objective 3 : Study of the loss model. Using the experiments as a basis and the generated data, study the loss rates . Compare loss ratios of Tfrc, Tcp and Udp. At the end of this semester should have a paper ready presenting the results of our experiments and the inferences gained. -Mayukh, clemson university

  8. Thesis work. • Long term : Possible directions : a) Continue with current project : Hopefully at the end we will have a better understanding of congestion control, and the loss model. Direct my thesis towards a better understanding of Tfrc and related loss models. Suggestions for better ways of obtaining the loss model OR congestion control mechanisms OR extensions to TFRC. -Mayukh, clemson university

  9. Thesis .. b. Extension of current project . Tie in the concept of loss with the security aspect, denial of service. Depending on my productivity this is what I envision myself to be doing a year from now. Relate the study of the loss models and tie them in with the detection of denial of service attacks. Study of patterns in loss event on a per flow basis (and aggregated flow s) along with other information (typical attack signatures) to detect and thwart typical distributed denial of service attacks. -Mayukh, clemson university

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