Microsoft Word - Lab 4 instructions 4. Laboratory 4 – Window Flow Control In class we have discussed the operation of Sliding Window flow control. In this lab, you will investigate how sliding windows...

Hi this is simple lab assignment of 3 parts everything is mentioned in attached document kindly do this for me.


Microsoft Word - Lab 4 instructions 4. Laboratory 4 – Window Flow Control  In class we have discussed the operation of Sliding Window flow control. In this lab, you will investigate how sliding windows affect transmission rates. Please note: This experiment will require you to run script files (.tcl) using the ns program in LINUX. These files can be obtained from the subject website for CSIT127. IMPORTANT: We use Ubuntu (not Windows) Revisit the instructions from previous weeks to access relevant ns scripts. You are ready to start! 4.1 Measuring Window Sizes  The lab_4 folder contains the .tcl scripts required for this experiment. Enter the following command: ns part_1.tcl You should see a new window, which shows a simple network. At the top of this window is a series of play buttons, similar to those on a tape recorder. Press the start button (i.e. the forward arrow). You will see a simple network topology, comprising a single link, and a graph showing the throughput obtained over the link. Describe the sequence of packet transmissions that you see. To ascertain whether a packet is data packet or acknowledgment packet right click on the packet. What do you think the window size is on this link? A graph will appear as well. From this graph, determine the average transmission rate on this link. Zoom in on the graph, by selecting a small area of the curve with the mouse. Sketch the portion of the graph that you see. Can you describe how the window affects the shape of the graph? Note: you may need to slow the simulation down. You can do this by moving the slider in the top right hand corner of the window (to the left) – around 100us works well for this experiment. Please to remember to adopt correct units of measure.  When talking about data transfer you need to make reference to “bits/sec or b/s”.  When referring to a description of packets we normally use “bytes”.  We assume 8 bits (b) to 1 byte (B).  It is safe to assume that 1000 bits = 1 kilobit or 1 kbit or 1kb 4.2 Changing Window Sizes  We have seen that the window size appears to affect the average rate that data crosses the link. Now we will look at how changes in the window size affect this rate. Close your previous ns windows, and enter the following command: ns part_2.tcl Press the start button on the window that appears. Describe the packet transmission sequence that you see, and determine the window size and the average transmission rate. Also, zoom in on the graph, and sketch what you see. How does this graph differ from the one you saw in part 1? Hopefully you have seen that the window size has changed. Describe the effect that this changed window size has had on the data transmission 4.3 The optimal window size   Clearly the window size affects the data transmission rate. If we wish to maximise this rate, then a suitable window size must be chosen. Close the ns windows and enter the following: ns part_3.tcl 5 Press the start button. Here you have specified a window size of 5. By entering different numbers, you can change the window size. Experiment with different window sizes, and by so doing, find the minimum window size which keeps the link full, this is the optimal window size.