Assignment 5

Due March 2, 2016 6:55pm via sakai

Introduction

Please answer the questions precisely and concisely. Every question can be answered in one or at most a few sentences. I will not have the patience to read long paragraphs or essays and you may lose credit for possibly correct answers.

Submit your work via sakai as a plain text or pdf document. No Microsoft Word, Apple Pages, ePub, et cetera formats.

Reading

Text: Chapter 3 Transport Layer through 3.4.4 (Selective Repeat), pages 185–230

Questions

(1) [Kurose & Ross text: page: 286, question R7]
Suppose a process in Host C has a UDP socket with port number 6789. Suppose both Host A and Host B each send a UDP segment to Host C with destination port number 6789. Will both of these segments be directed to the same socket at Host C? If so, how will the process at Host C know that these two segments originated from two different hosts?

(2) [Kurose & Ross text: page: 286, question R8]
Suppose that a Web server runs in Host C on port 80. Suppose this Web server uses persistent connections, and is currently receiving requests from two different Hosts, A and B. Are all of the requests being sent through the same socket at Host C? If they are being passed through different sockets, do both of the sockets have port 80? Discuss and explain.

(3) [Kurose & Ross text: page: 286, question R10]
In our rdt protocols, why did we need to introduce timers?

(4a,b,c). Visit the Go-Back-N Java applet at the companion web site. Go to Student Resources, select applets and click on Go-Back-N Protocol (Chapter 3). There is also a copy of this applet here. Be sure you enable Java in your browser … and then disable it when you’re done with this demo. The timer is set to a pretty long value, so either be patient or hit the Faster button.

(4a) Have the source send five packets,and then pause the animation before any of the five packets reach the destination. Then kill the first packet and resume the animation. Describe what happens.

(4b) Repeat the experiment,but now let the first packet reach the destination and kill the first acknowledgment. Describe again what happens.

(4c) Finally, try sending six packets. What happens?