ASSIGNMENT#1Date of Submission: 15/2/2011

1. Write a TCLCL code to implement a new FTP Agent . Show the usage of FTP Agent in Tool Command Language Script. Show the step by step changes that you will make in c++ code of Ns-2.34.

2. Define Quality of Service and its characteristics. Write a TCL Script to implement QoS characteristics. Explain the changes that you will make in C++ code of ns-2.

3. What is the difference between a host and an end system? List the types of end systems. Is a Web server an end system?

4. What are the types of transport services that the Internet provides to its applications? What are some characteristics of each of these services?

5. What advantages does a circuit-switched network have over a packet-switched network?

6. Why is it said that packet switching employs statistical multiplexing? Contrast statistical multiplexing with multiplexing that takes place in TDM.

7. What is the transmission rate of Ethernet LANs? For a given transmission rate, can each user on the LAN continuously transmit at that rate?

8. What is meant by handshaking protocol?

9. Consider an e-commerce site that wants to keep a purchase record for each of its customers. Describe how this can be done with cookies.

10. What is the difference between persistent HTTP with pipelining and persistent HTTP without pipelining? Which of the two is used by HTTP/1.1?

11. Describe how web caching can reduce the delay in receiving a requested object. Will web caching reduce the delay for all objects requested by a user or for only some of the objects? Why?

12. Consider an HTTP client that wants to retrieve a Web page at URL http://www.foo.com/blah.html. The IP address of the server is initially unknown. The page at the above URL has one embedded GIF image with URL http://www.foo.com/pic1.gif. Describe all application protocol interactions involved in this scenario and the transport protocols used for each interaction.

13. Consider an organization that uses a proxy for its HTTP. A direct download of an object (if there were no proxy) takes 1s. For a download from the origin server, the proxy adds 100ms local overhead. A download from the proxy cache takes 100ms. Assuming the cache hit rate of 40%, what is the average response time that HTTP clients in this organization experience?

14. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m meters, and suppose the propagation speed along the link is s meters/sec. Host A is to send a packet of size L bits to Host B.

i. Express the propagation delay, dprop, in terms of m and s. ii. Determine the transmission time of the packet, dtrans, in terms of L and R.

iii. Ignoring processing and queuing delays, obtain an expression for the end to-end delay. iv. Suppose Host A begins to transmit the packet at time t = 0. At time t = dtrans, where is the

last bit of the packet? v. Suppose dprop is greater than dtrans,.At time t = dtrans, where is the first bit of the packet?

vi. Suppose dprop is less than dtrans,.At time t = dtrans, where is the first bit of the packet?vii. Suppose s = 2.5 * 108, L = 100 bits, and R = 28 kbps. Find the distance m so that dprop is

equal to dtrans.

15. Suppose two hosts, A and B, are separated by 10,000 kilometers. And are connected by a direct link of R=l Mbps. suppose the propagation speed over the link is 2.5 * 108 meters/sec.

a. Calculate the bandwidth-delay product, R * tprop. b. Consider sending a file of 400,000 bits from Host A to Host B. Suppose the file is sent

continuously as one big message. What is the maximum number of bits that will be in the link at any given time?

c. Provide an interpretation of the bandwidth-delay product. d. What is the width (in meters) of a bit in the link? Is it longer than a football field? e. Derive a general expression for the width of a bit in terms of the propagation speed s, the

transmission rate R, and the length of the link m.