Problem 1
List five nonproprietary Internet applications and the application-layer protocols that they use.
Problem 1
True or false? a. A user requests a Web page that consists of some text and three images. For this page, the client will send one request message and receive four response messages. b. Two distinct Web pages (for example, www. mit. edu/research. html and www. mit. edu/students. html) can be sent over the same persistent connection. c. With nonpersistent connections between browser and origin server, it is possible for a single TCP segment to carry two distinct HTTP request messages. d. The Date: header in the HTTP response message indicates when the object in the response was last modified. e. HTTP response messages never have an empty message body.
Problem 2
What is the difference between network architecture and application architecture?
Problem 2
Read RFC 959 for FTP. List all of the client commands that are supported by the RFC.
Problem 3
Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP address of the HTTP server is initially unknown. What transport and application-layer protocols besides HTTP are needed in this scenario?
Problem 4
For a P2P file-sharing application, do you agree with the statement, “There is no notion of client and server sides of a communication session”? Why or why not?
Problem 6
Suppose you wanted to do a transaction from a remote client to a server as fast as possible. Would you use UDP or TCP? Why?
Problem 6
Obtain the HTTP/1.1 specification (RFC 2616). Answer the following questions: a. Explain the mechanism used for signaling between the client and server to indicate that a persistent connection is being closed. Can the client, the server, or both signal the close of a connection? b. What encryption services are provided by HTTP? c. Can a client open three or more simultaneous connections with a given server? d. Either a server or a client may close a transport connection between them if either one detects the connection has been idle for some time. Is it possible that one side starts closing a connection while the other side is transmitting data via this connection? Explain.
Problem 7
Suppose within your Web browser you click on a link to obtain a Web page. The IP address for the associated URL is not cached in your local host, so a DNS lookup is necessary to obtain the IP address. Suppose that \(n\) DNS servers are visited before your host receives the IP address from DNS; the successive visits incur an RTT of RTT \(_{1}, \ldots\), RTT \(_{n^{*}}\). Further suppose that the Web page associated with the link contains exactly one object, consisting of a small amount of HTML text. Let RTT \(_{0}\) denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object?
Problem 8
List the four broad classes of services that a transport protocol can provide. For each of the service classes, indicate if either UDP or TCP (or both) provides such a service.
