Questions

Homework Assignments:

1. List and discuss 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.

2. 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.

3. For the client-server application over TCP described in section 2.7 of the textbook, why must the server program be executed before the client program? For the client-server application in section 2.7 of the textbook, why may the client program be executed before the server program.

4. Wireshark Lab:

Carefully read both the Wireshark Labs (HTTP and DNS) available at textbook’s web site. Run Wireshark packet capture forhttp://www.umass.edu. As an alternative, you may also choose to answer the following questions and run ethereal packet capture forhttp://www.premiereleague.com. Answer the following questions:

5. Is your browser running HTTP version 1.0 or 1.1?

6. What languages (if any) does your browser indicate that it can accept to the server?

7. What version of HTTP is the server running?

8. When was the last time that your HTML file that you are retrieving, modified at the server?

9. How many HTTP GET request messages were sent by your browser?

10. To what IP address(s) is the DNS query message sent?

11. Are the DNS query and response messages sent over UDP or TCP?

12. Examine the DNS reply (response) message. What are the values of (Name, Value, Type, TTL) fields (See section 2.5.3 of the text)?

13. What is (are) the name(s) of the authoritative name server(s)?

Note:

14. Make sure that the Capture is not in the promiscuous mode. (The option in the packet capture window “Capture packets in promiscuous mode” should be unselected)

15. It is suggested to make sure your browser’s cache is empty every time you start capturing packets.

16. For question 6, 7 & 8 use “dns” as display filter.

17. Also submit the capture file with “All packets”.

18. Students should make their DNS caches empty by using dos command “ipconfig /flushdns” at the command prompt, before capturing packets for DNS related questions.

 

 

Solution Preview:

Answer 1: 1) Reliable Data Transfer (TCP) 2) Throughput (none can guarantee the throughput) 3) Timing (none can guarantee as the packets are routed through different networks) 4) Security (none can assure of the security) Answer 2: Cookie number can be assigned to the host on the first visit and when user visits the site again the purchase or the history………….for a complete answer, order your paper now…

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