Internet: Technology, Protocols and Services: Homework Assignment 2

1. One of the TCP options permits a receiver to specify the maximum segment size it is willing to accept. Why does TCP support an option to specify maximum segment size when it also has a window advertisement mechanism? (Comer 13.2)
2. Lost TCP acknowledgements do not necessarily force retransmission. Explain why. (Comer 13.4)
3. What are the arguments for and against automatically closing idle TCP connections? (Comer 13.8)
4. Describe (abnormal) circumstances that can leave one end of a connection in state FIN WAIT 2 indefinitely (hint: think of datagram loss and system crashes). (Comer 13.18)
5. Sketch a UDP echo client that sends a datagram to a specified echo server, awaits a reply and compares it to the original message. (Comer 19.1)
6. When is the listen call important? (Comer 20.3)
7. Sketch the socket-related parts of a finger server. Indicate some of the error conditions that might occur. Assume that the function call getuserinfo will return the necessary information from the local system.
8. GMD Fokus chose to place the following type A resource record entry in its domain name server: localhost.fokus.gmd.de 127.0.0.1. Explain what will happen if a remote site tries to ping a machine with domain name localhost.fokus.gmd.de. (Comer 22.15)
9. Assume that an MUA is located on an NFS server. It can send encrypted email messages. A corporate spy manages to get an account on a machine on the local Ethernet and wants to intercept messages from the MUA, without cracking the encoding. Any suggestions? (Hint: remember that on an Ethernet, every packet is broadcast. Assume that the spy has access to the source code of the MUA.)
10. In class, we saw a way of spoofing email. How can the receiver detect (most of) these forgeries?
11. What headers should an email mailing list program change or add? (A mailing list program distributes a single message sent to an email address to a list of receivers.)
12. Why should file transport protocols compute a checksum on the file data they receive, even when using a reliable end-to-end stream transfer protocol like TCP? (Comer 24.4)
13. What is the chief advantage of using separate TCP connections for FTP control and data transfer? (Hint: think of abnormal conditions) (Comer 24.4)
14. Would you expect TCP or UDP-based NFS to be faster on a local network? Reasons? How about a wide-area network?
15. Would RPC be suitable for implementing a remote login service? Why or why not?
16. Write an HTML form for buying pizza on the Internet.
17. Propose an extension to HTTP that allows the transfer of several pages in a single TCP connection.