Computer Networks, CS 414 & 514

Homework 1, 31 January 2013

This homework assignment has five questions; answer all of them. This assignment is due no later than 1:00 p.m. on Monday, 11 February.

If you mail in your assignment, please submit a printable document — a PostScript .ps or PDF .pdf document, for example — and not a source document — a Word .docx or Latex .tex document, for example.

1. Distinguish between envelopes and headers in RFC-822 format mail messages. Give an example of a problem that could arise of envelopes and headers were not distinguished.
2. The message HELO, a 4-byte string of 7-bit ASCII, is translated into an 11-byte message using a base64-like encoding. Show the encoded message. Justify your answer.
3. You have modified an HTTP server to implement within the server all the services usually implemented outside the server by CGI. Is it more appropriate to implement access to the new internal services using WSDL-SOAP or REST? Justify your answer.
4. Study the protocols implemented by SMTP, FTP, and perhaps one or two more of your choosing. Develop and describe a similar protocol for a tic-tac-toe server. Assume the server plays one game at a time, and one game per connection. Keep the protocol as simple as possible consistent with playing a game of tic-tac-toe.
5. An application copying bits from one place to another can send the bits in a stream or as a sequence of discrete-sized messages. Which approach is more powerful, in the sense of being to perform some action or have some characteristic that the other approach can't. Justify your answer.