MIME-Version: 1.0 Server: CERN/3.0 Date: Monday, 16-Dec-96 22:03:59 GMT Content-Type: text/html Content-Length: 3307 Last-Modified: Wednesday, 22-May-96 21:45:46 GMT CS514: Homework 3

CS514: Homework 3

Collaboration. Collaboration by up to three students is permitted on this assignment. When there is such a collaboration, a single solution should be submitted for grading and the solution should list the names of the collaborators. Other collaborations will be considered violations of Academic Integrity.

Submission Procedure. Solutions must be submitted by email to:

         cs514@cs.cornell.edu
The solution may by formatted as ASCII (i.e. plain text) or postscript.

Due Date. We must receive your email by 8:00(am) on Wed., April 3, 1996. Late Assignments will not be accepted.

Problem Description

Read RFC 821, The Simple Mail Transfer Protocol, and RFC 822, Standard for the Format of ARPA-Internet Text Messages. RFCs can be retrieved from rs.internic.net using anonymous ftp. A selection of the RFCs is available at the departemental machines in the directory /vol/doc/InterNet.

  1. Find out what a domain literal is from RFC 822. Try sending a mail message to yourself using one. Include a copy of the message you received in your homework solution. Click here for additional hints concerning this part of the assignment.

  2. Excluding the connection establisment and termination, what is the minimum number of network round trips to send a small mail message?

  3. TCP is a full-duplex protocol, yet SMTP uses TCP in a half-duplex fashion. The client sends a command then stops and waits for the reply. Why doesn't the client send multiple commands at once--for example, a single write that contains the HELO, MAIL, RCPT, DATA and QUIT commands (assuming the body isn't too large)?

  4. Consider an organization that is serviced by a collection of mail transfer agents. How can the DNS MX records and preference values be used to implement a load balancing scheme for incoming electronic mail?

This assignment requires using ftp to connect to machines outside the CS Department firewall. There are two options for this:

More information can be found in the tips-firewall manual page.