Tutorial #4
- What is your preferred electronic mail address? In general, what is the
format of an Internet email address?
- In his book Computer Networks 3/e, P646, Tanenbaum
quotes a study by Perry and Adam (1992) which reported that "Some companies
have estimated that email has improved their productivity by as much as 30
percent." Give some reasons why such a spectacular increase could occur
from the use of email in a business environment.
- What is the general format of an RFC822 electronic mail message?
- The SMTP protocol, in common with many other Internet application
protocols, uses a 3-digit code in all communications from the server to the
client. From the example given in the lecture, can you generalise about the
significance of the first digit of this code? What about the second digit?
- What is MIME? Explain briefly how MIME works to send a file (eg, a GIF
image) as an attachment to an email message.
- A MIME-encoded email message is still a perfectly valid RFC822 message.
What does this mean, how is it achieved, and why was it it regarded as
important?
- The MIME Type of an email attachment provides a hint to the "user agent"
software as to how to handle the data in the attachment. What do you think the
user agent software should be expected to do with attachments of the following
types
text/plain
text/html
audio/basic
application/octet-stream
?
- What is the Post Office Protocol (POP) used for? Why is it important that
POP uses authentication, whereas SMTP does not? What sorts of
commands do you think POP would implement?
- A file which has been encoded using Base64 is bigger than the unencoded
data. How much bigger, on average, would you expect it to be? Approximate
answers OK.
- Philosophical question: in today's lecture, some
security/privacy considerations of Web-based email systems were mentioned.
Do you believe these should be of concern to an average user? Is it possible
that privacy may actually be enhanced by using a Web-based email
system? How? Can you think of any other advantages (and disadvantages of Web-based
email services?
- Deep thinking question: In today's lecture, the slides which discussed
RFC821 (SMTP) and RFC822 both referred to email addresses. In SMTP, the
MAIL FROM:
and RCPT TO:
protocol messages both specify email addresses --- these are
called envelope addresses. The header of the RFC822 message
which is being delivered also contains From:
and
To:
lines -- these are header
addresses. The interesting question to contemplate is: "what happens
if the To:
header address and the
RCPT TO:
envelope address are
different" in an SMTP delivery operation? Where does the mail
get delivered?
See Prac #4 for the practical exercises accompanying this tutorial.
Copyright © 2004 by Philip
Scott, La Trobe University.