Lecture 12: Telnet, Email, etc.

The lecture given on wednesday, march 3rd, started, as always with a review of the previous lecture and then moved onto the new material: the application level protocols telnet, smtp, pop, imap and mime. From the previous lecture, Dr. Gunes repeated the key functions of a router, how much buffer was necessary, bridges, and spanning trees.

The new information was, in my opinion, more enjoyable. The reason I say this is obvious, application level protocols are easier to understand and experiement with. Almost all of the protocols mentioned in the class on Wednesday were not only explained, but demonstrated.

The first protocol that Dr. Gunes taught us about was telnet. Telnet is simple, bidirectional communication protocol that utilizes byte oriented communication. It is a generic TCP client that sends whatever you type into the host terminal over the TCP socket. Many unix machines have telnet servers offering functionality like echo running by default. The professor demonstrated several such examples during class to the delight of the students.

Next, the instructor educated us on several basic email protocols including smtp, pop, imap, and mime. Smtp, simple message transfer protocol is used to send emails. It can even be used through telnet! It was shown to be unsecure because it is very easy to send fraudulent emails. Next the instructor taught us about POP, post office protocol. This mail receiving protocol allows the client to read their emails by pulling them entirely from the server. this allows the emails to be read offline. After that, he taught us about IMAP, Internet Message Access protocol. This protocol is more flexible than pop3 and more complicated. Finally we discussecd webmail, which we are all quite familiar with.