What is "remote login"? What is the standard protocol which
provides remote login on the Internet?
The TELNET protocol defines a Network Virtual Terminal, (NVT)
which means that servers and clients don't need to know the details of
the actual terminal (if any) at the other end of the connection. The
alternative to this approach is to perform terminal emulation. What
is meant by terminal emulation, and why is the NVT approach better?
What are some of the characteristics of the TELNET NVT?
When the telnet program starts up, it informs the user as follows:
ironbark 27> telnet redgum
Trying 149.144.20.3...
Connected to redgum.bendigo.latrobe.edu.au.
Escape character is '^]'.
What is the "escape character" used for?
The[1] text file for RFC 854 (the TELNET protocol specification)
contains exactly 854 lines. Do you think there is cosmic significance in
this?
(Research question) How does TELNET perfom option negotiation?
Practical exercises:
Use netscape (or xmosaic) to fetch an RFC - RFC854 (Telnet) might
be a good one. You can do this by opening the URL given in the first
slide of the lecture.
Look at the file /etc/services on a nearby Unix system. It defines
the mapping between TCP port numbers and application protocols.
Find the port numbers for echo, finger and chargen. Use telnet to
connect to each of these ports. What do they do?
Try using telnet to connect to another machine, say A, then invoke
it on A to reach yet another machine, call it B. How does the
combination of two telnets work? Any problems?