What is meant by the term "remote login" in the context
of the telnet protocol?
The idea of plain ASCII text is fundamental in IT.
For example, computer programs (ie, source code) are always plain text files.
And, as we will see in later lectures, many Internet application
protocols are based on the exchange of ASCII text messages.
What do we mean by the term "printable ASCII"? How many printable ASCII
characters are there?
What is the conventional way to generate the ASCII control codes
from a computer keyboard?
What are the particular advantages of "plan ASCII text" compared to
other "character sets"?
What are some of the obvious disadvantages of ASCII text?
All computers support ASCII text files. However, the
convention for indicating the end of a text line is different in each.
Unix (and Linux) systems use a single Linefeed (LF, decimal 13), Macs use
a single Carriage Return (CR, decimal 10) and Microsoft systems
use both CR and LF, the same as the telnet NVT. What kinds of problems
could occur when text files are shared between each of these computer
types?
What are some of the characteristics of the telnet Network
Virtual Terminal (NVT)?
The telnet NVT "end-of-line" convention delimits
lines of text using the two character ASCII control code sequence
<CR><LF> (in English: Carriage Return followed by Line Feed).
Why do you suppose the designers of the protocol adopted this two
character sequence instead of just a single character <CR>,
or a single <LF>, or something else entirely?
The NVT approach used by the
telnet protocol means that servers and clients don't need to know the
details of the actual terminal or host (if any) at the other end of the
connection. The alternative is to perform terminal
emulation. What is meant by terminal emulation?
(Discussion question) The notion of how the NVT is used in telnet
leads on to a (moderately) serious philosophical
issue about how to map the requirements of different kinds of computer
systems to one another when you need to perform some kind of Networked
Computing function. Start by comparing the telnet NVT approach to terminal
emulation, and extend the discussion to the more general case.
When the telnet program starts up,
it informs the user as follows:
ironbark 27> telnet greybox
Trying 149.144.20.62...
Connected to greybox.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?