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 "plain 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 basic 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?
(Philosophical question) 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?
(Deeply philosophical 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 and discussion question) Once upon a time, The ASCII control
codes (ie, the ASCII characters less than 32decimal) had important
functions. Do some research, or just infer from the names of some of the
control characters, what these functions may have been. Which of the control
characters still have important meanings?
(Research question) How does telnet perfom option negotiation?
