Rlogin vs Telnet in terminal servers


Robert Elz (munnari!murtoa.cs.mu.oz.au!cs.mu.oz.au!kre@uunet.uu.net)
2 Nov 88 06:54:06 GMT


While this discussion on telnet has been most interesting, I don't
think that its entirely relevant to the original question, which
related to rlogin support in terminal servers.

The most likely reason for wanting "rlogin support" in a terminal
server is 100% unrelated to protocols, automatic login (which is
typically not applicable anyway) , terminal type negotiation, or
any of the rest of all of this "can telnet really do ...?" stuff.

The real reason is that users have become trained that the way
one connects to a destination host is by using

        rlogin host

and that after that everything that is typed is sent to the remote
end, until the sequence

        <cr>~.

after which the connection is broken, or until

        <cr>~^Z

which returns to the originating node, without breaking the connection.

If the terminal server implements that functionality, the actual protocol
that's used underneath will be irrelevant for 99% or users.

So, terminal server vendors, please do implement "rlogin", however, by
all means, if you want to, simply make it a front end to your telnet
client, which disables the return to telnet command mode magic character,
and implements the '~' sequences above. Just don't advertise it as
supporting "rlogin" unless you really do.

This is also likely to be the way that Berkeley can really get rid
of "rlogin" once the telnet client/server support all the required
functionality, the rlogin client can just become a modified telnet,
which does suitable negotiation to appear to be rlogin to the user.

Getting rid of the other r* commands will be rather harder (I suspect
rcp would need several ftp extensions before rcp could be seen as
an ftp alias, and rsh has no real alternative at all that I know of).

kre

ps: while discussion differences between telnet and rlogin, its useful
to remember that telnet client implements a virtual terminal for the
server, whereas rlogin implements a virtual DB25 socket... (or did
when it was created, its a little fancier now).



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