Re: TELNET SUPPRESS LOCAL ECHO OPTION as Experimental?

[Dave Crocker <dcrocker at brandenburg.com>]

At 10:26 AM 7/1/98 -0500, David Borman wrote:
>That depends.  In any scheme to automatically control the echoing
>of data to the users screen, the primary requirement is that the server
>know when data should or shouldn't be echoed.  A well coded application
>that is going to disable echoing to protect the typed data, should turn
>off the echoing before presenting the prompt to the user.  In that
>situation, propagation delay is not an issue because the client will
>have received "WILL ECHO" before the prompt.

David, your scenario presumes that the user's typing is controlled by the
appearance of the prompt.  As you may recall, back in the days of the slow
Arpanet, typing far ahead of the server's responses is not all that
uncommon.  As such, the server must be able to EXPLICITLY control the
clients handling of EACH character in a SYNCRHONIZED fashion, or else
proper control of echoing is a matter of statistical likelihood, rather
than real protocol control.

>We were serios about it 9 years ago with the development of the Linemode
>option.  The client code is pretty easy to run on most systems.  The

Right.  

As I recall it tried to cut a middle ground between per-character control
and protocol simplicity.  Always a good goal.

I suppose the real question, then, is why this stuff doesn't seem to get
adopted?

>The biggest problem is screen oriented applications that turn off tty
>echo and turn on single character input, so that they can have full

Right.  That was my own concern when Linemode came out.  It's good for
old-time Unix line-oriented work (although these days, shells that do
command completion and the like make even THAT problematic).  But not for
screen stuff.  The old RCTE option's model probably would be sufficient,
but as I noted, the protocol was buggy.

d/

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