rts/cts - a tutorial on flow control

[Chris Torek]

> The "negative" flow-control methods work (XOFF/XON) work satisfactorily
> if sufficient space is allocated for overrun.

True, but unfortunately, the amount of space that is sufficient has
recently gone way up...

> For example, (assuming 9600 Baud transmission)

And no end-to-end network delays!

> the receiver can allocate a 400 byte buffer, sending XOFF when there
> are 100 bytes unprocessed bytes in the terminal input buffer.  This
> gives the host about 600 msec. to stop output.

That's assuming the XOFF makes it from the stopper to the stoppee
without delay; untrue in general, now.  (If you gave yourself sufficient
buffering to handle up to 30 seconds of delay, I suppose I'd call
that sufficient: no one would want to wait longer for echo . . . .)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
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