dan@haddock.UUCP (05/28/85)
/* Written 5:33 pm May 85, 19783 by henry@utzoo in haddock:net.unix */ > ... What is really wanted is a standard method > of *positive* flow control ("I'm OK for another 347 characters now"). > I don't see much hope for getting one established, though. ETX/ACK comes close to being standard. The sender embeds ETX controls in the output stream; the receiver returns ACK controls each time it's freed up 80 bytes in its input buffer (at least; this is the part that's not standard). A naive implementation would send one ETX at the end of each 80 bytes, then wait for the ACK to come back. That's rather slow; a better way to use it is to send two ETXs 40 bytes apart. As soon as you get the first ACK back, you know you can send another 40 bytes and an ETX. If network delays are not too great, the output stream will be continuous. The important thing is that network delays only slow you down, rather than resulting in lost data as with XON/XOFF. A nice protocol, at least compared to XON/XOFF. Too bad it's not more widely used. Dan Franklin