🚀 go-pugleaf

> And while I agree that error correction (and recovery) really must be
> done at the application level, error recovery at lower levels can reduce
> the overal data-flow overhead, as the higher up the problems must be
> RECOVERED from, the more the overhead to perform the recovery...

Note the key word "can", not "will".  Upper levels sometimes need do
*less* work to perform recovery, because they know more about what's
going on.  An extreme case is packet voice, where it is usually better
*not* to attempt recovery at all, because the delay involved in
recovery is much more audible than just forgetting the bad packet
altogether and faking it until the next good one arrives.  (How to
"fake it"?  Repeat the last packet.  Or hold the sound output constant
at the last value of the last packet.  Or do any of several more
complicated things.  All less audible than a gap.)

Also don't forget that layered protocols can exact a terrible price in
performance, because of multiple layers of overhead.

If your lines are noisy and your performance needs are both moderate
and orthodox, low-level recovery is probably a win even though one
does need end-to-end checks as well.  If you care a lot about
performance and your transmission medium is pretty good (e.g.
Ethernet), the situation looks very different.
--
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry