On Wed, 23 Feb 2005, David S. Miller wrote:
> On Wed, 23 Feb 2005 17:04:08 -0500 (EST)
> John Heffner <jheffner@xxxxxxx> wrote:
> > Maybe this has something to do with the bi-directional nature of the flow?
> > Mac OS delaying ACK to try to piggyback on data or something like that.
> > One signature I noticed is that it seems the last packet sent by the Mac
> > before the long delack timeout is always a small data packet. (I didn't
> > rigorously verify this but it seems true.)
> I should be more specific when I say "PSH". Mac OS-X's algorithm is basically
> that it always delays ACKs to the delayed ACK timeout when the header
> fast path is hit. One way to "miss" the header prediction fast path is to
> set PSH (this is actually a bug, Linux fixed this long ago, PSH should be
> for header prediction fast path checking).
The point is it appears to be delaying ack even when PSH is set.
> Anyways, this Mac OS-X behavior has pretty much been universally agreed
> to as a severe bug, at least on this list :-)
Yep. The Mac behavior is clearly bizarre. :)