TCP delayed acks not being delayed?
list-freebsd-2004 at morbius.sent.com
Sun Mar 26 16:40:24 UTC 2006
On Saturday 25 March 2006 21:25, Bill Moran wrote:
> Are you sure you're not exceeding the capability of the system to delay
I would have thought not, it maxes-out with a receive space of 15k, and
increasing the setting from 20k to 32k had no effect.
> Besides, when you're transferring data in one
> direction only, it doesn't make sense to delay empty acks. only on a
> full-duplex transmissions do you get a benefit by taking measures to
> ensure that all packets have data. When you're downloading, _all_ your
> acks are empty, so who cares?
I though I might be seeing a bug. I was only measuring it because I was
thinking of switching to pf/altq and I wanted to know how much to allow for
However, I hadn't done the arithmetic before, and I was surprized to see that
13% of my upload was being used. On a 4MB connection, that would be over half
the bandwidth. Delayed acks don't affect the download speed on one tcp
connection, but they could improve the performance of other traffic, when a
download is taking place over a very asymmetric link.
> Additionally, if the client application turns nagle off, this will
> disable the use of delayed acks. For things like file transfer, it's
> pretty much typical practice to disable nagle,
I guess that explains it.
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