Re: TCP delayed acks not being delayed?

On Saturday 25 March 2006 21:25, Bill Moran wrote:

Are you sure you're not exceeding the capability of the system to delay
acks?

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
empty-acks.

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.
_______________________________________________
freebsd-questions@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-questions
To unsubscribe, send any mail to "freebsd-questions-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • Re: TCP delayed acks not being delayed?
    ... outgoing empty acks. ... If I download a single file with kget at 100 kbytes/s, ...
    (freebsd-questions)
  • TCP Delayed Ack implementation in 6.1
    ... I have a question about the TCP delayed ack implementation in FreeBSD 6.1 ... According to specs, if delayed acks are enabled, the receiver delays transmitting acks for the delack time period or acks every other incoming packet. ...
    (freebsd-net)
  • Re: the TCP MSS resource exhaustion commit
    ... > What about ACKs from a simple TCP device such as a microcontroller? ... If the microcontroller doesn't have enough RAM to do delayed ACKs ... The detection logic only applies to TCP packets containing payload, ...
    (freebsd-current)