topic Re: Delay_ack setting [ms] in Operating System - OpenVMS

Delay_ack setting [ms]

Kees van Rhijn — Wed, 22 Jun 2005 02:38:58 GMT

Hi,

To estimate the gain we may achieve after switching off Delayed Acknowledge, I like to know how long the System waits until it sends the Delayed Acknowledge.
UCX (TCP/IP) V4.2-21

Thanks

Kees

Re: Delay_ack setting [ms]

Wim Van den Wyngaert — Wed, 22 Jun 2005 03:31:56 GMT

Check this threat :
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=877912

Wim

Re: Delay_ack setting [ms]

Kees van Rhijn — Wed, 22 Jun 2005 03:48:26 GMT

Wim, thanks for the thread! The figure 200ms is mentionned, but I think that is the Win32 figure.

I have seen up to now:
Linux 2: 15-20ms
Solaris: 50ms
Win32: 200ms
UCX: ?

Kees

Re: Delay_ack setting [ms]

Wim Van den Wyngaert — Wed, 22 Jun 2005 05:05:07 GMT

Did some tcptrace in ucx 4.2 (for ftp sessions): it report delayed acks after received packages of about 20 100/sec or 200 ms against 0 when nodelay ack is active.

Did the same on tcp 5.3. The delay wasn't given. Changed functionality ?

Wim

Re: Delay_ack setting [ms]

Wim Van den Wyngaert — Wed, 22 Jun 2005 05:26:48 GMT

Noticed that in ucx and tcp the number of delayed acks are shown. I took a global trace of all traffic on 5.3 until I saw an increase in the counter. Than I searched for the delayed ack. Found it and the difference is 200 ms too. But not 100% sure that it is caused by delayed ack.

Wim

Re: Delay_ack setting [ms]

Kees van Rhijn — Wed, 22 Jun 2005 06:31:19 GMT

Wim, Thanks a lot. Seen your 200ms result I expect a significant improvement during our DICOM-transfer, when delayed acknowledge is disabled.
This was my first experience with the successor of Ask the Wizzard and it makes me a fan.

Kees

Re: Delay_ack setting [ms]

Kees van Rhijn — Wed, 22 Jun 2005 06:32:26 GMT

Please see my reply above.