[zeromq-dev] Help on TCP Buffer Tuning

[Thomas]

Hi all,
>From the web page, it suggests following settings.

"For large 0mq usage, 
you may need to set system tunables 
net.core.rmem_max and
net.core.wmem_max 
to something larger, such as 16777216. 
This applies even to supposedly self-tuning releases such as RHEL6."

I have written an application using zeromq as the message backbone.
The rate is about 4000 per second and the message size is around 1200 bytes.
There are 2 message streams from 2 machines at 1000 rate.
Each sending to a single multicast address on another machine. 
(3 machines in total are involved)

I tested the 16Mb settings. 
The messages arrive the destination with severe delay.
Then I used 32mb for the settings. 
The messages arrive without obvious delay!!!

I would like to know how 16 Mb buffer comes up.
And how can I figure the rough value using simple calculation?

I am looking forward to your suggestions and opinions.

Thanks,
Thomas