[linux-dvb] Re: datarates: any experiences?

[Bart De Gruyter <bartdg@pobox.com>]

Ralph Metzler wrote:
> 
>  > Bart De Gruyter writes:
>  > I've been able to test data rates up to 25 Mbit/s
>  > with the nova card. At higher speeds the socket
>  > calls start to lose more and more data. The strange
>  > thing is dat the statistics of the ifconfig command
>  > indicate the exact amount of data.
> 
> If the statistics counted the data it must have reached the network
> driver and been passed on to the TCP/IP stack.
> So, I don't know what could go wrong there.
> Is your test data all addressed to the same IP or are you including
> other kinds of packets when increasing the data rate?
> Maybe they are filtered out by the TCP/IP stack for some other reason?


I need to dive into the linux architecture as I do not have
any clue where the data went to ;-)

The test uses multicast udp data. I've tested the receiving
program on the ethernet interface -> works perfectly. But
if I try it on the dvb interface that has the filter for
the multicast reception I only receive 63 percent at the
socket calls. However, the ifconfig indicates everything
was received on the dvb interface -> given to the tcp/ip
stack.

The ethernet test and the multicast test use exactly
the same data, and we don't send any other unicast test
data.

The tcp/ip stack definitely filters out the data somewhere
as I've also changed the priority of the receiving program
to -20 and the linux box is doing nothing else ;-)

I'll move my question to a more linux tcp/ip stack related
list as it is getting off topic here.

Thanks for reassuring that when the ifconfig has it in the
stats then the linux tcp/ip stack should have received it.

> For high data rates you have to use the Nova card.
> 

thanks for this clear answer

greetings,

Bart De Gruyter




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