[LARTC] Ethernet bridge overflow ?

[Larry Brigman]

On 2/23/07, Sébastien CRAMATTE <s.cramatte at wanadoo.fr> wrote:
> Hello,
>
> I've setuped  an ethernet bridge on a debian sarge 3.1 with  l7-filter +
> ipp2 shapper rules
> The server is a supermicro p4sci + celeron pentium 4 base 3ghz  + 512Mb
> + 2 ethernet e1000
>
> One interface is connected to a cisco catalyst switch
> The other interface is connected directly to a CMTS (a sort of router
> for cable modem) configured as bridge too.
>
> More than 20Mbps of bandwith cross this bridge. Most of this traffic is
> p2p (~80%)
> When traffic goes over 14Mbps the  bridge seems to saturate (overflow ?
> ) and start to make colision and loose packets
>
> I've take a look to this  paper
> http://facweb.cti.depaul.edu/jyu/Publications/Yu-Linux-TSM2004.pdf
>
> And with a duron 1,3Ghz+512 mbps he obtain these values
>
> Input Rate   28,444,444
> (bps)
> Latency    29
> (us)
> Throughput 28,000,000
> (bps)
> Linux CPU 77%
> Occupancy
>
> A duron 1,3 is less powered than a celeron p4 3 ...  So I don't
> understand why I've got this problem :(
>
>
> When I make a  "top" or "uptime" all seems that works well ...
> I've got rrdtool graphs that check cpu and load and seems normal too ...
>
> Does someone  have got somes ideas ?
> Any clue or tips to isolate/resolve the problem are welcome
>

One thing that is possible it that you are getting receive starved.
Look to see if your
network drivers have NAPI configured.

Also look at the FAQ on the bridge site.
http://linux-net.osdl.org/index.php/Bridge
They have a mailing list also but it is not as active as LARTC.