[vortex] Re: vortex digest, Vol 1 #403 - 1 msg

[Hans Voss]

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I seem to be having the same kind of problem. (Multiple 3c905TX'es
screws up the whole thing.
I can see the three cards perfectly. The electrical signalling works
(my WXP laptop says it has a network connection when I do ifconfig
and says that it looses connection when I do ifconfig ... down). But
no PING (which is small packet size), sometimes some ping
- ----- Original Message ----- 
From: <vortex-request@scyld.com>
To: <vortex@scyld.com>
Sent: Wednesday, April 24, 2002 6:01 PM
Subject: vortex digest, Vol 1 #403 - 1 msg


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> Today's Topics:
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>    1. Packet-loss and/or interface blocking on 3c905C-TX cards
> (Gerrit Einhoff)  
> 
> --__--__--
> 
> Message: 1
> From: Gerrit Einhoff <einhoff@i4.informatik.rwth-aachen.de>
> Reply-To: einhoff@i4.informatik.rwth-aachen.de
> To: vortex@scyld.com
> Date: Wed, 24 Apr 2002 17:01:11 +0200
> Organization: RWTH-Aachen
> Cc: diepolder@i4.informatik.rwth-aachen.de
> Subject: [vortex] Packet-loss and/or interface blocking on
> 3c905C-TX cards  
> 
> Hello.
> 
> I got this address from the source of the 3c59x-driver. If this is
> the wrong  place to ask for help, please point me to a better one.
> Thanks.
> 
> We are experiencing weird problems with our 3Com nics. We use the
> following  setup:
> 
>  - 8 SMP (2 x 1GHz Pentium III) machines
>  - each has three 3Com 905C-TX nics
>  - the first one is connected two a switch, the second via a patch
> cable to  the third of the next machine to form a ring
>  - kernel is linux-2.4.17-mosix (the mosix-stuff wasn't used during
> our tests)  
> 
> To test the throughput of the interfaces I wrote a program that
> sends  UDP-packets from one system to the next and measures the 
> throughput/losses/jitter/etc. I used it to send batches of one
> million  packets over the second interface of one machine to the
> third of the next  (i.e. over the direct connection) with different
> packet-sizes.
> 
> First we tried it with the latest drivers from www.scyld.com.
> Unfortunately  after the first million packets, the sending
> interface suddenly blocked,  meaning it wouldn't send any more
> packets, although it returned fine from all  send()-calls. This
> could be solved by an 'ifconfig eth1 down' + 'ifconfig  eth1 up',
> but only for the next million packets.
> 
> Next, we tried the driver distributed with the kernel sources. With
> that, the  interface didn't block anymore, even after millions of
> packets. You can see  the results at http://www.einhoff.de/plot.png
> (sorry, the legend is in  German. Red is bandwidth in Mbps, green
> are losses in %). As you can see we  experienced packet losses up
> to 80%, but only for the packet-sizes from 112  bytes to 354 bytes.
> These results are reliable reproducible. With  packet-sizes of 354
> bytes, we have losses of 80%, with 355 bytes no losses at  all!
> Apparently the packets are lost at the sending side, because the
> program  finishes five times faster with 354 bytes packets than
> with 355 bytes packets.  
> 
> When we tried the scyld-driver again, with smaller packet batches,
> we noticed  that it produces losses to, this time from 91 to 385
> bytes. We didn't notice  the first time, because the interface kept
> blocking.
> 
> At last we tried the driver from the 3com website. This time we saw
> no  losses, but the interface started blocking again after a
> million packets.  
> 
> To summarize:
> 
>  - scyld-driver: losses for packet sizes from 91 to 385 bytes,
> interface  blocks after the first million packets.
>  - kernel-driver: losses for packet sizes from 112 to 354 bytes, no
> blocking. 
>  - 3Com-driver: no losses, interface blocks after first million
> packets.  
> 
> So we've seen all combinations of losses and blocking except the
> one we're  looking for...
> 
> We tried all this on several (identical) machines, so a
> hardware-failure is  highly unlikely.
> 
> Any ideas?
> 
> Thanks,
> 
>       Gerrit Einhoff
> 
> 
> 
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> End of vortex Digest

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