Cell Relay Archive

["O.Lins." <lins@tfh-berlin.de>]

Distribution: world

Hi everyone,

I have very bad result in TCP performance using a pci-network card (SMC ATM155)
under NT 4.0 in a LANE configuration.


The US support of SMC did not response at all
(except the UK support who told my that forwarded my request to the US support
:-).


I'm using a programm similar to ttcp. On a fast ethernet link my results are
about
45 - 50 Mbps. On the ATM card I only get about 25 Mbps. I am directly connected
to a
FORE asx-1000 switch. The other side is a SGI machine with about 6 cpu's and a
155Mbps link
to the switch. As far as I know there are no UPC's and no traffic shaping.

I have read the articles about tcp window size and receive/transmit buffer size.
Any changes I made on the NT side did not influence the result.

Any ideas why the performance is that bad ?

There are a few things I found out :

    There are a lot of "Invalid VC cells".  Where do they come from ?
    Same "Incorrectable HEC Errors".  Shouldn't they be nearly 0 ?
    A lot of dropped cells. When I reduce the bandwidth to 25 Mbps I have less
until 0
    dropped cells anymore. Does it mean the card or the driver is not fast
enough to
    reassemble the incoming cells?

My email : lins@thf-berlin.de

Thanks in advance.

Oliver