IEEE 1394b speed limitation.

Hi,
I have a strange(atleast to me) observation on the speed of the IEEE 1394b
cabel environment.

I have IEEE 1394b PCI cards with TI chipsets which supports 800 Mbps and i
have been using this cards for IP over 1394 , quality of service and
related work.

I have used different set of cables interchangeably with a length of 3
meters. Some cables are of 800 Mbps and some of 400 Mbps.

I tried to benchmark the speed of IP over 1394( using eth1394 )in kernel
2.6.5 and am able to acheive 450 Mbps by changing the MTU size to 4000
instead of default 1500.I tested with couple of benchmarking tools that are
Iperf and Thrulay and both gave me a consistent 450 Mbps bandwidth.

Regardless of the cable( S800 or S400) i use, i am getting a bandwith of 450
Mbps with the 800 Mbps 1394b cards.

My concern is though the cards support 800 Mbps but my cable medium is only
400 Mbps. In that case how i am able to acheive
450 Mbps. Is it possible to get a higher bandwidth than the specifcations. I
am guessing that coz of the shorter(3 meter) cable length it might be giving
a higher bandwidth.

Any comments are appreciated.

Thanking you all in advance.

Regards,
Sreehari

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Received on Wed Sep 8 12:16:48 2004