Beowulf with Gigabit Ethernet

Patrick Geoffray patrick at
Thu Jan 10 11:39:34 EST 2002

Hello Alberto,

Alberto Ramos wrote:
> know if this has some problems with latencies. In other words, Do you think
> that the improvement from fast Ethernet to Gigabit over cooper Ethernet is
> good enougth?

No. The latency of IP over GigE/cooper is roughly the same than IP over Fast 
Ethernet (it's even a little bit more, because the minimum GigE packet is a 
little bit larger than for Fast Ethernet).

>   Also we dont know very well what the latencies of gigabit over cooper are
> compared with fast ethernet and myrinet, maybe some of us can help us.

If it's IP, that's the same thing. The part of the NIC overhead in the IP 
latency is very tiny. 
If your protocol is IP and you concern is latency, go with Fast Ethernet. 
If your protocol is MPI, don't go GigE.

|   Patrick Geoffray, Ph.D.      patrick at 
|   Myricom, Inc.      
|   Cell:  865-389-8852          685 Emory Valley Rd (B)
|   Phone: 865-425-0978          Oak Ridge, TN 37830
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