Slow Gigabit Ethernet.

I've upgraded the machines in my home network to Gigabit Ethernet. I've used the Intel Pro GT NICs (only PCI slots available) and a Netgear G608 switch.

It present I'm only getting about 15 - 20 % link occupancy, and file copies between machines are slow. They are quicker than over 100 Meg Ethernet, but not much. A disk to disk copy, between 2 PATA drives on the same cable is much quicker than a copy over the network to a machine with a SATA drive. The speed between the 3 machines is consistent, and the bandwidth used does not seem to increase even when doing multiple copies, e.g. a file on PC A is copied to PC C at the same time as copying a file from PC B to PC C. The bandwidth used on PC C stays the same as if a single copy was being done.

I have enabled jumbo frames (9K) and have confirmed using wireshark that frames of 8960 bytes are being sent. I have also enabled the facility to offload the TCP checksums. The drivers are the latest from Intel's site. 2 of the PCs use XP Pro, and the other uses XP home. The utilites for the NIC give the chance to test the cables (2 meter cat 5E) and they show OK. I tried connecting PC to PC to cut out the switch and the bandwidth used was the same.

While googling about this I've seen a few people comment on the TCP window size, and that increasing this will increase the bandwidth available, at the expense of more memory used for each open socket.

On another forum someone posted the results of copying over their gigbit network, but the copy was done using ftp.

Can anyone comment about the low speed, and the sugested mod to the TCP window size?

Does any one know of an XP based NFS client and server. From memory NFS uses UDP, so would not be waiting for acknowledgments.

Thanks in advance for any help

Rob Murphy
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  1. Could you provide some more info about your systems please. Might help other find a solution to your problem
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