Recently I had a situation come up where someone had upgraded their network to all gig connections, all the way to the desktop. However they started having poor performance, and File transfer from a PC was Staggeringly slow. This is not the first time I have seen it but felt I should document a little of what I know because I see it so often.

Upgrading to Gig Ethernet not only makes the network faster it makes any problems you have increase as well. This is similar to upgrading from 10 mb to 100 mb Which would often show that you had cabling problems. Well with upgrading to GIG it will show problems in areas not seen before or maybe they were seen but were left as nothing to worry about because all is working fine.

NIC and NIC drivers seem to be one of the biggest culprits of Network speed degradation when moving to full Gig. When they have a problem the switch’s will not always record these errors so many network engineers miss the signs. This is often at the server level because it is the most taxed node on the network. If a choke point is added  between the server and the clients then the symptoms often disappear. However this is not the real solution. the solution is to find the culprit or actual problem.

A Sniffer is your friend and I am a firm believer in sniffing traffic. As I began to think about what was happening I became very curious. So I came home and began sniffing my network I was amazed to find out how many errors i was having on my network. Especially since I generally keep my Network card drivers semi updated. (they are updated once a year). As I dug into things more I found that I had 7 out of 10 NICS causing problems. so I started with Drivers and began updating them. I even found one network card that was bad. it was transmitting and working but had a lot of errors and TCP RETRANSMITS, AND Window RESIZEING going on. I upgraded it’s Drivers which did not help then changed NIC cards and all is well.

My network performance has increased as well. Now understand I did not have a problem at least one that I noticed so Now I am wondering if this is more common then I thought. I have seen it at multiple clients in the past 2 years but still I would be interested in knowing if more people had the same problem.

Thanks