Re: Packet loss?

From: Ed Horley (no-spamed-usergroups1_at_yahoo.com)
Date: 01/21/05 

Date: Fri, 21 Jan 2005 15:41:07 -0800

You might want to look at this:
http://www.ethereal.com/lists/ethereal-dev/200412/msg00024.html

It seems that "TCP Dup Ack" errors can be attributed to the OS changing tcp
window sizes. You might want to confirm that you are seeing the same
results as what is listed. If not, we can do some additional testing to
narrow things down.

You might want to tune your OS (XP pro/W2K3/W2K) so it performs better for
window size. There are a ton of sites that tell you have to do this, just
Google around. There are a lot of other parameters you can set also.

Some light reading on 2003 to get you started:
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/networking/tcpip03.mspx

Regards,
Ed Horley
Microsoft MVP Server-Networking

"-DC-" <DC@discussions.microsoft.com> wrote in message
news:AFAF1C80-611B-4A36-9C29-A3112BDACB24@microsoft.com...
> Hi Ed,
>
> The switch is a Linksys BEFSR41 running at 100Mbps Full Duplex. I've
> already tried all the different settings on the network card (10Mbps and
> 100Mbps both full and half duplex) with no improvement. I believe I was
> having this same problem a few months ago with a different switch as well.
> Right now I have the card forced to 100Mbps FD. Same goes for a second
> computer on the same switch which is not having any problems.
>
>
>
>
>
> "Ed Horley" wrote:
>
>> Need to know what sort of hub/switch you are plugged into, what the host
>> thinks the speed/duplex is and what the hub/switch thinks the
>> speed/duplex
>> is. Often different OS's negotiate differently speed and duplex with the
>> same NIC so you have to be careful about that. If it is a managed switch
>> (cisco/foundry/procurve/extreme/etc) try setting the speed and duplex and
>> doing the same on the host in the OS. If that fixes the problem then it
>> mostly likely is a auto negotiate issue.
>> Post back what you have and we can go from there.
>> Regards,
>> Ed Horley
>> Microsoft MVP Server-Networking
>>
>> "-DC-" <DC@discussions.microsoft.com> wrote in message
>> news:7B749090-C6D8-4715-AD31-02FE64FC5AB8@microsoft.com...
>> > I've got a strange problem with a Dell GX1. For a long time I've
>> > noticed
>> > that transfering files between this and another machine took longer
>> > than
>> > normal. Eventually I used Ethereal to do a sniff and found that there
>> > are
>> > many "TCP Dup Ack" errors on this PC. So I tried installing a
>> > different
>> > network card; no change. I booted using a DOS network boot disk and
>> > copied a
>> > file to the other computer while doing a sniff. The other computer
>> > indicated
>> > several retransmits. I hooked up a laptop to this same cable and got
>> > no
>> > errors.
>> >
>> > So I've eliminated the network hardware, the NIC, and the OS. What the
>> > heck
>> > is the problem? Is the computer simply not keeping up with the network
>> > card?
>> > Seems hard to imagine considering the card is built into the
>> > motherboard!
>> >
>>
>>
>>