[RndTbl] Network performance tuning

Sean Walberg swalberg at gmail.com
Mon Apr 5 20:12:26 CDT 2010

On a LAN, window sizes aren't going to make that much of a difference.

First look for the usual suspects - errors on the swich port or NIC.

If you can grab a copy of the traffic, such as with tcpdump -w test.pcap tcp
port 5001, you can pull it into wireshark and look for TCP zero window
conditions, retransmits, and duplicate ACKs. The TCP performance graph will
also show whether or not the transmission is stalling.

Is the performance similar using the UDP test? Does it show loss?


On Mon, Apr 5, 2010 at 7:27 PM, Kevin McGregor
<kevin.a.mcgregor at gmail.com>wrote:

> I've been trying to narrow down where my performance bottleneck(s) is
> (are). I just ran "iperf" from a Windows PC (XP SP3) to my Ubuntu 9.10
> server. With iperf in "server" mode on the PC, and the client running on the
> Ubuntu machine, I get
>  0.0-60.0 sec  4.23 GBytes   606 Mbits/sec
> Reversed (iperf "server" running on Ubuntu server, client running on the
> PC), I get
>  0.0-60.0 sec  1.13 GBytes   162 Mbits/sec
> Wha...?? Both client and server runs on the PC report TCP window size to be
> 8 KB, but the Linux client reports 22.4 KB and the Linux server reports 85.3
> KB. Increasing that to 256K on both ends has little effect. Does anyone have
> any suggestions?
> The Windows NIC is a Realtek RTL8169/8110 Family Gigabit Ethernet; the
> Ubuntu server is using the Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI
> Express Gigabit Ethernet controller (rev 01). Time to replace a NIC or two?
> Kevin
> _______________________________________________
> Roundtable mailing list
> Roundtable at muug.mb.ca
> http://www.muug.mb.ca/mailman/listinfo/roundtable

Sean Walberg <sean at ertw.com>    http://ertw.com/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.muug.mb.ca/pipermail/roundtable/attachments/20100405/68e9612b/attachment-0001.html 

More information about the Roundtable mailing list