RE: Hubs killing performance

Krasinski, Linda M (Linda.Krasinski@unisys.com)
Fri, 5 Nov 1999 16:12:13 -0500

Check the NIC settings - make sure they are set to auto.
Also try restarting the systems after they are plugged into the Hub. I
found that just by unplugging and then replugging into the Hub, I'm switched
to half duplex - a restart puts them back to full.

-----Original Message-----
From: spamhater03@birch.crd.ge.com [mailto:spamhater03@birch.crd.ge.com]
Sent: Friday, November 05, 1999 12:57 PM
To: netperf-talk@hpisrdq.cup.hp.com
Subject: Hubs killing performance

I have a Windows NT client talking to a Solaris server.
The CLient has a 10 MB/s card, the server has a 10/100 MB card.
Using the TCP_TCP_STREAM benchmark, we got two different results:

Using a cross-over cable (no hub) we got a value of 8.77

C:\netperf>netperf -Hdemo -l60 -v2
TCP STREAM TEST to demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

16384 8192 8192 60.00 8.77

Adding a NDC SOHO 10/100 mb autosensing hub, the performance is now:
C:\netperf>netperf -Hdemo -l60 -v2
TCP STREAM TEST to demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

16384 8192 8192 61.00 1.80

Why would a hub degrade the performance so much?
Is it the auto-sensing?
This is a simple hub with one switch (uplink on/off).