Hubs killing performance

spamhater03@birch.crd.ge.com
Fri, 5 Nov 1999 15:56:53 -0500 (EST)

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).