[Winpcap-users] WinPcap performance

[Terence Neill]

Hi folks,

I'm doing some performance testing with WinPcap  running under Windows
7.  My test setup is as follows:

1. Windows 7 PC (Q6600 4Gb RAM) and a Belkin RTL8169 based PCI GigE
network card.
2. SmartBits 200 to generate and monitor traffic.
3. The SmartBits is connected directly to the GigE network card using a
standard Cat5 cable.
4. The SmartBits is indicating that the link is established as Full-Duplex.
5. I have two WinPcap processes running, one that transmits packets and
one that receives packets.

When using Winpcap to transmit packets (1024 byte packets) using send
queues in batches of 255 packets, I'm finding that I can sustain a
transmit rate of 650Mbps (based on the network utilisation shown by
Windows) and no packets are lost.  This is significantly more than I
need for the application that I have in mind, so no problem there.

In the receive direction (with the SmartBits generating the traffic,
1024 byte packets again), I'm finding that I can receive a stream at a
rate of around 200Mbps without WinPcap reporting any lost packets. 
Again, this is well in excess of what I require for my application, so
no problem there.

The problem that I'm seeing that if I try to support bi-directional
traffic (sending and receiving) then I can only sustain a transmit and
receive rate of around 15Mbps before WinPcap starts reporting packets
being dropped.

To me, this looks like a problem with collisions, but as the GigE link
is reported as full duplex, I don't see how this could be the case.

Is there anything obvious that I'm doing incorrectly?  Any help would be
appreciated!

Thanks,

Terry