Question : Switch and 10Mbit device problem...

Hello.  This is my first question here so forgive me if my format is wrong or I ask to much.  I have a customer with a network problem.  As I understand it, their network is approximately 500 computers, segmented with Vlans.  On any particular segment, the switch has a mix of 10 and 100mbit devices connected.  My product uses a SMSC 91c96 ISA based 10mBit device, (about 30 of the 500).  Basically, they claim that our controller causes too many collisions and 'chokes' the network, where it causes connectivity problems for other users and sometimes the switch shuts down the ports.  They claim that on a 24 port switch, if 5-10 of the ports are plugged into my device, then they have these problems because my nics flood the network.  They use Nortel 450 and 350 switches.

So, my question is...  What could be happening with my 10mBit devices that would cause this behavior?  (if it's even my fault)  They are claiming that there are excessive collisions on the ports connected to my device.  They know there are collisions because they are monitoring the statistics reported by the switch.  I know that each port is a separate collision domain, and under heavy traffic the switch will sometimes send a collision alert to a nic to tell it to back off.  But collisions shouldn't be that frequent in a switched network right?  The auto-negotiation isnt an issue as everything is set to 10 half.  Please help!

Thanks!
Ben.

Answer : Switch and 10Mbit device problem...

Yes, this the 30 second version of Multicast. That is all correct. Collisions do not occur "on a network".  Collisions occur on a collision domain.  In the case of a switched network, your collision domain consists only of your PC and the port to which it is attached. If there were some Hubs mixed in there it would be a different story. The only thing that should be affected by the collisions is your PC, and a slight possibility of the switch. This should only make your network performance for your PC be very slow. That's the only thing I have ever seen collisions do. NOT take down whole switched networks.

The most likely reason is that you have a 1/2 duplex connection. Meaning you can send OR receive, but not both at the same time. Since the multicast is a constant stream of data, any packets you try and send out will collide with the constant stream coming in.

My advice is still the same. Enable multicast filtering, and/or stop multicasting and see how the counters are again.