The system I have has several devices connected in a ring configuration using one Ethernet port IN and one Ethernet port out.  The system uses RSTP for loop free operation.  The idea is simplicity for installation, you just unplug and plugin a new device in the ring plus you gain redundancy, if one Ethernet cable breaks you still have another one.  This works but my client has never had more then a half dozen devices on the network yet.

When I say devices just imagine very large machines.  The number of devices could be as many as 100 in the ring or network.  Everything I've researched on RSTP says over 8 devices and its not effective/efficient so I'm researching other Ethernet failover/failsafe/redundant solutions.

So, the local network configuration needs to scale up to 100 devices, have redundancy, and low latency for M2M control.  Any thoughts?  

Thanks

Kelly