I've been trying to lower the price point for a customer by using a new topology on their network.
They are intending to use MPLS fast reroute just because they have been told the convergence time goes down to 50ms.
Of course, the advisor would gladly provide them with the required hardware upgrade from 3560 to 65xx switches.
I am tellim the customer that as long as they keep the LAN Ethernet 1000SX based ring topology with two exit routers and all other ports marked as edge ports, there is no need for MPLS because:
- topology changes such as link down and switch down are propagated inmediately with no waiting time, all delays involved are protocol procesing on the switch and negotiation between switches
- RSTP may no be as fast as 50ms in their scenario but its convergence time would be in the range of 100-200ms at a 10% the cost of the MPLS FRR option (far beyond their needs).
Am I right? Can you think of any way to find out the true convergence time without disrupting their network? The ring is made up by two 7600 as exit routers connected to the RSTP ring on two of thirteen Catalyst 3560 on the ring.