I'm reading the STP defined by 802.1d and can't understand one thing.
All bridges are is uniquely identified by 64-bit long IDs, that in fact is a concatenation of a globally-unique 48-bit bridge MAC address and 16-bit priority value. The MAC address is included to make the BridgeID unique, it's clear.
What isn't clear to me is what happens when priority field values are the same, how will the spanning protocol elect the root? MAC addresses aren't necessary to be comparable in terms of arithmetic. Could anybody explain this to me?