as shown in fig4 during normal operation secondary node 233 in network 230 sends the second set of the data to destination node 231 over route 236 and primary node 232 sends the first set of the data to destination node 231 over route 235 destination node 231 then performs a service selection ss function node 231 chooses one of the two incoming sets of data i e the set of data from secondary node 233 in network 230 or the set of data from primary node 232 the fig4 embodiment is designed to survive any single node or link failure per network except for a failure of the source or the destination which cannot be survived in any case for most failures two sets of data continue to be sent from network 210 to network 230 if there is a failure between source 211 and primary node 212 in network 210 primary node 212 uses a detector function to detect the failure and notify source node 211 which uses a selector function to switch the first set of data traffic to an alternate protection path 218 if there is a failure between source 211 and secondary node 213 in network 210 secondary node 213 uses a detector function to detect the failure and notify source node 211 which uses a selector function to switch the second set of data traffic to an alternate protection path 219 in either case two sets of data continue to be received at nodes 212 and 213 if secondary node 213 in network 210 fails source node 211 and.