| 477 |  | * transmission of all collected feature replies from the lower tiers (no two low-tier controllers connect to the same switch) | 
          
            | 478 |  | * escalation of topology data (!PacketIn and !PortStats, required by topology and link discovery modules) | 
          
            | 479 |  |  | 
          
            |  | 477 | * transmission of all collected feature replies from the lower tiers (no two low-tier controllers connect to the same switch) | 
          
            |  | 478 | * escalation of topology data (!PacketIn and !PortStats, required by topology and link discovery modules) | 
          
            |  | 479 | 1. Need to work out the details of what is needed/not needed for a control plane to be deemed functional. Do we need all of the controllers properly running? Currently this is the case. However, if each controller is a separate functional component, technically not all components are equally critical to the core functions of a NOS. |