The control layer of an SDN architecture is responsible for making decisions about where traffic is sent in the network. This layer acts as the 'brain' of the SDN and maintains a comprehensive view of the network, which allows it to dictate how the underlying systems (like switches and routers) should handle network traffic. The application layer consists of programs that use the SDN network to deliver services to end-users. The infrastructure layer includes the physical switches and routers that carry out the control layer's decisions. The management plane, while involved in monitoring and administering the network, does not make decisions on the flow of traffic.