Global and local knowledge in SDN

It appears to be SDN dogma that middleboxes are bad. However middleboxes form near half the elements that comprise today´s networks and at least three active research fields are exploring how to improve their functionality. Fifteen recent SDN survey papers were examined for evidence to support the SDN dogma and its assertion that all network functionality belongs in the control plane, without success. In fact many chose to ignore the subject. Consequently this paper critically examines what is almost an SDN article of faith and finds this dogma creates a number of interesting and avoidable problems. Three common middlebox types are examined: firewall, NAT and load balancer to highlight the preferred SDN architecture and generate critical thinking. Finally the concept of global and local knowledge is used in a framework to determine whether an application should reside in the control plane or data plane.