This document discusses different SDN deployment models including centralized vs distributed control, symmetric vs asymmetric, flood-based vs floodless, host-based vs network centric, reactive vs proactive, and flow routing vs aggregation. Under centralized control, SDN global information is held at a central controller, while distributed control distributes information and functions across multiple controllers. Reactive systems install flow entries in response to traffic, while proactive systems pre-populate flow tables to avoid setup delays. Flow routing uses exact-match entries for fine-grained control, while aggregation uses wildcard entries for large numbers of flows.