About SDN
The salient features of SDN are:
Directly programmable: SDN decouples the network control and forwarding functions. SDN allows programming the network control plane by abstracting the physical infrastructure.
Agile: Decoupling and abstracting network control from forwarding helps administrators dynamically adjust network-wide traffic flow to meet the changing needs in the networks.
Centrally managed: Network intelligence is centralized (logically) in software based SDN controllers that maintain a global view of the network, which appear to applications and policy engines as a single, logical switch.
Programmatically configured: SDN lets network managers configure, manage, secure, and optimize network resources very quickly via dynamic, automated SDN programs, which they can write easily and quickly, because the programs do not depend on proprietary software.
Open standards-based and vendor-neutral: Because SDN is implemented through open standards, SDN simplifies network design and operation because instructions are provided by SDN controllers instead of multiple, vendor-specific devices and protocols.