SOFTWARE DEFINED NETWORK

Software attempts to build a computer network by separating it into two systems , the first system is the control plane which provides performance and fault management via NetFlow , IP fix , SNMP and other protocols . SDN was created in response to demands from large data centers , who found problems with coping with very unpredictable traffic patterns these patterns could be have very high demand for existing network infrastructure , hence SDN is ideal for customers who have rapid changes in their day to day network load such as social networking sites , search engines , large data centers which have geographically dispersed resources and workload in specific locations . SDN has a key protocol called OpenFlow ,the data path of an OpenFlow Switch presents a clean flow table abstraction; each flow table entry contains a set of packet fields to match, and an action (such as send-out-port, modify-field, or drop). When an OpenFlow Switch receives a packet it has never seen before, for which it has no matching flow entries, it sends this packet to the controller. The controller then makes a decision on how to handle this packet. It can drop the packet, or it can add a flow entry directing the switch on how to forward similar packets in the future., provides a way to control the behavior of switches through the networking dynamically and programmatically