SDN is short for software defined networking. Software defined networking (SDN) is an approach to using open protocols , such as open flow, to apply globally aware software control at the edges of the network to access network switches and routers that typically would use closed and proprietary firmware.
Benefits of Software Defined Networking
Software defined networking offers numerous benefits including on-demand provisioning, automated load balancing, streamlined physical infrastructure and the ability to scale network resources in lockstep with application and data needs. As noted on enterprise networking concept, coupled with the ongoing virtualization of servers and storage, SDN ushers in no less than the completely virtualized data center, where end-to-end compute environments will be deployed and decommissioned on a whim.
An open flow switch separates these two functions. The data path portion still resides on the switch, while high-level routing decisions are moved to a separate controller, typically a standard server. The Open-Flow Switch and Controller communicate via the OpenFlow protocol, which defines messages, such as packet-received, send-packet-out, modify-forwarding-table, and get-stats.
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.
In other words it provides one, open-standard methodology of optimizing traffic, end-to-end, and in the near future SDN is bound to change the way communication network is managed.
Deptt of CSE