Software-defined networking (SDN)

Software-defined networking (SDN) is an approach to networking in whichcontrol is decoupled from hardware and given to a software application.

When a packet arrives at a switch in a conventional network, rules built into the switch's proprietary firmware tell the switch where to forward the packet. The switch treats sends each packet going to the same destination along the same path, and each packet is treated the exact same way.

In an SDN, however, the network administrator uses third-party software to shape trafficfrom a centralized control console. The administrator can change the switch's rules when necessary -- prioritizing, de-prioritizing or even blocking specific types of packets with a very granular level of control. This is especially helpful in a cloud computing multi-tenantarchitecture because it allows the administrator to manage traffic loads in a flexible and more efficient manner.

SDN is sometimes referred to as the "Cisco killer" because it allows network engineers to support a switching fabric across multi-vendor hardware and application-specific integrated circuits (ASICs). Currently, the most popular specification for creating an SDN is an openstandard called OpenFlow.