OpenFlow is the first standard communications interface defined between the controls and forwarding layers of SDN architecture. It mainly allows direct access and manipulation of the forwarding plane of network devices (e.g., routers and switches) both physical and virtual. There is no other standard capable of doing what OpenFlow can do, it’s needed to move network control out of the networking switches to logically centralized control software.
Generally, the protocol specifies basic primitives that can be used by an external software application to program the forwarding plane of network devices. It’s function similar to a CPU where a set of CPU would program a computer system. OpenFlow always implemented on both sides of the interface between network infrastructure devices and the SDN control software. It identifies network traffic based on pre-defined match rules that can be statically or dynamically programmed by the SDN control software.
The beauty of the OpenFlow protocol is that it can define how traffic should flow through the network devices based on parameters such as usage patterns, applications and cloud resources. This way it provides extremely granular control, enabling the network to respond to real-time changes at the application and users. The current network does not provide this level of control as all flows between two end points must follow the same oath through the network. The OpenFlow protocol is the key to enable SDN and it’s the only standard for SDN currently.
OpenFlow Switching can be deployed on existing networks, both physical and virtual. Network devices can support OpenFlow forwarding as well as traditional forwarding which makes it very easy for enterprises and carriers to progressively introduce SDN technologies in the multi-vendor network environment.
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