OpenFlow is the name given to the standard communications interface defined for communications between the control and forwarding or infrastructure layers of a software defined network, SDN.
OpenFlow allows direct access to the infrastructure or forwarding plane of the software defined network to enable manipulation and control of its operation.
Using the OpenFlow protocol, it provides control of all elements including switches, routers and other devices in the infrastructure plane.
OpenFlow SDN background
OpenFlow is a new technology within the networking arena. Its beginnings lie in work undertaken by a PhD student at Stanford University in Silicon Valley, California who developed a flow based network and a controller system called Ethane.
This software was developed by teams at Stanford and the University of California, Berkeley and ultimately was able to control network entities and it was renamed OpenFlow.
The next stage in the development of OpenFlow as a software defined networking cornerstone occurred in 2011 when the Open Networking Foundation was established. Its aim was to standardise emerging networking and data management centre technologies and to support their uptake. The Open Networking Foundation originally had members including Google, Facebook and Microsoft, with later members including: Citrix, Cisco, Dell, HP, F5 Networks, IBM, NEC, Huawei, Juniper Networks, Oracle and VMware.
The first version of OpenFlow was released in February 2011. It was only after this initial release that the Open Networking Foundation took over the standardisation and it was updated to Version 1.2.
OpenFlow SDN basics
OpenFlow is an open interface for remotely controlling the forwarding tables in network switches, routers, and access points. Upon this low-level primitive, researchers can build networks with new high-level properties.
OpenFlow is not SDN and it is not the only interface and protocol that could be used within a software defined networking environment. However it has been standardised and is currently the most widely used in these applications.
OpenFlow is an open API. It provides a standard interface for programming the data plane switches.
In terms of its overall structure, it has many similarities to the x86 instruction set for the networks.
As such OpenFlow for software defined networks provides open interface to networking nodes including routers, switches and the like. It enables visibility and openness in network.
The OpenFlow Switch data flow consists of a Flow Table. The control path consists of a controller which programs the flow entry in the flow table.
SDN OpenFlow is based on an Ethernet switch, with an internal flow-table, and a standardized interface to add and remove flow entries.
SDN OpenFlow protocol
The OpenFlow protocol is implemented on both sides of the interface that exists between the Control Layer and Interface Layer.
The OpenFlow protocol uses the concept of flows to identify network traffic based upon pre-defined match rules that can be dynamically or even statically programmed by the software defined network control software.
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