OpenFlow is a standard protocol of SDN which assist SDN Controller to communicate directly with the forwarding plane of network devices such as switches and routers, both physical and virtual (hypervisor-based), so it can better adapt to changing business requirements.
Generally the conventional switches forwards the packets which are called the Forwarding Plane and do high-level routing that happens on the Control Plane which occur on same device but in OpenFlow switch it separates the forward plane from the control plane. The data plane or forwarding plane portion resides on the switch itself, whereas a separate controller makes high-level routing decisions. The switch and controller communicate by means of the OpenFlow protocol.
SDN Controller is the main core of Software Defined Network it relay the network information to switches/routers ‘below’ (via southbound APIs) and the applications and business logic ‘above’ (via northbound APIs).
Figure: High Level diagram of SDN with OpenFlow (Source ResearchGate)
SDN controller platforms reduce the load on network devices by removing it from the network hardware and putting the control plane centralized in SDN. SDN Controller use protocols such as OpenFlow and OVSDB to control traffic and configure network devices, typically via an assortment of modules that are able to provide different functions.
Benefits of OpenFlow:
- Enable innovation/differentiation
- Accelerate new features and services introduction
- Simplify provisioning
- Optimize performance
- Granular policy management
- Decoupling of Hardware & Software, Control plane & forwarding, and Physical & logical configuration.
The original concept for OpenFlow begun at Stanford University in 2008. By December 2009, Version 1.0 of the OpenFlow switch specification was released. Since its inception, OpenFlow has been managed by the Open Networking Foundation (ONF), a user-led organization dedicated to open standards and SDN adoption.
Since its release, multiple companies and open source projects like the OpenDaylight Project support OpenFlow, and even provide OpenDaylight Controllers. Other companies like Cisco and Brocade also offer OpenFlow enabled controllers, with Cisco XNC and Brocade Vyatta Controller.
Several established companies including IBM, Google, and HP have either fully utilized, or announced their intention to support, the OpenFlow standard. Big Switch Networks, an SDN firm headquartered in Palo Alto, California, has implemented OpenFlow networks that run on top of traditional networks, making it possible to place virtual machines anywhere in a data center to reclaim stranded computing capacity. By early 2012, Google’s internal network ran entirely on OpenFlow.