Definition - What does Hybrid Software-Defined-Network (Hybrid SDN) mean?
A hybrid software-defined network (hybrid SDN) is a networking approach in which traditional networking and software-defined network (SDN) protocols are used and operate in the same environment. In SDN, the control is passed to a controller software application instead of the hardware. With a hybrid SDN, network engineers were able to develop new SDN technologies and support switched fabrics throughout multi-vendor hardware and application-specific integrated circuits. This essentially allowed traditional networking hardware or legacy environments to run SDN technology, like OpenFlow, without the need for a complete infrastructure overhaul.
Two major approaches have gained popularity. Their differences in pedigree and implementation make each one useful to different markets, but not so much that it causes fragmentation.
Removes the entire control plane from the network equipment, downgrading it to a data-plane only role, thus making data monitoring easier and faster. New mechanisms of network control are made and stored on a server/cloud, an online storage device. OpenFlow is applicable to a wide area network (WAN), but earlier applications focused on data storage or center and campus applications. No matter what modifications are done, an OpenFlow device should support OpenFlow before the path is available.
Path Computation Element (PCE)
The migration of SDN to a PCE-based approach can be regular or partial. Unlike OpenFlow, the network elements that are not yet upgraded in PCE may still be used in paths and may also continue to function as ingress nodes using their existing path communication function. This approach has less cost, less risk and is less disruptive than OpenFlow.
Recently, Google shared its foundation for SDN. Because the hardware is separated from the software, it is easy for Google to focus on one or the other. It can choose hardware-based features, while at the same time developing and organizing software timelines. SDN also provides logically centralized control that makes it more efficient, fault-tolerant and deterministic, compared to non-SDN environments. Finally, automation helps Google separate monitoring, allowing the company to specify different aspects of its system, and to manage and operate it from individual boxes.