The past few years have seen the mainstream network vendors jump into SDN with both feet. They still offer feature-rich, turnkey switches with all the support and services mainstream enterprises have come to rely on but with a vendor-provided SDN controller. Many of the mainstream vendors also offer support for third-party controllers.
The primary value is in reduction of operational expenses through the automation of configuration and management tasks instead of focusing on hardware costs. In actuality, network hardware accounts for less than 10% of overall data-center spend, while personnel costs can be well over half of a data center’s total cost of ownership. A small reduction in operational costs can pay significant dividends for the business.
One of the most important distinctions between traditional networks and SDNs is that the SDN controllers (or controller functionality if not on a dedicated appliance) have northbound interfaces that can communicate with applications via application programming interfaces (APIs), which enables application developers to program the network directly.
For example, using APIs, a videoconferencing application could automatically create a dedicated path between the video endpoints to guarantee the highest performance. Once the call was finished, the application could let go of the reserved bandwidth. In the past, network operations would need to get involved to reserve the bandwidth and then release it post-call. Historically this could only be achieved if a network-savvy software developer could reprogram the network through CLI commands, but software developers who understand network protocols is rare.
Businesses that want to software-define a network without upgrading the network can choose a solution that operates as a pure software overlay. With this model, virtual network tunnels are initiated and terminated on devices such as firewalls, WAN optimizers or even hypervisors. The benefit of this model is that non-network teams, such as security or server operations can manage their own overlay. The downside is that troubleshooting network problems can be a challenge as the underlay and overlay are invisible to one other.
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