In Software Defined Networking the controller is the focal point of network architecture, sitting between applications that will make demands of the network and the network devices themselves. For network professionals, the centralized controller takes on the role of the control-plane, where distributed routing protocols such as BGP and OSPF have traditionally sat.
We are still in early days of SDN with groups and vendors jockeying for position and dominance, and as such there are an abundance of controllers to choose from. SDN controllers fit into the following categories.
- Academic projects.
- Industry-backed open source projects.
- Vertically-aligned, vendor-specific products.
In fact, someone new to SDN could be overwhelmed by all of the choices.
However, upon further inspection, a trend is becoming evident in the SDN controller market — that of consolidation. While there are still many controllers in play, slowly but surely the market is seeing two key rallying points, both in the open source world. One is the Linux Foundation’s OpenDaylight Project. The other is ON.Lab’s Open Network Operating System.
This consolidation is an important step in the SDN world:
• Enterprise shops have been stymied by the variety of controllers out there. It’s hard to bet on an SDN controller this early in the game, especially when trying to build a new operational strategy around the platform. Consolidation means they can make a choice they can live with.
• Vendors interested in interoperability are also impacted by having too many controllers to contend with. But, with ODL and ONOS gaining broad acceptance, vendors can build a controller based on one with little risk it will become an orphan.
• Some SDN application developers have been in a “sit back and wait” mode, as it takes both time and money to support an application on a variety of controller platforms. As the industry settles on ODL and ONOS, application developers can release products for these platforms knowing they will work across the larger part of the user community.
This takes nothing away from the important contributions made by the many academic SDN controller projects. These efforts remain useful as proofs of concepts, or to try out new ideas. But they weren’t necessarily designed to work at scale or to handle every SDN use case that an enterprise or service provider might have.
In addition, vertically integrated controllers designed by a vendor to work within their own ecosystem are just that - part of a specific stack intended to work in a unified product line. These vendor-specific controllers are unlikely to ever go away, as they may forever be integral to certain vendor product offerings.
And that’s not a bad thing. There’s room in customer networks for more than one controller, depending on the problems being solved and the products used. However, it is interesting to see that part of the consolidation movement comes from vendors. A number of them are basing their controllers on open source projects, OpenDaylight in particular.
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