The controller is a software application that can “program” the network by manipulating the forwarding tables on infrastructure and creating dynamic configuration that is
often described as Software Defined Networking. The controller derives forwarding paths through the network driven by algorithms, logic and process. The OpenFlow
controller can be integrated with management applications providing automated network configuration change control. It’s the automation that is the current focus for many cloud companies and eagerly anticipated.
The wider impact of merchant silicon has seen the emphasis shift from manufacturing to features, and now it’s shifting to manageability. A network is a discontiguous system, with hundreds of individual elements all loosely coupled via routing protocols and spanning tree. An Ethernet switch that has a minimal OS can be “programmed” by OpenFlow. The switch OS is simple, possibly Open Source and a commodity product.
The impact to the perception of product value is significant. Instead of the focus being completely on the network device, primary functions will shift to the controller. Thus, the value proposition moves from the equipment to the software controller.
Because the configuration complexity has now been shifted into the controller, the profile of network equipment is much reduced. Day-to-day administration activities such as virtual LAN (VLAN) creation, port allocation and access control lists (ACLs) can now be handled by an OpenFlow controller. The controller can be rules-driven or heuristically capable. Importantly, it will also have a coherent view of all devices in its database, and will be able to model configuration changes ensuring they are sane and correct before deployment.
Compare this with your network designer, who must be able to sort through hundreds of details and options to be able to determine the requirements for any change to the network from his or her own experience. The reduction in operational friction is perfect for public and private cloud networks in the data center, but also for large campus networks with switches and wireless devices, where the operational challenge is huge.
