23. SDN Controllers

Much of what has been discussed previously has focused on SDN, but has only skirted around the devices that make SDN possible: SDN controllers. We know from the SDN architecture that the controller is the keystone, the top of the architecture hierarchy, which serves as the brain of the system. However, what is not so clear is how that controller functions or even fits into our network topology.

This section looks at how controllers function and how they play an integral part in regulating the data flow between the application layer (the applications we use) and the physical layer (the routers and switches our data has to cross). For instance, if you are going to replace the control layer of every device—router or switch—you ...

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