Software Defined Networking (SDN) should be of interest to Cisco certification candidates. Why? Traditional networking functions that you learn in the Cisco Certified Entry Network Technician (CCENT) and Cisco Certified Network Associate (CCNA) programs are old. There are newer technologies and concepts that will be emerging over the years to come. It’s likely that those starting out in networking today will be dealing with those technologies in the near future. This post aims to provide a CCENT or CCNA candidate a brief introduction into what SDN is and how it compares to traditional switching/forwarding.
The following graphic is roughly how a network device functions. Network Devices have a control plane that provides information used to build a forwarding table. They also consist of a data plane that consults the forwarding table. The forwarding table is used by the network device to make a decision on where to send frames or packets entering the device. Both of these planes exist directly on the networking device.
Software Defined Networking
Software Defined Networking abstracts this concept, and places the Control Plane functions on an SDN controller. The SDN controller can be a server running SDN software. The Controller communicates with a physical or virtual switch Data Plane through a protocol called OpenFlow. OpenFlow conveys the instructions to the data plane on how to forward data. The network device must run the OpenFlow protocol for this to be possible. You can see how SDN differs from traditional networking in the following graphic.
What’s the point of doing something like this? SDN creates and dynamic and flexible network architecture that can change as the business requirements change. There are additional benefits that come from using a centralized control. And there are also benefits in the form of Network Automation. By using an API, your controller can implement network commands to multiple devices without the need to learn the command line syntax of multiple vendor products. These are just a few of the benefits seen with SDN.
Wrapping your head around some of the basics here is just the tip of the iceberg. We’ll tackle the details of Software Defined Networking in another post, but as we mentioned already, you’re going to want to keep an eye on SDN. No doubt you’ll be using it in your networking future. While Cisco may be considered one of the slower responders to SDN, there are other vendors that you should look at. Check out Big Switch, who is presenting at Networking Field Day 6.