An Introduction to Software Defined Networking

An Introduction to Software Defined Networking

March 16

We’re all familiar with how servers and storage have been virtualized making them easier configure and maintain. Well, what if I told you the network is undergoing similar changes? Software-defined networking (SDN) is a way to virtualize networks making them easier to manage. SDN isn’t as far along in this journey. But it has made considerable progress over the past few years. Networks are so vital to business that it’s wise to keep an eye on how they are evolving.

SDN - software defined networking

A number of technology companies have SDN initiatives. Companies like Cisco, IBM, Dell, Google, Intel and Verizon are all on board with SDN. Given their reliance on data center technology, it makes sense for them to roll out SDNs in these and other areas. Today’s networks are complex and resistant to change, but SDN promises to change that.

Let’s take a look at some of the features that define the SDN along with the benefits they promise to deliver.

SDN vs. Legacy

Networks are built around equipment such as routers, switches, and firewalls. Both the control plane and the data plane are baked into these hardware devices. The control plane determines where the traffic is sent. The data plane forwards that traffic based on how the control plane is configured. Making changes to the network configuration requires new hardware and more configuration.  Legacy networks also do not respond efficiently to changing network condition. Today that’s important as virtualization and mobility work best on dynamic networks.

SDNs take a play out of the server virtualization playbook and insert an abstraction layer. This layer separates the control plane from the data plane. SDN effectively decouples the hardware from the software layer. This separation makes network virtualization a reality because you’re no longer executing control roles from the hardware devices. Legacy networks take time and effort to modify. SDNs promise administrators the ability to shape the network any way they want. The SDN also gives administrators the ability to set the rules and controls through a software interface.

Network administrators will embrace SDN because it allows for granular control of network traffic. It also promises to decrease reliance on hardware with proprietary firmware to perform these functions.

Read More: How to Build a Home Network That Will Make Any Business Jealous

Primary Benefits

As I mentioned earlier, the SDN gives the administrator more control over how data flows along the network. It also allows them to change the network traffic rules on the fly. This saves both time and money. Let’s look at a few more benefits:

Centralized Provisioning – Because SDN is an open-source product, its will work with hardware across many vendors. Today one may standardize on Cisco hardware because it works well together. One can add hardware from other vendors, but that often makes the deployment and management of those assets a more complex. SDN moves the management layer to a software interface that promises to support hardware from any vendor.

Improved Security – Virtualization has made networks more complex and challenging for IT managers. Virtual machines come and go. That makes applying firewall and policies a challenge. Add mobile products like tablets, phones and  BYOD, and your security problems escalate quickly. The SDN controller gives the administrator a central point from which to enforce and distribute security policies.

Read More: 4 Security Tips For Implementing BYOD

Cloud Support – Whether you’ve migrated some or all of your services to the cloud, it’s here to stay. SDN will help companies extend the datacenter infrastructure to support various cloud environments without having to worry about the underlying protocols. This will allow them to connect various cloud services for their users and make hybrid cloud creation a lot easier.

Improved Content Delivery –  Not only is the amount of content increasing, but users are demanding it across all devices. Much of this content is in high definition. Companies like Netflix have benefited from new streaming technology that allows this rich content to be cached on the edge of the network. SDN provides the responsiveness that is required to deliver this content to the user.

Hardware Savings – SDN will not commoditize all hardware, but it will certainly reduce vendor lock-in. Moving the intelligence to the SDN controller allows IT to use less expensive hardware.


The biggest advantage of SDN today is that it’s still largely unproven. A lot of the benefits cited by companies with investments in the underlying technology are theoretical. That doesn’t mean they won’t work in practice, but it’s too early to know for certain. Networking tools have been evolving now for more than 50 years. Whenever a new technology arrives and promises to overhaul the incumbent, there’s bound to be a few naysayers. I liken SDN to where the cloud was about a decade ago.

“At this time, there’s a lot to like about SDN – except the reality.” – Sam Masud

Another issue SDN will have to work through is its reliance on software. Hardware is expensive and takes time to configure. But once optimized, it works for a long time. Software is buggy and requires developers to maintain it. The reliability of your network relies on the stability of the software managing it. Moving the intelligence from the hardware to the software layer sounds great in theory. And when it works, it will be a dream for administrators. But when it goes down, that dream will turn into a nightmare.


There’s a lot of excitement, angst and confusion around SDN. Some believe that SDN is a buzzword vendors use to sell updated equipment. I’m not as cynical because I believe the benefits outweigh the few negatives. A lot of pundits questioned the cloud for years until Amazon and Microsoft released their cloud products. One would sound foolish to question the power and influence of the cloud today. SDN will arrive, but it will take time.

I have no doubt that SDNs will be a boon for those companies that rely on virtualization. SDNs provide a fundamental change in this area of computing that continues to grow at a rapid pace. Being able to configure networks on the fly to handle more cloud resources as well as disaster recovery scenarios is a huge advantage that isn’t going away.

For more information about SDN, I recommend Software Defined Networking for Dummies. Cisco provides the book as a free PDF for download.