The network world is abuzz with the technology revolution provided by Software Defined Networking (SDN), but what is so great about SDN that has got the networking experts in both the Enterprise and Service Provider worlds so excited?

Over the last couple of decades, network technologies have refreshed around a ten-year cycle. The nineties technology shift moved us from leased lines and Time Division Multiplexing (TDM) to the world of ATM, Frame Relay and the emergence of Ethernet as the standard for local area networks.

The 2000s cemented both IP and Ethernet as the de facto protocols and provided us with both scale and performance guarantees with the underpinning of MPLS. With these technology shifts the speeds increased but the fundamental frameworks or architectures for building networks remained the same.

This meant that the functionality for specific local area, wide area and computer centre network islands got worked on separately to meet the increasing demands.

For the most part these networks evolved in sync with the IT host and application lifecycles. During both decades the investment and rollout of new business wide IT applications were based on long-tail business cases for customised applications and their proprietary hosting hardware.

This meant that there was adequate time to augment the business networks to support the new application traffic as a part of the yearlong IT project rollout.

Late in the 2000s this all changed with virtualised computing, which had made the leap from IT sandbox to mainstream production. The upward march in performance (Moores law) was putting computing power at a cost level where it became viable to host applications on shared infrastructure.

This step-change in the operation of the IT systems led to the modernisation of the computer centre network and the migration to a more scalable data center network fabric.

Up until this point, the majority of network equipment in the computing centres was LAN grade. Basically, higher capacity versions of the wiring closet equipment that was driving the local area networking out to the desktop.

Specialised data center networking equipment assisted in meeting the traffic growth of the move to virtualised computing but the switching and routing protocols they ran were based on local area network environments.

This meant that deploying highly resilient networking architectures that maintained the availability of the IT applications to their users was extremely complex. The result was a network that was out of step with the speed of the computing/application world.

The IT application teams could turn up new virtual computing instances and deploy their applications within minutes, but the network configuration changes to provide the connectivity to the application users could take weeks or even months. Something needed to change.

The speed and agility of business information systems was forever increasing, and the constructs around networking were unable to keep up with the speed of change.

The resulting change following the implementation of SDN has been a complete rethink of the way the network is built and operated, which can be summed up in three key areas.