Why is Software-Defined Networking (SDN) Important?

The SDN acronym seems to be every where these days. Since it is still relatively new to many people in the industry, it seemed good to do a quick primer on SDN, some of the key players in the space, and why SDN is needed in the industry.

Before SDN

In traditional networks we see a range of hardware devices; primarily routers, switches and firewalls. These devices include hardware connectivity which move the data through them and software elements which are configured to control the movement of data through the hardware (based on rules and regulations about data movement). For many years this has been the norm and has met the requirements of the organisations using these networks to connect all there business machines together.

Over the past few years we have seen many changes in these data networks which have driven the technologists developing these devices and networks to try and evolve this model. The main drivers for change is the size of the networks which have grown massively due to the number of devices which need connectivity; from virtual machines sprawl to tablets and smart phones.

The rate of change in configuration of the devices is also driven by the explosive rollout of applications being developed using new agile methodologies; allowing for new software to be released in weeks and days instead of months and years. The size of networks and the rate in configuration change have created a massive amount of complexity in administering these network devices and more importantly making changes at an acceptable rate when additional devices or applications need to be supported.

In order to make changes to these devices a network admin has to connect to each device and make the configuration change. To add to the complexity each device vendor uses their own configuration language, user interface and syntax making it a highly skilled time consuming task.

What is SDN?

The original goal of software defined networking was to separate the Control and Data planes of network devices. The Control plane makes decisions about were the packets it received should be sent and the Data plane physically moves the packets through the device and sends them on through the network. SDN proposes that the Control plane should be centralised so that the configuration of the network can be maintained and changed in a highly agile adaptable way.

When a network engineer needs to provision additional capacity or make changes to existing rules or regulations about data movement they do not need to connect to multiple devices and make manual changes. The change is made centrally allowing them to shape and adapt the network in a highly efficient and rapid way.

As vendors attempt to define and implement SDN it has become more of a broad term used to group a host of networking technologies which are trying to make networks more dynamic. The term has moved more towards network virtualisation which like server and storage virtualisation is about separating the hardware from the function of the hardware by using software layers between. The functions of SDN therefore are centralised programmable software networks which separate the Control and Data planes allowing for provisioning and changes to be implemented at the same accelerated rate as the servers and storage around them.

The other important capability of a successful SDN will be the ability to scale in terms of the massive amount of bandwidth required and number of devices which is growing exponentially without the management overhead increasing at the same rate.

As with all things IT Vendors begin to address these challenges in their own ways using proprietary technologies and implementations. With SDN there is an initiative to try and curb this using some open standards such as OpenFlow.

The Future of SDN

SDN is an exciting and evolving area in the modern data centre which we will see more interest and adoption of in the upcoming year. Will it be based on open standards and interoperability? or will it be another era of proprietary network configuration languages and vendor lock-in.

We will have to wait and see, what we know for sure is that networks are getting larger, bandwidth requirements are increasing along with the number of connected devices and our data networks will have to change and adapt to that growth and rate of change to keep up with the rest of Datacenter technologies.