SDN needed for network virtualisation

Brent Lees looks ahead to the software-defined, fully virtualised datacentre

Networking has advanced by leaps and bounds in the past decade. Virtualisation in the datacentre has taken off, particularly in the area of servers.

In the early stages this took the form of simple virtual LANs (VLANs). However, as virtualisation capabilities have advanced, network virtualisation has become more flexible.

The idea of a fully virtualised network is now the subject of much discussion. But is it feasible? Is it even beneficial? And what can resellers do to support customers?

The physical network has certain limitations in the modern age of mobility and on-demand computing. Physical network components are, essentially, hardware devices of fixed sizes and capacities, wired together in static topologies.

On-demand reallocation of network resources in a hardware-based environment is difficult, and applications must often conform to the network. The result can be less than ideal, hampering functionality and creating management challenges.

In a fully virtualised network, the control logic is decoupled from the network's underlying physical hardware.

These functions are implemented as software-based services that adapt freely to changing network traffic, encompassing all segments, tracking state changes across the entire network, and adapting policy enforcement mechanisms such as QoS according to application requirements.

While it is possible to build virtualised networks in different ways, resellers should be encouraging customers to adopt software-defined networking (SDN).

SDN provides the decoupling that allows the control plane to be operated completely independently of the forwarding plane. It establishes a framework to create a virtualised network that looks like an ordinary physical network to top-layer services such as operating systems and applications.

In a virtual network, built on SDN, network resources can be allocated as needed, just as processing capacity and storage are provisioned dynamically on a virtualised server.

And by changing the focus from open protocols to open application programming interfaces (APIs), SDN-based virtual networks help programmers develop more flexibly.

You can build a virtual network without using SDN, but it's probably not as useful; virtualisation maps multiple logical networks across a common physical fabric.

However, state management becomes more difficult when logical networks could be located just about anywhere. It turns out that SDN is very good at managing large numbers of states.

At the same time, it can provide a reasonable degree of consistency across operations, because it can permit changes to the forwarding plane.

With SDN, entire datacentres can be comprised purely of software, and the software-defined datacentre (SDDC) is a next logical step.

SDN-based virtual networks can help cut business costs and improve agility, delivering applications effectively while simplifying the underlying physical infrastructure. All resellers should advise customers to move in this direction.

For many, a truly virtualised network will be some way off, but the right infrastructure elements should be adopted in advance. Customers can begin to implement virtualisation and SDN when they are able.

Brent Lees is senior product marketing manager at Riverbed