Software defined networking is one of the most misunderstood concepts in infrastructure computing. It's a phenomenon that's growing in relevance, but it's still mysterious to many CIOs, particularly those who were not reared in overly technical practice. Many myths still surround SDN. What exactly is the notion behind the technology? How can you apply SDN at your business? And how can your organization benefit from it.
Software-Defined Networking Basics
Essentially, SDN takes the virtualization phenomenon that's been sweeping datacenters around the globe for the past several years and extends it from computing hardware and storage devices to network infrastructure itself. By inserting a layer of intelligent software between network devices (such as switches, routers and network cards) and the operating system that talks to the wire, software defined networking lets an IT professional or administrator configure networks using only software. No longer must he travel to every physical device and configure-or, in many cases, reconfigure-settings.
SDN achieves the same abstraction that hardware virtualization does. With hardware virtualization, the hypervisor inserts itself between the physical components of a computer (the motherboard, main bus, processor, memory and so on) and the operating system. The operating system sees virtualized components and operates with those, and the hypervisor itself translates the instructions coming to these virtualized components into instructions the underlying physical hardware can handle.
As a result, you can move virtual machines to different computers made up of different underlying hardware as long as the hypervisor is the same or is compatible. That's because the operating system in the virtual machine has to know only how to talk to the virtualized components; it can't see or interact directly with the underlying hardware. This abstraction provides a freedom and more capability to configure and reconfigure computers and servers as ongoing operational needs dictate.
This abstraction idea is the same in SDN. It just involves different pieces of hardware. Networks are virtualized so software can configure how networks are built, routed and configured. While the underlying physical network components still route the actual traffic, the place where that traffic flow is controlled-which is called the control plane in SDN parlance-moves from the hardware to the software running on top of it.
This is useful because the network then transforms from a bunch of wires physically connected to a lot of different devices-as you might guess, this is the data plane in SDN vernacular-into a quasi-intelligent fabric that can be controlled, rerouted, redesigned and troubleshooted (troubleshot?) from a software console.
In particular, it allows for self-service network reconfiguration. When users request resources for themselves, the network can automatically accommodate connectivity for those requests-even if the resources are located in different physical areas. The network appears to be one "unit" to the end user, a main benefit of this type of virtualization.
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