SDN: An Enabler For NFV

Millions of consumers and businesses are connected to some type of network on a daily basis. Yet, chances are, most can’t begin to understand the complexity of what’s going on in that network. What they do understand is their need for greater bandwidth and that places even greater stress on the network infrastructure. Fortunately, software-defined networking (SDN) and network functions virtualization (NFV) promise to help mitigate this challenge and in the process transform the future of networks.

While both SDN and NFV are key industry buzzwords these days, many people are still confused about the technologies. Simply put, SDN manages network complexity via a network-wide software platform that enables centralized network coordination, control and programmability. The OpenFlow communications protocol is one key example of an instantiation of SDN.

NFV makes networks more scalable, agile and efficient by allowing users to replace dedicated network function appliances with functions instantiated as virtual machines running on a server. Both NFV and SDN work to address overall network complexity, but they do so in different ways and accomplish very different things.

The classic firewall provides the perfect example of NFV in action. The firewall restricts access to a network based on a set of policies or rules so that only certain users with the appropriate credentials are granted access; all others are blocked. Traditionally, firewalls have been available as dedicated hardware-specific implementations. With NFV, however, that same functionality can now be run as a pure software machine running on a server. The same scenario holds true for devices like routers and VPN gateways.

Because NFV allows network functions to be implemented in software, they can be easily moved to various locations in the network without having to install new equipment. Rather than deploying lots of hard assets, low-cost high-volume server infrastructure can instead be deployed with virtual machines running on top. And because the use of virtualization eliminates any dependency between a network function and its hardware, physical hardware can be shared by multiple virtualized network functions.

The challenge with NVF is that the user needs to configure the network so that the software function running on the server gets tied into the network in the appropriate place and with the appropriate connectivity. That’s where SDN comes in, and it’s what it does to help manage this process that’s key to understanding how exactly it differs from NFV.

SDN provides a programmable and customizable interface that controls and orchestrates the operation of a collection of devices at different levels of abstraction. With it, users can dynamically reconfigure the network to plumb in a function running on a server in the appropriate place in the network using just software mechanisms.

To better understand how SDN works, consider the example of an orchestra with a conductor. In the orchestra, you have various musicians, each playing an instrument (e.g., violin, cello, flute, etc.) and each with their own sheet music. Leading the musicians and making sure they play the music together in the right way and at the right pace is the conductor. SDN essentially performs the same role as the conductor, only for the network.

Like the conductor, SDN makes sure that the network operates in a coordinated fashion. Rather than treating the network like individual instruments or devices, it treats it like a collection of devices (platform) that gets programmed as a whole. This level of abstraction allows users, through software, to tell the network things like: “I want you to implement this policy for this set of users to be able to go through this firewall that I’m going to instantiate on that server.”

These types of high-level instructions get broken down into a set of commands that go out to all devices in the network and programs them appropriately. The result is much more agile, higher performance data centers, as well as more effective use of data center assets.

What this mean is that SDN and NFV really go hand in hand. While SDN is not technically necessary to use NFV -- as it can also be used with non-NFV implementations -- it is an enabler. SDN just makes it that much easier and more efficient to implement and control NFV. Without it, NFV would require much more manual intervention to configure the network to appropriately plumb in software-instantiated functions.

Granted, not everyone has adopted NFV or will even adopt it tomorrow, but for those already using SDN to manage and control the classical elements on their network, the future transition will be that much simpler.

It’s clear that with bandwidth demand exploding, the need for more scalable, manageable and configurable networks is becoming absolutely essential. SDN and NFV are two technologies designed to enable just that: Allowing network operators, service providers and IT professionals to more easily scale out the compute and IT infrastructure, while also making it more manageable and configurable.

The combination of SDN and NFV  promises to have a truly transformative effect on the network and society at large.