There has been a lot of talk about Software-Defined Networking (SDN) and how it will change the way we view (or do) networking. There has been quite a bit, too, about how it will automate network provisioning and make networks both adaptive and application-oriented. What could perhaps use more explanation is how SDN fits in with other elements of the modern data center.
One way to envisage SDN is as the networking analog of storage virtualization: in separating the control plane from the data plane, SDN is taking physical resources, collecting them into a logical pool, and then allocating them to applications as programmed. In a way, it is network virtualization — only no one wants to call it that, because we already have VLANs and it’s not one of those.
The term “infrastructure virtualization” for SDN has been bandied about in some quarters, but it is a bit unwieldy, and of course networking — software-defined or not — is just one element of the typical data center infrastructure.
What’s important, though, is that, just like storage and server virtualization, software-defined networks are about more than just automation. Yes, automated network provision and configuration is essential for scalability, but SDN also holds out the promise of meeting application needs rather better than does a one-size-fits-all network.
Currently we have hypervisor-level tools and frameworks which bring together server and storage virtualization and management so they can deploy a working virtual system in one go. They already include an amount of automated network set-up so those new VMs can hit the cloud running.
The snag is that typically these tools have little or no visibility into the prevailing conditions on the network, and conversely, the network has little awareness of the servers and applications that are generating traffic. So while you may have broken the physical link between applications and hardware on the server side, on the network side you are still back in the days of dedicated hardware and siloed applications.
This is where coordination with SDN will come in, and it means SDN must do more than just automate the configuration of network elements, from VLANs and QoS to WAN optimization. It should also include policy-based control, as well as awareness of, and visibility into, the applications running on the network — application fluency, as some call it. Some have referred to this kind of concept as the Software-Defined Data Center (SDDC) or even Software-Defined Everything.
SDE sounds like a joke, but it’s not. The concepts behind it are not even all that new — for example, a decade has passed since HP unveiled what it called its Adaptive Enterprise strategy, in response to IBM pushing its vision for utility computing. Both aimed to create application-fluid and dynamic data centers, and both saw some acceptance among large organizations, but they also faced several problems.
First, the technology was not quite up to it. They were having to build large and complicated frameworks which relied on proprietary technologies. Second, no one at that point was thinking much about multi-tenanted clouds and the like (though yes, you can draw a conceptual genealogy from cloud all the way back to mainframe bureaus). It is no surprise, then, that those primitive initiatives have been pretty much swept under their creators’ carpets.
Of course, a lot has happened since then. A big change has been the arrival of open, programmable, and automated architectures — in this case, SDN. It promises to improve IT agility, efficiency and analytics, cut costs, and perhaps most importantly yield a better and more consistent user experience — but this is only if it is done right, which means as part of a collaborative and open approach, which puts service first.
A few go-ahead companies are already on the way there. I recently heard about Belgian digital media solutions company CandIT Media, which has partnered with Alcatel-Lucent to build a content-aware and application-fluent network. Working with digital media, CandIT needs to store and move around huge amounts of data, and says SDN has helped it cut costs while at the same time coping better with large traffic spikes.
So when it comes down to it, SDN simply makes sense. We already virtualize our servers and our storage, and we are on the way to virtualizing our desktops and applications. We even virtualize our WAN optimizers, firewalls, application controllers, and other black-box appliances. All that’s left is the network — oh, and the little job of seamlessly tying it all together, of course!
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