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SD-What? Understanding SD-WAN

by Jessica Scarpati
Features and E-zine Editor at TargetTech.com

More than just a buzzword, software-defined WAN (SD-WAN) is already delivering benefits to early adopters. Skeptics warn, however, it’s no magical elixir.

Eager to break away from the crowds at the Interop trade show in Las Vegas back in 2010, John Mulhall stepped into a quieter aisle of the expo hall.

The booths in that row weren’t glitzy — no sign of hourly iPad raffles or other crowd-pleasing gimmicks. They were populated by vendors that Mulhall, an IT director at Sno-Isle Libraries in Washington state, had never encountered before. One of them was a startup called Talari Networks, which back then billed its technology as “adaptive private networking.” The company claimed its appliances could supplant a costly MPLS network by aggregating multiple Internet connections and dynamically selecting the best path for traffic, based on the real-time conditions of those links.

Sound familiar? It’s one of the basic premises of what is now marketed as software-defined WAN (SD-WAN) by a growing pool of vendors that come from all corners of the networking market. It includes routing giants like Cisco, WAN optimization specialists like Silver Peak Systems, niche players like Talari, and a handful of startups like CloudGenix, Velocloud and Viptela.

SD-WAN is an alternative approach to designing and deploying enterprise WANs. It aims to replace traditional branch routers with appliances that use virtualization, application-level policies and network overlays to make several consumer-grade Internet links behave like a dedicated circuit. The intention is to simplify setup so that the only thing branch office personnel need to do is plug in a cable for the appliance to “phone home” and automatically receive its configuration from a central controller.

The ultimate goal is to eliminate or reduce the need for private WAN technologies like MPLS — plagued by long provisioning times and expensive contracts — while also making the WAN more responsive and less complex. But as many large companies hesitate to fully abandon the guaranteed control, reliability and performance of MPLS, SD-WAN is expected to be deployed mostly in hybrid WAN architectures that use a combination of public and private connections.

“It’s a technology that I think is going to begin replacing MPLS if MPLS doesn’t get cheaper,” says John Shaffer, CIO of Greenhill and Co., an investment banking firm based in New York that’s in the process of deploying Vitpela’s SD-WAN boxes at its 15 offices. “A lot of our offices work independently of each other aside from email. You start wondering what you’re using MPLS for and why you’re paying so much money for it.”

Yet not everyone believes SD-WAN is the panacea to all the world’s WAN woes. The degree of abstraction these appliances use makes network engineers like Ivan Pepelnjak nervous. He contends the same ends can be — and have been — achieved with technologies that have been around for at least a decade. They do, however, require more manual labor.

“People always want to believe in Santa Claus and magic,” says Pepelnjak, an independent network architect in Slovenia who operates ipSpace.net AG, a consultancy that provides software-defined networking (SDN) training and services. “They want to believe that there is new stuff that you can just deploy and it works — and then the reality sets in, unfortunately.”

But whether it’s new and transformative or simply an old bag of tricks going by a catchier name, one fact about SD-WAN is undisputed: It has rapidly attracted interest over the past year as users increasingly access applications via the cloud, diminishing the need for dedicated pipes to enterprise data centers.

“The whole SDN movement opened up the market’s eyes to the fact that there are better ways to solve longstanding challenges,” says Andrew Lerner, a research director at Gartner. “Although SD-WAN is not SDN, that whole mindset and cultural shift brought in with SDN had an impact on the entire market.

“And while all the early talk about SDN was in the data center,” Lerner continues, “if you actually talk to end customers, a big percentage of their spend on the network is typically on telecom — in MPLS and branch connectivity.”

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