SD-WAN 101: What You Need to Know

February 7th, 2017
SD-WAN 101: What You Need to Know

Every few years, we IT professionals woefully accept the pleasure of enduring another round of fresh industry buzzwords, and then placing our proverbial bets on what will (and won’t) take off. From virtualization to hyper-converged, cutting through the static and landing on a generally-accepted definition is oftentimes a task in itself. Enter the term Software-Defined WAN. What does it mean? What is it applied to? How is something software-defined? Why would you consider it? When should you consider it? Who are the leaders in the space to consider?

This blog aims to answer those common questions and provide you with the basic understanding necessary to intelligently decide if SD-WAN solutions are right for you and your business.

Before doing so, we must first agree on a generally-accepted definition of the term.

What is SD-WAN?

What does it mean when something is software-defined? In its purest form, the term describes the idea that software is the focus of the solution, and the primary driver for innovation and feature set, rather than (in years past) hardware-centric improvements being the main catalyst for speed and innovation. How does this translate to a Software-Defined WAN? Simply put, an SD-WAN is a wide area network designed with the idea that software and application performance/consistency is paramount to all else. For that reason, SD-WAN solutions move much of their network control into the cloud, to allow for more flexibility and agility, and to dramatically simplify the delivery of network services to remote/branch offices and datacenters. Further, it abstracts the network control plane and traffic from the physical hardware and connections it is bound to, using software-based virtualization that is eerily similar to what VMware pushed when it introduced the buzzword-turned-savior known as virtualization. This allows for an entirely new way of looking at how traffic actually gets from Point A to Point B, and some very exciting ways of lowering branch connectivity costs while increasing application reliability and even QoS.

How Does it Work?

We’ve established that SD-WAN solutions aren’t anything special from a hardware perspective, and it’s all in the software sauce. We’ve established that our old friend virtualization has a role in this. We’ve established that deploying an SD-WAN solution can lower your management costs, your risk, your monthly MPLS bills, and even end-user complaints. Now, let’s discuss at a high level just how this occurs.

The basic principle to understand is abstraction – that is, the idea that you can abstract the network into a set of capabilities that are completely independent of how those capabilities are provided. It doesn’t care about the hardware WAN circuit, it just cares about the network services you’re trying to deliver, delivering them, and simplifying the management and deployment on either end.

Next, we must understand the difference between a data plane and a control plane. The control plane is the intelligent part of your network that is making decisions on routing and traffic signaling, and is also where your device management and configuration happens. The data plane is simply the part of your network that carries application and user data. In traditional networks, each data plane has its own control plane – which makes managing large, geographically distributed WANs, a nightmare. In SD-WANs, there is only one control plane to rule all data planes – putting the power back in your hands, no matter where those remote offices are. This is how SD-WAN providers are giving customers back their sleep-filled nights, their management time, and their travel expenses. Still though, how are we able to lower MPLS costs or improve application performance?

The answer goes back to the abstraction of data and control planes. Because SD-WAN solutions virtualize the network operations, and traffic and provide a secure network overlay, the traffic is able to be carried from Point A to Point B completely independent of the router, switches, and even internet link available to it. This means that SD-WAN solutions do not care if your Windstream MPLS is your primary, and a bonded T1 with Comcast is a failover circuit – it will see them together as a unified pool of network bandwidth available to the WAN and its traffic. This results in dramatically increased data speeds across the WAN – oftentimes, to the extent of customers cutting their monthly MPLS bills in half. If you need 1G throughput on your WAN, you no longer need a 1G primary link and 1G failover link (or smaller if business-critical only).  With an SD-WAN, you can pay for a 500MB primary link and 500MB failover link and yet, your WAN will perform at 1G speeds, due to the aggregation of all available bandwidth into a single pool. This is what lowers your monthly bill.

But wait, there’s more! The ability to use multiple links from multiple providers gives you a level of redundancy and application-QoS that wasn’t previously attainable on a traditional WAN architecture. Because of virtualization, applications no longer have a static tie to the link it must traverse, allowing administrators to add/remove/change applications with exceptional ease. Additionally, many SD-WANs are self-healing by nature of being virtualized, and as such, can typically experience degraded links, and even full provider outages with very little to no impact on application performance.

We once saw a video demo from an unnamed SD-WAN partner who yanked the Ethernet cable from the very switch port we were holding the video demo over. Nothing happened. It was amazing.

Why to Consider SD-WAN

- Reduces Internet Costs

- Reduces Management Time, Costs, Complexity

- Virtualizes the Network

- Application QoS

- High Availability of Network and Application Services

- Enables a Secure Overlay for your entire WAN

- Simplifies and Accelerates Network Service Delivery

- Interoperability

- Supports Open Networking

- Support Network Automation

- Usually deployed on commodity hardware ($)


When to Consider SD-WAN

The best time to think about investigating if a Software-Defined Wide Area Network is for you, is about 4-6 months before your next ISP renewal. This allows for ample time to learn, investigate, design and POC an SD-WAN solution before making a purchasing decision. That purchasing decision could be the difference between you signing off on the ISP’s renewal, and telling them to sharpen their pencil with half as much bandwidth, because you don’t need it.

Another great time to consider looking at SD-WAN solutions is when re-architecting or refreshing WAN technologies such as routers and core switches. Many times, SD-WAN solutions can be deployed on commodity hardware, allowing you to extend the life of current gear, or even move some physical network control operations to a VM on a physical server you already own.

Lastly, we’ve seen customers look at SD-WAN solutions when faced with multiple remote office openings/acquisitions in a given year. These customers are typically moving at such a fast pace that their IT departments are always looking for a way to deploy and deliver network services more rapidly, more predictably, and with more ease. SD-WAN becomes their answer and allows them to spend more time at HQ and less time on planes, trains and automobiles.

Who to Consider Involving

Some Key Innovators in the SD-WAN Marketplace are:

- Cisco/Meraki

- VMware

- Talari Networks

- Riverbed

A Key Partner to ensure it’s the right fit:

  • High Availability, Inc.

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