Traditional WAN vs. SD-WAN. Here’s What You Need to Know


Are you facing issues with your current network infrastructure? Do you have a cloud migration strategy? If you haven't considered the benefits of a Software Defined WAN solution, now might be the time. By being delivered through the cloud, SD-WAN reduces capital expenditures and simplifies network operations.

Traditional WAN solutions often incorporate a hybrid of public and leased lines. MPLS, a traditional WAN connectivity method, is used so that that you can assign preference based on SLA guarantees, and you can determine timeliness for delivery of traffic. This becomes very important particularly for voice and video-based applications. In addition, traditional WAN leverages internet-based backup as a secondary transport should the primary path become unavailable.

Let's take a look at the traditional WAN architecture:

  • Failover is completely dependent upon the state of the link (up/down). This means you must depend on routing protocol re-convergence. This can cause multiple seconds worth of outage resulting in dropped or lost video or phone calls.

  • Configuration is distributed, meaning that configuration is housed locally on each individual router, but is typically templated

  • New policies must be managed on a per-device basis and require a touch of each individual device as policies change

  • Significant time is needed for new site turn-up. This includes time for circuit delivery, equipment provisioning, and change management. New sites can take months to turn up due to the complexities of change management and project coordination.

What's all the buzz around SD-WAN?

SD-WAN is a shift in the way a Wide Area Network is deployed and managed. As its name implies, SD-WAN is a software driven technology with application awareness that is managed from a centralized point in the network. SD-WAN solutions are deployed as an overlay technology to an existing topology, which allows for ease of integration and adoption over time. Driving factors for SD-WAN include:


Thinking about SD-WAN technology selection?

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  • Lower Circuit Costs – SD-WAN technology allows for the elimination costly MPLS circuits. It makes use of lower cost, higher-speed options for connectivity such as broadband or DSL. Of course, MPLS circuits can still be utilized based on circuit availability, additional SLA requirements, and ease of integration.

  • Adoption of Cloud Based Services – With traditional architecture, traffic typically routes back to the data centers with need to have constant filtering in place. This results in sub-optimal routing and potential latency for cloud hosted providers like Office 365. SD-WAN moves us toward local internet offloading and getting user traffic closer to cloud services.

  • SDWAN provides simplified QoS and prioritization of critical applications across the WAN. Rather than waiting for an up/down event, SD-WAN provided real time traffic monitoring to divert business critical traffic around brown out events.

  • We're seeing the requirement for higher bandwidth intensive application on the WAN, also driving toward local internet offload when applicable

How does SD-WAN work?

SD-WAN is an overlay to the existing network – essentially a network running on top of a network. This is accomplished by using tunneling technology to differentiate the physical network from the logical network.

SD-WAN implements a centralized controller, acting as a single pane of glass for managing the entire solution. It is used to set and maintain policy. This policy is used to control traffic paths, SLAs, failover, monitoring, etc. The SLAs are written based on application-specific information. Once policies are defined, they are pushed from that centralized controller to each SD-WAN node for more "hands-off" configuration. Once the policy is pushed, it intelligently monitors the performance on a link. It migrates traffic based on that particular SLA. At this point, we are no longer dependent on a circuit outage to swing traffic to a backup or redundant link.

SD-WAN is bringing new agility and speed of provisioning to the WAN that we've never seen before, all the while driving down the total cost of the WAN solution. As new technologies emerge, the capabilities and definitions around SD-WAN solutions will shift over time. 

It’s also critical to reconcile your SD-WAN strategy with your cloud ambitions. Check out our blog post on that topic here.

August 14, 2017


Want to learn more?

To find out more about SD-WAN and find out if it is the right approach for your organizations, view this brief educational webinar hosted by Kevin Rainey, Director of Architecture at Burwood Group. Kevin discusses the pros and cons of SD-WAN technology in various environments.