SD-WAN Fundamentals: The Overlay

SD-WAN Fundamentals:
The Overlay

We laid the “groundwork” with our previous post on the Underlay network, and now in this edition of the fundamentals, we focus on the Overlay.  We will define the concepts but be forewarned – this is an area that may differ greatly from vendor to vendor, and even between specific deployments.  The versatility and flexibility therein can be valuable characteristics as long as one applies an optimal design strategy. 

The SD-WAN Overlay presents the main feature of the technology: designing the required application network connectivity through a software platform.  The software defines a virtual network by taking two endpoints and creating a virtual connection between them.  Multiple secure overlays can be built using software over existing networking infrastructure. These endpoints could be actual physical locations, such as a network port, or they could be logical locations designated by a logical/software address.

Most Overlay networks involve some type of encapsulation, which wraps up and encrypts the data for transport through a “tunnel” on its way to endpoint delivery.  The designated tunnel endpoints will be different combinations depending upon origination and destination of the traffic.  Some carriers, which build in Middle Mile replacement, will have tunnels terminate on their core network.  They then route to their destination over that core transport as opposed to the Public Internet.  This is all programmatically configured in the software through a method commonly known as Orchestration. 

    So what questions are important to compare different vendors? 

  • Outlining a client’s priority applications and where the data flows travel is imperative to delineating and comparing/contrasting the application paths.   
  • Do the client sites communicate to one another directly, or mostly hub-and-spoke communication to a certain main site? 
  • What technologies are used to provide higher level Quality of Service?
    • Is the technology standards-based or proprietary?  
    • What are the performance implications, and how are they measured? 
  • What visibility exists on a per application basis within the Orchestrator? 
  • How is cyber security offered and potentially layered into the software Overlay? 
  • What is the vendor’s or service provider’s flexibility to add any other Virtualized Network Functions, current or future state? 

These queries are just the starting point to compare the many factors involved in the Software Definition part of the SD-WAN term – the Overlay network.  The versatility of the platform must provide the building blocks required for a well-designed, high-performing solution.  ChoiceTel has the experience, the knowledge, and the partnerships to help you find solid solutions to compare and design.  Strengthen your performance and security posture as your network steps forward and evolves into SD-WAN –  the Choice is clear. 

To learn more about ChoiceTel and what we can do for your small, medium or enterprise organization, visit our website at Or to schedule a consultation, call us at (248) 922-1150.


Choice Telecommunications, Inc

7640 Dixie Highway, Suite 150

Clarkston, MI 48346

Phone: 248-922-1150

Email: [email protected]

U.S. Offices

7000 Central Pkwy.

Suite 1600

Atlanta, GA 30328

(800) 815-3320

Go to Top