In this edition of our SD-WAN Fundamentals, we define and examine the actual foundation of Software Defined Wide Area Networks – the Underlay Network.
The Underlay consists of the combination of physical media for signal propagation (Fiber/Copper/Radio Frequency, etc.), Data Link Layer Communication modalities (Switching), and Network Layer Communications Protocols (IPv4/v6 Routing). The Underlay is the basic full communication channel that will need to exist between Business sites before any SD-WAN can be built to engage in site-to-site transmission. Many new SD-WAN solutions are built with Public Internet as the underlay, but other private/virtual private network connection types can be used, such as MPLS or Ethernet Virtual Private Line.