Software-defined WAN (SD-WAN) – Understanding Network and Security for Near-Edge Computing

SD-WAN is the application of SDN principles to networks outside your data center or span of control. The problems that SDN solves within your data center are even larger challenges on the internet, where you definitely won’t be given access to modify equipment you don’t own.

The general idea is to implement a logical overlay between one site and another on the internet. This is very similar to how a standard VPN works. The difference is that SD-WAN tunnels can span multiple networks, both public and private:

Figure 2.7 – SD-WAN spanning public and private networks

Figure 2.7 shows an example of this. From the perspective of the server on the left, there is a single Layer 3 hop to reach the EC2 instance on the right. However, the underlying situation is more complex. Connections to the internet from two different ISPs and a private MPLS fabric are all used simultaneously.

The following section describes some reasons you might do this.

Improved performance

SD-WAN allows intelligent path selection and dynamically routing traffic based on application requirements and network conditions. This enables the efficient use of available bandwidth, ensuring optimal performance for critical applications, and reducing latency and packet loss.

Cost savings

By using SD-WAN, organizations can reduce their reliance on expensive, dedicated MPLS circuits for WAN connectivity. Instead, they can leverage a combination of lower-cost broadband, fiber, or cellular connections to achieve similar performance levels at a reduced cost. Alternatively, if MPLS is still used, packets can be selectively routed over it based on, say, how mission-critical the traffic is, thereby lowering the bandwidth needed for MPLS.

Simplified management

SD-WAN centralizes the management and control of the network, providing a unified interface for administrators to monitor, configure, and troubleshoot the entire WAN infrastructure. This simplification reduces the need for manual intervention and makes it easier to manage complex networks.