By default, these are set to 100% for all endpoint groups attached to a listener. This results in the default behavior where connections always go to the closest region. When these values are altered, things can get a little tricky to understand, so let’s walk through some examples:

Figure 8.20 – AWS Global Accelerator traffic management across regions

First, let’s take the simplest example of an active/standby setup. Here, we would set a traffic dial to 0 for the standby region and 100 for the active region. This is shown in the on the left of the preceding figure.

Second, let’s say we set both regions to 50%. In this case, AWS Global Accelerator will ensure that 50% of connections are sent to both regions, regardless of where they originate from. The remaining connections will be allowed to follow the normal rules where they are sent to the closest region.

Using the AWS global backbone as a private WAN

Given the ubiquitous presence and high quality of the AWS Global Network, many customers have sought to build a private WAN infrastructure on top of it. This has been possible for some time through the use of third-party appliances from the AWS marketplace. Companies such as Aviatrix, Cisco, and Palo Alto Networks can build an overlay on top of EC2 instances running in different regions and use the AWS backbone as transport between them.

Until recently, however, there wasn’t a native AWS service that could combine this with the power of AWS Direct Connect. Consider the following diagram. A customer has data centers in two different countries with AWS Direct Connect to their closest region and a gateway in the middle. It might make sense for some of the customer’s traffic to never enter the AWS region at all and head straight for the other on-premises data center:

Figure 8.21 – AWS Direct Connect gateway paths

AWS Direct Connect SiteLink is a feature that enables routing from one virtual interface (VIF) connected to an AWS Direct Connect Gateway to another. It allows the red path shown in the preceding figure:

Figure 8.22 – Enabling AWS Direct Connect SiteLink on a VIF