For non-HTTP(s) applications or AWS Wavelength Zones outside the US, it is possible to use Amazon Route53 weighted routing policies for load balancing (see Chapter 6). However, unlike using it in standard regions or AWS Local Zones, it is not possible to use the health check feature in the normal way. This is because the Amazon Route53 health checkers do not have access to the carrier IPs on any MNO’s 5G fabric:

Figure 7.11 – Using an EC2 instance’s status check to determine health

Instead, you can create an Amazon CloudWatch alarm that monitors something the AWS control plane is already aware of. For instance, you could set the alarm to watch an EC2 instance’s status checks. In turn, you configure the Amazon Route53 health check to monitor this alarm. The preceding figure shows an example of this configuration.

Edge Discovery Service (EDS)

One of the key benefits of building an application that runs directly on an MNO’s 5G edge is the ability to take advantage of network slicing. This allows us to maintain QoS parameters from the mobile device to a server in an MEC architecture. However, this only works if the traffic never leaves the MNO’s 5G fabric. The moment traffic leaves the UPF and enters the general internet, the MNO loses control of connection quality.

This is no big deal for an application that lives only in one AWS Wavelength Zone. The load-balancing mechanisms discussed so far can handle that. But in cases where our app spans multiple geographies, how do we make sure traffic goes from a given mobile device to the closest carrier gateway? Because the IP address of a mobile device (also known as a UE Identity) isn’t routable on the internet, IP Anycast services such as AWS Global Accelerator can’t help us. Nor can Global Server Load Balancing (GSLB) mechanisms such as Amazon Route53.

Client-side triangulation

One approach would be to do ping triangulation from within the application on the mobile device, as shown in the following diagram:

Figure 7.12 – Ping triangulation from a mobile device

This can be tricky because it requires a mechanism to keep the list of carrier IPs updated on mobile devices. Customers who implement this typically use a managed GraphQL service such as AWS AppSync. GraphQL is an alternative to REST APIs. It supports a publish/subscribe model as opposed to the constant polling from all mobile devices involved that would be needed with REST.