Anycast and Load Balancing as the Foundation of Edge Architecture

TL;DR

Anycast load balancing combines global reachability with targeted traffic distribution. Anycast determines which Edge PoP handles a request, while Layer 4 and Layer 7 load balancing direct the traffic there based on connections, protocols, and application characteristics. Only the interplay creates a resilient public access to applications and APIs.

Introduction

A globally reachable service is not automatically resilient. Anycast is often equated with load balancing, although they fulfill different roles: Anycast influences the network path to an edge instance, while load balancing distributes already accepted traffic to available backends. If these layers are not considered separately, unclear failover mechanisms, unnecessary dependencies on the provider network, and difficult-to-control operational states arise. A resilient edge architecture must therefore model routing, protocol level, and backend state together. Anycast load balancing is not a single mechanism but the combination of multiple control layers.

1. Anycast Determines Access to the Edge

In Anycast, multiple geographically distributed network nodes use the same IP address or prefix. Internet routing decides which node is preferred from the network’s perspective. This decision is based not on the load of a single application but on routing information and the topology between client and edge.

For public access, this reduces the need to address individual locations directly. If an Edge PoP fails or is removed from routing, traffic can reach another available instance. This requires that the edge infrastructure is present at multiple points and processes traffic consistently there.

However, Anycast does not replace health checks or backend failover. An accessible Edge PoP can still forward to an unavailable backend. Therefore, network availability and application availability must be monitored separately. The ayedo Edge Cloud uses a distributed multi-PoP architecture, its own Autonomous System, and an active-active principle for this purpose. These characteristics form the infrastructural basis on which further traffic decisions are made.

2. Layer 4 Distributes Connections, Layer 7 Requests

Layer 4 load balancing operates at the transport level, typically based on TCP or UDP connections. It can distribute new connections to available targets without needing to interpret the content of an application. This is particularly relevant for protocols where deeper analysis is not required or possible.

Layer 7 load balancing, on the other hand, processes application protocols like HTTP or HTTPS. This allows hostnames, paths, or other request characteristics to influence the forwarding decision. At the same time, additional requirements for TLS processing, protocol understanding, and state management arise.

The layers are not interchangeable. Layer 4 offers low semantic depth and is suitable for generic, performant forwarding. Layer 7 enables more precise rules but ties the edge more closely to the application protocol. An edge platform must therefore support both models instead of reducing every problem to HTTP routing. The ayedo Edge Cloud combines Anycast-based Layer 4 and Layer 7 load balancing with TLS termination at the edge when application-related processing is required.

3. Traffic Routing Does Not End at the Edge PoP

Once Anycast has selected an Edge PoP, the actual distribution within the edge begins. It is decided which backend group receives a connection or request. Not only static configurations are relevant for this. Health checks must determine whether a target is technically reachable and actually usable for the respective service.

This distinction is important for APIs and stateful applications. An open TCP port says little about whether a service provides correct responses. If faulty backends are not removed from the pool, the edge distributes technically correctly but operationally incorrectly. Failover must therefore be linked to backend states, not just to the reachability of the Edge PoP.

Additionally, the edge can hide the actual backend addresses. Backend cloaking reduces the direct exposure of the compute infrastructure and separates the public entry from the internal target. In the ayedo Edge Cloud, both self-managed or provider-hosted Kubernetes clusters can be connected, as well as ayedo Managed Kubernetes. The edge functions remain separate from the respective compute location.

4. Distributed Edge Architecture Changes Operations

Anycast load balancing shifts part of the operational responsibility from the individual data center to the distributed edge. This improves the separation of public traffic and compute but increases the requirements for observability and error analysis. In the event of a disruption, teams must be able to distinguish whether the problem lies in global routing, the Edge PoP, the transport connection, or the backend.

Security functions also benefit from this separation. DDoS protection and scrubbing can intercept traffic before it reaches the backend. A web application firewall can inspect HTTP and HTTPS requests at the edge before they reach internal services. This reduces the volume and risk scope of traffic forwarded to the compute infrastructure.

Architecturally, this creates a clear division of responsibilities: The edge handles public entry, routing, protection, termination, and load distribution. The compute infrastructure runs applications and workloads. For platform teams, this separation is relevant because a Kubernetes cluster does not necessarily have to organize global routing, protection, and public exposure itself. At the same time, the Kubernetes integration remains provider-independent.

Operational Scenario: An API Service with Two Backend Locations

A company operates an API in two Kubernetes clusters with different providers. Both clusters are accessible via the same edge address. Anycast directs clients to an available Edge PoP. There, Layer 7 takes over HTTPS processing and assigns the request to the appropriate API service. Health checks detect that while a cluster accepts network connections, it no longer provides valid responses. This backend is removed from forwarding; traffic goes to the remaining location.

Without this separation, the client or an upstream DNS mechanism would have to detect the disruption. This extends the switchover time and distributes responsibility across multiple systems. The edge, on the other hand, bundles routing, termination, health checks, and failover at a public entry, while the clusters retain their role as compute targets.

FAQ

Is Anycast Already Load Balancing?

No. Anycast influences which network node is reached. Load balancing distributes traffic within the reached infrastructure to connections, services, or backends.

When Is Layer 7 Load Balancing Necessary?

When routing decisions depend on HTTP or HTTPS characteristics, such as hostnames or paths. For generic TCP or UDP connections, Layer 4 is often sufficient.

Does the Application Have to Run in an ayedo Kubernetes Cluster?

No. The ayedo Edge Cloud can also be used with self-managed or provider-hosted Kubernetes clusters .

Conclusion

Anycast load balancing is an architectural model for multiple layers: Global routing brings traffic to an available edge instance, Layer 4 or Layer 7 distributes it further there, and health checks tie these decisions to the state of the backends. For companies, this creates a clear separation between public access and compute. The ayedo Edge Cloud implements this principle as a distributed, active-active edge platform with its own network infrastructure and provider-independent backend connectivity.