Cilium vs Envoy: What are the differences?

Cilium and Envoy are both powerful networking technologies used in modern cloud-native environments. Here are some key differences between Cilium and Envoy:

1. Functionality and Scope: Cilium is a comprehensive networking and security solution designed for Kubernetes environments. It operates at the kernel level, providing fast and efficient packet-level networking and security features, such as load balancing, network policy enforcement, and encryption. On the other hand, Envoy is a high-performance proxy and edge load balancer that operates at the application layer. It is designed to handle complex network traffic management, including load balancing, traffic routing, and observability, making it suitable for a wide range of use cases beyond Kubernetes, such as service mesh architectures.

2. Deployment and Integration: Cilium is tightly integrated with Kubernetes and is often used as the networking and security solution within a Kubernetes cluster. It leverages Kubernetes' native capabilities for service discovery and network policy management. In contrast, Envoy is a standalone proxy that can be deployed as a sidecar alongside application containers or as an edge proxy in front of microservices. It can be integrated with various service mesh frameworks, such as Istio and Linkerd, as well as used as a standalone load balancer in non-Kubernetes environments.

3. Network Visibility and Observability: Cilium provides deep network visibility into Kubernetes applications, offering insights into network traffic, connections, and security policies. It supports fine-grained network policies based on application identity, labels, and Kubernetes namespaces. Cilium also offers observability features like service level observability (SLOs/SLIs) and integration with monitoring systems like Prometheus. In comparison, Envoy offers powerful observability capabilities through features like distributed tracing, request/response logging, and statistics aggregation. Its rich set of metrics and observability features make it well-suited for complex network debugging and performance optimization.

4. Performance and Efficiency: Cilium's eBPF-based approach allows it to achieve high-performance networking and security operations with minimal overhead on the kernel. It benefits from kernel-level optimizations and efficiently handles network traffic within the Kubernetes cluster. Envoy, being an application-level proxy, may introduce additional latency compared to kernel-based solutions like Cilium. However, Envoy is designed for high scalability and can efficiently handle a large number of connections and network requests.

In summary, Cilium is a Kubernetes-native networking and security solution, leveraging eBPF for fast packet-level operations within the kernel. It excels in providing network visibility and security features within Kubernetes clusters. On the other hand, Envoy is a versatile proxy and load balancer that operates at the application layer, offering rich observability and traffic management capabilities. It can be used in various deployment scenarios, including Kubernetes service meshes and non-Kubernetes environments.