Categorizing Istio, Cilium, and Envoy

Istio: The Full-Featured Service Mesh

Category: Service Mesh (Control Plane & Data Plane)

Istio is a complete service mesh implementation. It provides both:

1. A control plane (istiod) that you configure to manage traffic rules, security policies, and telemetry.
2. A data plane, which consists of Envoy proxies that Istio automatically deploys and configures.

Think of Istio as the entire system that gives you service mesh capabilities out of the box.

Envoy: The Service Mesh Data Plane

Category: Service Proxy / Data Plane

Envoy is not a service mesh by itself. It is a high-performance proxy that serves as the data plane for many service meshes, including Istio. Its job is to handle the traffic as directed by a control plane.

You can use Envoy as a standalone proxy (e.g., as an edge gateway), but to get service mesh functionality like dynamic configuration and mesh-wide policies, you need a control plane like Istio to manage it.

Cilium: The CNI and eBPF-Powered Service Mesh

Category: CNI (Container Network Interface) & Service Mesh

Cilium's role is the most nuanced and has evolved significantly.

1. Primarily a CNI: At its core, Cilium is a CNI responsible for providing network connectivity to your pods. It uses eBPF to do this in a highly efficient and secure way, operating at the Linux kernel level.
2. Evolving into a Service Mesh: Cilium has increasingly added service mesh capabilities. With Cilium Service Mesh, it can provide L7 traffic management, observability, and security features without relying on a traditional sidecar proxy like Envoy in every pod. It leverages its eBPF foundation to implement these features, which can lead to better performance and lower resource overhead.

Linkerd: The Ultra-Lightweight Service Mesh

Category: Service Mesh

Linkerd is known for its focus on simplicity, performance, and security. It is a complete service mesh that provides a control plane and its own ultralight, Rust-based "micro-proxy" as the data plane.

Key characteristics:

• Simplicity and Ease of Use: Linkerd is designed to be very easy to install and operate, often requiring minimal configuration to get started.
• Performance: Its Rust-based proxies are extremely lightweight and fast, consuming a fraction of the resources of Envoy.
• Security: Linkerd enables zero-config, default-on mTLS for all TCP traffic.

Consul: The Service Networking Platform

Category: Service Discovery & Service Mesh

Consul, by HashiCorp, started as a service discovery and key-value store solution. It has since evolved into a full-featured service networking platform that includes service mesh capabilities.

Key characteristics:

• Platform Agnostic: Consul is designed to work across various environments, including Kubernetes, VMs, and bare-metal servers, making it a strong choice for hybrid and multi-cloud setups.
• Service Discovery Core: Its powerful service discovery features remain at its core.
• Envoy-based Data Plane: Like Istio, Consul uses Envoy as its data plane proxy.

Kuma: The Universal Service Mesh

Category: Service Mesh

Kuma, created by Kong and now a CNCF project, is a universal service mesh control plane. It is designed to be platform-agnostic and easy to use across both Kubernetes and traditional VM environments.

Key characteristics:

• Universal Control Plane: Kuma's standout feature is its ability to run across multiple zones (e.g., different clusters, clouds, or data centers) from a single global control plane, simplifying multi-mesh management.
• Built-in Gateway: Provides a built-in gateway to facilitate cross-zone communication.
• Envoy-based Data Plane: Kuma also uses Envoy as its data plane proxy.

NGINX Service Mesh

Category: Service Mesh

Developed by F5, NGINX Service Mesh is a lightweight and easily configurable service mesh. It is designed for developers who want a simple way to implement traffic management and security.

Key characteristics:

• NGINX Plus Data Plane: It uses a purpose-built version of NGINX Plus as its sidecar proxy, which can be a draw for teams already heavily invested in the NGINX ecosystem.
• SMI Compatibility: It is compatible with the Service Mesh Interface (SMI), a standard interface for service meshes on Kubernetes.
• Integration with NGINX Ingress Controller: Offers seamless integration with NGINX Ingress Controller for managing north-south traffic.

Summary Table

Tool	Primary Category	Description
Istio	Service Mesh	A complete control plane that manages a data plane of Envoy proxies to provide traffic management, security, and observability.
Envoy	Service Proxy / Data Plane	The workhorse proxy that handles traffic. It is the data plane component used by Istio and other service meshes.
Cilium	CNI / Service Mesh	A powerful CNI that uses eBPF for networking and security. It also offers service mesh features, sometimes as a more efficient, sidecar-less alternative to traditional service meshes.
Linkerd	Service Mesh	An ultralight and simple service mesh with a focus on performance and security, using its own Rust-based micro-proxies.
Consul	Service Discovery & Service Mesh	A service networking platform that provides service discovery and a service mesh, well-suited for hybrid and multi-cloud environments.
Kuma	Service Mesh	A universal control plane for service mesh that excels in multi-zone and multi-cluster deployments, running on both Kubernetes and VMs.
NGINX Service Mesh	Service Mesh	A lightweight service mesh that uses NGINX Plus as the data plane, integrating well with the NGINX ecosystem.

In short:

• Istio is the management suite.
• Envoy is the worker proxy that Istio manages.
• Cilium is the network foundation that can also act as a service mesh itself.
• Linkerd is a lightweight, performance-focused service mesh.
• Consul is a service discovery platform that has expanded to offer service mesh capabilities, particularly for hybrid environments.
• Kuma is a universal control plane ideal for multi-cloud and multi-cluster meshes.
• NGINX Service Mesh is a simpler, NGINX-native option for service mesh.