Profile

Cilium is an open-source networking, security, and observability tool for cloud-native environments, built on eBPF technology. As a CNCF graduated project, it provides a high-performance Container Network Interface (CNI) for Kubernetes that handles networking, load balancing, security policies, and observability at the kernel level. The tool's key innovation lies in its eBPF-based architecture, which enables superior performance, granular security controls, and deep observability without requiring application modifications or additional proxies.

Focus

Cilium addresses fundamental challenges in cloud-native networking by providing efficient pod connectivity, identity-based security policies, and comprehensive network observability. It solves persistent issues around network performance at scale, security policy enforcement in dynamic environments, and visibility into service-to-service communications. Primary users include platform engineering teams, network operators, and security professionals who need to manage complex containerized environments. Core benefits include reduced operational overhead, improved security posture, and simplified troubleshooting through kernel-level visibility.

Background

Originally created by Isovalent, Cilium emerged from the need to leverage eBPF technology for cloud-native networking. The project has evolved from a basic CNI plugin to a comprehensive platform adopted by major cloud providers including Google GKE, Amazon EKS, and Microsoft Azure. Following Cisco's acquisition of Isovalent, the project maintains independence through CNCF governance with maintainers from multiple organizations. Notable production deployments include Bloomberg's financial platform, OpenAI's AI infrastructure, and Bell Canada's telecommunications network.

Main features

Identity-based security with multi-layer policy enforcement

Cilium implements a revolutionary security model that decouples policy enforcement from network addressing. The system assigns cryptographic identities to workloads based on Kubernetes labels and metadata, enabling policies that remain valid even as pods move between nodes. The implementation spans Layer 3 through Layer 7, allowing teams to define policies based on IP addresses, ports, HTTP methods, gRPC calls, and Kafka topics. This architecture enables zero-trust networking while maintaining high performance through eBPF-based enforcement at the kernel level.

Kernel-level observability through Hubble integration

Hubble provides comprehensive network visibility by capturing flow data directly from the kernel through eBPF. The system collects detailed metrics about service dependencies, network flows, and policy decisions without requiring application instrumentation. Platform engineers can visualize service maps, analyze traffic patterns, and troubleshoot connectivity issues through both real-time and historical data. The implementation includes protocol-aware monitoring for HTTP, gRPC, and DNS traffic, enabling deep insights into application behavior and performance.

High-performance networking with eBPF datapath

The networking architecture leverages eBPF to implement a flat Layer 3 network that can operate in both native routing and overlay modes. The datapath processes packets directly in the kernel, eliminating traditional networking stack overhead. This design enables advanced features like XDP-based load balancing, socket-level redirection, and efficient service mesh functionality without sidecars. The implementation supports direct server return, consistent hashing, and hardware-accelerated packet processing, delivering microsecond-level latency for container communications.