Container Network Interface (CNI) is not a specific software entity but rather a specification and set of libraries that define a standardized way of managing network interfaces in Linux containers. It plays a crucial role in enabling multiple container networking plugins to work seamlessly within a Kubernetes cluster or other container orchestration systems.

Think of CNI as a common language that container runtimes and networking plugins use to communicate and configure network interfaces for individual containers. This standardization offers several benefits:

Key Advantages of CNI:

• Flexibility and Choice: Allows deployment of diverse networking plugins based on specific needs or environments.

• Vendor Neutrality: Not tied to any single vendor, promoting open-source solutions and interoperability.

• Simplified Development: Offers tools and libraries for writing custom plugins tailored to unique requirements.

• Easy Integration: Works with various container runtimes and orchestration systems like Kubernetes.

• Active Community: Backed by a strong community driving development and support.

Exploring the CNI GitHub Repository:

• spec/main.md: Defines the core CNI specification details, including JSON format and plugin interactions.

• plugins/: Houses various reference and example plugins showcasing different networking scenarios.

• vendor/: Contains external dependencies and libraries used by CNI components.

• tests/: Ensures code quality and functionality through comprehensive test suites.

• contrib/: Additional tools and contributions from the community.

Key CNI Concepts:

• Container Network Plugin (CNI Plugin): Software implementing the CNI specification to configure network interfaces for containers.

• Network Attachment Definition (NAD): YAML file specifying desired network configuration for a container.

• CNI JSON Payload: Data exchanged between the container runtime and plugin during interface configuration.