Beginner's Guide to Cilium

In recent years, a new way of building and running applications has gained a lot of popularity. This approach involves breaking down large applications into smaller, more manageable pieces called containers. These containers are like self-contained units that contain everything needed to run an application, including its code, libraries, and dependencies. This approach, known as containerization, allows applications to be more flexible, scalable, and easily deployed across different environments.

Alongside containerization, another trend called microservices has emerged. Microservices architecture is a way of designing applications as a collection of smaller, independent services that work together to form the complete application. Each microservice focuses on a specific task and communicates with other microservices through a network.

While containerization and microservices offer numerous benefits, they also introduce new challenges, particularly in terms of networking and security. Traditional networking approaches might not be sufficient for managing and securing applications in these dynamic and distributed environments.

As containerization and microservices architectures become increasingly popular, networking and security challenges arise in managing and securing applications in these environments. This is where Cilium comes into play

This essay aims to serve as a beginner’s guide to Cilium, covering its core concepts, the integration with eBPF, installation, and usage on Kubernetes and Docker, as well as its benefits and potential risks.

What is Cilium?

Cilium Architecture
Figure 1.0 | Cilium Architecture

Cilium is an open-source project designed to address the networking and security challenges that arise in modern cloud-native environments. Cilium provides enhanced networking and observability capabilities for containerized applications and microservices architectures. It simplifies the management and security of applications in these dynamic and distributed environments, ensuring efficient and secure communication between containers and microservices.

Cilium leverages the capabilities of a new Linux kernel technology called eBPF (extended Berkeley Packet Filter) to provide high-performance networking, multi-cluster and multi-cloud capabilities, advanced load balancing, transparent encryption, extensive network security capabilities, transparent observability, and much more. It operates at the network layer and can be deployed as a Linux kernel module or as a user-space daemon. Because eBPF runs inside the Linux kernel, Cilium security policies can be applied and updated without any changes to the application code or container configuration.

Cilium comprises an agent that operates on every node and server within your environment, ensuring networking, security, and observability for the workloads running on each respective node. These workloads can either be containerized or run directly on the system without containerization.

Getting Started with Cilium

Before installing Cilium, it is essential to verify if your system meets the minimum requirements. It’s worth noting that the majority of modern Linux distributions typically satisfy these requirements out of the box.

To install Cilium on Kubernetes, you can utilize the Helm package manager or use the Kubernetes YAML manifest directly. The official Cilium documentation provides detailed instructions for installation on various Kubernetes platforms. Once installed, Cilium operates as a Kubernetes network plugin, replacing the default networking implementation. It seamlessly integrates with Kubernetes to provide enhanced networking and security capabilities to the cluster.

Once the installation process is completed and Cilium is running, you can start leveraging its networking and security features in your Kubernetes cluster. You can begin by defining and applying network policies to control the flow of traffic between pods and services. You can use Kubernetes Network Policy objects to define these policies. Refer to the Cilium documentation for examples and details on how to define network policies. Explore other advanced features provided by Cilium, such as service discovery, load balancing, and identity-aware security. The Cilium documentation and user guides provide in-depth information on utilizing these features effectively.

You can also take advantage of Cilium’s observability features to monitor and troubleshoot your network and security setup. Enable metrics collection, network flow logging, and distributed tracing integration as per your requirements. Use the network monitoring and observability tools of your choice to visualize and analyze the collected data.

Cilium and eBPF

Cilium and eBPF (extended Berkeley Packet Filter) are closely intertwined, with Cilium utilizing eBPF technology as the underlying mechanism to enhance networking and security in containerized environments. eBPF is a flexible and powerful technology that allows for the execution of custom programs within the Linux kernel. It provides a safe and efficient way to extend kernel functionality and perform various tasks, including network packet processing, tracing, and more.

Cilium leverages eBPF to implement its data plane, which is responsible for intercepting and processing network packets in real-time. By utilizing eBPF programs within its data plane, Cilium achieves advanced network policies, identity-aware security, and comprehensive observability. The combination of Cilium and eBPF enables organizations to build secure, scalable, and performant containerized applications while maintaining fine-grained control over network traffic.

Networking Capabilities of Cilium

In a containerized and microservices environment, thousands of containers may be communicating with each other over a network. Ensuring that these containers can find and communicate with each other efficiently and securely can be challenging. Cilium helps solve this challenge by providing advanced networking capabilities specifically designed for these environments.

Cilium acts as a middle layer between the containers, handling their network traffic. It ensures that the right containers can talk to each other while blocking any unauthorized communication. It also allows for load balancing, which means it can distribute the network traffic evenly across multiple instances of a service to avoid overwhelming any one container. The following critical capabilities of Cilium address the networking complexities in modern cloud-native environments.

  • High-Performance Networking (CNI) Kubernetes offers a wide range of CNIs (Container Network Interfaces), each with its own unique set of features, scalability, and performance characteristics. However, Many of them depend on legacy technology (iptables) that struggles to handle the dynamic nature and scale of Kubernetes environments. Consequently, this can result in higher latency and reduced throughput. Cilium’s control and data plane has been built from the ground up for large-scale and highly dynamic cloud native environments where 100s and even 1000s of containers are created and destroyed within seconds.
  • Layer 4 Load Balancer Setting up and managing load balancing within your cluster can present challenges due to the intricacies involved in establishing connectivity and synchronization between the clusters and external entities. Cilium offers a resilient and high-performance load-balancing solution specifically designed to handle the dynamic nature and scale of cloud-native environments. By utilizing Cilium as a standalone load balancer, you have the opportunity to replace costly legacy infrastructure components in your network.
  • Bandwidth and Latency Optimization Kubernetes currently does not possess built-in traffic control capabilities, making Traffic Rate-Limiting crucial for efficient resource utilization and preventing bandwidth depletion. Although Kubernetes does provide experimental Bandwidth Rate-Limiting, it can potentially impact latency negatively. Cilium’s Bandwidth Manager offers the ability to apply rate-limiting per Pod with a simple, one-line YAML configuration. In comparison to other alternatives, the Bandwidth Manager delivers a significant reduction in latency, up to four times, ensuring a seamless network experience.
  • Cluster Mesh Adopting multi-cluster Kubernetes configurations is common to achieve fault isolation, scalability, and geographical distribution advantages. However, such setups can introduce networking complexities. Cilium Cluster Mesh offers a solution by enabling network connectivity across multiple clusters. With Cilium as the CNI in each cluster, pods within each cluster can seamlessly discover and access services in all other clusters within the mesh. This effectively unifies multiple clusters into a larger, interconnected network, simplifying the communication between them.

Security Capabilities of Cilium

In a distributed environment with many containers and microservices, ensuring the security of the applications becomes crucial. Each microservice needs to communicate securely and ensure that only authorized services can access it. Cilium helps address these security challenges by providing transparent encryption, network policy, and runtime enforcement.

  • Transparent Encryption Numerous compliance frameworks necessitate encryption, yet Kubernetes does not possess built-in encryption for communication between nodes. Two prevalent approaches to address this issue involve incorporating encryption within the application itself or utilizing a service mesh. Integrating encryption within the application is intricate and demands expertise in both application development and security. Conversely, most implementations of service mesh are highly intricate and present difficulties in management and operation. Cilium offers a simple and convenient solution to enable encryption for all traffic between nodes by toggling a single switch. By configuring all nodes in all clusters with a shared key, Cilium automatically encrypts all communication between the pods.
  • Network Policy Kubernetes network policies offer a structure centered around applications to establish security policies at the L3/L4 level. One of the key obstacles lies in effectively implementing these security policies when traditional IP rules are not applicable. In modern systems, IP addresses frequently change dynamically, making it challenging to rely solely on TCP/UDP ports and IP addresses for scaling security policies.
  • Runtime Enforcement Cilium’s Tetragon leverages its eBPF-based technology to facilitate seamless security observability and real-time enforcement at runtime. It enables comprehensive visibility into system security without necessitating any modifications to the application. By utilizing in-kernel filtering and aggregation logic integrated into the eBPF-based kernel-level collector, Tetragon operates with minimal overhead. Additionally, Tetragon’s built-in enforcement layer empowers access control functionalities at different levels, including system call control.

Observability Capabilities of Cilium

In traditional monolithic applications, it is relatively easy to monitor and understand how the different parts of the application are working. However, in a containerized and microservices environment, the complexity increases significantly. It becomes challenging to trace network traffic, identify performance bottlenecks, and debug issues when they occur.

Cilium addresses these observability challenges by providing comprehensive monitoring and observability features. It collects network data, metrics, and logs, allowing administrators to gain insights into the behavior and performance of the application. This helps in troubleshooting issues, understanding the flow of data between microservices, and identifying any anomalies or performance bottlenecks. The following key capabilities of Cilium address the observability bottlenecks in modern cloud-native environments:

  • Service Maps When troubleshooting cloud-native environments, the issue could be lurking between any layer of the network, environment, or its dependencies. Hubble – eBPF-powered network, service, and security observability for Kubernetes Hubble provide a range of monitoring capabilities, including service dependencies and communication maps, network monitoring, application monitoring, and security observability.
  • Metrics and Tracing Export With Cilium’s export feature for Metrics and Tracing, users gain a seamless and integrated solution that facilitates effortless monitoring, analysis, and optimization of Kubernetes environments. By harnessing the capabilities of Prometheus metrics and utilizing Hubble’s insights into network behavior, Cilium empowers users with comprehensive visibility into their applications and network. This enhanced visibility simplifies the setup and configuration process, making it easier to gain valuable insights and effectively manage the Kubernetes environment.
  • Advanced Network Protocol Visibility Conventional network observability tools primarily offer visibility at the packet level, which may not be adequate in complex environments like cloud-native setups with diverse application protocols and intricate communication patterns. Cilium’s protocol-aware visibility, on the other hand, delivers comprehensive insights into the communications of application workloads at the protocol level. Cilium possesses native comprehension of various application protocols, including TLS, gRPC, Kafka, DNS, and HTTP, as well as others like SCTP. This enables fine-grained observability of API-specific endpoints and DNS identities for external endpoints, empowering application owners with deeper visibility into their workloads.

Cilium for Kubernetes Networking: Challenges and Considerations

Cilium offers powerful networking capabilities for Kubernetes, but it also comes with its limitations and considerations. Organizations must carefully evaluate the learning curve associated with eBPF, the complexity of configuration, kernel compatibility, debugging challenges, and others.

  • Learning Curve Cilium’s eBPF-based data plane operates at a lower level in the networking stack, which can make it more challenging for users who are not familiar with eBPF technology. Understanding the intricacies of eBPF and its integration with Cilium may require additional learning and expertise, especially for those new to eBPF.
  • Complexity of Configuration Cilium’s rich feature set can introduce complexity in configuration and management. Defining and maintaining network policies, service discovery, and load balancing rules requires a solid understanding of Cilium’s architecture and Kubernetes networking concepts. Organizations need to invest time and resources to ensure proper configuration and prevent misconfigurations that could impact application behavior.
  • Kernel Compatibility Cilium relies on eBPF programs executing within the Linux kernel. As a result, the compatibility and stability of Cilium may be influenced by the kernel version and specific features supported by the underlying kernel. Organizations must ensure that their kernel versions and configurations are compatible with the Cilium requirements to avoid potential issues.
  • Debugging and Troubleshooting Troubleshooting network-related issues in a Cilium-enabled Kubernetes environment can be more challenging due to the involvement of eBPF programs. Debugging complex interactions between eBPF programs, Kubernetes components, and other networking layers may require specialized knowledge and tools. Organizations should invest in developing expertise in debugging and troubleshooting Cilium-specific issues.

By understanding these limitations and making informed decisions, organizations can leverage Cilium effectively, addressing their networking requirements while mitigating potential challenges and ensuring a robust and secure Kubernetes networking infrastructure.

Major Cilium Deployments and Use Cases

Cilium empowers organizations across various industries, enabling them to build and manage resilient and secure containerized applications effectively. Cilium has found significant adoption in major organizations such as Google, AWS, GitLab, Datadog, Adobe, and many more. These organizations leverage Cilium’s advanced networking and security capabilities to enhance performance, strengthen security, and achieve comprehensive observability in their containerized environments. By integrating Cilium into their infrastructure, these organizations ensure secure and efficient communication between microservices, enforce fine-grained network policies, and gain valuable insights into network traffic and security events.

  • Google Has incorporated Cilium into its Google Kubernetes Engine (GKE) to improve networking performance and security. Cilium’s eBPF-based data plane allows Google to handle network traffic at scale, enforcing fine-grained policies and improving network visibility. Cilium’s service discovery and load-balancing capabilities are utilized by Google to automate the management of services and endpoints within GKE clusters, enabling efficient and resilient communication between microservices.
  • Amazon Web Services (AWS) Has embraced Cilium to enhance networking and security in its managed Kubernetes service, Amazon Elastic Kubernetes Service (EKS). By integrating Cilium, AWS offers customers advanced network policies and identity-aware security controls, ensuring secure communication within EKS clusters. Cilium’s observability features enable AWS customers to gain deep insights into network flows, performance metrics, and security events within their EKS clusters, facilitating efficient troubleshooting and monitoring.
  • GitLab A popular DevOps platform, utilizes Cilium to enhance network security and visibility for its containerized applications. By leveraging Cilium’s network policies, GitLab enforces strict access controls, securing communication between microservices and protecting sensitive data. Cilium’s observability features enable GitLab to monitor and analyze network traffic, aiding in detecting anomalies, optimizing performance, and ensuring compliance with security policies.
  • Datadog A leading monitoring and analytics platform, integrates with Cilium to provide comprehensive observability for Kubernetes environments. By leveraging Cilium’s network flow logging and metrics collection capabilities, Datadog offers customers detailed insights into network traffic, enabling efficient troubleshooting and performance optimization. Cilium’s integration with distributed tracing systems enhances Datadog’s ability to trace and analyze network interactions, providing end-to-end visibility into microservices architectures.
  • Adobe Has adopted Cilium to strengthen security and improve networking performance in its containerized environments. Cilium’s identity-aware security features enable Adobe to enforce fine-grained access controls based on cryptographic workload identities, ensuring secure communication within their containerized applications. Cilium’s eBPF-based data plane allows Adobe to handle network traffic efficiently, reducing latency and improving overall application performance.