Cloud-native architectures are evolving rapidly to meet ever-changing business needs. Also, the last few years have seen a greater shift towards the adoption of microservices architecture, and this has further increased the complexity of managing networking and security at scale. To overcome these challenges, organizations are increasingly turning to software platforms, with Cilium being one such platform.
Cilium is an open-source project that offers observability and security for all kinds of networks. What makes this platform stand out in a crowded market is its use of an advanced technology called Extended Berkeley Packet Filter (eBPF) that optimizes traffic while providing the visibility you require. Besides this technology, Cilium also leverages other technologies to enhance networking, security, and observability in modern cloud-native environments.
Read on, as we explore the features of Cilium, its working, benefits, shortcomings, and real-world use cases.
What is Cilium?
Cilium is a cloud-native and open-source networking and security solution. It particularly works well for application services that are deployed using Linux container management platforms, including Docker and Kubernetes. Often used as a Container Network Interface (CNI) plugin for Kubernetes, Cilium leverages eBPF to balance workloads. If you've not heard of eBPF before, it's an advanced in-kernel technology that allows you to dynamically insert visibility and control logic within Linux. The advantage of using this technology is you can have comprehensive visibility into all that goes on within your environment. At the same time, you can quickly apply security policies without having to make changes to the container or the application. Such flexibility enables your organization to remain secure without compromising on agility.
Why Use Cilium?
Cilium is unique in many ways. Besides being open source, it also improves efficiency and visibility at a granular level, and this provides the transparency you need to quickly detect and fix bottlenecks in your system. eBPF comes with capabilities to handle virtual machines and Linux processes in addition to traditional workloads, and this means you have the flexibility to use Cilium across different applications.
In particular, Cilium is highly conducive to microservices architecture. The dynamic nature of these microservices makes them difficult to secure. But Cilium's eBPF enables you to add security policies at the kernel level, without impacting the application. Plus, you can also implement granular access control policies to further boost security.
Other than security, Cilium also supports load balancing and enables your organization to scale up quickly, regardless of the size of your environment. Due to these factors, Cilium can be a great addition to any organization.
Key Features of Cilium
In the earlier section, we briefly looked into why you must consider implementing Cilium in your tech stack, and now let's do a deep dive into its features.
- Network Security: Cilium empowers you to implement fine-grained network security policies. Using its support for layer 7 network policies, you can define access controls based on HTTP headers, gRPC metadata, and more. This granular security enforcement helps organizations adhere to Zero Trust principles and establish strong authentication and authorization policies. In addition, you can control access to critical resources and have complete visibility into all the activities that happen within your network.
- Service Discovery and Load Balancing: Cilium seamlessly integrates with popular service discovery mechanisms, including Kubernetes' DNS service, to help you monitor who is what resources. Also, to improve network efficiency, Cilium uses the Layer 7-aware load balancing techniques to distribute traffic across your microservices. Moreover, this dynamic load balancing enhances application resilience and scalability by intelligently routing traffic to healthy instances.
- Observability and Network Visibility: Another important feature is in-depth visibility. Cilium provides comprehensive observability features to monitor and gain insights into microservices-based applications. It collects rich network flow and performance metrics and analyzes them to provide a snapshot of the state of your network, as well as a detailed context. Using this information, your employees can quickly troubleshoot issues, analyze traffic patterns to identify anomalies, and take the necessary steps to optimize application performance. Such unified visibility also helps ensure the reliability and efficiency of your cloud-native deployments.
- API-aware Network Routing: Cilium operates at the API layer, and hence, enables advanced API-aware network routing and filtering. What this essentially means is that Cilium can intelligently route traffic based on the API endpoints, versions, and other API-specific attributes. You can leverage this capability to implement sophisticated routing policies in your network based on your network demand. Also, it can help to manage microservices communication with ease.
- Data Security: Data security takes on a new meaning with a microservices' architecture, as quick communication is a key part of its smooth functioning. During such communications, data can be intercepted or become visible to unauthorized entities. To avoid such issues, Cilium has IPSec capabilities that are built into the Linux kernel. As a result, all communications are encrypted between and within workloads and this means, data is secure at rest and during transit.
- Connectivity Among Clusters: One of the characteristics of Kubernetes is that each cluster operates as an island, making it difficult to connect workloads across multiple clusters. Cilium eases this problem by creating a single zone of connectivity for all the Kubernetes clusters. Such connectivity makes it easy for you to balance workloads and increase security and observability across all the clusters. In turn, this can enable you to leverage high-performance cross-cluster connectivity.
The above features clearly show the many ways in which Cilium can make a difference to your organization.
Moving on, let's see how Cilium works at a high level.
How Cilium Works?
As mentioned earlier, Cilium's core operations leverage the eBPF technology to intercept, analyze, and manipulate network packets as they traverse the kernel. You can do all of this without altering any code in your applications and, at the same, gain the visibility and security you need without sacrificing performance.
But how does this eBPF work, and what are the broad steps involved? Here's a step-by-step breakdown of how Cilium works
- Step 1: eBPF Integration As a first step, Cilium integrates tightly with the Linux kernel through eBPF. Using this technology, Cilium attaches programs to specific hooks or entry points within the kernel's networking stack.
- Step 2: Program Attachments Cilium attaches eBPF programs at critical points in the networking path. Some possible points include the ingress and egress points of network interfaces, socket creation points, connection establishment endpoints, and packet forwarding ports. Using these program attachments, Cilium intercepts and processes network packets at various stages of their journey.
- Step 3: Packet Processing After the programs are attached to the hooks, the program is executed when a network packet passes through the hook. You can customize this program to do many things, like inspecting and modifying the packet headers, filtering based on defined policies, applying security measures, and even routing packets based on specific criteria.
- Step 4: Security Cilium uses the eBPF programs to enforce fine-grained network security policies. You can customize the programs to examine packet contents, including application layer information such as HTTP headers or gRPC metadata. Based on these packet attributes, Cilium applies security rules and access controls to allow or deny network traffic.
- Step 5: Load Balancing Cilium integrates with service discovery mechanisms, like Kubernetes' DNS service. Again, It uses the eBPF programs to implement Layer 7-aware load balancing. These programs dynamically route traffic across microservices based on defined load-balancing policies. In turn, this results in efficient traffic distribution and optimal resource utilization.
- Step 6. Observability The eBPF programs ease the observability process as well. Cilium collects extensive network flow and performance metrics using these eBPF programs. Such network metrics provide valuable insights into network traffic patterns, application performance, latency, and resource utilization. You can also use this data to troubleshoot issues and gain a comprehensive understanding of your cloud-native environment.
Thus, this is how Cilium uses eBPF to help you gain the benefits of load balancing, security, and observability. Note that Cilium's functionality is not limited to the Linux kernel alone. It seamlessly integrates with container orchestration platforms like Kubernetes, enabling organizations to leverage its capabilities within their containerized deployments.
Now that we have seen the features and workings of Cilium, let's look into its shortcomings, so you can plan for them.
Cilium Shortcomings
Though Cilium offers many benefits, its implementation is largely confined to Linux environments only. Microsoft attempted to implement eBPF on Windows, but it was not successful, as it can support only a few workloads. This means Windows production environments are not conducive to implementing Cilium. Also, eBPF runs efficiently only from kernel version 4.19.57, so older Linux kernels may not fully support Cilium. In all, if you run older versions of Linux kernel or Windows-based nodes inside Kubernetes clusters, Cilium may not be a good choice for you.
Despite this limitation, many prominent companies in the world like Adobe, Bloomberg, and Capital One use Cilium as a part of their operations. Cilium finds practical application in a variety of scenarios. In microservices architectures, Cilium's network security capabilities help enforce access controls and protect sensitive data. Its observability features enable operators to monitor and analyze network traffic, aiding in troubleshooting and ensuring optimal performance. Cilium's API-aware network routing is valuable in environments where API versioning and granular traffic routing are critical. Additionally, organizations leveraging Kubernetes benefit from Cilium's seamless integration with Kubernetes' networking and service discovery mechanisms.
Final Thoughts
Cilium is a powerful open-source solution that addresses the networking and security challenges in cloud-native environments and microservices architectures. Powered by eBPF technology, Cilium's advanced features provide network security, service discovery, observability, and API-aware routing capabilities to organizations. In the process, it helps organizations build scalable, secure, and resilient microservices-based applications. While Cilium offers numerous benefits, its adoption requires an understanding of the underlying eBPF technology. Also, it merits noting that Cilium is not conducive for Windows environments and for older kernels. Despite this limitation, Cilium continues to be used widely because of its many benefits. As it continues to evolve and expand its capabilities, Cilium is undoubtedly poised to play a significant role in shaping the future of cloud-native networking and security.
