Design of a CDN

CDN design

We’ll explain our CDN design in two phases. In the first phase, we’ll cover the components that comprise a CDN. By the end of this phase, we’ll understand why we need a specific component. In the second phase, we’ll explore the workflow by explaining how each component interacts with others to develop a fully functional CDN. Let’s dive in.

CDN components

The following components comprise a CDN:

• Clients: End users use various clients, like browsers, smartphones, and other devices, to request content from the CDN.
• Routing system: The routing system directs clients to the nearest CDN facility. To do that effectively, this component receives input from various systems to understand where content is placed, how many requests are made for particular content, the load a particular set of servers is handling, and the URI (Uniform Resource Identifier) namespace of various contents. In the next lesson, we’ll discuss different routing mechanisms to forward users to the nearest CDN facility.
• Scrubber servers: Scrubber servers are used to separate the good traffic from malicious traffic and protect against well-known attacks, like DDoS. Scrubber servers are generally used only when an attack is detected. In that case, the traffic is scrubbed or cleaned and then routed to the target destination.
• Proxy servers: The proxy or edge proxy servers serve the content from RAM to the users. Proxy servers store hot data in RAM, though they can store cold data in SSD or hard drive as well. These servers also provide accounting information and receive content from the distribution system.
• Distribution system: The distribution system is responsible for distributing content to all the edge proxy servers to different CDN facilities. This system uses the Internet and intelligent broadcast-like approaches to distribute content across the active edge proxy servers.
• Origin servers: The CDN infrastructure facilitates users with data received from the origin servers. The origin servers serve any unavailable data at the CDN to clients. Origin servers will use appropriate stores to keep content and other mapping metadata. Though, we won’t discuss the internal architecture of origin infrastructure here.
• Management system: The management systems are important in CDNs from a business and managerial aspect where resource usage and statistics are constantly observed. This component measures important metrics, like latency, downtime, packet loss, server load, and so on. For third-party CDNs, accounting information can also be used for billing purposes.