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Content Delivery Networks (CDN)

This article will give readers a complete understanding of Content Delivery Networks (CDN).

By Rupal Shirpurkar, Business Head (Cloud BU - APAC) of Click2Cloud Inc. and Alibaba Cloud MVP

Alibaba Cloud CDN is a virtual network that consists of globally distributed edge nodes. Alibaba Cloud CDN reduces the load on origin servers and prevents network congestion. Alibaba Cloud CDN can accelerate content delivery for websites across multiple regions or scenarios.

Origin servers can cache files to globally distributed edge nodes using Alibaba Cloud CDN. Rather than accessing origin servers, users can retrieve resources from the nearest edge node. This speeds up content delivery and reduces loads on origin servers. IPv6 is supported by a few edge nodes.

Content Delivery Networks (CDN) is a service that accelerates content delivery. A CDN helps minimize delays in web page content loading by reducing the physical distance between the server and the user. The same high-quality content can be viewed by users worldwide without affecting the loading speed. The main benefit of a CDN is that it makes your website faster.

Let's dive deeper into the inner workings of a CDN with an example. Consider a scenario where a server that is hosting a website went down, supporting users worldwide. They are accessing this server, and the website is down. You can consider a scenario where these users are located at different locations, such as Mainland China, Hong Kong, or Singapore. They all are utilizing the same website from a particular location where this website is hosted. The problem they face is that the farther the location, the slower the website runs for those users. This is where the CDN comes into the picture.

Does it accomplish the speed increase by reducing the distance between the user and the content or the server providing the content? It places its CDN endpoints in as many locations around the world as possible. In that case, if a user from a specific region tries to access the content from a website, it is retrieved by the CDN service first and then distributed worldwide. Hence, users can access the content from their nearest geographical locations. It benefits the reduction of load, increases in uptime, and increases in security.

Fig. 1 illustrates Alibaba Cloud CDN's architecture. Alibaba Cloud CDN contains scheduling, link quality, caching, and support systems.

Fig 1: Alibaba Cloud CDN Architecture

  • Scheduling System: Supports Domain Name System (DNS) resolution, HTTPDNS, 302 redirections, and a policy center. The scheduling system handles the request once the DNS resolution resolves the client's request.
  • Link Quality System: Monitors and reports all nodes and links and their health conditions to the scheduling system in real-time. According to the IP address information of the requests, such as Internet Service Provider (ISP), the scheduling system decides the most appropriate access point.
  • Caching System: Requests are redirected to edge nodes based on the request's access points. Resources cached on the edge nodes are returned to the client immediately if they are already available on the edge nodes. The request is redirected to the origin server if the requested resource is not cached on L1 or L2 nodes. In addition, once the retrieved resource has been cached on the edge nodes, it is returned to the client. The resources can be retrieved directly from the edge nodes for subsequent requests. Alibaba Cloud CDN accelerates content delivery, reduces bandwidth consumption, and improves user experience.
  • Support System: The support system manages data intelligence and configuration controls of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Monitoring resources, analyzing data, and managing configurations are all possible with the support system.

    1. Resource Monitoring: Monitor the status of the cache services. For example, a domain name that is accelerated by Alibaba Cloud CDN is monitored in terms of the number of queries per second (QPS), bandwidth, and HTTP status codes.
    2. Data Analytics: You can analyze data by analyzing your Alibaba Cloud CDN domain name's top N most frequently requested URLs, page views, and unique visitors.
    3. Configuration Management: You can create and manage cache expiration rules to enhance the efficiency of caching. Cache expiration rules can be created for specific types of documents, or parameter filters can be enabled.

Features and Benefits

Alibaba Cloud CDN can separate the acceleration of static and dynamic content. Some of the benefits of Alibaba Cloud CDN are listed below:

  • A Large Number of Nodes: Alibaba Cloud CDN directs requests to the closest nodes owned by the client's Internet Service Provider (ISP). This approach makes delivering content across ISP borders faster and more efficient.
  • Resource Scalability and Availability: Alibaba Cloud CDN has over 2,500 global edge nodes, ensuring service availability and scalability.
  • Real-Time Monitoring: Alibaba Cloud CDN monitors the health status of the edge nodes in real-time, and the scheduling system directs requests to the most appropriate nodes based on the client's location and ISP. This improves acceleration.
  • Connection Optimization: Alibaba Cloud CDN always seeks to improve data delivery performance using various optimization technologies, such as protocol and connection optimization.
  • Caching Efficiency: Alibaba Cloud CDN increases cache hits by allowing requests to reach cache on the nearest edge nodes, streamlining the content delivery process.
  • Reduced IT Costs: Edge nodes offer to compute power, bandwidth, and connections. This reduces IT expenses.
  • Alibaba Cloud CDN Is Capable of High Bandwidth: Alibaba Cloud CDN's total bandwidth can reach up to 150 Tbit/s.
  • Easy-to-Use API: Alibaba Cloud CDN can perform a variety of operations through its API.

Fig 2: Key Benefits of Alibaba Cloud CDN


This article explains Content Delivery Networks (CDN) and how they work. Alibaba Cloud CDN makes your web content scalable, secure, smooth and results in IT cost reduction.

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