More and more websites and APPs use CDN caching, and CDN has even become standard for website construction. Looking at the industrial development of CDN by observing the technology of CDN, we can see that CDN will be an integral part of cloud computing. By understanding the theoretical basis, a basic knowledge outline can be formed in the mind, and it can be used with ease.
What is a CDN?
The full name of CDN is Content Delivery Network, that is, content distribution network, also known as content delivery network. It is an intelligent virtual network built on the basis of the existing network, relying on edge servers deployed in various places, through the load balancing, content distribution, scheduling and other functional modules of the central platform, so that users can obtain the desired content nearby, reducing network congestion, Improve user access response speed and hit rate, solve access delay problems caused by distribution, bandwidth, and server performance, and improve availability.
How does CDN work?
The traditional http access process is that the user fills in the domain name to be accessed in the browser; the browser calls the domain name resolution function library to parse the domain name to obtain the IP address corresponding to the domain name, and sends the service host of the domain name through this IP address. Data access request, get the requested data, and finally return the required content.
Website access process after using CDN cache:
- The user provides the browser with the domain name to be accessed;
- The browser calls the domain name resolution library to resolve the domain name. Since the CDN has adjusted the domain name resolution process, the resolution function library generally obtains the CNAME record corresponding to the domain name. In order to obtain the actual IP address, the browser needs to re-interpret the obtained CNAME record. The domain name is resolved to obtain the actual IP address; in this process, global load balancing DNS resolution is used, and the corresponding IP address is resolved according to the geographical location information, so that users can access nearby;
- The IP address of the CDN cache server is obtained through the resolution, and the browser sends an access request to the cache server after obtaining the actual IP address;
- According to the domain name to be accessed provided by the browser, the cache server obtains the actual IP address of the domain name through Cache’s internal dedicated DNS resolution, and then the cache server submits an access request to the actual IP address;
- After the cache server obtains the content from the actual IP address, on the one hand, it saves it locally for later use, and on the other hand, it returns the obtained data to the client to complete the data service process;
- After the client gets the data returned by the cache server, it displays it and completes the entire browsing data request process.
What scenarios are suitable for CDN?
website acceleration
For business scenarios such as portal websites, e-commerce, and UGC communities, CDN provides powerful static content (such as webpage styles, pictures, and small files) to accelerate the distribution and processing capabilities, which significantly improves the experience of webpage users.
download acceleration
For business scenarios such as game installation package acquisition, mobile ROM upgrade, and application package download, CDN provides stable and high-quality download acceleration. Massive elastic bandwidth reserves, with the ability to carry sudden large-scale traffic, allow business users to obtain extremely fast download experience.
Audio and video acceleration
For online audio and video playback business scenarios, CDN can provide a stable, smooth and rich viewing experience.
What problem does CDN solve?
- Solve the problem that the network bandwidth is small, and users access resources slowly. Use CDN to reduce bandwidth costs and improve user access experience;
- The user access volume is large, and the server hard disk read and write pressure is high. Use CDN to reduce server costs;
- The self-built data center is distributed in a small number of areas, and the physical distance from the access users is far away, and the user access network transmission time is long. Use CDN to quickly respond to requests and improve user access experience through the nearest algorithm.
What are the well-known CDN service providers in China
Alibaba Cloud CDN : 2800+ global nodes, 150T bandwidth capacity, covering six continents. Disadvantage: Additional charges for HTTPS requests.
Tencent Cloud CDN : Covering 70+ countries and regions around the world, the entire network bandwidth is 150Tbps+. There are 2000+ acceleration nodes in China, covering China Mobile, China Unicom, China Telecom and more than a dozen small and medium-sized operators, and 800+ acceleration nodes outside China. New users have a free quota for the first 6 months.
Baidu Cloud CDN : Baidu’s self-built 1000+ high-quality nodes, 100T+ bandwidth, single node 80G-160G. The characteristic is dynamic acceleration service. In addition, Baidu Cloud Accelerator , a subsidiary of Baidu, is also a CDN-based product.
Wangsu Technology CDN : For eight consecutive years, the market share of commercial CDNs is the first in China, with 1500+ global nodes, covering more than 70 countries and regions, and supported by over 100+ operators. Apart from the high price, there is nothing to complain about.
Another cloud : 1100+ global nodes, 10Tbps bandwidth reserve, supported by domestic mainstream operators, through technical means such as TCP protocol optimization, link optimization, content optimization, intelligent scheduling, etc., the acceleration performance is increased by more than 100% on average.
Qiniu Cloud : An intelligent management service that further optimizes data network acceleration based on traditional CDN. Through comprehensive CDN quality monitoring and intelligent and easy-to-use node scheduling, it provides stable and fast network access services. 2000+ nodes worldwide.