Shulou(Shulou.com)06/02 Report--

Many people know that CDN is the acceleration of content distribution. The so-called content distribution is to distribute the content originally located on the origin server to nodes across the country to facilitate users to access the content they need nearby. With the generation-by-generation technological changes such as mobile Internet and cloud computing, CDN has become an important Internet infrastructure to alleviate Internet network congestion, improve application response rate, and improve user experience.

According to the forward-looking Industrial Research Institute, more than 50 per cent of Internet traffic will be accelerated through CDN in 2019, and the global CDN market will grow to $15.73 billion by 2020. In other words, more and more enterprises are beginning to realize the necessity of using CDN. Especially in 2019, China officially enters the first year of 5G commercial, and the application scenarios of large bandwidth, low delay and large connection will burst, which has higher requirements for CDN node coverage and response speed, which will also promote the further development of CDN edge nodes.

The "indispensable" of CDN seems to have become a consensus, so how on earth did this consensus come into being? What would the online world be like without CDN? As Internet aborigines, what kind of problems will we face?

Scene 1: when you want to shop online

The picture loading is slow, the video is loading, the transaction is stuck. Without the pleasant experience of online shopping, it seems that the baby has lost its fragrance.

Scene 2: when you watch the game

The explanation is always a few seconds faster than the goal, and the feeling that the cheer is not on the point is really uncomfortable.

Scene 3: when you want an online class

Because of Catton, there was a ghost style in a good online class. Cue, the teacher, would no longer have to pretend to be still to avoid answering questions, because it was really stuck.

Scenario 4: when your company wants to do a website to do business online

It is said that when users visit a website, if they wait for the page to open for more than 8 seconds, more than 30% of people will give up waiting. How to break the terrible 8-second spell? It takes a lot of effort to get users to the official website, but what if they can't keep them?

Just to name a few, without CDN, the whole online world would slow down, congestion, slow loading, stutter, delay, frame drop, blurred screen. And other problems follow, access speed becomes slower, access to information will slow down, the original rich content can not be viewed, exciting interactive experience can not be completed, will you give up browsing because of this?

In fact, as heavy netizens, we enjoy the high-quality network access experience brought by CDN all the time, such as brushing short videos, grabbing train tickets, playing games, watching live broadcasts, downloading mobile phone APP, and visiting forums and blogs. The distribution acceleration behind this is provided by CDN. Especially in the context of hard-core "epidemic prevention" at the beginning of this year, everything is on the cloud, cloud shopping, cloud medical treatment, cloud classes, cloud office, cloud shopping scenic spots, cloud buying luxury houses, cloud court meetings, and so on, CDN has become a very sought-after strategic resource reserve, carrying the entire Internet traffic and escorting the home life of hundreds of millions of netizens.

So, what exactly is the principle of CDN?

Next, let's introduce the principle of CDN. The simplest CDN network consists of a DNS server and several caching servers:

① when the user clicks on the content URL on the page of the website, after the local DNS system parses, the DNS system will finally transfer the resolution right of the domain name to the CDN dedicated DNS server pointed to by CNAME.

The DNS server of ② CDN returns the global load balancing device IP address of CDN to the user.

The ③ user initiates a content URL access request to the global load balancing device of CDN.

The ④ CDN global load balancer device selects a regional load balancer device in the user's region based on the user's IP address and the content URL requested by the user, and tells the user to initiate a request to the device.

The ⑤ regional load balancer equipment will select a suitable cache server to provide services for users. The selection basis includes: judging which server is closest to the user according to the user's IP address; judging which server has the content required by the user according to the content name in the URL requested by the user; and querying the current load of each server to determine which server still has service capacity. After a comprehensive analysis based on the above conditions, the regional load balancer will return the IP address of a cache server to the global load balancer.

The ⑥ global load balancing device returns the IP address of the server to the user.

The ⑦ user initiates a request to the cache server, and the cache server responds to the user's request and transmits the content needed by the user to the user terminal. If there is no content that the user wants on the cache server, and the zone balancing device still assigns it to the user, then the server will request the content from its higher-level cache server until the source server that traces back to the site pulls the content locally.

Why does it have to be CDN?

1. In order to improve the user access experience

Cache the static content, such as pictures, video, audio, JS files, CSS files, static pages and so on to the CDN node to achieve the nearest access after the user request and reduce the transmission link delay.

two。 In order to achieve cross-operator and cross-regional network coverage

Various factors such as non-interconnection, regional ISP limitations, export bandwidth restrictions and other factors have caused the regional inaccessibility of the website. CDN acceleration can cover lines all over the world, cooperate with operators to deploy IDC resources, reasonably deploy CDN edge distribution storage nodes in the national backbone nodes, make full use of bandwidth resources, and balance origin server traffic.

3. To ensure the security of your website

CDN's load balancing and distributed storage technology can enhance the reliability of the website, which is equivalent to virtually adding an umbrella to your origin server, isolating most Internet attacks from the origin server, and avoiding business shutdown or asset losses caused by malicious attacks on the origin server.

4. In order to provide backup in different places

When a server fails unexpectedly, the system will call other nearby health server nodes for service, thus providing nearly 100% reliability, so that your website can never go down.

5. In order to save cost and investment

Using CDN acceleration can achieve the national deployment of the website. You don't have to consider buying servers and subsequent hosting operations, mirror synchronization between servers, and you don't have to worry about managing and maintaining technicians, saving manpower, energy and financial resources.

6. In order for you to focus more on the business itself,

CDN acceleration vendors generally provide one-stop service, which is not limited to CDN, but also includes cloud storage, big data service, video cloud service, etc., and generally provides 7x24 OPS monitoring support to ensure that the network is smooth at any time, so you can rest assured to use it. And put more energy into the development of their own core business.

Aliyun CDN has more than 2800 nodes around the world, which can maximize resource coverage and business stability, and help users get the best acceleration experience. On May 20, Aliyun CDN will hold an online launch of government-enterprise security acceleration solutions, when product and technical experts will come to talk with you about CDN industry applications, security systems, and state secret algorithms. Click to make an appointment to register: https://yq.aliyun.com/live/2748

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