How does CDN work? How CDN works and what it does

Like this question, my understanding is this:

a) 1Users access ** through domain names, and then the requests of users in various places are deployed to local CDN nodes.

The node will get the content from the real source** and then spit it out to the user. If the content can be cached, the CDN will exist for a while depending on the protocol. If another user accesses the CDN next time, it is possible to get the cached content and return it directly.

3 If you have a small site, after careful management, the traffic will gradually increase, or you want to do an event, the number of requests will be much higher than usual. The network may be blown up, causing the entire ** to open slower. If you want to expand the bandwidth but find that the dedicated bandwidth is expensive, you can use CDN.

4 If you have a store, the business is slowly growing, and customers are all over the country or even the world, and you often receive complaints from customers that your ** is slow to open in a certain area. Then you can use CDN, which can be handled on the Alibaba Cloud platform.

2) 1. Solve the problem of Internet network congestion and DDoS attacks by peers.

2. Improve the response speed of user access.

3. Technically, it comprehensively solves the problem of slow response speed of user access caused by small network bandwidth, large user access, uneven node diversion and other reasons.

Network Traffic Distribution (CDN) is a new type of network construction method, which is a network coverage layer that is specially optimized for the distribution of broadband richness in traditional IP networks. In a broad sense, CDN represents a network service model based on quality and order.

To put it simply, CDN is a strategically deployed overall system, including distributed storage, load balancing, network request redirection and content management, while content management and global network traffic management are the core of CDN.

CDN, Chinese called Content Delivery Network, its role is to reduce propagation delay and find the nearest node.

All nodes of Rabbit CDN are connected to 10 Gigabit network cards, with a single-node storage capacity of 40TB, a bandwidth load of 40Gbps and 200Gbps, and a bandwidth reserve capacity of 130Tbps.

Rabbit CDN

Dynamic and static IP lines are supported.

I don't know which one is the best in China, most people around me use this, and the evaluation is very good.

Features of CDN:

EMAI Cloud Converged CDN is a converged management service that further optimizes data network acceleration on the basis of traditional CDN. In addition to serving Yu Yin. Look.

Frequently. Dot. Broadcast, file, application and web acceleration, as well as various value-added scenarios In addition to various value-added scenarios, EMAI Cloud Convergence CDN also ensures the continuity of user services and provides stable network access quality through all-round CDN quality monitoring and intelligent and easy-to-use accelerated node scheduling.

1. Fast speed.

The BGP line is used as the CDN node to ensure the speed of the CDN when reading the original data.

2. The bandwidth cost is greatly reduced.

Because 70% of telecom customers access the speed itself is fast and does not need to be accelerated, this part of the traffic is completely saved. Acceleration is only for about 25% of Netcom customers.

3. Good security.

The original server of the user and the CDN acceleration node are encrypted and compressed for transmission, and the ** in the node server exists in the form of a file. Even if a node server is compromised, hackers won't be able to get any valuable data.

4. High reliability.

In the CDN acceleration system, the network interruption, attack paralysis, or system crash of any node server does not hinder the operation of the overall network and the access of the vast majority of users. The system can automatically determine and guide users to the node with the fastest access speed among the remaining nodes.

5. Easy to deploy.

You only need to modify the DNS record to the specified alias, and no other operations are required.

The content of the user's origin server is cached on CDN nodes in different regions and different operators, so that visitors can access the nearest place.

For example, the source station is China Unicom Beijing. Then the visitors of Guangdong Telecom may be very slow to access the origin server, and after using CDN, the visitors of Guangdong Telecom will be resolved to the CDN node of Guangdong Telecom, so that the speed will be much faster.

If the content being accessed is dynamic and cannot be cached by the CDN, then when the request is resolved to the CDN node, it will temporarily send a request to the origin server, get the result, and then return it to the visitor.

In this case, if the CDN node is telecom and the origin server is China Unicom, the acceleration effect may not be ideal. However, if the CDN node is dual-pass, or multi-line, then the acceleration will still have an effect, at least to solve the problem of cross-carrier).

For example, the speed of home A is 100m, but he only uses the speed of 10m, and the speed of home B is 10m, but he needs a speed of 15m. What to do. C is a CDN service provider, and A has a node (just like A is a sponsor) and B buys CDN acceleration services at C.

When B's speed is insufficient, CDN Acceleration will select a surplus node to help B and improve B's speed. In this way, the speed of b can reach or exceed 15m, and everyone is happy. A didn't waste it, B speed was there, C made money.

When there are many nodes of c in the whole country. Then you use the CDN acceleration service of home C, and you will be flying like a fly. c = octave network.

Due to the performance bottleneck of the user's access to the origin server, CDN technology is used to cache the content of the origin server to multiple nodes. When a user sends a request to the domain name of the origin server, the request is scheduled to the service node closest to the user, and the service node directly responds quickly, effectively reducing user access latency and improving availability.

To understand CDN, you need to understand the knowledge points first:

No matter how much it is, it's not as good as practical application, let's take an example to understand the DNS resolution process.

nslookup is the command for dns resolution, and server is the ip of the company's internal dns serveris the IP address of the requested domain name.

The detailed process can be viewed using the dig command.

Let's take a step-by-step analysis of the parsing process

cname stands for: alias record. This type of record allows you to map multiple names to another domain name.

It is usually used on computers that provide both www and mail services. For example, there is a computer named "a record"). It provides both www and mail services for the convenience of users.

You can set two aliases (cnames) for this computer: www and mail. The full name of these two aliases.

and " " actually they all point to " ".

The implementation principle in CDN is to add CNMAE to the domain name of the origin server, alias the domain name of the acceleration node. When a user makes a request to the origin server, the DNS server finds that there is a cnmae record when the origin server resolves the domain name of the origin server, and the DNS server sends a request to the CNAME domain name, and the request is scheduled to the domain name of the acceleration node.

For example, if the domain name of your business origin server is , and your users initiate an HTTP request after the domain name is connected to the CDN and you start using the acceleration service, the actual processing process is shown in the following figure: link.

1. The full name of CDN is Content Delivery Network. CDN is to build an intelligent virtual sales network on the basis of the existing network, relying on the 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 content they need nearby, reduce network congestion, and improve user access response speed and hit rate. The key technologies of CDN mainly include content storage and distribution technology.

2. The basic principle of CDN is to widely use a variety of cache servers, distribute these cache servers to the user access to the relatively concentrated area or network, and use the global load technology to point the user's access to the nearest normal cache server, and the cache server directly responds to the user's request.

What is a CDN license? CDN content delivery network business refers to the use of node server groups distributed in different regions to form a traffic distribution management network platform, to provide users with content scattered storage, positive judgment storage and cache, and according to the dynamic traffic and load of the network to distribute content to a fast and stable cache server, improve the access response speed of user content and the availability of services.

Referred to as CDN license, CDN qualification, and CDN license, it belongs to the content distribution network service in the first category of value-added telecommunications services.

The process of applying for a CDN license is as follows: fill in the evaluation application form - review - test - submit the license application materials - review - approval. CDN license application Shanghai enterprises must have a corresponding business management system, and can enter the license application stage only after the technical evaluation of the evaluation agency designated by the Ministry of Industry and Information Technology.

Enterprises that need technical assessment include: enterprises newly applying for CDN licenses; Enterprises that renew their CDN license or expand their business scope.

List of application materials for inspection and correction of Shanghai CDN License Office:

1) Letter of commitment to operate telecommunications business in accordance with the law (signed and sealed by the legal person).

2) Application form for cross-regional value-added telecommunications business license (signed and sealed by legal person).

3) Company profile personnel information table.

4) A copy of the business license of the company's corporate legal person and the ID card of the legal representative.

5) Articles of Association (stamped with the original copy of the file inquiry seal of the Industrial and Commercial Bureau).

6) Complete and detailed shareholding structure chart (signature of the legal person and company seal) and related certificates.

7) A copy of the business license for the establishment of a branch or a business license of a holding subsidiary and the articles of association of the holding subsidiary (optional).

8) ID card of the company's main management and technical personnel.

9) The social security certificate provided by the company for the employee recently (should be stamped with the red seal of the social security institution).

10) has obtained a telecommunications business license (text page, attached page, special provisions, annual inspection record page) (there are other applied licenses, need to be submitted).

11) Responsible for the operation of telecommunications business institutions.

1. The full name of CDN is Content Delivery Network. CDN 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 content they need nearby, reduce network congestion, and improve user access response speed and hit rate. The key technologies of CDN mainly include content storage and distribution technology.

2. The basic principle of CDN is to widely use a variety of cache servers, distribute these cache servers to areas or networks where user access is relatively concentrated, and when users access, use global load technology to point to the nearest working cache server, and the cache server directly responds to user requests.