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This article mainly explains "what are the advantages of using CDN". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the advantages of using CDN"?

CDN

Full name: Content Delivery Network or Content Ddistribute Network, or content delivery network

Basic ideas:

Try to avoid the bottlenecks and links that may affect the speed and stability of data transmission on the Internet, so as to make the content transmission faster and more stable. By placing node servers everywhere in the network to form a layer of intelligent virtual network based on the existing Internet, the CDN system can redirect the user's request to the nearest service node in real time according to the comprehensive information such as network traffic, connection of each node, load status, distance to the user and response time.

Objective:

To solve the access delay caused by distribution, bandwidth and server performance, it is suitable for site acceleration, VOD, LVB and other scenarios. So that users can get the content they need nearby, solve the situation of Internet network congestion, and improve the response speed and success rate of users visiting the website.

Control delay is undoubtedly an important indicator of modern information technology. The intention of CDN is to reduce resources as much as possible in the case of forwarding, transmission, link jitter and so on to ensure the consistency of information.

CDN is to play the role of escort and accelerator, faster, more accurate and ruthless trigger information and reach every user, bringing a more extreme user experience.

A key word is introduced here: control delay

There is no doubt that it is an important indicator of modern information technology. The intention of CDN is to reduce resources as much as possible to ensure the continuity of information in the case of forwarding, transmission, link jitter, etc.

According to the paper "WAITING TIMES IN QUALITY OF EXPERIENCE FOR WEB BASED SERVICES":

It points out that it is based on the different conscious behaviors produced by the human brain when waiting for information for different periods of time, and then the different sensory experience of information acquisition.

Perceived duration VS objective duration

According to the research findings:

When people get sound messages such as Voice, their good feelings decline most rapidly with the passage of time, and the "evaluation opinion level" has dropped by 70% in only 16 minutes, which shows that audio and video resources are affected by buffer time.

✫ 0.1s: users can hardly sense whether the system is incoherent.

✫ 1.0s: users obviously notice the occurrence of delay, but their thinking is still consistent during that time.

✫ 10s: the delay beyond this time will make the user lose the willingness to wait.

Control delay is undoubtedly an important indicator of modern information technology. The intention of CDN is to reduce resources as much as possible in the case of forwarding, transmission, link jitter and so on to ensure the consistency of information.

To put it more popularly, under the premise of a certain Internet speed, CDN is like a courier in the network.

And CDN, the courier, is very smart.

TA is not running or bumping around with brute force.

TA also built a lot of express points, the nearest express (cache)

TA is good at optimizing express delivery routes (scheduling)

The package will also be repackaged more reasonably (protocol optimization)

Infrastructure:

The simplest CDN network consists of a DNS server and several caching servers:

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 hand over the resolution right of the domain name to the CDN dedicated DNS server pointed to by CNAME.

CDN's DNS server returns the global load balancing device IP address of CDN to the user.

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

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

The 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.

Service model:

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 (Traffic Management) are the core of CDN.

By judging the proximity of users and server load, CDN ensures that content serves users' requests in a very efficient way.

Examples are as follows:

Domestic websites, live streaming and video platforms with high visit volume all use CDN network acceleration technology. Although the visit of the website is huge, it will feel very fast no matter where it is visited. In general, if the server is in Netcom, the access of telecom users is very slow, and if the server is in telecom, the access of Netcom users is very slow.

By adding a new network architecture to the existing Internet, publishing the content of the website to the cache server closest to the user, and through the technology of DNS load balancing, we can judge the user source to visit the cache server nearby to get the required content, solve the Internet network congestion, and improve the response speed of users visiting the website, just like providing multiple accelerators distributed in different places. In order to achieve the goal of fast and redundant acceleration for multiple websites.

CDN services were originally used to ensure fast and reliable distribution of static content that can be cached and best suited for storage and distribution in a fast network that covers CDN network servers in more than a dozen networks in dozens of countries. Because dynamic content must be transmitted over the Internet, it is necessary to provide a fast network experience. Today's CDN is suitable for large files, small files, on-demand, live broadcast, and movement.

Main features:

1. Local Cache acceleration improves the access speed of enterprise sites (especially sites with a large number of pictures and static pages), and greatly improves the stability of sites of the above nature.

2. The mirroring service eliminates the impact caused by the bottleneck of interconnection between different operators, realizes the network acceleration across operators, and ensures that users in different networks can get good access quality.

3. Remote acceleration remote access users automatically select Cache servers according to DNS load balancing technology, and choose the fastest Cache server to speed up remote access.

4. Bandwidth optimization automatically generates the remote Mirror (mirror) cache server of the server. Remote users read data from the cache server when accessing, reducing the bandwidth of remote access, sharing network traffic, reducing the load of the original site WEB server and other functions.

5. Cluster anti-attack widely distributed CDN nodes and intelligent redundancy mechanism between nodes can effectively prevent hacker intrusion and reduce the impact of various D.D.o.S attacks on websites, while ensuring a better quality of service.

Key technologies:

Content distribution: with the help of indexing, caching, stream splitting, Multicast and other technologies

Content routing: it is a holistic network load balancing technology that balances user requests on multiple remote POP through the redirect (DNS) mechanism in the content router, so that user requests are responded to by the nearest content source.

Content switching: it intelligently balances load and traffic on POP cache servers based on content availability, server availability and user background, using application layer switching, stream splitting, redirection (ICP, WCCP) and other technologies.

Performance management: through internal and external monitoring systems, it obtains the status information of network components and measures the end-to-end performance of content distribution (such as packet loss, delay, average bandwidth, startup time, frame rate, etc.). Ensure that the network is in the best running state.

Q & A

Does 1.CDN acceleration accelerate the server on which the site is located or on its domain name?

CDN is only accelerated for a specific domain name of the site. If there are multiple domain names on the same website, visitors will not be able to get the CDN effect if they visit the domain name that joined CDN, or if they visit the domain name that has not joined CDN, or if they visit the IP address directly.

What are the advantages of 2.CDN and mirror sites?

CDN is completely transparent to the visitors of the website, and there is no need for visitors to manually select the mirror site to visit, which ensures that the website is friendly to visitors. CDN has an availability check for each node, and unqualified nodes will be removed as soon as possible, thus ensuring a very high availability rate, which cannot be achieved by the mirror site. CDN is easy to deploy and can take effect without making any changes to the original station.

What are the advantages of 3.CDN compared with two-line computer room?

The common two-line computer room can only solve the problem of slow access between Netcom and telecom, while the interworking of other ISP (such as Education Network, Mobile Network, TieTong) has not been solved. On the other hand, CDN allows visitors to access data, while CDN has nodes all over the ISP, thus ensuring the speed of visiting the website to any ISP. In addition, because of the principle of diverting traffic to each node, CDN naturally gains the ability to resist network attacks.

After the use of 4.CDN, does the original website need to be modified and what changes should be made?

In general, websites can use CDN to achieve acceleration without any modification. Only if you need to judge the guest IP program, do you need to make a few changes.

5. Why after my website is updated, after passing the CDN, I see the web page or the old web page? how to solve it?

Because CDN adopts the caching mechanism of each node, after the static web page and picture of the website are modified, if the CDN cache is not updated accordingly, you will still see the old web page. To solve this problem, URL push service is provided in the CDN management panel to inform each CDN node to flush its own cache. Enter a specific URL or image address in the URL push address bar, and the cached content in each node will be deleted and take effect immediately. If you need to push too many URLs and pictures, you can choose directory push. Enter http://www.kkk.com/news to refresh all the pages and pictures under the news directory under the website.

6. Is it possible for CDN not to cache some web pages and images that require high immediacy?

You only need to use dynamic pages, asp,php,jsp and other dynamic technologies to make pages that are not cached by CDN and do not need to be refreshed every time. Or use a website with two domain names, one with CDN enabled and the other without CDN, and put the pages and images that require high immediacy under the domain name that does not use CDN.

7. A lot of new pages and pictures have been added to the site. Do you need to use URL to push these?

Later added pages and images do not need to use URL push, because they do not exist in the cache.

8. After the website uses CDN, some areas reflect that it is inaccessible, what should I do?

After CDN is enabled, there are many possibilities that visitors cannot access the website. It may be due to the problem of CDN, the failure of the source site or the shutdown of the source site, or the problem with the network where the visitor is located. Even in our actual troubleshooting, the customer's own computer has been poisoned, resulting in inability to access the website. When the customer reports the fault, you can contact our 24-hour technical department at any time to deal with it.

9. In what situations is CDN recommended?

Generally speaking, websites based on information, content, etc., have a certain volume of visits.

Websites based on dynamic content, such as information websites, government agency websites, industry platform websites, shopping malls, etc.

Forums, blogs, making friends, SNS, online games, search / query, finance, etc. A website that provides http downloads

Software developers, content service providers, online game operators, source code downloads and other websites with a large number of streaming media-on-demand applications

Telecom operators with video-on-demand platforms, content service providers, sports channels, broadband channels, online education, video blogs, etc.

10. What are the situations that do not apply to CDN?

You are not recommended to use CDN services in such extreme situations

Thank you for your reading, the above is the content of "what are the advantages of using CDN". After the study of this article, I believe you have a deeper understanding of the advantages of using CDN, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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