The advantages and disadvantages of CDN acceleration and the difference between two-line server

What is a CDN?

The full name of CDN is the Content Delivery Network, the content distribution network. The purpose is to add the new network architecture to the existing Internet, and publish the content of the website to the network closest to the user, “edge”, so that users can get the required content nearby and improve the user's access to the website. responding speed.

CDN is different from mirroring because it is smarter than mirroring, or it can be used as a metaphor: CDN= smarter mirroring + cache + traffic diversion. Therefore, CDN can significantly improve the efficiency of information flow in the Internet. Technically comprehensively solves the problem of slow response time of users visiting websites due to problems such as small network bandwidth, large user access, and uneven distribution of network points.

To better understand the CDN, let's take a look at the CDN workflow. When a user visits a website that has joined the CDN service, the best CDN node closest to the user is first determined by the DNS redirection technique, and the user's request is directed to the node. When the user's request arrives at the specified node, the CDN's server (the cache on the node) is responsible for providing the content requested by the user to the user. The specific process is as follows: The user inputs the domain name of the website to be accessed in his browser, the browser requests the local DNS to resolve the domain name, and the local DNS sends the request to the primary DNS of the website, and the primary DNS determines according to a series of policies. The most appropriate CDN node at that time, and the result of the parsing (IP address) is sent to the user, and the user requests the content of the corresponding website from the given CDN node.

What is a double line?

Better two-line access does not require the use of two IP addresses.

Network-wide routing or dual-line access is a link-layer technology for network access. It means that the data center room where the server is located has multiple network outlets such as Netcom and Telecom. The network-wide routing technology is set on the upper switch of the equipment room, so that the server can be automatically assigned to the fastest chain every time it connects to the external network. On the road. Thereby, both telecom and Netcom users can simultaneously access at high speed.

But this technology can solve the problem of interconnection when data is output, but the connection from your computer terminal to the server is usually unable to automatically select the link mode, so the speed when you upload data is still Will be affected by network interconnection issues. But usually we only need a very small number of uploads to make a website, and most of them provide the content of the webpage to the viewer for download.

In addition to network-wide routing (two-wire access), CDN technology can also achieve fast access to each network. However, in addition to the slow uploading of CDN technology, the more troublesome is the content caching and synchronization cycle limitation. Yes, your content cannot be released in time, and the user browses for information that is relatively lagging.

Therefore, dual-line access has become the best solution for the current website to solve the interconnection problem.

The two-line computer room is a unique product in such a special network environment. The two-line computer room can only solve the problems of Netcom and telecom access to bottle wells, the link problem in network transmission and other ISP intercommunication problems. Still not solved.

The principle of CDN is edge access, and the accessor takes data nearby, which greatly shortens the transmission distance between the visitor and the source site. It can solve all ISP interworking and network link problems.

Advantages of two-line computer room hosting:

Resolving Netcom and telecom access bottle wells No data synchronization problems Disadvantages of two-line computer room hosting:

Two-line machine room currently on the market The bandwidth is very expensive. The price is much more expensive than the ordinary hosting. Need to do intelligent analysis. The server needs to move. For a powerful enterprise, you can build a two-line computer room yourself, but the investment is too big, and the implementation is more complicated and difficult. It is better to choose CDN.

Advantages of CDN

Simple maintenance, automatic synchronization of website data Resolve all ISP interworking problems, and network link problems Reduce the pressure on the source server Effective anti-DDOS attacks Save backbone resources

Disadvantages of CDN

Implementation Complexity Investment

At present, most CDNs are only accelerating static content, which is not good for dynamic acceleration; Static is the same.

Summary of the difference between CDN and two-line computer room:

CDN covers a wider range, and the two-line computer room only solves the problem of Netcom and Telecom access bottle wells, and can't solve the network one kilometer (from The speed of IDC to the network between the telecommunications bureaus where the users are located;

CDN is a good solution for solving the access speed and quality of large websites, and solving telecom and Netcom access to bottle wells. It is a good choice to solve the problem of accessing bottle wells between Netcom and Telecom.

If you don't want to add any fees and do not change the existing status, it is the best solution to solve the problem of Netcom and telecom access to the bottle well.

Let's talk about the two-line, multi-line server rental hosting landscape.

I. Railcom (Mobile, Unicom): There are many friends who host the server in China Railcom (Mobile, China Unicom)

In fact, putting the server in Railcom is almost a discount for telecom users and Netcom users. In the middle of the method, for example, the server is placed in telecommunications, the telecom user needs 1 second to open the website, and the Netcom user needs 5 seconds. If it is placed in the rail, it may be 3 seconds for both the telecom and the Netcom user. This actually involves the average customer. Tolerance waiting time, for example, the average person tolerate a website open for 4 seconds, then it is a very good solution to be placed in the Railcom, so that telecom users and Netcom users can tolerate. But if the server is used for video teaching, for example, this method is not very good, which will make the access speed of telecom and Netcom users slow. Put it in the rail, the general price is relatively cheap (relative to the real dual-line computer room), if the friends are mainly doing WEB, members are not particularly demanding speed, then you choose Tietong is a good solution.

Second, dual-line dual IP hosting

This situation can be subdivided according to whether there are 2 public network outlets:

1. Have 2 public network outlets : This dual-line dual IP hosting effect is better, but the hosting price is relatively high, and the bandwidth resources are relatively expensive. This kind of computer room resources are very scarce. Currently, there are only two public network outlets in the country. One, because the SARFT does not allow Telecom and China Netcom to engage in dual-line equipment rooms. It feels that this is a big blow to telecom and China Netcom, which is not conducive to the development of telecommunications and Netcom. The only dual-line computer room with public network exit is because of 2000. I have already applied for it, it is not easy to withdraw, and no application has been approved.

2, there is no public network export: such a trustee is generally from the telecommunications strap 100M exclusive fiber, Netcom pull strip 100M exclusive fiber, and then buy some IP, this is almost The most common double-line on the market, and generally such agent technology and equipment are not very close, need to set up dual IP through dual network card, and the computer room with public network exit, equipment and technical strength are not bad, all through a single network card Bind dual IP.

In fact, one of the biggest features of this model is that 100M exclusive fiber is actually 100M connection with the operator's switch (can also be understood as 100M on the metro network), instead of 100M on the public network exit, it is estimated that the 100M exclusive fiber in the general provincial capital can be divided into 20M on the public network exit. This is not bad. According to the overall bandwidth resources of the city, if the city has bandwidth resources. Very loose, it is possible that 100M exclusive on this metropolitan area network can also run very high on the public network exit.

3, has a public network export: In fact, this model of agents do not have their own small computer room, he is doing business through the telecommunications cabinet, and later in Netcom to host a machine, buy a piece of IP, Do a proxy server, after doing this, you can also help customers set up 2 IPs on the server, but the resolution of the Netcom line through the proxy server is slower and the network access speed is slower, so this effect is not very good, friends are choosing Try not to choose such dual line hosting when you are on a dual line.

Three, dual line single IP hosting

1, there is a public network export: such a host has originally had such a good resource, such as Telecom, they have a better effect, and It is a single IP implementation, but such resources are also very scarce. The general custodians can't get such resources. The Zhengzhou Jingan data center where Yunet is located is implemented by BGP technology, but Stability is really disappointing.

2, there is no public network exit: that is, from the telecommunications and Netcom pull the fiber out, the latter through the device to set the route, is also assigned an IP to the user to achieve dual lines, but temporarily on the market I didn't see that the effect was very good, and the reputation was good. It may be because there is no public network export, and there are reasons why the equipment is not advanced enough.

Understand this knowledge, let me talk about how to choose:

Let me talk about the hosting of dual IP. Zhengzhou two-line computer room (technical and environmental facilities are very good, stability is also very good, but can not put SF, bandwidth allocation is also quite sufficient - each machine's bandwidth exclusive 5M, which in the same kind of two-line computer room in the country 59 interconnection Provided is the absolute cost-effective.) If it is a single-line hosting, it is recommended not to choose Shanghai, although Shanghai's computer room environment and all aspects are China's best location. However, the large computer rooms including Zhangjiang, Waigaoqiao and Wusheng are basically full. Shanghai has dragged too many servers, and now in the past, there is not too much bandwidth for you.

In terms of telecommunications, you can choose Changchun Chongqing Guangdong, Jiangxi Telecom Xi'an Telecom, etc. Netcom, you can choose Henan Netcom, Zhengzhou Erchang Netcom, Shanghai Netcom (less bandwidth, high price)

Beijing Local, bandwidth is not enough, and the general price is very high, that is, the technology is good, the stability is good, the anti-attack ability is also very strong, and there is a better anti-attack capability room, basically in Zhengzhou double line, Zhejiang, etc. Land, Shanghai is also good, but the bandwidth is not enough, the firewall is no good and … …

Playing so many words, just hope that the friends who are looking for, can have a good choice &hellip ;… shop around, choose it well