CDN acceleration in China

Source: Internet
Author: User
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What is CDN

CDN stands for content delivery network (CDN. Is a network application located between the network layer and the application layer. The purpose is to add a new network architecture to the existing Internet, publish the website content to the "edge" closest to the user's network, so that the user can obtain the desired content nearby, solve the internet congestion, and improve the response speed of users accessing the website. It comprehensively solves the problem of slow response speed caused by large user visits and unevenly distributed outlets.

Content Delivery Network (CDN) is an overall system that is strategically deployed, including four requirements: distributed storage, Server Load balancer, network request redirection, and content management, content management and global network traffic management are the core of CDN. Based on users' proximity and server load judgment, CDN ensures that the content provides services for users' requests in an extremely efficient manner.

In general, the content service is based on a cache server, also known as a proxy cache (surrogate). It is located at the edge of the network and is only "One hop" away from the user. At the same time, the proxy cache is a transparent image of the content provider source server (usually located in the data center of the CDN service provider. This architecture enables CDN service providers to provide end users with the best possible experience on behalf of their customers, that is, content providers. These users cannot tolerate any latency in request response time. According to statistics, CDN technology can be used to process 70%-of the entire website page ~ 95% of content access Traffic reduces the load on the server and improves the performance and scalability of the website.

Compared with the existing content publishing mode, CDN emphasizes the importance of the network in content publishing. By introducing active content management and global load balancing, CDN is fundamentally different from the traditional content publishing mode. In the traditional content publishing mode, content publishing is completed by the ICP application server, and the network only shows as a transparent data transmission channel, this transparency is manifested in the quality assurance of the network, which only stays at the layer of data packets, but cannot distinguish the quality of service based on different content objects. In addition, because of the "Best Effort" feature of the IP network, the quality assurance is achieved by providing sufficient end-to-end bandwidth between the user and the application server, far greater than the actual needs. In this content publishing mode, not only is a large amount of valuable backbone bandwidth occupied, but the load of the ICP application server also becomes very heavy and unpredictable. In the event of some hot events and traffic waves, local hot spots will occur, so that the application server is overloaded and leaves the server. Another drawback of this center-based app server's content publishing model is the lack of personalized services and the distortion of the broadband service value chain, the content provider undertakes the content distribution service that they should not do or do not do well.

Throughout the value chain of broadband services, content providers and users are located at both ends of the entire value chain, and network service providers are used in the middle to connect them. With the maturity of the Internet industry and the transformation of business models, more and more roles in this value chain are becoming increasingly subdivided. Such as content/Application operators, managed service providers, backbone network service providers, and access service providers. In this value chain, each role must work in a division of labor and perform their respective duties to provide good services to customers, resulting in a win-win situation. From the perspective of the combination of content and network, content publishing has gone through two stages: content (Application) server and IDC. The IDC boom also gave birth to the role of hosting service providers. However, IDC cannot solve the issue of effective content publishing. The content in the center of the network does not address the occupation of backbone bandwidth and the traffic order on the IP network. Therefore, pushing content to the edge of the network to provide nearby edge services for users, thus ensuring the service quality and the access order on the entire network becomes an obvious choice. This is the CDN service mode. The establishment of CDN solves the dilemma of "centralization and decentralization" for content operators, which is undoubtedly valuable for building a good Internet value chain and an indispensable optimal website acceleration service.

Technical Principles of CDN

After describing the implementation principle of CDN, Let's first look at the access process of the traditional cache service, so that we can understand the differences between the CDN cache access method and the cache access method:


As you can see, the process for users to access websites that are not cached using CDN is as follows:

1) The user provides the domain name to be accessed to the browser;

2) the browser calls the domain name resolution function library to parse the domain name to obtain the IP address corresponding to this domain name.

3) the browser uses the obtained IP address, and the service host of the domain name sends a data access request.

4) the browser displays the webpage content based on the data returned by the domain name host.

Through the above four steps, the browser completes the whole process from receiving the domain name accessed by the user to obtaining data from the domain name service host. The CDN network adds a cache layer between the user and the server. How to direct users' requests to the cache to obtain data from the source server is mainly achieved by taking over DNS, let's take a look at the process of accessing the website cached by CDN:


We can see that the website access process after CDN cache is changed

1) The user provides the domain name to be accessed to the browser;

2) the browser calls the domain name resolution library to resolve the domain name. Because CDN has adjusted the domain name resolution process, the parsing function library generally obtains the cname record corresponding to the domain name, to obtain the actual IP address, the browser needs to resolve the obtained cname domain name again to obtain the actual IP address. In this process, the Global Server Load balancer DNS resolution is used, for example, you can resolve the corresponding IP address based on the geographic location information so that the user can access the nearest address.

3) the IP address of the CDN Cache Server is obtained through this resolution. After obtaining the actual IP address, the browser sends an access request to the cache server;

4) The Cache Server obtains the actual IP address of the domain name based on the domain name to be accessed provided by the browser through private DNS resolution within the cache, and then submits access requests to the actual IP Address by the cache server;

5) after obtaining the content from the actual IP address, the Cache Server saves the content locally for future use, and returns the obtained data to the client to complete the data service process;

6) after the client obtains the data returned by the cache server, the client displays the data and completes the browsing data request process. Through the above analysis, we can see that in order to achieve transparency to normal users (that is, after the cache is added, the user client does not need to make any settings, and can directly access the original Domain Name of the accelerated website ), in addition, when providing acceleration services for a specified website and reducing the impact on ICP, you only need to modify the domain name resolution Section during the entire access process to achieve transparent acceleration service, the following describes how to implement the CDN network.

1) As an ICP, you only need to give the domain name Interpretation Right to the CDN operator, and do not need to make any changes to other aspects. During the operation, the ICP modifies the resolution record of your domain name, generally, cname is used to point to the address of the CDN network cache server.

2) as a CDN carrier, you must first provide public resolution for the ICP domain name. To achieve sortlist, the ICP domain name interpretation result is generally directed to a cname record;

3) When sorlist is required, the CDN operator can use DNS to perform special processing on the domain name resolution Process pointed to by cname, so that the DNS server can receive client requests according to the Client IP address, returns different IP addresses of the same domain name;

4) because the IP address obtained from cname carries the Hostname Information, after the request arrives at the cache, the cache must know the IP address of the source server. Therefore, the CDN operator maintains an internal DNS server, it is used to explain the real IP address of the domain name accessed by the user;

5) when maintaining the internal DNS server, you also need to maintain an authorization server to control which domain names can be cached and which do not, so as to avoid opening the proxy.

CDN applications

The current CDN service is mainly used in securities, financial insurance, ISP, ICP, online trading, portal websites, large and medium-sized companies, network teaching and other fields. In addition, it can be used in industry private networks, the internet, or even LAN optimization. Using CDN, these websites do not need to invest in expensive servers, set up sub-sites, especially the wide application of streaming media information, remote teaching courseware, and other media information that consumes a lot of bandwidth resources, and use CDN networks, copying content to the edge of the network minimizes the distance between the content request point and the delivery point, thus promoting the improvement of the web site performance. CDN networks are mainly built by enterprises to serve enterprises. CDN networks of IDCs are mainly used for IDCs and value-added services. CDN networks built on network operations are mainly used for CDN networks, it mainly provides content push services. CDN network service providers and specially constructed CDN are used for services. Users cooperate with CDN institutions to transfer information and ensure normal information transmission, the website only needs content maintenance and does not need to consider traffic issues.

CDN can guarantee the speed, security, stability, and scalability of the network.

IDC establishes a CDN network. IDC operators generally need to have multiple IDCs distributed across different regions. The service targets customers hosted in IDCs. using existing network resources, there is less investment, easy to build. For example, an IDC has 10 data centers in China. It is added to the CDN network of the IDC and is hosted on a Web server on a node. The equivalent is that it has 10 backup servers, which are accessible to customers nearby. Broadband man, the speed of the intra-domain network is very fast, and the out-of-town bandwidth is generally a bottleneck. To reflect the high-speed experience of the man, the solution is to cache the content on the Internet to a local device at a high speed, deploy the cache on various pop points in the Metropolitan Area Network to form an efficient and orderly network. Users can access most of the content in one hop. This is also an application to accelerate CDN for all websites.

Status quo in China

In fact, the CDN penetration rate in China is still very low, that is, the use of large portal websites and large e-commerce websites. Generally, the usage of Small and Medium-sized websites is very low, and the CDN usage in China is one thousandth off. Almost all of the websites we know in the United States that can be named are using CDN. Compared with the vast domestic network ocean, there are only a few websites using chinacache CDN. This is in great contrast to foreign situations. For example, South Korea's CDN only has eight nodes, but these eight nodes can support about GB of traffic.

Although many Chinese companies are providing CDN services, the current position of CDN in the domestic Internet industry is still not as high as that in the United States.

CDN problems with dynamic page Acceleration

At present, CDN has solved the problem of dynamic page acceleration in China. They are far more than some other colleagues in this field, and look at how chinacache solves this problem.

Dynamic Web pages are web pages written in PHP, ASP,, and other web script languages. When a user accesses a website, the server calls the background database to generate real-time web pages. There are some basic frameworks on the website, and most of the webpage content is stored in the database. There is a lot of interaction between users and sites. websites are not just content publishing, but an application )". Chinacache dynamic web page acceleration is an acceleration service designed specifically for dynamic web page content based on database technology, chinacache uses the smart channel technology to establish a dedicated high-speed channel between users and ICP origin sites to bypass the congestion nodes on the Internet, it also integrates a variety of advanced web page acceleration technologies, such as network transmission optimization (parallel TCP optimization), to greatly reduce the latency of users accessing dynamic web pages. Chinacache Dynamic Content Acceleration system also includes professional service subsystems such as the network management center, billing center, and log processing center to ensure high-quality online monitoring and management for websites.

There are just a few families who are happy with each other. There are only a few domestic cdns that have done a lot of success. First, let's talk about what has been done successfully and see where the secrets of their success in CDN are?

Chinacache is the earliest professional CDN service company in China. After more than six years of development, significant advantages have been established in terms of technological maturity, customer service capabilities, industrial applications, and operation experience. Chinacache has accumulated a wealth of CDN operation experience, which can effectively combine the CDN service with the varied website content of the customer to provide the most suitable Acceleration Solution for the customer. At the same time, we also have strong differentiated service capabilities, which can provide corresponding solutions to different customer needs, so that more customers can enjoy the CDN-enabled website acceleration experience.

Comprehensive network coverage: chinacache has the widest coverage in China and the longest commercial use of the CDN network. Currently, it has nearly 350 nodes in more than 80 major cities nationwide, and the network processing capability reaches 400 Gbps, its CDN network covers China Telecom, China Netcom, China Mobile, China Unicom, China Education and Scientific Research Network, China tietong, and other major operators, this ensures that users in different regions and networks can enjoy excellent access quality.

Comprehensive Redundancy mechanism: provides complete redundancy at the device, node, and network levels to ensure that normal user access is not affected when a device or node fails.

Powerful security protection mechanism: a complete security mechanism in system design can effectively prevent hacker intrusion and reduce various D. d. o. s attack impact on the website, while ensuring good service quality.

Simpler content management: unlike traditional image services, the system is managed by using the content management technology independently developed by chinacache. Websites can conveniently manage content published to the CDN network, ensure that the content you see is completely synchronized with the content on the website source server.

More professional services: chinacache has a complete CDN service process, from requirement analysis, acceleration recommendations, performance testing, project implementation, to customer service, there are complete and professional processes; chinacache's self-developed professional customer service system allows website customers to use browsers to query various statistical data in real time, including the CDN service bandwidth used by the website and the page view accessed by users; chinacache has a dedicated customer service department to provide various technical support to customers at any time. It can provide various services such as statistical analysis data, service evaluation reports, and website optimization suggestions based on customer requirements, make the customer feel considerate and considerate.

Chinanetcenter Technology

With a strong R & D team and technical strength, chinanetcenter has successfully developed a data center management platform and CDN technical platform, streaming media distribution acceleration platform, high-speed download platform, and express connect VPN management platform, among which express connect VPN management platform is recognized as the "National High-tech achievement conversion project ".

Chinanetcenter is located in China's five major carriers (China Telecom, China Netcom, China tietong, China Mobile, China Unicom) and two junior colleges (China Education and Scientific Research computer network, China Science and Technology Network) the CDN edge distribution and storage nodes that are covered by the municipalities directly under the central government and autonomous region have been reasonably deployed, making full use of Bandwidth Resources and Balancing large network traffic.

Chinanetcenter (cdnoc) monitors and manages the network link status of CDN nodes, node equipment running status, customer Website access effect, customer website service response, and customer source site network status in real time around the clock, this effectively guarantees the operation quality of the CDN platform and fulfills the cdnsla commitment standards.

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