The full name of the CDN is the Content Delivery network, which is the contents distribution networks. The goal is to add a new layer of network architecture to the existing Internet, publish the content of the site to the "Edge" of the network closest to the user, so that users can get the content they need, solve the congestion on the Internet, and increase the responsiveness of users to the site. The problem of the slow response speed of the user visiting website caused by the small network bandwidth, the large number of users, and the uneven distribution of dot is comprehensively solved technically. (that is, the content of a server, the average division to multiple servers, the server intelligent identification, so that users get to the nearest user server, improve speed.)
Introduction to CDN Technology (Content Delivery Network)
CDN Technology is one of the most effective means to solve the problem of Internet performance, which has arisen and developed rapidly in America in recent years. The basic idea is to avoid the internet can affect the speed and stability of data transmission bottlenecks and links, so that content transmission faster and more stable. By placing the node servers in the network, a layer of intelligent virtual network based on the existing Internet, the CDN system can re-direct the user's request to the nearest service node according to the network traffic and the connection of each node, the load condition and the distance and response time of the user.
The role of CDN in fact, the content sub-distribution network (CDN) is a new way of network construction, it is to be able to publish broadband rich media in the traditional IP network, especially optimized network coverage layer, and from a broad perspective, CDN represents a quality and order based network service model. Simply put, the Content Publishing network (CDN) is a strategic deployment of the overall system, including distributed storage, load balancing, network request redirection and Content Management 4 elements, while content management and global network traffic Management (traffic Management) is the core of the CDN. By judging the user's proximity and server load, the CDN ensures that the content serves the user's requests in an extremely efficient manner. In general, the content service is based on a cache server, also known as the proxy cache (surrogate), which 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's source server, which is typically located in the CDN service provider's Datacenter. Such architectures enable CDN service providers to provide the best possible experience to end users on behalf of their customers, content providers, who cannot tolerate any delay in request response time. According to statistics, the use of CDN technology, can handle the entire Site page 70%~95% content access, reduce the pressure on the server, improve the performance and scalability of the site.
Compared with the current content publishing model, CDN emphasizes the importance of the network in content publishing. By introducing the active Content management layer and global load balancing, the CDN is fundamentally different from the traditional content publishing model. In the traditional content publishing model, the publishing of content is done by the application server of the ICP, and the network only
CDN Principle
Performance as a transparent data transmission channel, this transparency in the network quality assurance only stay at the level of the packet, but not according to the different content objects differentiated service quality. In addition, because of the "best effort" nature of the IP network, its quality assurance relies on the end-to-end provision of sufficient bandwidth flux between the user and the application server, which is much larger than the actual requirement. In such a content publishing mode, not only a large number of valuable backbone bandwidth is occupied, but also the application server of the ICP load is very heavy, and not predictable. When there are some hot events and surge flow, there is a local hotspot effect, which causes the application server to overload and exit the service. Another drawback of this hub-centric application server's content publishing model is the lack of personalized services and the distortions in the value chain of broadband services, which content providers assume they should not do or do poorly in content publishing services.
Throughout the value chain of broadband services, content providers and users are located at both ends of the entire value chain, relying on network service providers to connect them together. With the maturity of the Internet industry and the transformation of business model, the role of this value chain is more and more subdivided. such as content/application operators, managed service providers, backbone network service providers, access service providers, and so on. Each role in this value chain has to be a division of labor to provide customers with good service, resulting in a multi-win situation. From the combination of content and network mode, the release of content has gone through the content of ICP (application) server and IDC two phases. The boom in IDC also spawned the role of managed service providers. However, IDC does not address the issue of effective publishing of content. Content located in the center of the network does not solve the backbone bandwidth consumption and establish the traffic order on the IP network. As a result, the content is pushed to the edge of the network, providing a near edge service to the user, thus guaranteeing the quality of the service and the order of access throughout the network becomes an obvious choice. And this is the Content publishing network (CDN) service model. The establishment of CDN solves the dilemma of "centralization and decentralization" of content operators, which is undoubtedly valuable for building a good Internet value chain, and is also an indispensable and optimal website accelerator service.
CDN Concept + function + features + principle
