CDN Content Distribution Network

The full name of the CDN is the Content Delivery network, which is the contents distribution networks. The basic idea is to avoid the bottleneck and link of the Internet which may affect the speed and stability of data transmission, and make the 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 goal is to enable users to get the content they need, solve the congestion of Internet networks, and improve the responsiveness of users to websites.

First, the service model

Content distribution Network (CDN) is a new way of network construction, it is a network covering layer which can be specially optimized for releasing rich media in traditional IP network, and CDN represents a network service model based on quality and order in a broad sense.

Simply put, content distribution network (CDN) is a strategic deployment of the overall system, including distributed storage, load balancing, network request redirection and Content Management 4 elements, and 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.

Second, the main features

1, local cache acceleration to improve the enterprise site (especially with a large number of images and static page site) access speed, and greatly improve the stability of the above properties of the site

2, the mirror service eliminates the bottleneck caused by the interconnection between different carriers, realizes the network acceleration of the cross-carriers, and ensures that the users in different networks can get good access quality.

3, Remote acceleration remote access users based on DNS load Balancing Technology Intelligent Automatic Selection cache server, select the fastest cache server, speed up remote access

4, bandwidth optimization automatically generate server remote mirror (mirror) cache server, remote user access from the cache server to read data, reduce the bandwidth of remote access, share network traffic, reduce the original site Web server load and other functions.

5, cluster anti-attack widely distributed CDN node plus the intelligent redundancy mechanism between nodes, can effectively prevent hacking and reduce the impact of various D.D.O.S attacks on the website, while ensuring a better quality of service.

Three, the key technology

(1) Content Publishing: It uses the technology of indexing, cache, stream splitting, multicast (multicast) to publish or post the content to the remote service point (POP) nearest to the user;

(2) Content routing: It is the overall Network Load balancing technology, through the content router redirection (DNS) mechanism, on multiple remote POPs to balance the user's request, so that the user request to get the latest content source response;

(3) Content Exchange: It based on the availability of content, server availability and user background, on the pop cache server, the use of application layer switching, flow splitting, redirection (ICP, WCCP) and other technologies to intelligently balance the load flow;

(4) Performance management: It obtains the status information of the network parts through the internal and external monitoring system, and measures the end-to-end performance of the content release (such as packet loss, delay, average bandwidth, startup time, frame rate, etc.) to ensure that the network is in the best running state.

Iv. Advantages

CDN can cover almost all domestic lines. In the case of reliability, the CDN realizes multi-point redundancy in structure, even if one node fails unexpectedly, the access to the website can be automatically directed to other healthy nodes to respond. CDN can easily implement the national installation of the site, regardless of the server's input and hosting, do not have to consider the cost of new bandwidth, do not have to consider multiple server mirroring synchronization, do not have to consider more management and maintenance technicians.

This article is for the personal study record, the content reference Baidu encyclopedia.

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CDN Content Distribution Network