Today's CDN website Acceleration Technology, the CDN

Source: Internet
Author: User

The application of CDN technology is more and more widely used by major internet companies. has become an Internet enterprise inseparable from a network operation and maintenance mode. What is a CDN?

CDN leverages global load balancing technology to direct users ' access to the most recently working streaming media server, which is directly responsive to user requests by the streaming media server. If there is no content that the user wants to access in the server, the corresponding content is automatically fetched from the original server and provided to the user according to the configuration. IPTV can make use of CDN to provide VOD service to users, and through CDN distributing the video content to the Cdn node near the client, it can guarantee the end-to-end service quality to some extent.

Load Balancing

Load balancing technology is not only used in CDN , but has been widely used in many areas of the network, such as server load balancing and network traffic load balancing. As the name implies, the load balance in the network is to distribute the network traffic as evenly as possible to several servers or network nodes that can accomplish the same task, thus avoiding the overloading of some network nodes. This can improve the network traffic, but also improve the overall performance of the network. In a CDN , load balancing is divided into server load balancing and server overall load balancing (also known as server Global load balancing). Server load balancing is the ability to assign tasks between servers with different performance, which can ensure that the servers with poor performance are not the bottleneck of the system, and that the resources of high performance servers can be fully utilized. Server-wide load Balancing allows Web network hosts, portals, and businesses to distribute content and services based on geographic location. Improve fault tolerance and availability by using multi-site content and services to prevent failures due to outages, power outages, or natural disasters in local or regional networks. In the CDN Scheme, the server overall load balance will play an important role, its performance will directly affect the performance of the whole CDN .

As we all know, the speed of Web site access response depends on many factors, such as whether the bandwidth of the network has bottlenecks, whether the route in transit is blocked and delayed, the processing power and access distance of the Web server. In most cases, the responsiveness of the website and the distance between the visitor and the Web server are closely related. If the distance between the visitor and the website is too far, the communication between them needs to pass through the heavy route forwarding and processing, the network delay inevitably. One effective way is to use content distribution and replication technology to replicate most of the static Web pages, images, and streaming data distributed by the main body of the site to accelerating nodes everywhere. Therefore, dynamic content distribution and replication technology is also a major technology required by the Blue Flood CDN .

Caching technology

Caching technology is no longer a fresh technology. The Web caching service improves user response times in several ways, such as the proxy cache service, the transparent proxy cache service, the transparent proxy caching service using the redirection service, and so on. The Web caching service allows users to minimize the WAN traffic when they visit a Web page. For corporate intranet users, this means caching content locally without having to retrieve the page through a dedicated WAN. For Internet users, this means storing content in their ISP's cache without having to retrieve Web pages over the Internet. This will undoubtedly increase the user's access speed. The core role of the Blue flood CDN is to improve the speed of network access, so the caching technology will be another major technology used by the blue flood CDN .

The main technical means to realize CDN is cache, mirror server. Can work in DNS resolution or HTTP redirection two ways, through the cache server, or offsite mirror site to complete the transfer of content and synchronization updates. DNS mode The accuracy rate of the user location is greater than the accuracy of 85%,http method is more than 99%; In general, users of each cache server farm have a ratio of 2:1 to 3:1 of the amount of data accessed from the cache server to the original site, which is 50% to 70% The amount of data that is repeated to the original web site, and for mirroring, the rest of the traffic, except for data synchronization, is done locally without accessing the original server. [1]

The mirrored site (Mirror site) server is something that we can often see, which allows content to be distributed in a straightforward way, for both static and quasi-Dynamic Data synchronization. However, the cost of purchasing and maintaining a new server is high, and a mirror server must be set up in each region with professional technicians for management and maintenance. Large Web sites at any time to update the server at the same time, the demand for bandwidth will also increase significantly, so the general Internet companies will not establish too many mirror servers.

Caching means lower cost and is suitable for static content. Internet statistics show that more than 80% of users often visit the content of 20% of the site, under this rule, the cache server can handle the majority of customer static requests, and the original WWW server only need to process about 20% of non-cached requests and dynamic requests, This greatly accelerates the response time of customer requests and reduces the load on the original WWW server. As an important indicator of the CDN , the cache market is growing at a rate of nearly 100% a year and global turnover will reach $4.5 billion in 2004, according to IDC, a US survey. The development of network streaming media will stimulate the demand of this market.

CDN Network Architecture mainly consists of two parts, the center and the Edge, the center refers to the CDN Management Center and DNS Redirection resolution Center, responsible for global load balancing, equipment system installed in the management center of the computer room, edge mainly refers to the remote node,CDN the distribution of the carrier, mainly by the cache and load balancer, and other components.

When a user accesses a website that joins a CDN service, the domain name resolution request is eventually handed over to the global load Balancer DNS for processing. Global load Balancing DNS uses a predefined set of policies to provide the user with a node address that is closest to the user, enabling users to get a quick service. At the same time, it maintains communication with all CDNC nodes distributed around the world, collects the communication state of each node, ensures that the user's request is not assigned to the unavailable CDN node, and actually does global load balancing through DNS.

For ordinary Internet users, each CDN node is the equivalent of a web that is placed around it. With global load balancing DNS control, the user's request is transparently directed to the node closest to him, and the CDN Server in the node responds to the user's request as if it were the site's original server. Because it is closer to the user, the response time must be faster.

Each CDN node consists of two parts: a load balancer device and a cache server

Load balancer is responsible for the load balancing of each cache in each node, which ensures the efficiency of the nodes, and the load balancing device is responsible for collecting the information of the nodes and the surrounding environment, maintaining the communication with the global load DNS, and realizing the load balance of the whole system.

The cache server (cache) is responsible for storing a large amount of information about a customer's website, responding to a local user's access request as if it were a Web server close to the user.

The management system of CDN is the guarantee that the whole system can operate normally. It can not only monitor the subsystems and equipment in real time, but also produce corresponding alarms for various faults, and can monitor the total traffic and the traffic of each node in real-time, and keep in the database of the system, so that the network manager can make further analysis conveniently. Through the perfect network management system, the user can modify the system configuration.

Theoretically, the simplest CDN Network has a DNS that is responsible for global load balancing and one cache for each node to run. DNS supports resolving different IPs according to the user source IP address to achieve the nearest access. To ensure high availability, it is necessary to monitor the traffic, health status, etc. of each node. A node of a single cache bearer is not enough, only need more than one cache, more than one cache at the same time, only need a load balancer, so that the cache group work together. Welcome to join us to explore CDN q:27874381

Today's CDN website Acceleration Technology, the CDN

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