Today, you will walk into the mysterious world of content distribution networks and explore the secrets. The so-called CDN is the content distribution network, the full name is ContentDeliveryNetwork. The basic idea is to avoid the bottlenecks and links on the Internet that may affect the speed and stability of data transmission, so that the content transmission is faster and more stable. By placing a layer of intelligent virtual network based on the existing Internet on the network, the CDN system can real-time based on network traffic and connection, load status, and distance and response time to users. The integrated information redirects the user's request to the service node closest to the user. The purpose is to enable users to obtain the required content in the vicinity, solve the congestion of the Internet network, and improve the response speed of users visiting the website. The Content Distribution Network (CDN) is a new type of network construction that is specifically optimized for the release of broadband rich media over traditional IP networks. From a broad perspective, CDN represents a quality and order. Network service model. Simply put, the Content Distribution Network (CDN) is a strategically deployed overall system that includes distributed storage, load balancing, network request redirection and content management, and content management and global network traffic management ( TrafficManagement) is at the heart of the CDN. Through the judgment of user proximity and server load, the CDN ensures that the content serves the user's request in an extremely efficient manner. In general, the content service is based on a cache server, also known as a proxy cache (Surrogate), which is located at the edge of the network and is only a "single" 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). Such an architecture enables CDN service providers to provide end users with the best possible experience on behalf of their customers, content providers, who are intolerant of any delay in request response times. Application comparison cdn application Firstly, the traditional dynamic system access method is simply described: As shown in the right diagram (1), the user's request process is expressed. The user transmits the route A and B through the network, and finally sends the request to the network. Dynamic system to deal with, but due to the "best effort principle" of the IP network itself, the complex environment in the network link and the unreliability of the hardware do exist, causing the user to have the status of repeated requests, so eventually The phenomenon that the user's request appears in the process of submission and the data loading time is too long. The slowness of these online submission systems directly affects the work efficiency of the office staff, which also restricts the cooperation of many large enterprises. In the construction of information technology such as OA, ERP, and SAP, the most problems arise. The CDN distribution solution addresses the performance and reliability issues associated with static websites, and in today's online business experience, the unique challenges associated with distributing static and dynamic elements and applications are accelerated by Dynamic Web's dynamic website (dynamic website) Accelerate) to solve. Main features 1. Local Cache acceleration improves the access speed of enterprise sites (especially including a large number of pictures and static page sites), and greatly improves the stability of sites of the above nature. 2. Image services eliminate the bottleneck caused by interconnection between different operators. Impact, realizes network acceleration across operators, and ensures that users in different networks can get good access quality. 3, remote acceleration remote access users according to DNS load balancing technology intelligent automatic selection of Cache server, select the fastest Cache server, speed up the speed of remote access 4, bandwidth optimization automatically generate the server's remote Mirror (mirror) cache server, remote user access Read data from the cache server, reduce the bandwidth of remote access, share network traffic, and reduce the load on the original site WEB server. 5, the cluster anti-attack widely distributed CDN nodes plus 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 better service quality. Key technologies (1) Content distribution: It publishes or delivers content to the nearest remote service point (POP) by means of indexing, caching, stream splitting, multicast, etc. (2) Content routing : It is a holistic network load balancing technology that balances user requests on multiple remote POPs through a redirection (DNS) mechanism in the content router to enable users to request responses from recent content sources; (3) Content exchange It intelligently balances load traffic on the POP cache server, using application layer switching, stream splitting, redirection (ICP, WCCP), etc. based on content availability, server availability, and user context; (4) Performance Management: It obtains the status information of network components through internal and external monitoring systems, and measures the end-to-end performance of content distribution (such as packet loss, delay, average bandwidth, startup time, frame rate, etc.) to ensure that the network is optimal. Operating status. Product Advantages CDN can cover almost all domestic routes. In terms of reliability, the CDN achieves multiple points of redundancy in the structure. Even if a node fails due to an accident, the access to the website can be automatically directed to other healthy nodes to respond. CDN can easily realize the nationwide laying of the website, regardless of the server's investment and hosting, without having to consider the cost of adding new bandwidth, not having to consider the mirror synchronization of multiple servers, and not having to consider more management and maintenance technicians. In the early days, China's CDN market developed slowly. After 2006, the market suddenly heated up. The more famous CDN service providers in China have Spiral [1], Lancome, etc., but the overall CDN market size, operational maturity, service capability and technology research and development are relatively high. There is a certain gap in foreign countries. At present, we have the following types of CDN service providers: CDN service providers advantage disadvantages Professional CDN service providers focus on core business development, easy to expand business scale into the [2] market earlier, with mature operating mechanisms and higher service capabilities. Subject to the bandwidth lease fee of telecom operators, the bandwidth cost is rigid and cannot form a price advantage. Due to the inflexibility of the telecom operator's operation support system, the bandwidth tariff setting is not flexible and cannot be requested on demand. As a result, the price of the CDN is high. The IDC operator providing the CDN service has the advantage of bandwidth resources. It is easier to enter the market and need to add a large number of servers. , network equipment and storage equipment, high investment costs of telecom operators, 1. Has huge bandwidth and network advantages, its bandwidth cost is flexible, can be configured with the best CDN service network capital is strong, have the strength to build a large CDN network With brand advantages and close relationship with many Internet companies, it can guide Internet companies to use CDN services. 2. The dedicated CDN network such as streaming media has been upgraded and modified on this basis, and various CDN services can be quickly launched. 1. The CDN industry is a technology-driven industry, and the CDN technology reserves of telecom operators are weak. 2. Interconnection problems cause operators to only do CDN services on their own networks. The problem of cross-network operation is difficult to solve. 3. CDN is not the main business of telecom operators, and lacks operational experience and service capabilities. Self-built CDN mutual cost savings, high controllability 2. Free from CDN market price fluctuations, conducive to cost reduction 1. Initial investment is large, and increase operating and R&D costs 2. Non-core business, easy to disperse The energy of the main business 3. The number of nodes is small, can not fully meet the needs of foreign CDN service providers 1. Strong capital, with technical, operational and service strength, is conducive to business development. 2. Start building nodes in China, which is conducive to market development. 1. It is difficult to carry out its own services by means of agency cooperation with some IDCs and ISPs in China. It is difficult to carry out business on a large scale. 2. Unconventional competition, there are security risks, and the domain name resolution right is controlled in the hands of foreign operators. Free self-service CDN1. CDN products are provided free of charge and focus on one-stop solutions to website operation and maintenance technology. 2. Self-service CDN solution, easy to use, complete monitoring and analysis functions.