CDN and DNS

Original address: http://www.cnblogs.com/xitang/p/3575255.html

Believe that a lot of friends will be some of these nouns around some of the head, many friends think that smart DNS with two-line acceleration, CDN acceleration is similar technology. In fact, although their purpose is one: to allow users to access the site faster. But the principles of their application are vastly different.
It must be clear to everyone that these are more common ways to host acceleration. So the text mainly introduces "Intelligent DNS resolution", "CDN Acceleration Technology", "two-line host acceleration" Basic acceleration principle, when you understand these can find a more suitable for your host in the acceleration mode.

First, what is the two-line acceleration

Two-wire acceleration comparison is commonly used is "dual-line dual-IP" and "dual-line single-IP", "BGP dual-line single IP"

• Dual-line dual IP.
  Dual IP dual-line implementation means that a server installed two network cards, respectively, access to the telecom network cable and Netcom network cable and set up a netcom IP and a telecommunications IP, so that a server has two IP addresses (that is, the domain name resolution to which IP can be accessed), It is necessary to add the routing table of Netcom or telecom to the server to realize the access of Netcom users and telecom users from different lines respectively.
  Two-wire dual-IP comparison is commonly used in both modes:
  1. Use two different domain names to resolve to the two IP, on the site to put a different connection, Netcom users click to access the line of Netcom, telecom users click to access the line of telecommunications. (Smart DNS is not widely used before it is a more common way).
  2. Intelligent DNS, so-called intelligence is not required by the user to judge, but to the domain name resolution server. Intelligent judgment of the user's line, if the telecommunications users to resolve to the telecommunications IP, Netcom users to resolve to the Netcom IP.
• Dual Line single IP.
  As the name implies, two lines an IP address. A server is configured with a network card IP address, this IP is a network IP or telecommunications IP, through the routing device set up the packet is through the telecommunications networks or Netcom network issued to achieve the dual-line technology. This scheme can also improve the access speed of Netcom users and telecom users, and solve the problem that dual IP dual-line needs to set up routing on the server, but because the IP address uses the IP of Netcom or telecom, the access user will not automatically discriminate the best route when sending the request packet.
• BGP Dual Line single IP.
  BGP (Bordergatewayprotocol) Border Gateway protocol. The specific function of BGP is to control the propagation of routes and choose the best route. This two-line implementation must be IDC room operators and telecommunications, Netcom can reach a cooperative agreement, through the backbone of the network router to give the best route choice, all, for the server and users have no burden. The server requires only a single IP and works best. But how can such cooperation negotiations be so easy. So the current BGP-based solution is basically for an absolute high-end user.

Second, what is intelligent DNS

See the above two-line dual-IP concept, you should be aware of the smart DNS for who prepared it! Yes, in order not to waste dual-line dual-IP, in order to better user experience, to access the user intelligent line judgment, so that the telecommunications users on the high-speed telecommunications, so that netcom users on the high-speed netcom. Recommended service provider for free smart DNS--dnspod

Third, what is CDN acceleration

CDN Acceleration = Smart dns+ Multi-server

As the above formula, CDN is a combination of multiple servers plus intelligent DNS. CDN Service, in fact, is to cache the static page to a number of special cache servers in different regions, and then according to the region of the user route through the CND service provider's intelligent DNS automatically select a recent cache server to let users access to improve speed, this scheme for static page effect is very good, It also requires the help of intelligent DNS to enable users to boot to their nearest cache server. A good CND service provider must have good intelligent DNS to do the groundwork.

Advantages: Local cache acceleration, mirroring acceleration, remote acceleration, bandwidth optimization, cluster anti-attack.

CDN acceleration is also different from mirroring technology. Look at the formula: cdn= more intelligent mirror + cache + traffic diversion. (A burst of material, Assange's "WikiLeaks" site in the limelight, make more than 1000 mirror sites, there is a picture of the truth)

Comparison of various acceleration modes: (Two-wire dual-IP vs. dual-line single-IP comparison for reference only)

To sum up, the above various two-line implementation of the way each has advantages and disadvantages, intelligent dns+ Dual-line dual IP cost is low, but the network is not stable and occupies a large number of server resources, ordinary two-line single IP only realize the effect of partial dual-line, so the access speed is not good, CDN Way to static Web page effect is very good, but the interactivity is very strong web page effect is not ideal, BGP single IP dual-line solves all of the above problems is the best way to implement but the domestic use of such a scheme of IDC service providers less, if you can combine BGP single IP dual-line and CDN acceleration will be the best solution. At present, there are many data centers with BGP technology solutions, but most of them serve special customers, and there are few rooms for ordinary users and IDC vendors.

CDN and DNS