DNS Literacy Series III: About Smart DNS (Bind+view)

Intelligent DNS is the function realization of bind+view. At home, the first smart DNS into the market is a I (how to give people not humble feeling it). I think bind9.x introduced view (view) function is not for China, but this function just can solve the interconnection between network operators in China, is the pie in the sky. This article unifies oneself these several years to erect maintains the intelligence DNS the experience to write some things casually, hoped to have the help to everybody.     The time is short and the knowledge is limited, inevitably the mistake place, everybody discusses together. The premise of Intelligent DNS: The use of intelligent DNS has a premise that all network operators have their own public network DNS for their users to provide domain name resolution services. If this is not the case, then there is no need for intelligent DNS to exist (the reason is discussed below).   Fortunately, the current situation is basically satisfied with this condition, netcom, telecommunications, education network, etc. are self-contained system. The function of Intelligent DNS: the most basic function of intelligent DNS is to intelligently judge the users who visit your website, and then resolve your domain name (domain name record) to different addresses according to different visitors. If the visitors are Netcom users, smart DNS server will be your domain name corresponding to the Netcom IP address resolution to this visitor. If the user is a telecommunications user, the smart DNS server will resolve the IP address of your domain name to the caller. From this we can let netcom, telecommunications, education network, mobile, foreign users intelligent choice to visit your server. The principle of Intelligent DNS: take abc.com domain name for example. When the user accesses the WWW.ABC.COM, the process is shown in the figure. This omits the details that are irrelevant to the discussion in this article, with the aim of simplifying the complexity.

1. Netcom users to the local DNS request resolution WWW.ABC.COM. 2. Local DNS to abc.com authoritative DNS (authoritative DNS Here must be smart DNS). 3. Smart DNS matches the IP address of the requester (this is local DNS) in its own ACL, and then returns the matching result to the local DNS. 4. Local DNS tells the user the results and caches the results. 5. The user accesses the website server on the Netcom line.
Smart DNS is a special concern: there are several important issues that deserve to be listed separately, otherwise you'll be surprised to see it in the process of using smart DNS. 1. Smart DNS determines the source of a user based on "local DNS" rather than the user's own IP address. 2. Extended from the above, if the telecommunications users use the Netcom DNS, through the smart DNS will be matched to the results of the analysis of Netcom. 3. Local DNS typically does not resolve to intelligent DNS requests personally, as determined by the network topology of local DNS, see another Post "Literacy series: About public network DNS" http://www.2cto.com/net/201210/161839.html
The problem facing smart DNS: 1. Each network operator's IP address collection difficulty, has it is like "the Great Wall Broadband", "the wide grid" and so on small operators their user uses DNS multifarious, is not suitable to use the intelligent DNS at all. Therefore, smart DNS is not the division of the operator the finer the better. In short, the ability to combine their own is good. 2. Each major network operators of mutual infiltration of the situation (fortunately is a phenomenon, but to attract attention), such as Guangdong Telecom's public network DNS background There are an unknown number of servers set up to Netcom's line. This result is clearly using the telecommunications DNS, but sometimes the results of the analysis to the Netcom. 3. The well-known cyber attacks have fallen to DNS more and more, this thing is very helpless. Finally, the installation of smart DNS technology details here is not discussed, I believe it is easy to find online.