Tag Archives: dns
Dns is a very critical part of the Internet. If you have a site which is has a huge amount of traffic then you may want to consider more than one IP address for your site for load balancing purposes.
Simply put dns round robin means that the first request will goto the first IP address and the second will goto the second IP address and so.
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Now our application is presented with http://www.cranzgot.co.za. The following sequence of lookups takes place to resolve this name into an IP address. This procedure is called host name resolution and the algorithm that performs this operation is called the resolver.
1. The application checks certain special databases on the local machine. If it can get an answer directly from them, it proceeds no further.
2. The application looks up a geographically close name server from the local machine’s configuration file. Let’s say this machine is called ns.
3. The application queries ns with “ http://www.cranzgot.co.za?”.
4. ns determines whether that IP has been recently looked up. If it has, there is no need to ask further, since the result would be stored in a local cache.
5. ns checks whether the domain is local. That is, whether it is a computer about which it has direct information. In this case, this would only be true if the ns were cranzgot.co.za’s very own name server.
6. ns strips out the TLD (top level domain) .za. It queries a root name server, asking what name server is responsible for .za. The answer will be ucthpx.uct.ac.za of IP address 22.214.171.124.
7. ns strips out the next highest domain co.za It queries 126.96.36.199, asking what name server is responsible for .co.za. The answer will be secdns1.posix.co.za of IP address 188.8.131.52.
8. ns strips out the next highest domain cranzgot.co.za. It queries 184.108.40.206, asking what name server is responsible for cranzgot.co.za. The answer will be pizza.cranzgot.co.za of IP address 220.127.116.11.
9. ns queries 18.104.22.168 asking for the IP address of http://www.cranzgot.co.za. The answer will be 22.214.171.124.
10. ns returns the result to the application.
11. ns stores each of these results in a local cache with an expiration date, to avoid having to look them up a second time.
The DNS structure on the Internet actually works like this.
There are computers that service requests for IP numbers–millions of them. They are called name servers (or DNS servers), and a request is called a DNS lookup (or just a lookup). However, each name server only has information about a specific part of the Internet, and they constantly query each other.
There are 13 root name servers on the Internet.
Each country also has a name server, and in turn each organization has a name server. Each name server only has information about machines in its own domain, as well as information about other name servers. The root name servers only have information on the IP addresses of the name servers of .com, .edu, .za, etc. The .za name server only has information on the IP addresses of the name servers of .org.za, .ac.za, .co.za, etc. The .co.za name server only has information on the name servers of all South African companies, like .cranzgot.co.za, .icon.co.za, .mweb.co.za, etc. The .cranzgot.co.za, name server only has info on the machines at Cranzgot Systems, like http://www.cranzgot.co.za.
Your own machine will defined in its configuration files a name server that is geographically close to it. The responsibilities of this name server will be to directly answer any queries about its own domain that it has information about and to answer any other queries by querying as many other name servers on the Internet as is necessary.
One of the greatest things about the Internet is that nobody really owns it. It is a global collection of networks, both big and small. I found this article that perfectly explains how it works.
If there was anything you wanted to know about the internet or were confused about something this should clear your doubts