DNS - Domain Naming Service
Domain Naming Service is a service that lists all the devices in a domain, or local area network, or a wide area network. The service can be on one
Server or it can work in conjunction with a group of servers spread over a wide area called a Zone.
Just what does Domain Naming
Service do? It collects all the names and IP addresses of all the devices on the
connected network and then when a name search is initiated by another device it
supplies the associated IP address to the request.
Pretty simple in it's theory but in operation there is more going on behind the scenes.
Each NIC in a device will send out what is called a poll every so often (in milli seconds) and part of that poll are three pieces of information:
- The NIC MAC
- The NIC IP
- The device name
Kinda looks like gobbolygook doesn't it. This is what the NIC sent out:
- NIC MAC - 2b5c9d01
- NIC IP - 220.127.116.11
- Device name - My Computer
You need to print a document on a network shared printer, you select 'Print' from the file menu or click the print icon, the Print window opens up and you select the printer such as 'Laser 3, third floor, sw". Now the printer program (called a spooler) has this printer properties by name but not by IP or MAC. So the print spooler has to query the DNS server for the IP address of the printer on the third floor in the south west corner called Laser 3.
When the Domain Naming Service server receives the query it goes through it's data base and find that the device name Laser 3 is at IP address 10.101.22.44 and the MAC is 30b19fcc, it then returns this information to your print spooler. The print spooler then sends a query to the printer for service - 'Are you ready for a job?' or something to that effect. If the printer is busy it will return with a 'printer busy' or if it is idle it will return 'ready for print job' and then the spooler will either retry the job after a set period of time or send the job to the printer and notify you that the printer is processing the job.
Or suppose your boss has given you a job to modify an existing document on a server such as -
- Document name: Get to work
- Sever: Lastonestanding
- Folder: Your new work
How would you go about finding first the server, then the folder that has your document?
- By doing a search for the name of the server: Lastonestanding
- Your query would go to the DNS server which in turn would search the DNS data base and then return the IP and MAC of the server . The name will be listed in the search results side of the search window. Then you just double click on the server name and a new window will open with all the shared folders.
- From there you find the folder: Your new work
- Then your document: Get to work
Note: If your boss was really up on domain naming and sharing you would get this instead: //Lastonestanding/Your new work/Get to work.doc and all you would have to do is double click on it to open the document and start working, but that is another story ...
What if you are looking for a web site such as this one?
You could use a search engine which incorporates Domain Naming Service in the data base along with other information about the web site and each page of the web site and a few other features such as Google, Yahoo!, or Live.
But what if you decided to just type in the name of the web site such as: www.diy-computer-repair.net?
Then the local DNS server will search it's data base for the IP/MAC if it doesn't find the IP/MAC it forwards the query to a "Forwarder"
Domain Naming Service server in it's local zone (See page 70 in
Build a Server Guide for more information on Zones) if the information is in one of the forwarder data bases it returns the IP to the browser and the browser connects to the web site, if not then the query is sent out of the Zone to other
Domain Naming Service servers until either the IP/MAC is found or the browser returns an error address/name not found.
WAN DNS servers are normally local ISP servers, then once you go beyond the WAN to the WWW there are large data base servers (called Internet Registry) such as InterNIC that serve large areas such as North America, Nominet for UK, and so on.
This is one of the reasons that when you type in a web site in your browser it takes a little time before you see the web site displayed in your browser.
So the answer is: Yes we do need DNS! Otherwise the www would not be as large as it is, say 1980ish. A thought... :)