History of DNS server
How DNS server evolved?
To understand why we require DNS server we have to go back to initial stages of networking the computers around late 1960’s and early 1970’s where it all started in Universities(especially Barkley University). Initially there is single computer for university due to cost and other factors, then to multiple systems per university. When computers started increasing exponentially in universities at this time people are forced to share documents/printers service etc of one system to other systems for maximizing the resources. This made people to inter network between the systems in labs so there will be effective utilization of resources attached to system. This made many people to remember the servers with numbers. So they started giving numbers to servers in Universities. So initially this worked fine to remember numbers, but when computers started growing faster they felt to give names instead of numbers(As humans prefer names more than numbers for easy remembrance).
Hosts File evolution(/etc/hosts or c:/windows/system32/etc/HOSTS):
To make it easy to communicate with different systems they came up with hosts file concept. Every system in the lab should have hosts file and it should contain name to number conversation table.
So if I say one lab is having 10 machines each machine should have 10 entries for these servers as show below.
Hosts file content:
So becomes easy to remember by users.
Disadvantages of hosts file?
One disadvantage from this hosts file is if we want to add 11th machine in the lab all the hosts files on each system to should be modified to add this host details. Ok, it’s just 10 machines but consider labs having 100’s or thousands of servers. When a new machine is added to the network this machine entry should be added to these thousands of machines which a heavy job for the admin.
What’s the solution?
Go for a centralized monitoring/configuration system where every machine will point their Name quires to a centralized server. This machine should serve all the queries. At this point DNS (Domain Name Server/service) came in to existence.
Disadvantages of initial DNS server?
When DNS server is implemented again it’s a mapping between numbers to host names and vice versa as shown below.
For Berkeley servers:
If you see there is no proper naming convention and it’s bit difficult to find where one server is located in given University.
FQDN is the solution
Researcher came with FQDN (Fully Qualified Domain Name) convention so that’s it’s easy to remember and easy to point where the server located.
FQDN is a hierarchical and tree like structure for naming convention which contain below details.
1) Hostname –Name of the server
2) Domain name – Defines a realm administrative authority or control on a group of machines.
3) Top Level Domains (TLD) – ie .com, .in, co.uk, co.us etc.
What are root name servers?
DNS is a hierarchical in structure where if a server is unable to give answer to host requests, it will send this to it’s superior servers and so on. This will reach to the upper levels to the initial master servers which are called as root name server which can serve all the answer queries if the host exists in internet.
Why there are only 13 root name servers?
This is due to UDP porotocal size which stores DNS information.
How many TOP level and Country specific domains are there?
There are 20 generic TLD’s (gTLD) and 248 country specific TLD’s(ccTLD) are there.
Stay tuned to our next post on “How name resolution works?”
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