domain name system
DESCRIPTION
TRANSCRIPT
Kapil Khatiwada
What is the Internet?Network of networks
Uses the standardized Internet Protocol Suite(TCP/IP).
Millions of private and public, academic, business and govt. networks of local to global scope.
Linked by copper wires, fiber-optic cables, wireless connections, and other technologies.
A network of computers connected to each other.
What is the Internet?
How do they Connect?
Computers needed to know which computer they were connecting to, with the help of unique number – an IP (Internet Protocol) number.
Ex. 121.245.078.2 Greater numbers of users demand for an easier
system and one that was less confusing.
• In the mid 1980’s the Domain Name System was implemented and the initial top-level domain names, including .com, .net, and .org, were introduced.
• Suddenly 121.245.078.2 became 'company.com'.
Foundation Of DNS
DNS Definition
The Internet users use DNS to reference anything by name on the Internet.
The mechanism by which Internet software translates names to addresses and vice versa.
DNS Definition
IP assigns 32-bit addresses to hosts (interfaces) – Binary addresses are easy for computers to manage .– All applications use IP addresses through the TCP/IP
protocol software.– Difficult for humans to remember.
Domain names comprise a hierarchy so that names are unique, easy to remember.
Domain Names
A domain name is the sequence of labels from a node to the root, separated by dots (“.”s), read left to right.
Example domain names:– www.filehippo.com– www.bbc.co.uk
Parts of a Domain Name
A domain name usually consists of two or more parts (technically labels), which are separated by dots, such as filehippo.com
DNS Naming Structure
http://www.filehippo.com
Top level domains
2nd Level Domains
SERVER
Top-Level Domains (TLDs)
Second-Level Domains
Within every top-level domain there is a huge list of 2nd level domains
For example, in the .COM second-level domain, we've got:
yahoo msn microsoft plus millions of others...
Name Servers Also called a DNS server
Manages a massive database that maps domain names to IP addresses.
Servers are distributed widely on the Internet.
Iterative and Recursive Name Servers• Iterative servers can only answer information they know
or have cached.
• Recursive know how to ask others for information.
DNS Naming Structure
http://www.nccs.edu.np
2nd level domains3rd Level DomainsSERVER
ccTLD
How DNS Servers work(web)
Step 1: Your PC sends a resolution request to its configured DNS Server, typically at your ISP.
Your PC
ISP “Recursive” DNS server
Tell me the Address of “www.google.com”
You type http://www.google.com into your web browser and hit enter.
Step 2: Your ISPs recursive name server starts by asking one of the root servers predefined in its “hints” file.
Tell me the Address of “www.google.com”
ISP “Recursive” DNS serverRoot Servers
I don’t know the address but I know who’s authoritative for the ”com”
domain ask them
Step 3: Your ISPs recursive name server then asks one of the “com” name servers as directed.
ISP “Recursive” DNS server“com” DNS servers
Tell me the Address of “www.google.com”
I don’t know the address but I know who’s authoritative for the
”google.com” domain ask them
Step 4: Your ISPs recursive name server then asks one of the “google.com” name servers as directed.
ISP “Recursive” DNS server google.com DNS server
Tell me the Address of “www.google.com”
The Address of www.google.com is 216.239.53.99
Step 5: ISP DNS server then send the answer back to your PC. The DNS server will “remember” the answer for a period of time.
Your PC
ISP “Recursive” DNS server
The Address of www.google.com is 216.239.53.99
Step 6: Your PC can then make the actual HTTP request to the web server.
Your PC
www.google.com web server
Here it is!
Thank you!
That’s ALL!