10 November 2016

How Internet Access Result?

Today I’m going to tell you How Internet Access Result?’
Internet is a short term used for the word Inter-Networks – The network of Networks. If any system has access to the internet, it is connected to the global network and also to every other computer with internet access.

Nowadays, whooping large number of computers are now connected to the internet.

Internet hence classified as Network-of-Networks. It smartly connects to billions of computers and is also able to access any of your requested webpage in the time frame of milliseconds.
Internet have more than 30 billion web pages hosted on the network, the internet is a huge resource of information. So, first question arise that, ‘How internet access result?’ many answers are available in many books and websites. They all tell you like this:

If we type a website URL (for example www.nextiseasy.com) into our browser, then the browser search for the web server of ‘nextiseasy.com’ and then retrieve data of the website from it.
But this is a basic and simple explanation which everybody known! And this is not tell you all. But we tell you every step how the Internet access results.
We will study/read about in detail and in brief.
So let’s start the journey to Internet access.

WARNING: This article contain many technical words so firstly search internet’s dictionary to quickly know the full form and uses of those words (like IP : Internet Protocol) in internet.  This will help you understand more efficiently and quickly.

Journey to Internet Access
If you turn ON your computer and connect it to the Ethernet to view (download) a webpage, this is what happens:

1.      Initially the computer does not have its IP address to connect to the internet.

2.      Hence it first uses DHCP request to obtain IP address.

3.      Computer first creates a special IP datagram (packet with its headers, encapsulated bits and actual data) destined to (broadcast address) in the DHCP server. This is termed as the discovery step.

4.      A DHCP server then assigns an IP address to the computer

5.      Along with that it also gives additional information to the computer like first-hop router address, the subnet mask and the address of local DNS (Domain Name Server) servers.

6.      Since the computer’s ARP (Address Resolution Protocol) cache is initially empty the computer will use ARP protocol to get the MAC addresses f the first-hop router and the local DNS (Domain Name Server) server.

7.      The computer first will get the IP address of the web page we wish to download.

8.      If the local DNS server does not have the IP address, then the computer will use DNS protocol to find the IP address of the Webpage.

9.      Once the computer has the IP address of the Webpage, it will send out the HTTP request.

10. This request is sent via the first-hop router, if the Webpage is not stored in a local Web Server.

11. The HTTP request messages will be segmented and encapsulated into TCP packets (in the transport layer), and then further encapsulated into IP packets (in the network layer), and finally encapsulated into Ethernet frames (in the data link layer).

12. The computer sends the Ethernet frames to the first-hop router.

13. Once the router receives the frames, it checks its routing table, and then sends the packets top the right link where it can reach its destination (the web server where the web page is hosted).
14. Then the server hosting the web page will send back the web page to the computer via HTTP response messages.

15. In the backwards journey of the web page data, the messages will be encapsulated into TCP packets and then further into IP packets.

16. Those IP packets follow IP routes and finally reach the first-hop router, and then the router will forward those IP packets to the computer by encapsulating them into Ethernet frames.

17. It goes all the way from the data link layer right up to the Application layer (web browser) by the process of decapsulation and you can see the web page.

So, now you understand every steps of Internet, then go to your friends and tell them.

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