In 21st Century, Internet
is become essential after food. Maybe, still many people will not agree
with this statement now but once they start using internet they will be
agree .
Well, you are reading this article so i hope you are already aware of 'what internet is'.
Are you?
I know you will say 'Yes i know what is internet'
But is it enough ? Don't
you ever wonder how internet works? Maybe you already know how it works
if you are IT student or teacher but still i think everyone should know
this because internet is common and it is for everyone. So Its study
should not be only for IT student.
The greatest thing about the Internet is that nobody really owns it. It
is a global collection of networks, both big and small connected
together in many different ways to form the single entity that we know
as the Internet. The name 'Internet' comes from this idea of interconnected networks
Since its beginning in 1969, the Internet has grown from four host computer systems to tens of millions.
However, just because nobody owns the Internet, it doesn't mean it is not monitored and maintained in different ways.
The
Internet Society, a non-profit group established in 1992, oversees the
formation of the policies and protocols that define how we use and
interact with the Internet.
How computer connects to internet.Every computer that is connected to the Internet is part of a network, even the one in your home.
When
you connect to your ISP (Internet service provider), you become part of
their network. The ISP may then connect to a larger network and become
part of their network.
The Internet is simply a network of networks.
Most large
communications companies have their own dedicated backbones connecting
various regions. In each region, the company has a Point of Presence
(POP).
The POP is a place for local users to access the company's network,
often through a local phone number or dedicated line. The amazing thing
here is that there is no overall controlling network. Instead, there are
several high-level networks connecting to each other through Network
Access Points or NAPs.
Exmple:
Imagine that Company A is a large ISP.
In
each major city, Company A has a POP. the POP in each city is a rack
full of modems that the ISP's customers dial into. Company A use fiber
optic (a cable) to communicate.
Imagine that Company B is a corporate ISP. Company B builds large
buildings in major cities and corporations locate their Internet server
machines in these buildings. Company B is such a large company that it
runs its own fiber optic lines between its buildings
so that they are all interconnected.
In
this arrangement, all of Company A's customers can talk to each other,
and all of Company B's customers can talk to each other, but there is no
way for Company A's customers and Company B's customers to
intercommunicate.
The Function of an Internet Router (Message
passing)Therefore, Company A and Company B both agree to connect to NAPs
in various cities, and traffic between the two companies flows between
the networks at the NAPs.
In the real Internet, dozens of large
Internet providers interconnect at NAPs in various cities, and trillions
of bytes of data flow between the individual networks at these points.
The Internet is a collection of huge corporate networks that agree to all intercommunicate with each other at the NAPs.
In this way, every computer on the Internet connects to every other.
How Message passes between computers
All of the networks rely on NAPs, backbones and routers to talk to each other.
What
is incredible about this process is that a message can leave one
computer and travel halfway across the world through several different
networks and arrive at another computer in a fraction of a second!
The routers determine where to send information from one computer to another.
Routers
are specialized computers that send your messages and those of every
other Internet user speeding to their destinations along thousands of
pathways.
A router has two separate, but related, jobs:
* It ensures that information doesn't go where it's not needed.
* It makes sure that information does make it to the intended destination.
In performing these two jobs, a router is extremely useful in dealing with two separate computer networks.
It
joins the two networks, passing information from one to the other. It
also protects the networks from one another, preventing the traffic on
one from unnecessarily spilling over to the other.
Regardless of how many networks are attached, the basic operation and function of the router remains the same.
Since
the Internet is one huge network made up of tens of thousands of
smaller networks, its use of routers is an absolute necessity.
Internet Backbone
Backbones
are typically fiber optic trunk lines. The trunk line has multiple
fiber optic cables combined together to increase the capacity.
Fiber optic cables are designated OC for optical carrier, such as OC-3,
OC-12 or OC-48. An OC-3 line is capable of transmitting 155 Mbps while
an OC-48 can transmit 2,488 Mbps (2.488 Gbps). Compare that to a typical
56K modem transmitting 56,000 bps and you see just how fast a modern
backbone is.
The National Science Foundation(NSF) created the
first high-speed backbone in 1987. Called NSFNET, it was a T1 line that
connected 170 smaller networks together and operated at 1.544 Mbps
(million bits per second). IBM, MCI and Merit worked with NSF to create
the backbone and developed a T3 (45 Mbps) backbone the following year.
Today there are many companies that operate their own high-capacity
backbones, and all of them interconnect at various NAPs around the
world.
In this way, everyone on the Internet, no matter where they are and
what company they use, is able to talk to everyone else on the planet.
The entire Internet is a gigantic, sprawling agreement between companies to intercommunicate freely.
Internet Protocol: IP Addresses and Domain
Every machine on the Internet has a unique identifying number, called an IP Address.
The IP stands for Internet Protocol, which is the language that computers use to communicate over the Internet.
A protocol is the pre-defined way that someone who wants to use a
service talks with that service. The "someone" could be a person, but
more often it is a computer program like a Web browser.
To make it easier for us humans to remember, IP addresses are normally expressed in decimal format.
E.g. 216.27.20.164.
But computers communicate in binaryform.
the four numbers in an IP address are called octets, because they each
have eight positions when viewed in binary form. If you add all the
positions together, you get 32, which is why IP addresses are considered
32-bit numbers.
Since each of the eight positions can have two different states (1 or
zero), the total number of possible combinations per octet is 28 or 256.
So each octet can contain any value between zero and 255.
Combine the four octets and you get 232 or a possible 4,294,967,296 unique values!
Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses.
For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.
The octets serve a purpose other than simply separating the numbers.
They
are used to create classes of IP addresses that can be assigned to a
particular business, government or other entity based on size and need.
The octets are split into two sections: Net and Host.
The Net section always contains the first octet. It is used to identify the network that a computer belongs to.
Host (sometimes referred to as Node) identifies the actual computer on the network.
The Host section always contains the last octet.
There are five IP classes plus certain special addresses.
DOMAIN NAME SYSTEM:
Its very complex to use and remember IP addresses of the computer you wanted to establish a link with.
For example, a typical IP address might be 216.27.20.164.
This was fine when there were only a few hosts out there, but it became unwieldy as more and more systems came online.
The first solution to the problem was a simple text file maintained
by the Network Information Center that mapped names to IP addresses.
Soon this text file became so large it was too cumbersome to manage.
In 1983, the University of Wisconsin created the Domain Name System (DNS), which maps text names to IP addresses automatically.
This way you only need to remember www.technotification.com, Instead of How technotification.com's IP address.
URL: Uniform Resource Locator
When you use the Web or send an e-mail message, you use a domain name to do it.
For
example, the Uniform Resource Locator (URL) "
http://www.technotification.com" contains the domain name
technotification.com.
Every time you use a domain name, you use the
Internet's DNS servers to translate the human-readable domain name into
the machine-readable IP address.
Top-level domain names, also
called first-level domain names, include .COM, .ORG, .NET, .EDU and
.GOV. Within every top-level domain there is a huge list of second-level
domains. For example, in the .COM first-level domain there is:
- Google
- Yahoo
- Microsoft
Every name in the .COM top-level domain must be unique.
The left-most word, like www, is the host name.
It specifies the name of a specific machine (with a specific IP address) in a domain.
A
given domain can, potentially, contain millions of host names as long
as they are all unique within that domain. DNS servers accept requests
from programs and other name servers to convert domain names into IP
addresses.
When a request comes in, the DNS server can do one of four things with it:
1. It can answer the request with an IP address because it already knows the IP address for the requested domain.
2.
It can contact another DNS server and try to find the IP address for
the name requested. It may have to do this multiple times.
3. It can
say, "I don't know the IP address for the domain you requested, but
here's the IP address for a DNS server that knows more than I do."
4. It can return an error message because the requested domain name is invalid or does not exist.
How DNS, and URL works? (EXMPLE)
Let's
say that you type the URL www.technotification.com into your browser
and than The browser contacts a DNS server to get the IP address.
A
DNS server would start its search for an IP address by contacting one
of theroot DNS servers. The root servers know the IP addresses for all
of the DNS servers that handle the top-level domains (. COM, . NET, .
ORG, etc.).
Your DNS server would ask the root
for www.technotification.com, and the root would say, "I don't know the
IP address for www.technotification.com, but here's the IP address for
the .COM DNS server."
Your name server then sends a query to the . COM DNS server asking it if
it knows the IP address for www.technotification.com. The DNS server
for the .COM domain knows the IP addresses for the name servers handling
the www. technotification.com domain, so it returns those.
Your name
server then contacts the DNS server for www.technotification.com and
asks if it knows the IP address for www.technotification.com. It
actually does, so it returns the IP address to your DNS server, which
returns it to the browser, which can then contact the server
for www.technotification.com to get a Web page.
One of the keys
to making this work is redundancy. There are multiple DNS servers at
every level, so that if one fails, there are others to handle the
requests. The other key is caching. Once a DNS server resolves a
request, it caches the IP address it receives.
Once it has made a
request to a root DNS server for any .COM domain, it knows the IP
address for a DNS server handling the .COM domain, so it doesn't have to
bug the root DNS servers again for that information.
DNS servers can do this for every request, and this caching helps to keep things from bogging down.
Even
though it is totally invisible, DNS servers handle billions of requests
every day and they are essential to the Internet's smooth functioning.
The fact that this distributed database works so well and so invisibly day in and day out is a testimony to the design.
Internet Servers, Clients and Ports, http
Internet
servers make the Internet possible. All of the machines on the Internet
are either servers or clients. The machines that provide services to
other machines are servers. And the machines that are used to connect to
those services are clients. There are Web servers, e-mail servers, FTP
servers and so on serving the needs of Internet users all over the
world.
When you connect to www.technotification.com to read a
page, you are a user sitting at a client's machine. You are accessing
the Blogger's Web server (as technotification.com is hosted on
blogger). The server machine finds the page you requested and sends it
to you. Clients that come to a server machine do so with a specific
intent, so clients direct their requests to a specific software server
running on the server machine.
For example, if you are running a
Web browser on your machine, it will want to talk to the Web server on
the server machine, not the e-mail server. A server has a static IP
address that does not change very often.
A home machine that is
dialing up through a modem, on the other hand, typically has an IP
address assigned by the ISP every time you dial in.
That IP
address is unique for your session -- it may be different the next time
you dial in. This way, an ISP only needs one IP address for each modem
it supports, rather than one for each customer.
Ports and HTTP
Any server machine makes its services available using numbered ports. One for each service that is available on the server.
For
exmple, If a server machine is running a Web server and a file transfer
protocol (FTP) server, the Web server would typically be available on
port 80, and the FTP server would be available on port 21. Clients
connect to a service at a specific IP address and on a specific port
number.
Once a client has connected to a service on a particular
port, it accesses the service using a specific protocol. Protocols are
often text and simply describe how the client and server will have their
conversation. Every Web server on the Internet conforms to the
hypertext transfer protocol (HTTP).
That's all for now. If you understand it well i ca say now you know how
internet works and every basic concepts related to it. share this
article to help your friends too .
