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childrenpenNetworking and Communications

Oct 26, 2013 (3 years and 10 months ago)

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The Web Architecture and Components, which enable Internet
and Web Functionality


In this article I will go overt the main architecture and components witch enable
the Internet and web functionally to work. I will explain what some of the
components are
and what they do; also I will show a diagram and explain how
the Internet works step by step.


Web architecture
: Internet Service Providers (ISP); web hosting services;

Domain

structure; domain name registrars; worldwide web


Components
: hardware eg web,
mail and proxy servers; routers; software
e.g.

browser, email; Protocols: transport and addressing
e.g.

TCP/IP; application
layer
e.g.

HTTP, HTTPS, SMTP


Web functionality
: Web 2.0; blogs; online applications; cloud computing



Transmission Control Protoco
l/Internet Protocol (TCP/IP)

A suite of protocols that turns data into blocks of information called
packets,
which

are then sent across the Internet. The standard protocol used by the
Internet.

Transmission Control Protocol/Internet Protocol

(
TCP/IP
)

allo
ws
computers from different vendors with various operating systems and
capabilities (from mainframe to desktop computers) to communicate.

Today, it is the most widely used networking protocol suite in the world, and it is
the language of communication on
the Internet
.
If one of the connections, or
routes, between two computers is not working, the nearby computers simply
stop using that route until the connection is repaired.

Routers recognise damaged connections and send data through other routes.
The r
outing flexibility of
TCP/IP

software ensures an accurate and steady flow of
information.


Hypertext Transfer Protocol (HTTP)

is the protocol used to transfer web
pages from a web server to a web client


usually a web browser. Specifically,
HTTP

is the s
et of rules required to exchange files


such as text, images, video
and multimedia content


across the Web.



There

are some numbered steps below
so I can demonstrate some
of the concepts to you more effectively.


1.

Every request/response starts by typin
g a Universal Resource

Locator (URL) into the address bar of your web browser, web
browsers actually don’t use URLs to request web sites from
servers; they use
Internet Protocol

or
IP addresses

(which are
basically like phone numbers or postal addresses
that identify
servers.) For example, the IP address of http://www.apple.com
is 17.149.160.10.

2.

Try opening a new browser tab or window, typing
http://www.apple.com and hitting enter; then type
http://17.149.160.10/ and hit enter

you will get to the same
pla
ce.

http://www.apple.com is basically acting as an alias for
http://17.149.160.10/, but why, and how? This is because
people are better at remembering words than long strings of
numbers. The system that makes this work is called the
Domain name system (DNS
), which is essentially a
comprehensive automatic directory of all of the machines
connected to the Internet. When you punch
http://dev.opera.com into your address bar and hit enter, that
address is sent off to a name server that tries to associate it to
i
ts IP address. There are a ton of machines connected to the
Internet, and not every DNS server has a listing for every
machine online, so there’s a system in place where your
request can get referred on to the right server to fulfill your
request.

So the
DNS system looks up the www.opera.com
web site, finds that it is located at 17.149.160.10, and sends
this IP address back to your web browser.

Your machine
sends a request to the machine at the IP address specified and
waits to get a response back. If all

goes well, the server
machine sends a short message back to the client with a
message saying that everything is okay (see Figure 1,) followed
by the web page itself. This type of message is contained in an
HTTP header
.


If something goes wrong, for exam
ple you typed the URL
incorrectly, you’ll get an
HTTP error

returned to your web
browser instead

the infamous 404 “page not found” error is
the most common example you’ll come across.

Try typing in
http://dev.opera.com/joniscool.html
. The page doesn’t
exi
st, so you’ll get a 404 error returned. Try it with a few pages, on
different web sites, that don’t exist, and you’ll see a variety of
different pages retuned. This is because some web developers have
just left the web server to return their default error
pages, and others
have coded custom error pages to appear when a non
-
existent page
is returned.