•What is the internet ? How did it originate? •Networks / Intranets / Addresses •HTML (to make a webpage from source)

http://www.learningwithmaria.com/computing

“What is the Internet? How did it originate?”.

The internet is a network of networks that are interconnected.

It carries a vast range of information and provides with the technological infrastructure that supports the World Wide Web.

History: it is considered that the internet was born on the 29th October 1969, when the Advanced Research Projects Agency (ARPA) constructed a link in a proposed network (ARPANET).

The development of the internet as a distributed network without a central command hub was due to fear of a nuclear attack.

“What is the Internet? How did it originate?”.

Its name, Internet, would come afterwards.

In 1974 a communication language was created: TCP (Transmission Control Protocol). It would wrap the messages of all connected computers to make easier their transmission over different networks. However, this wasn’t convenient enough and a second protocol was created in 1976 : IP (Internet Protocol).

By 1978, these two protocols combined were proposed as the universal standard: TCP/IP and it was “Internet” in “Internet protocol” that was to give the Internet its name.

“What is a network?”.

A network is a set of computers or other devices that are interconnected. The internet is a type of network, the same as local area networks (intranets) in homes or offices.

“Distinction between Internet and Intranets”.

There's one major distinction between an intranet and the Internet:

The Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but as a rule it's protected by a password and accessible only to employees or other authorized users.

From within a company, an intranet server may respond much more quickly than a typical Web site. This is because the public Internet is at the mercy of traffic spikes, server breakdowns and other problems that may slow the network.

“Distinction between Internet and Intranet”.

“Extranet and Intranet”.

The Extranet is a portion of an organization's Intranet that is made accessible to authorized outside users without full access to an entire organization's intranet.

“Extranet and Intranet”.

“Infrastructure”.

To set up a network you need:

One or more devices (with the appropriate network cards) and a way to connect them (wirelessly or wired).

“LANs VS WANs”.

Local Area Networks are confined to a small geographical area while Wide Area Networks cover a broad area. WANs are generally used to connect LANs. The Internet itself could be considered as a public WAN.

“Topology”.

Topology refers to the physical layout of the network. There are many different types, but the most used are: Star Mesh Ring

“Internet topology”.

The internet has a mesh topology as you can see in the picture.

“Nature of addresses. Uniqueness”.

Every device on a network has an address. Each one of them has an unique address assigned to it by the network.

Here we are going to see that every address is unique:

- Start the Command Prompt (Go to Start button, All programs, Accessories).

- Type ipconfig and find the IP address.

“Standards IPv4 and IPv6”.

IPv4: stands for Internet Protocol version 4. It is the underlying technology that makes it possible for us to connect our devices to the internet and other networks. Whenever a device accesses the Internet it is assigned a unique, numerical IP address. To send data from one computer to another, a data packet must be transferred across the network containing IP addresses of both devices.

IPv6: the new IP standard that we are currently transitioning towards. (It uses 128 bits instead of 32 and it will resolve our current problem of running out of IPv4 Internet addresses).

“Standards IPv4 and IPv6”.

“Domain Names”.

Apart from using numeric IP addresses, alphanumeric addresses can be used. This is done by a protocol known as DNS.

The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most importantly, it translates domain names meaningful to humans into the numerical identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide.

“Domain Names”.

Here we are going to see how DNS translates domain names into numeric addresses:

- Start the Command Prompt (Go to Start button, All programs, Accessories).

- Type ping google.com

-Note the numeric IP address

-Mini assignment: Find out IP address of learningwithmaria.com

“Private and Public Address Ranges”.

Computers not connected to the Internet, do not need to have a globally unique address. In other words, they do not have an Internet address but a private network address. There are 3 ranges that are always used for private networks:

-10.x.x.x-172.16.x.x to 172.31.x.x-192.168.x.x

(X is any number between 0 and 255)IP addresses outside of this range, are public internet addresses.

“Protocols”.

There are many protocols that allow users to communicate over the Internet. Some common ones are:

World Wide Web (HTTP)

File Transfer Protocol (FTP)

Email Protocols (SMTP, POP3, IMAP...)

Internet Relay Chat (IRC)

Facebook Chat (XMPP)

IP

TCP

HTTP SMTP XMPP

“Origin of the World Wide Web”.

Origin: Tim Berners – Lee (1990). He conceived how to put hypertext and computer networks together. He wanted to create “a point-and-click browser/editor” so that a user would be able to click on a “hypertext” link within a web page to move through to a different page with more detailed information.

He wrote the “Hypertext Transfer Protocol” HTTP that would allow the access to a hypertext document held on a website located on a remote server. He also developed the URL (Uniform Resource Locator) in order to identify each destination uniquely.

He also set up the first website: http://info.cern.ch/

“Hypertext mark-up Language”.

Hypertext Mark-up Language (HTML) is the predominant mark-up language for web pages.

HTML elements are the basic building-blocks of web pages. HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content.

The browser does not display the HTML tags, but uses the tags to render the content of the page.

In this part we will learn the basic tags to create web pages.

“How to create a webpage from source code”.

Structure of an HTML page<html><head>

<title>I am beautiful</title></head><body>

<p>Hello, world!</p></body></html>

“How to create a webpage from source code”.

Tags <anything inside these brackets are called tags>

Generally, content is enclosed within tags. The beginning of a tag is <tag> and the end of it is </tag>.

Bold <b>sample text</b>Paragraph<p>sample text</p>Links <p>Take me to <a href=“google.com”>Google</a>.</p>

Images <img src=“filename.gif”/> (notice that this only works if the image is in the same directory as the webpage).

“Using search engines effectively”

There are three elements to the traditional search engine:

-The spider: It crawls the web and puts everything that it finds into the index.

-The index: a gigantic database that stores all the information that the spider finds.

-The search software and user interface: where the user enters the search parameters and gets the results.

In this module we have learned...

The origins of the internet. What a network is.

The difference between intranets and internet.

How IP addresses are constructed

The origins of the World Wide Web.

How to find IP addresses, how to create a web page from source and how to use search engines effectively.