Internet Principles of Operation

 

In this section we will look at HTML and the processes, software and hardware which are necessary to connect to the internet

THE ROLE OF THE BROWSER IN CONNECTING TO THE INTERNET

Everyone who views the World Wide Web does so using an internet browser. It is important before we go any further to make a distinction between the internet and the world wide web as people often confuse them.

The internet is the global network of computers which are all connected allowing us to share information and communicate with each other.

The world wide web is the series of web pages and files which are stored on the internet. You don't always use the world wide web when you're on the internet. For example, you might be making a Skype call or playing an online game. You're still using the internet but you're not using the world wide web as you're not looking at web pages or files which are stored on the internet. Each time you type WWW or see it in your browser, this is when you are using the world wide web.

A web browser is a piece of software for converting the code in which web pages are written in to things you can see and understand. The web browser displays the text, images and video which are contained on the internet in to a clear structure so they can be browsed and viewed easily. Without a web browser you would still be able to look at web pages, but they might not make any sense since they will be written in code which has not been translated.

For example, consider the web page you are on at the moment. For you to view this page, the web browser has fetched the document containing the code from the web server and displayed it as you see it now. Without a web browser, it would look like this:

html

As you can tell, you can still make sense of it, but it doesn't look anything like when the browser reads it.

Modern browsers also have other things built in to them to help you on the web. Some of them have security settings which will check the websites you are visiting to ensure you don't get viruses from them. They may also have built in search functions, the ability to bookmark pages and a storage of your browsing history to make things easier to find.

There is also a recent trend for some browsers to allow third-party plug-ins. A plug in is a piece of software which attaches itself to your browser when you install it. They can do a variety of things. For example, some will block annoying internet advertisements and pop-ups. However, some may covertly install on your browser without you knowing (usually from other software you have installed) and actually cause more advertisements and pop-ups than you had before.

HTML

HTML stands for Hypertext Markup Language. It is the programming language that web sites are written in. In the early days of the world wide web, programmers would just only this language to create entire web pages. However, modern web programming usually uses a combination of manually written HTML and web design programs which write some of the HTML for you.

HTML looks like this:

This is the basic HTML which you will find on every web page before any content has been entered. The text inside the <> symbols are called TAGS. These are used to give certain properties that are inside them. For example, take a look at the following line:

<title>Hello HTML</title>

This will tell the web page to have the title 'Hello HTML'. The title is the name of the website which appears at the top of the browser. For example, this page is called Internet Principles of Operation.

The <head> tags are used to give the website a main heading. This is usually the thing that search engines look for when they are finding websites. Whatever is put here will probably be the title of the page when someone looks for it on Google or Bing.

The <body> tags are where the main part of the web page goes. This is all the text, images and video that are the main content of your web page.

Finally, the whole thing is wrapped in <html> tags. These tags tell the browser that the web page has been written in HTML. You might think this is obvious but web designers can also use other languages like Javascript and place them inside <javascript> tags which can also be read by browsers.

Web designers used to use a lot of other tags in HTML to create web pages. For example, <center> would be used to centre text and <b> would be used to make something bold. However, modern web pages are usually created using a combination of HTML and CSS (a language which deals with the formatting of web elements) and so actual HTML is being used less and less.

FIREWALLS AND PROXY SERVERS

Two very important technologies in allowing you to safely and easily connect to the internet are firewalls and proxy servers.

A firewall is a piece of software or a physical device which goes between your computer and the internet. It checks all the incoming and outgoing connections to see if any of them may be harmful. For example, a website may be pushing files on to the your computer or a virus on your computer may be sending files out to a hacker. Think of it like a bouncer at a nightclub.

firewall

A proxy server is a computer which goes between your computer and the final internet server (after the firewall). The job of a proxy sevrer is to collect web pages to that you access and make them easier to access if you go back on them. For example, if yo've just visited Amazon.com a copy of the page will be stored in the proxy server. If you then go back on the page shortly after it will fetch it from the closer proxy server rather than going all the way to Amazon.com's server again. This greatly speeds up access to the internet. Proxy servers can also be used for privacy reasons. If you're using a proxy server, then the web server where you are getting your web pages doesn't know who you are, as you went through an intermediary channel. Only the proxy server knows who you are. Therefore, if you are blocked from a website because of your IP address or location, you can get around this by using a proxy server so the web server doesn't know who you are.

proxyfirewall

MAC ADDRESSES, IP ADDRESSES AND COOKIES

Each device that connects to the internet needs to have a name? The name is useful because the device supplying the internet connection needs to know which devices are which, and control which ones are on the network. The name given to each device is called a MAC address. MAC stands for Media Access Control and looks something like this:

40-61-86-CF-1C-E6

You will notice that the address is not all numbers, but also includes letters. This is because Mac addresses use the hexadecimal number system.

Mac addresses are split up in to the following 2 sections:

netgearmac

Mac addresses are important because they allow the network controller to allow and deny access to certain devices which are connected to it. Without a Mac address the server or router wouldn't know what was connected to it and wouldn't be able to distinguish between devices. They also wouldn't be able to send data to a specific device on the server.

IP addresses are the physical addresses of the internet connections. Your router in your house will have an IP address which is specific to that one device. Others computers connected to the internet can then send data to that IP address. They can also tell the general location of the device. Without IP addresses there would be no way of being able to distinguish the billions of computers connected to the internet.

IP addresses come in two types, static and dynamic. A static IP address remains the same at all times whereas a dynamic IP frequently changes. Static IP addresses are useful for tasks where the user needs to be easily located at all times - for example online gaming. Dynamic IP addresses are a bunch of addresses which are shared out between users on a temporary basis every time they connect to the internet.

IP addresses can either be IPV4 or IPV4. IPV4 addresses look like this

154.126.85.4

When the IPV4 system was decided upon, the internet was still a relatively small network compared to what it is today. After a while it was realised that we might eventually run out of unique IP addresses for everyone. That's why some network connections are now assigned IPV6 addresses which look like this

2a02:587:410e:3d00:a847:a14d:2985:4659

These are much longer and are made up of hexadecimal numbers rather than denary.

IP addresses, like MAC addresses are split up in to different sections. The first half of an IP address if the network address. This is the physical address of the network. Thnk of it as your street name. The last part is the host. This is the name of the computer which is actually on this address. Think of this as the house number.

ipaddress

A cookie is a small text file which is stored on your computer by a website. It contains information about what you did on that website, such as changes you made and things you personalised. For example, you might have clicked on 'English' in the top corner so that the website would be displayed in the English language. This change would then be saved by the website on your computer so that next time you visit it can display the English version to you immediately. This may cause problems when sharing a computer with others and some people do not like the idea of websites storing information about them on their own computer. For this reason, it is now EU law that websites warn you if they want to leave a cookie on your computer.

1) What are MAC addresses used for?

2) Give an advantage and disadvantage of websites using cookies