Communication & InternetChapter 2: IGCSE BookBy: Prof. A. Lawson

Learning Objectives

• How to be able to explain how antivirus software can protect and help users from security risks.

• Understand the role of the internet browser and internet service provider (ISP)

• Understand HTML structure and presentation and what is meant by HTML and hypertext transfer protocol

• Understand the concepts of MAC addresses, internet protocol address, uniform resource locator and cookies

You should be able to show understanding of the role of the browser and internet server

2.03 – Internet Principles of Operation

The Internet Service Provider (ISP) – The internet is a global wide area network (WAN) of interconnected computers and devices. To access the internet we normally need an internet service provider. The ISP is a company that provides users with access to the internet, usually for a fee. We then use the ISP modem to connect our computer to the internet. There are a few ways of connecting to the internet via broadband telephone wires, cabling, and fibre-optics. ISP companies usually provide internet services with a contract of terms which users need to follow such as: limitation of service, amount of data that is allowed to be used, downloads, and it can also cover legal issues when using the service by not allowing people to hack.

Internet Browser – A website consists of one or more pages of information that can be accessed by other computers. These pages are known as webpages. A browser is a program that allows the computer user to visit, retrieve and display the information that a webpage has. There are several ways that webpages display content such as: text, images, video and sound. Some other forms of content, such as animation, cannot always be presented directly on your browser without the use of additional software know as plugins. Not all plugins work with all browsers.

Key Term:Modem – a hardware device that converts data so that it can be transmitted from computer to computer over

telephone wires

Browser – a program used to access the World Wide Web that displays HTML files

Packet – a unit of data that can be sent across a network

Protocol – an agreed format of set of rules to transmit data

2.03 – Internet Principles of Operation

DID YOU KNOWThe Raspberry Pi and Arduino are very small computers that can do most of the tasks

performed by a desktop computer. They are not as powerful as a desktop computer but are great for use in projects such as creating a basic web server.

2.03 – Internet Principles of OperationWeb Server – A computer that hosts websites are better know as web servers. The webserver stores each page of the website and its related contents. Retrieving information from a webserver is known as downloading. Sending information to a webserver is know as uploading. To access a website you need a request. Webservers are designed to handle as many requests from users and clients simultaneously. Request information is downloaded from a webserver in packets. Since each packet has only a few bytes, many packets can be sent to many computers in a very short space of time. Webservers can also be used to manage facilities by doing such tasks as storing data, online multiplayer gaming and emails.

What is meant by hypertext transfer protocol (http and https) and HTML. What's the difference? between HTML structures and presentations?

2.03 – Internet Principles of OperationInternet Protocols – Hypertext transfer protocols (http) is the core protocol that governs transmission of data via the internet. It is an access protocol. Http works as a request-response action system. The actual transfer of the information is governed by another protocol. This is known as the transmission control protocol (TCP). TCP handles the transfer of the data and checks to ensure the transmission has no errors. Although http is widely used online this form of transmission is not very secure and unsuitable for applications such as banking or internet shopping, where private customers and financial data may be intercepted. Instead a secure version of http know as https is used. Https encrypts the messages making them extremely difficult to understand by anyone other than the intended recipient that might intercept them.

2.03 – Internet Principles of Operation

Mark-Up Language – The transmission that is given out by a webserver is often in the form of hypertext mark-up language (HTML). A HTML document consists of two parts: the content displayed and the instructions on how to interpret the content. HTML mark-ups take the form of tags. Tags enclose contents on a webpage with an opening tag <> at the beginning and closes the contents with the tag </> at the very end.

2.03 – Internet Principles of Operation

Cascading Style Sheets – When you create a website it is useful to separate the contents and structure from the presentation. By separating the style from the presentation it makes it easier to make any necessary changes if needed quicker by having a CSS created. Usually a CSS is created separately and later can be applied to the HTML webpage.

2.03 – Internet Principles of OperationInternet Address – IP address networks and the internet use transmissions-controlled protocols (TCP) to communicate. Every device that’s connected to the internet has an address. Similar to your house address, each has to have an address in order for the internet transmission to reach it. Without an address it is impossible to connect to the device because TCP would not know where to send the communication to. The address on each device is called an internet protocol address (IP address). Every IP consists of a 32-bit code. Each one of these codes have a range of numbers between 0 to 255. an example of an IP address would be 192.168.002.255. each one of the 32-bit is converted from binary to denary as shown.

What is meant by a MAC address, Internet Protocol (IP) address and cookies

What do you know

This version of IP addressing is also known as IPv4. Due to the growth of the internet and a number of new IP addresses being created IP addressing has been launched in newer versions such as IPv6 which uses 128-bits to assign addresses. IP addresses can either be static or dynamic. Each device is assigned a fixed (static) address. Dynamic addresses are assigned only for a limited time similar to a lease. When your lease if over your address changes over or is re-assigned. Home Ips are usually dynamic due to changes of companies and internet services.

2.03 – Internet Principles of OperationUniform Resource Locator – The URL is what we recognize and call a website address. The URL is made up of different access protocols (http or https) and a given domain name. an example of URLs would be https://www.mrlawsonsclassroom.weebly.com. When we want to visit a website, we usually type in the URL on our internet browsers.

What is meant by a MAC address, Internet Protocol (IP) address and cookies

What do you know

MAC Address – There is also another address that each device connected to a network has and that’s called a MAC (Media Access Control) address. MAC addresses are usually assigned to a device directly from its manufacturer. Unlike an IP address that is assigned by a network provider. This means that even if you change your IP address or internet provider you MAC address will still remain the same. MAC Addresses consists of six pairs of two-digit hexadecimal numbers, which is translated into a 48-bit binary code used by the device. An example of a MAC address can be written as 1a2f08a1234c which would translate to 000110100010111100001000101000010010001101001100

2.03 – Internet Principles of OperationCookies – These are the tiny pieces of data that are downloaded by a computer when it visits a website. These cookies are stored by the computer’s browser and are accessed by the website every time you revisit the site. Cookies have many tasks some make sure that the site you visiting is secure others store dynamic data such as online shopping information or what you have added to your shopping basket. While many cookies are very useful to make websites work properly some are used to track users information and navigation history to use adverts to interests the users have shown while surfing the internet. Some cookies also store sensitive information from the user such as credit card information as well as usernames and passwords.