Networks: End of Year 9 Computer Science Revision

Networks

• A computer network is when two or more computers are connected together to allow them to communicate. Computer networks allow you to contact people across the world and provide many other benefits.

• Emails do not directly go from the sender to the recipient. The email is passed onto many mail servers along the way to help it get to the recipient.

• Protocols are rules in place in order to pass messages successfully. All methods of communication need them. An example is that email must have a ‘@’ symbol and the email address but be unique.

https://www.instagram.com/

From the above link, we can see protocols in use. All website addresses start with ‘‘http://” followed by “www.” All website addresses are unique (like emails) and they use dots to separate each part of the address.

• The internet is a worldwide network of computers. Internet activities include playing online games, checking Instagram or sending emails.

• VoIP allows voice data to be sent over the internet. Spam are emails that are unwanted.

• Internet services describes a number of activities that are provided over the internet, including VoIP, email and the World Wide Web (part of the internet that contains websites and web pages).

Connection

Network cables

• You need cables to connect together different devices.

• Cables have plastic bugs that connect into sockets on devices.

• The cable is made up of a number of copper wires.

• Data can be sent in both directions across a cable.

• Image you had 4 computers to connect with cables. You would have 6 connections. If you had 5 computers, there would be 10 connections. There will be 15 connections between 6 computers.

Hubs

• A hub connects a number of computers together in a network.

• Ports allow cables to be plugged in from each connected computer.

• A message sent from one computer to another travels via the hub. You do not need a hub to connect to the internet.

• Since all messages between computers will pass through the hub, the hub becomes the central device in the network.

Servers

• Some networks will have a server, a powerful computer which provides services to a network.

• There are many different types of servers (such as file servers which store files that can be accessed by all devices on the network).

• A file server can allow multiple computers to store their files in a central location, meaning that the personal computers are no longer reliant on each other. All files can be stored and accessed centrally on the file server.

Routers

• When a network needs to be connected to another network over a large area, a router is needed.

• Routers forward messages from one network to another, acting like a gateway.

• A common job of the router is to join a home network to the internet via an internet service provider (ISP), acting like a gateway to the internet. This means all personal computers connected to the router can use the web via the internet.

• The router can be connected to the hub, just like the server, and all personal computers can have access to the router.

Types of networks

• PAN (Personal Area Network): this may be a single user with many devices connected (such as a laptop and smartwatch that is connected to a smartphone to share internet access or to notify the user of new messages).

• LAN (Local Area Network): this is a network with multiple users and is typically situated in a single building or room. The devices on the network are ‘local’ to each other. A small office (with multiple workstations, a switch/hub, a printer and a file server) will typically use LAN to allow shared access to files. LAN may also be found in a household where members of the household might have laptops, smartphones, computers, TVs and other smart devices connected via LAN.

• WAN (Wide Area Network): this is where devices are connected across a wider geographical area. Often, lots of LANs are connected together to form a WAN. People who use WAN include large businesses to share files and resources across multiple buildings and different locations/branches.

• Networks allow you to share hardware such as printers, software (allowing multiple users to run the same program on different devices) and data so that anyone can access shared work.

• Without networks, you wouldn’t be able to use your computer to communicate, however, if the network breaks, it can make a number of tasks it can be used for difficult (such as sharing photographs).

• Computers and devices networked together can expose ourselves to hackers and viruses. Most viruses spread over networks and the majority of hackers use networks the access people’s computers. Without networks, hackers would have to physically go to your computer.

The World Wide Web

Browsers examples: Google Chrome, Internet Explorer, Safari, etc.

Search engine examples: Bing, Google, etc.

Website examples: youtube.com, bbc.co.uk, etc.

Here are the parts of a web address:

https://www.unicef.org/

• URL stands for ‘Uniform Resource Locator’. It is the address of a World Wide Web page and is sometimes called the ‘web address’. This is the whole part of the text above.

• The “www” tells us this is a website.

• The “unicef.org” is known as the domain name. No two websites can have the same domain name.

• The “https:” is the protocol

• The top-level domain in a URL is the part following the last dot and suggests the content of a website. For example, “.org” tells us this is an organisation. Here are some more examples: