Section 6 - Networks

Section 6 - Networks

1. Key facts

   • A LAN (Local Area Network) covers small areas such as: businesses and schools.
   • A WAN (Wide Area Network) connects several LANs across multiple different countries. Organisations hire infrastructure from certain companies who own and manage the WAN.
   • A PAN (Personal Area Network) connects devices over a very short range, usually centred around a single user.
   • In order for networks to connect, they require an NIC (Network Interface Card) - this is requred for both wired and wireless networks.
   • Routers are used to transmit data between networks, and is most commonly used to connect devices to the internet.
   • To connect devices on a LAN, switches are used.
   • There are multiple different cables that can be used to connect devices in a wired network. They are chosen based on cost, bandwidth, and how far the data needs to be transferred.
     • Fibre optic cables: They transmit data as light and are high performance and expensive. They can transmit data over large distances at a high bandwidth without loss of signal quality.
     • CAT 5e and CAT 6: They are both common types of Ethernet cables. They are made of pairs of copper wire twisted together. They are usually used in homes as they are cheaper than fibre optic cables but still have a decent bandwidth.
     • Coaxial cables: They are made of a single copper wire, surrounded by plastic fro insulation and to protect from outside interference. They tend to be very cheap and have a low bandwidth.

2. Wireless networks

   • Local wireless networks are known as WLANs (wireless LANs). WiFi is a specific family of WLANs.
   • Wireless networks use radio waves to transmit data
   • In order to set up a wireless network, you need a WAP device (Wireless Access Point). A WAP is ultimately a switch that allows devices to connect wirelessly.
   • In order to connect wirelessly, the devices themselves need wireless capability. This is often built in, but if not a dongle can be used.
     • USB dongles: Can be plugged into computers to allow them to connect wirelessly.
     • HDMI dongles: Can use wireless networks to stream high-quality video to a TV.

3. Network toplogies

   • Star topology
     • Has a central switch to allow many devices to access the server simultaneously.
     • May be wired or wireless.
   • Bus topology
     • Use a single backbone cable, called a bus, to connect all devices.
     • Two terminators are placed at either end of the topology to prevent data from reflecting back. Otherwise reflected signals would interfere and make the network unusable.

4. Network protocols

   • A protocol is a set of rules for how devices communicate and how data is transmitted across a network.
   • Protocols cover how communication should start and end, how data should be organised, and what devices should do if data goes missing.
   • Data sent between networks is split into packets containing extra information (like the destination and sort address.
   • Layers
     • A layer is a group of protocols which have similar finctions.
     • Layers can do their jobs without worrying about what happens in other layers.
     • Each layer does hidden work needed for the action of the layer above.
     • There are 4 layers to the TCP/IP model:
       • Application layer (layer 4): Providing networking services to applications, e.g. HTTP, FTP, SMTP.
       • Transport layer (layer 3): Setting up communications between 2 devices, splitting data into packets, and checking packets are correctly sent and delivered, e.g TCP, UDP.
       • Internet layer (layer 2): Adding IP addresses to data packets, directing them between devices, and handling traffic, e.g. IP.
       • Link layer (layer 1): Passing data over the physical network, and responsible for how data is sent, e.g. Wi-Fi, Ethernet.

5. Cyber security threats

   • Cyber security aims to protect networks, data, programmes, and computers against damage, and cyber attacks.
   • Penetration testing
     • Penetration testing is when organisations employee specialists to simulate potential attacks in order to identify weaknesses in their security.
     • There are two types:
       • White box: The person carrying out the test will be given user credentials.
       • Black box: The person carrying out the test will not be given user credentials.
   • Malware
     • Malware is code designed to cause harm or gain unauthorised access to a computer system. It is often installed on a device without the users knowledge or consent.
     • Malware can be installed through an email attachment or through a USB or SD card.
     • Malware usually: deletes or modifies files, locks files, displays unwanted ads, monitors the user, or alters permission.
     • Malware can be spread by: attaching to files, self replicating, or being disguised as legitimate software.
   • Social engineering
     • Pharming: When a user is directed to a fake version of a website so criminals gain access to personal details.
     • Phishing: When a user is directed to a fake website via an email so criminals gain access to personal details.
     • Shouldering: When criminals watch over somebodies shoulder to see somebodies personal details.
     • Blagging: When somebody makes up a story to persuade somebody to give personal details or money.