What is a computer network ?
A computer network is 2 or more computing devices that are connected together that share data and resources
What are the advantages and disadvantages of computer networks ?
Advantages:
- users can share files and resources including internet access and printers
- users can be monitored
- users can access files from any computer on the network
- increase available storage
Disadvantages:
- networks can be targeted by hackers, allowing unauthorised access to user’s files
- potential for a single point of failure
- malware and viruses can easily spread between computers
What are the main types of computer network ?
- Personal area network (PAN) - connects devices over a short range, centred around one user, often use short range wireless technology e.g Bluetooth.
- Local area Network (LAN) - covers a small geographical area located on a single site, hardware is owned by the organisation that uses it, found in schools, businesses and universities, can be wired or wireless
- Wide area network (WAN) - large geographic areas, made up of lots of LANS connected together, Hardware is lended from 3rd party telecommunication companies, connects through telephone lines, radio waves or fibre-optic cables e.g internet
What do wired and wireless networks involve ?
networks can be wired, wireless or both
Wired networks can use different cables to connect devices:
- fibre optic - transmits data as light, high performance over large distances
- twisted copper cable - also referred to as Ethernet cable, 8 individual wires, arranged into pairs that are twisted together to reduce interference, cheaper but can only be used for short distances
Wireless networks use radio waves to transmit data:
- involves WiFi for connecting devices in LAN’s and Bluetooth for connecting devices in PAN’s
- **involves wireless access points (WAP) to allow Wi-Fi devices to join a wired network
What are the advantages and disadvantages of wired network ?
Advantages:
- they offer higher bandwidth, allowing faster data transmission between devices
- connections are more secure, since devices have to be physically connected to a network and are intercepted less easily
Disadvantages:
- lack of flexibility, adding new devices to the network requires additional hardware meaning it can be costly and difficult
- devices must be physically connected, meaning devices connected to the network are much less portable
What are the advantages and disadvantages of wireless networks
Advantages:
- New devices can easily be added since there is no additional hardware required, there is no additional cost
- wireless networks can easily be extended by adding wireless access points, no need for extra cables
Disadvantages:
- they are less secure since wireless communications can be received by any device within range, increasing the risk of interception by 3rd parties
- Radio waves can be blocked by physical objects meaning the signal has decreased strength and quality, meaning there is a limit on how far the network can reach.
What is a wired network topology ?
It is the arrangement of devices within a network
What is a bus topology ?
- simplest way of connecting devices in a network
- each node and computer connects to a central back bone(the bus)
- data sent from one node is broadcasted to all nodes in the network meaning only one device can communicate at one time to avoid data collisions
- 2 terminators on each end to prevent data reflecting back along the bus
What is a star topology ?
- devices are connected via a central switch
- each device is individually connected to the switch, meaning if one device fails it will not affect the rest of the network
- allows all devices to communicate with each other simultaneously without data collisions since the central switch creates on-the-go connections with the 2 devices
What the advantages and disadvantages of bus topology ?
Advantages:
- cheaper than star networks, since there is less cable required and no need for a central switch
- easier to install, since they use less cabling
Disadvantages:
- more likely to experience data collisions, reducing transmission rates especially under heavy use
- less secure as data is broadcasted to all nodes on the network
What are the advantages and disadvantages of star topology’s ?
Advantages:
- less likely to experience data collisions, since data is only being transmitted between the 2 devices
- more secure, data is only being sent to the intended recipient
Disadvantages:
- uses more cable, therefore more expensive
- single point of failure, central switch
What is a network protocol ?
A protocol is a set of rules for how devices communicate and how data is transmitted between 2 or more devices across a network.
What is the 4 layer TPC/IP network protocol model ?
- A layer is a group of protocol with similar functions
- each layer is responsible for one aspect in communicating across the network
Layer 1 - application layer e.g (HTTP, HTTPS, FTP, SMTP, IMAP)
Layer 2 - transport layer e.g (TCP, UDP)
Layer 3 - internet layer e.g (IP)
Layer 4 - link layer e.g (Wi-Fi, Ethernet)
What happens at the application layer?
1)Network applications e.g web browsers, email clients operate the the application layer
2) applications create data that is sent and interpret data that is received
What are the protocols which operate at the application layer ?
- HTTP, hypertext transfer protocol, manages the transmission of data between a web server and browser, providing a way for users to interact with web resources
- HTTPS, hypertext transfer protocol secure, an extension of HTTP that encrypts communications between the web server and the client
- IMAP, internet messaging protocol, allows email client applications to interact with mail servers, allows users to retrieve emails from the server and allows them to read and organise messages and changes are synchronised with the server
- SMTP, simple mail transfer protocol, controls the sending of emails from the user’s client to their mail server, also from one users mail server to another.
- FTP, file transfer protocol, used to access, edit and move files between client and server computers
What happens at the transport layer ?
The transport layer sets up communication between hosts and determines thing like the size of packets which will be sent across the network
What protocols operate at the transport layer ?
- TCP, Transmission Control Protocol, splits data into numbered packets, which can be reassembled into the original data once the packets reach their destination, it then communicates with the receiving device to ensure that all packets have been received, if not the missing packets will be resent.
- UDP, user datagram protocol, simply splits data into packets without numbering them and is not concerned with whether they arrive or not
What happens at the internet layer ?
Here packets are given IP addresses, and are directed between devices by routers
What is the protocol which operates at the internet layer ?
- IP, internet protocol, it is responsible for directing packets to the correct destination over the internet by assigning ip addresses, in a process called packet switching
What happens at the link layer ?
- The link layer is where the physical transmission of packets takes place
- Network interface cards NIC turn packets into electrical signals or radio waves, these are sent to other link-layer devices e.g switches or wireless access points
What protocols operate at the link layer ?
- ethernet is a family of protocols which are responsible for transmission of data as electric signals across the link layer
- WIFI is a family of protocols which are responsible for transmission of data as radio waves across the link layer, generic term for networks of this nature is WLAN
What is the need for network security ?
Connecting computers to a network exposes organisations to risk of:
- loss or theft of data, or unauthorised access to data by 3rd parties or insiders
- damage to data and systems through the spread of malware
What are the different methods of securing networks ?
- authentication
- encryption
- firewalls
- Mac address filtering
What is authentication ?
Authentication is the process of determining who you are and what you can access through:
- usernames and passwords
- 2FA
- biometric authentication
Compares credentials to a known database of valid credentials.
