A network describes 2 or more computers (laptops, phones, shop tills etc.) which are connected together to share information and data between them. We use networks to share files, access the internet and communicate. There are several types of network that include:
Client-server networks - A network with at least one server which provides services to the 'client' computers
Peer-to-peer network - A network without any centralised servers where each computer acts as both a 'client' and a 'server' both requesting and providing a service where necessary
A client is a computer which is making a request.
Server - A server is a powerful computer that provides the network with 'services' like...
- LAN Networks - This stands for 'Local Area Network' which is a network that covers a relatively small geographical area. LAN networks are small networks typically used in homes or buildings. If you have a network at home, this is probably a LAN network.
- WLAN Networks - This simply stands for 'Wireless Local Area Network' which is a wireless version of LANs
- WAN Networks- This stands for 'Wide Area Network' which is a network of 2 or more LANs that covers a large geographical area. WAN networks are very large, and often span over countries. The biggest example of a WAN network is the Internet.
- PAN Networks- This stands for 'Personal Area Network'. PAN networks are even smaller than LAN networks and are usually used to connect a computer to another device i.e a printer or a phone to headphones via Bluetooth.
Client-server networks - A network with at least one server which provides services to the 'client' computers
Peer-to-peer network - A network without any centralised servers where each computer acts as both a 'client' and a 'server' both requesting and providing a service where necessary
A client is a computer which is making a request.
Server - A server is a powerful computer that provides the network with 'services' like...
- Storing files and back-ups
- Sending/receiving emails
- Security and authentication
- A client will connect to the server using it's address by requesting a connection
- The client will then make a service request to the server
- The server will carry out the request (if it is valid) and use the address from step 1 to send any data to the client
There are four types of network topologies: Bus, Ring, Star and mesh. You can think of topologies as shapes or layouts that make up a network, each with their own practical advantages and disadvantages.
A bus network is the simplest of the lot. It works by a single cable known as the bus connecting all the devices together, with two terminators on either end that help to make the data bounce back. It is done by sending a signal through the cable and all the devices check to see if the data packet is registered to them.
The advantages of this network are...
A bus network is the simplest of the lot. It works by a single cable known as the bus connecting all the devices together, with two terminators on either end that help to make the data bounce back. It is done by sending a signal through the cable and all the devices check to see if the data packet is registered to them.
The advantages of this network are...
- It is easy to install and to expand at any given time, so it is a good starting point for many networks.
- It is relatively cheap and only needs one cable
- A bus topology is not particularly reliable because if there is an issue with the bus connecting all the devices together, then all the devices fail.
- The more devices there are, the slower they are due to only one piece of data being able to be sent at a time without causing data collisions (which cause data packets to almost "break apart")
- Other devices on the network could potentially view your data and the fact that data is sent to all devices in the network is a security risk
Although a bus network operates in a line, with two terminators acting as barriers on either side, a ring network operates in a circle, hence the name. As such, data packets are sent in one direction around all the devices until it finds the one it is looking for. Because of this, data collisions do not occur as there will never be two data packets going in opposite directions, unlike a bus network where they bounce back and fourth. New devices can also easily be added without affecting the performance though the entire network has to be shut down first. However, if only one computer isn't functioning properly or stops working, then the entire network will fail. and as data goes to all computers, there is a security risk. Faults are also difficult to find on this network topology and it is more expensive than a bus network as it needs more wire.
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A star network is often thought of to be the most reliable. It has a switch or hub located in the centre of the network, which all devices are connected to via a cable each, and issues are generally not a problem because one computer failing doesn't affect the whole network and errors are easy to locate and fix. Data collisions amongst this network are very rare because it doesn't need to deal with other computers- only the switch but because of the sheer amount of cables, this network is quite expensive to set up running and to expand. As well as this, if the switch/hub fails then so does the entire network.
- Switch - Receives messages/data and sends them only to the computers that need them
- Hub - Receives messages/data and sends them to all computers
In a mesh network, all devices are interconnected to one another, like a more complex variation of the ring topology. In this topology, it is easy for devices to be removed from the network and for data to be sent around at high speeds. Like the star network, however, mesh networks are quite expensive due to the amount of cables but unlike the star network, it is difficult to locate and fix an error though errors are usually not much of a problem due to the various potential routes for data to travel. In cases of a particularly large network, every device needs its own switch, making the network more expensive and complex.
A mesh network can be fully connected or partially connected. The latter uses fewer wires and so is cheaper and has fewer connections between each computer. As a result, data is routed through computers to get from one to another if they are not directly linked.
The biggest network an the biggest mesh network is the internet.
A mesh network can be fully connected or partially connected. The latter uses fewer wires and so is cheaper and has fewer connections between each computer. As a result, data is routed through computers to get from one to another if they are not directly linked.
The biggest network an the biggest mesh network is the internet.
Network Hardware
Copper/Coaxial Cable
Copper is an electrical conductor so it carries electrical signals which are read by the computers. The presence of a signal is a 1 and the absence is a 0 in binary. These signals deteriorate over long distances. Ethernet cables use twin copper cables which are copper cables twisted around each other.
Fibre Optic Cable
Fibre optic cable is made of glass and reflects light across it. When read, the presence of light is a 1 and the absence is a 0. As it is the reflection of light, this data travels at light speed and also travels much greater distances without deteriorating.
Wireless Connection
Wireless connection is the transmission of radiowaves (as well as microwaves and infra-red light). Wireless connections can only travel across limited distances and are slower than wired connections. Wireless Access Points are pieces of hardware that connects wireless signals to hardware. If you use WiFi at home, you probably have an all-in-one hub which is a router, switch and WAP all at the same time.
Router - connects a device to the internet.
Copper is an electrical conductor so it carries electrical signals which are read by the computers. The presence of a signal is a 1 and the absence is a 0 in binary. These signals deteriorate over long distances. Ethernet cables use twin copper cables which are copper cables twisted around each other.
Fibre Optic Cable
Fibre optic cable is made of glass and reflects light across it. When read, the presence of light is a 1 and the absence is a 0. As it is the reflection of light, this data travels at light speed and also travels much greater distances without deteriorating.
Wireless Connection
Wireless connection is the transmission of radiowaves (as well as microwaves and infra-red light). Wireless connections can only travel across limited distances and are slower than wired connections. Wireless Access Points are pieces of hardware that connects wireless signals to hardware. If you use WiFi at home, you probably have an all-in-one hub which is a router, switch and WAP all at the same time.
Router - connects a device to the internet.
Wired Advantages |
Wired Disadvantages |
Wireless Advantages |
Wireless Disadvantages |
Faster than wireless |
Expensive to install and configure |
No need for cables |
Can be slower than wired |
Not easy to intercept data |
Requires many cables on site |
Users can use their own devices |
Interference from other devices can affect performance |
Less susceptible to interference |
A wider range of devices can communicate |
Walls and physical objects can affect performance |
|
Data must be encrypted to prevent interception |
NIC - Network Interface Card - This is a physical card which allows you access to a network so you can connect. It also contains your permanent MAC (Media Access Control) address
Bandwidth - the amount of data that can be transmitted on a network in a given period of time measured in bps (bits per second)
Web server - A file storage facility that holds web pages
Packet - a small part of data sent through a network when data is 'broken down'. They are labelled with the sender's address, the recipient's address, the packet number and how many packets the data was split into.
Protocol - a set of rules that determine how communications on a network are formatted and what data is included. Protocols may contain...
Protocol stack - A group of protocols that work together
Using the Internet
TCP/IP Protocol Stack
TCP/IP =Transmission Control Protocol/Internet Protocol
This protocol stack is split into 4 layers:
Application
This layer interacts with the user to provide access to the services the user wants. HTTP (Hyper-Text-Transfer Protocol), FTP (File Transfer Protocol) and mail protocols (SMTP, POP3 and IMAP) are all in this layer.
HTTP/S - This sends and receives data between web browsers and web servers and determines how data should be formatted. When you are on a web page, in the address bar, you will see either HTTP or HTTPS. The S simply stands for secure and indicates that the data is encrypted.
FTP - This transfers files overnetworks that use TCP and sends web pages from a web-developer to the web server.
Mail Protocols - SMTP (Simple Mail Transfer Protocol) sends emails through the internet and details the formatting. POP3 (Post Office Protocol 3) retrieves an email from the email server (normally deleting messages from the server in the process). IMAP (Internet Message Access Protocol) allows more than one email client to access an email by keeping mail on the server instead of deleting it (unless you delete it).
Transport
This manages end to end communication using TCP (or UDP)
TCP - Transmission Control Protocol makes sure data has been sent and received properly by making the receiving computer send messages back to see when data has been sent. It also uses checksums (a mathematical formula that should produce the same number as when the message was sent) to ensure data is accurate when received. It also carries out flow control which ensures the data travels at a speed at which it can be processed well. It also ensures data sent back to the application layer is sent correctly without duplicates.
UDP takes up less space on the network as it doesn't ask for the confirmation data to verify the message was sent.
Network/IP
This layer sends data across the network and routes it using IP (Internet Protocol)
When you type in a web page address (URL -Universal Resource Locator) into your web browser, it goes through DNS (the Domain Name System) which uses DNS Servers to find the IP address of the page so the URL can be converted into its IP address.
An IP Address is a unique address of a particular web page also used for identifying computers and servers. It allows packets to be routed as it holds their destination.
Link
The final layer controls the transmission and reception of packets to/from the network. It is the physical connection between network nodes and the MAC address that data is going to is added and removed.
Bandwidth - the amount of data that can be transmitted on a network in a given period of time measured in bps (bits per second)
Web server - A file storage facility that holds web pages
Packet - a small part of data sent through a network when data is 'broken down'. They are labelled with the sender's address, the recipient's address, the packet number and how many packets the data was split into.
Protocol - a set of rules that determine how communications on a network are formatted and what data is included. Protocols may contain...
- The addresses/identification of computers
- The routing of data
- Sequencing of data
- Error checks
Protocol stack - A group of protocols that work together
Using the Internet
TCP/IP Protocol Stack
TCP/IP =Transmission Control Protocol/Internet Protocol
This protocol stack is split into 4 layers:
Application
This layer interacts with the user to provide access to the services the user wants. HTTP (Hyper-Text-Transfer Protocol), FTP (File Transfer Protocol) and mail protocols (SMTP, POP3 and IMAP) are all in this layer.
HTTP/S - This sends and receives data between web browsers and web servers and determines how data should be formatted. When you are on a web page, in the address bar, you will see either HTTP or HTTPS. The S simply stands for secure and indicates that the data is encrypted.
FTP - This transfers files overnetworks that use TCP and sends web pages from a web-developer to the web server.
Mail Protocols - SMTP (Simple Mail Transfer Protocol) sends emails through the internet and details the formatting. POP3 (Post Office Protocol 3) retrieves an email from the email server (normally deleting messages from the server in the process). IMAP (Internet Message Access Protocol) allows more than one email client to access an email by keeping mail on the server instead of deleting it (unless you delete it).
Transport
This manages end to end communication using TCP (or UDP)
TCP - Transmission Control Protocol makes sure data has been sent and received properly by making the receiving computer send messages back to see when data has been sent. It also uses checksums (a mathematical formula that should produce the same number as when the message was sent) to ensure data is accurate when received. It also carries out flow control which ensures the data travels at a speed at which it can be processed well. It also ensures data sent back to the application layer is sent correctly without duplicates.
UDP takes up less space on the network as it doesn't ask for the confirmation data to verify the message was sent.
Network/IP
This layer sends data across the network and routes it using IP (Internet Protocol)
When you type in a web page address (URL -Universal Resource Locator) into your web browser, it goes through DNS (the Domain Name System) which uses DNS Servers to find the IP address of the page so the URL can be converted into its IP address.
An IP Address is a unique address of a particular web page also used for identifying computers and servers. It allows packets to be routed as it holds their destination.
Link
The final layer controls the transmission and reception of packets to/from the network. It is the physical connection between network nodes and the MAC address that data is going to is added and removed.