Section Six- Networks Flashcards
What does LAN stand for?
It stands for local area network. It covers a small geographical area.
What does WAN stand for?
WAN stands for Wide area network. A WAN connects LANs that are different geographical locations.
What does PAN stand for?
It stands for personal area network. They connect devices over a very short range. They are normally centred around a single user. PAN often use common wireless technology to connect devices like Bluetooth.
Benefits of networking computers
Sharing files is easier- network users can access the same files, work on them at the same time and copy files between machines.
You can share the same hardware between multiple devices.
You can install and update software on all computers all at once.
You can communicate across the network cheaply and easily.
User accounts are kept centrally, so it can be accessed by any devices on that network.
Drawbacks of networks
They can be expensive to set up, as you often need a lot of extra hardware.
Networks can be vulnerable to hacking, and malware can easily spread between networked computers.
Some networks are dependent on one or more servers. If those servers go down it can be quite disruptive for people trying to use the network.
Large networks are difficult to manage.
What hardware does a network require?
A Network Interface Care is a piece of hardware inside a device that allows it to connect to networks.
Switches are used to connect devices on a LAN, while routers transmit data between different networks, and are most commonly used to connect to the Internet.
Most routers contain this including a WAP.
What are the different cables that can connect you to the network?
Fibre optic cables- transmits data as light. They are high performance and expensive cables- they don’t suffer interference and can transmit over very large distances at a high bandwidth without the loss of signal quality.
CAT 5e and CAT 6 are common types of Ethernet cables. They contain pairs of copper wires which are twisted together to reduce internal interference. They’re cheaper than fibre optic cables and have a decent bandwidth, which is why they are commonly used in homes and offices to connect devices on a LAN.
Coaxial cables are made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference. They tend to be very cheap, although they also have a low bandwidth.
What does WLANs stand for?
Local wireless networks. They are also known as Wi-Fi, but Wi-Fi is a specific family of WLAN protocols.
What do wireless networks use to transmit data?
Radio waves
What do you need to setup a wireless network?
You need a wireless access point (WAP). It’s basically a switch that allows you to connect wirelessly.
Benefits of a wireless networks
Wireless networks are convenient, as you can get your device to automatically connect to the network, and can also move around while connected to the network.
They can be cheaper and better for the environment as you don’t need any wires.
Very easy to add more users to a wireless network- you don’t need to install extra wires or do any complex setup.
Drawbacks of wireless networks
Wireless networks are generally less secure than wired networks- access points are usually visible to all devices, not just trusted ones, which allow hackers to gain access.
There is a limit on how far a wireless network can reach.
They generally have a lower bandwidth and is less reliable than wired networks.
In a star topology, how are all the devices connected?
All the devices are connected all around the centre.
All the devices are connected to a central switch or server that controls the network. The central switch allows multiple devices to access the server simultaneously.
Pros of a star topology
If a device fails or a cable is disconnected, the rest of the network is unaffected.
Simple to add more devices to the network.
Tend to have a better performance than other setups- data goes straight to the central device so all devices can transmit data at the same time.
Very few data collisions on a star network compared with other topologies.
Cons of a star topology
In wired networks, every device needs a cable to connect to the central switch or server. This can be expensive.
The switch is expensive.
If there is a problem with the switch or server then the whole network is affected.
There is a maximum number of devices able to be connected to one switch. So you may have to buy another one.
How are the devices connected in a bus topology?
Bus topologies use a single ‘backbone’ cable called a bus, to connect all devices.
Two terminators are placed at the ends of the bus to stop data reflecting back along the bus. Without the terminators, reflected signals would cause interference and potentially make the network unusable.
Pros of a bus topology
The network is unaffected if a device fails.
Bus networks aren’t dependent on a central switch working to keep the whole network running.
They’re relatively cheap to set up. The total length of wiring needed is much less, and the hardware you need is cheaper than switches, both to buy and maintain.
Cons of a bus topology
Data collisions are common on a bus network. When there is a data collision the data must be resent, which slows the network down.
The more devices you add to the network, the more likely data collisions are. This makes bus topologies unsuitable for a large network.
To try and avoid data collisions, devices must wait for the bus to be available before they can send any data- this can also slow the network down.
If the bus cable gets broken, it splits the network into separate parts. Since the separated networks don’t have terminals at both ends of the bus, there will be a lot of reflected signals which shuts down the entire network.
What is a protocol?
A protocol is a set of rules for how devices communicate and how data is transmitted across a network.
(Extra information) Protocols cover how communication between two devices should start and end, how the data should be organised, and what the devices should do if the data goes missing.
What are layers in a protocol?
A layer is a group of protocols which have similar functions.
Layers are self-contained - protocols in each layer do their job without needing to know what’s happening in other layers.
Each layer serves the layer above it- it does the hidden work needed for an action on the layer above.
What are the 4 layers of the TCP/IP model?
Layer 1- Link layer
Passing data over the physical network . Responsible for how data is sent as electrical signals over cables, wireless and other hardware, and for interpreting signals using device drivers.
Wi-Fi, Internet
Layer 2- Internet Layer
Adding IP addresses to data packets, directing them between devices and handling traffic. Used by routers.
IP
Layer 3- Transport Layer
Setting up communications between two devices, splitting data into packets and checking packets correctly sent and delivered.
TCP,UCP
Layer 4- Application layer
Providing networking services to applications.
HTTP, FTP,SMTP,HTTPS
What are the advantages of using layers?
Breaks the network communication into manageable pieces.
As layers are self contained, they can be changed without other layers being affected.
Having set rules for each layer forces companies to make compatible, universal hardware and software, so different brands will work with each other and always work in basically the same way.
What does the protocol HTTP, HTTPS, FTP, IMAP, SMTP stand for and what is it used for?
HTTP- Hyper text transfer protocol- used by web browsers to access websites and to communicate with web servers.
HTTPS- Hyper Text Transfer Protocol Secure- a more secure version of HTTP. Encrypts all information sent and received.
FTP- File Transfer Protocol- Used to access,edit and move files between devices on a network.
IMAP- Internet Message Access Protocol- Used to retrieve emails from a server.
SMTP- Simple Mail Transfer Protocol- used to send emails. Also, used to transfer emails between servers.
What are TCP and UDP?
They are transport layer protocols which control the packaging and unpacking of data.
