computer networks Flashcards
what is a computer network
A computer network is more than one computer connected together and able to share resources/ communicate
Networks allow computers to exchange DATA
what are the advantages of computer networks
you can share documents easily
Users can connect with people in other countries
It can be more reliable
Backups can be centralised
Software and storage can be shared across the network
Share devices, like printers
what are the disadvantages of computer networks
Networks are expensive to set up
Managing a network requires specialist skills
Viruses can be spread through connections
Managing security over an entire network requires specialist skills
Hackers could gain access to an entire network if it isn’t protected
What is PAN
personal area network
This is typically limited to a single user in the network with multiple connected devices.
PAN’s typically will use wireless technology such as Bluetooth to transfer data
what is a LAN
local area network
LANs can be WIRED, WIRELESS or a mixture of both
LAN – know that these usually cover relatively small geographical areas.
LAN – know that these are often owned and controlled/managed by a single person or organisation.
what is a WAN
wide area network
WAN – know that the Internet is the biggest example of a WAN.
WAN – know that these usually cover a wide geographic area.
WAN – know that these are often under collective or distributed ownership.
A WAN will normally consist of a lots of LANs are connected together by cables to create a WAN.
is the internet PAN , LAN or WAN
WAN
what is wired transmission media
Wired transmission media is a physical cable that connects one device to another.
This is often shown as a solid or a long dashed line in a graph or a diagram.
what is wireless transmission media
Wireless transmission media doesn’t require a physical cable. Wireless signals are sent through the air.
A wireless connection is often shown using a short dotted line or a wave symbol.
is copper cable wired or wireless
Copper cable is a type of wired transmission media. It uses electrical signals to transmit data.
is fibre optic cable wired or wireless
Fibre optic cable is a type of wired transmission media. It uses light pulses as signals to transmit data.
A 1 is represented by the light being on.
A 0 is represented by the light being off.
is wifi wired or wireless (how does it transmit data)
WiFi is a suite of protocols used for wireless transmission. It uses radio frequencies to send signals.
Changes in the radio frequency signify a 1 or a 0.
WiFi signals can transmit data up to 50 metres.
is bluetooth wired or wireless
Bluetooth is another form of wireless transmission media. It also uses radio frequencies to transmit data.
Bluetooth signals can transmit data up to 10 metres.
what is bandwidth
Bandwidth is the amount of data that can be moved from one point to another in a given time. Higher bandwidth = more data per second
what are the advantages and disadvantages of wired networks
Advantages
Faster connection (little to no interference)
Higher bandwidth
Better security
Disadvantages
Cables can be a trip hazard and look unpleasant
More expensive and time-consuming to add devices, as each device needs cables
Devices are in fixed positions (no portability)
what are the advantages and disadvantages of wireless networks
Advantages
No trailing wires/no trip hazard
It is quick and cheap to connect new devices
Allows portability
Disadvantages
Lower bandwidth
Wireless connections can be weakened by walls and ceilings
Less secure
what is a topology
There are many different arrangements for network engineers to choose from.
These arrangements are called topologies.
describe a bus topology
In this arrangement, each node is connected to a single cable. When data is sent from one node to another it is sent in both directions.
Terminators are placed at the end of the cable to stop the signal being reflected back down the cable.
This was the earliest type of LAN topology used
in a bus topology the data is sent down the main cable (the bus) and all nodes connected to the bus will monitor the messages.
It is only accepted by the node that requires it, other nodes ignore it.
what are the disadvantages of a bus topology
data traffic was passing through all NODES and this often caused congestion
If the Ring or Bus was broken the entire network will fail
no longer used
describe a star topology
This is a graph for a star topology.
The arrangement has one central node with all of the other nodes connected to it.
The central node would typically be a hub or a switch that could transfer data between nodes.
If a hub is in the central node then it will broadcast the data to all nodes connected to it.
It is only accepted by the node that requires it, other nodes ignore it.
If a switch is in the central node then it will transfer the data to the required location.
what are the advantages and disadvantages of star topology
advantages
a damaged link only affects the attached node
you can easily add new nodes
works well under heavy load
disadvantage
central node is a single point of failure
requires many more cables than bus which is expensive
what is a network protocol
a set of rules for communication
what is ethernet
Ethernet isn’t just a type of cable. It is a suite of protocols used in a wired network.
Any network hardware that uses the ethernet protocols will work with any other hardware that uses the ethernet protocols.
what is WiFi
WiFi is a suite of protocols used in wireless communication.
It enables the transmission of data through radio signals.
Wi-Fi is a trademark and that the generic term for networks of this nature is WLAN.
what is HTTP and HTTPS
HTTP stands for Hypertext Transfer Protocol. It is a protocol that is used to identify, request, and transfer web pages across the internet.
HTTPS is a secure version of this protocol that adds in extra protection for the data that is transmitted.
what is FTP
FTP stands for file transfer protocol. It deals with uploading and downloading files from a server.
FTP is sometimes used for uploading personal web pages to a web server.
It is also used to deal with other types of files like PDFs and images.
What is POP
POP stands for post office protocol. This type of email protocol is less common nowadays.
The POP protocol retrieves the email from the email server, delivers it to your computer or device, and then deletes it from the email server.
Once you download the email, it only exists on your device and is not backed up on a server.
what is IMAP
IMAP is an alternative protocol to POP and is the more commonly used one now
IMAP stands for internet message access protocol.
IMAP retrieves the email from the email server but also leaves a copy of it on the remote server.
This is helpful if you want to view your emails on your phone and also view them in a web browser.
what is SMTP
SMTP stands for simple mail transfer protocol.
This protocol deals with sending an email to an email server.
what is the TCP/IP model
The TCP/IP model is a suites of protocols that is used across most Networks including LANs and WANs (including the Internet)
It uses packet switching.
This means it breaking data into packets, distributing them over the network, and reassembles them at the destination.
what are the 4 layers of the TCP/IP model
application
transport
internet
link
what happens in the application layer
The top layer of the TCP/IP model is the application layer.
This layer is used by applications, such as web browsers or email clients .
The application layer has protocols for preparing (or encoding) data for sending.
Protocols are also used to decode any received data into a meaningful form for the end user.
what is the transportation layer
The next layer is the transport layer.
The transport layer accepts ‘messages’ from the application layer as application data.
It takes this data and splits it into segments.
Each segment is given a header that contains information, such as the segment number and number of segments.
what is the internet layer
The third layer is the internet layer. This layer receives segments from the transport layer, adds the addresses data to build the IP packets.
This includes both the sender and receiver’s IP addresses.
This is so that the packets can be distributed to the correct location.
what is the link layer
The fourth layer is the link layer.
The link layer is responsible for transporting IP packets across each of the individual links that make up the path between the client and the server.
what is UDP
UDP -User Datagram Protocol- similar to TCP, but because messages are sent instead of packets -chunks - it is often faster, allowing for gaming or video calls over the internet
why is it important to ensure data is kept safe
To protect people from:
Fraud
Phishing scams
Identity theft
To avoid the loss of sensitive data
Networks are extremely vulnerable to attack. This is because they can:
Span large geographical areas
Have large numbers of users
Be expensive to maintain and keep up to date with the latest security threats
It is important for network engineers to protect the network from attack.
