Fundamentals of Communication and Networking Flashcards
What is serial transmission?
Sending and receiving data one bit at a time in sequence down a single wire.
What is parallel transmission?
Sending and receiving multiple bits of data simultaneously using multiple wires.
What are examples of things that use serial transmission?
Ethernet
USB
Peripherals
What are the advantages of serial transmission?
Cheap
Reliable for long distances, as no synchronisation issues.
Less interferance
What are the advantages of parallel transmission?
Faster data transfer
Better for large amounts of data
Better for short distances
What are the disadvantages of serial transmission?
Slower for short distances
What are the disadvantages of parallel transmission?
Expensive
Signal degrades over long distances
Synchronisation is harder the more wires there are.
Interference.
What is synchronous data transmission?
When the pulse of the sending and receiving devices clocks are synchronised.
What is asynchronous data transmission?
When the two devices clock’s signals aren’t synchronised and only synchronise for the duration of the transmission by sending start and stop bits.
What are advantages of synchronous data transmission?
Faster transmission rates
Less overhead
Good for large data transfers
What are disadvantages of synchronous data transmission?
Complex
Expensive
If not perfectly synchronized results in data loss.
Requires a continuous connection
What are advantages of asynchronous data transmission?
Simple
Cheap
Good for small data transfer
What are disadvantages of asynchronous data transmission?
Slower
Greater overhead
More prone to timing issues
What does a start bit in asynchronous transmission do?
Causes the receivers clock to synchronise to the same rate as the senders.
What does a stop bit in asynchronous transmission do?
Indicates the data has arrived and allows the receiving computer to identify when the next start bit arrives.
What is bandwidth?
The range of frequencies that can be transmitted across a network connection.
What is bandwidth related to?
The range of frequencies available on the carrier wave that carries the data.
How do you increase bandwidth?
Increase the range of frequencies, as more data can be transferred in a given time.
What is bandwidth measured in?
Hertz (Hz)
What is bit rate?
The rate at which data is being transmitted.
What is bit rate measured in?
Bits per second.
What is the link between bit rate and bandwidth?
They are directly proportional.
What is baud rate?
The rate at which data can be transmitted.
Number of signal changes in a given amount of time.
What does one baud mean?
That there is one electronic state change per second.
What is an electronic state change?
A change in the frequency of carrier wave.
Change in voltage
Shift in waveform.
How can more than one bit be sent per state change?
By varying voltage levels to represent multiple bits, symbols worth multiple bits are transmitted.
What is latency?
The time delay when any component within a computer system is responding to an instruction.
What are the 3 causes of latency?
Propagation
Transmission
Processing
What is propagation latency caused by?
The time taken for a logic gate to transmit data.
What is transmission latency caused by?
The time taken for data to pass through a cable.
What is processing latency caused by?
The time taken for data to travel around a network.
What does PING do?
When data is sent to another device on the network it calculates how long it takes to come back.
What is a network?
Devices connected together in order to share and manage data and resources.
What is a Network Interface Card (NIC)?
A device that enables devices to connect to a network.
What is a Peer-to-Peer network?
A network methodology where all devices in a network share resources between themselves.
What are the advantages of a Peer-to-Peer networks?
Cheap
Easy to set up
Works well for small offices/homes
No central point of failure
What are the disadvantages of a Peer-to-Peer networks?
Less security
No centralized management
What is a Client-Server network?
A network methodology where one computer has the main processing power and storage and the other devices act as clients requesting services from the server.
What are the advantages of a Client-Server network?
Centralized updates
Clients failing doesn’t affect the network
Easy to add new clients
Security
What are the disadvantages of a Client-Server network?
Expensive set up
Requires specialist maintenance
Network traffic
If server fails whole network fails
What is a network topology?
The conceptual layout of a network.
How does a bus topology work?
It uses one main cable as a backbone to transmit data. Data is sent to every device and only accepted by the intended receiver. Contains terminators which prevent signal deflection down the wire.
What are the advantages of the bus topology?
Easy to set up and install
Works if a client switches off
Cheaper
What are the disadvantages of the bus topology?
Main cable failing means whole network fails
Slows down if more devices are added
Less secure
Less reliable
How does a star topology work?
All devices are connected to a central hub or switch which sends data to the intended recipient, by controlling the flow of data or by sending data to all devices.
What are the advantages of the star topology?
More reliable
No collisions
Easy to add new clients
More clients doesn’t affect speed
More secure
What are the disadvantages of the star topology?
Expensive
Difficult to install
If switch/ hub fails network fails
Can get congested
What is a physical topology?
The way in which devices are physically connected, how the hardware is set up.
What is a logical topology?
How data is transmitted around a network.
How would a physical star topology configured as a logical bus topology be set up?
Hardware set up as a star topology with all devices connected to a central node. The central node being a hub which sends data to all the clients and the receiver accepts. (Bus logical topology)
How do wireless networks work?
Instead of using physical cables to connect devices data is transmitted using radio waves.
What does a Wireless Access Point do?
Enables devices to wirelessly connect to a wired network by providing a Wi-Fi signal and acting as a bridge.
What is a Media Access Control Address (MAC address)?
A unique code that identifies a particular device on a network.
Hexadecimal number
What is a LAN?
A network that connects devices within a limited area, allowing them to share resources.
What is a WAN?
A network that covers a large geographic area, connecting multiple LANs, allowing communication and sharing resources.
What is a WLAN?
Wireless Local Area Network
A LAN that uses radio waves.
Where are WLAN’s used?
In a home or small office.
What is WWAN?
Wireless Wide Area Network
WAN that uses radio waves.
How does a WLAN work?
A wireless router connects to the internet using physical cabling while providing wireless access to devices, allowing them to connect to the internet.
How do WWAN’s work?
Uses mobile phone networks which use satellites and transmitters and receivers to transmit signals over long distances.
What is Wi-Fi?
A method for connecting devices wirelessly to a network and to the internet.
WWAN
How does Wi-Fi work?
Uses a generic international standard ensuring all devices are compliant and can connect and transmit data around a network.
What is a protocol?
A set of rules allowing devices to communicate with each other.
What does CSMA/CA do?
Enables networked devices to transmit data at high speeds without interference.
By checking if the transmission channel is being used before sending any data.
How is data transmitted around networks?
It is sent around in frames which are re-assembled when received.
How does CSMA/CA work?
Checks if the transmission channel is being used.
If the channel is idle data is sent
If the channel isn’t the device waits a random amount of time before trying again to prevent collisions.
What does RTS/CTS stand for?
Request To Send/ Clear To Send
How does the RTS/CTS protocol work?
Sends a RTS message to the receiving node and only sends data frames once the CTS message is sent back by the receiving device.
What is SSID?
A 32-character unique code that identifies a device on a wireless network.
Seen on the header of every frame.
What does the SSID do?
Identifies the correct WLAN being used so devices connect to the right network.
What is required for a SSID to work?
For the NIC to have the same code so the device can connect.
What are disadvantages of wireless networks?
Less secure as radio signals are easy to intercept.
More interference
Limited range
What are advantages of wireless networks?
Easy installation
Flexable
What is WPA (WiFi Protected Access)?
A protocol for encrypting data and ensuring security on Wi-Fi networks.
How can security be improved on wireless networks?
Change and hide the SSID
Ensure all devices are WPA compliant
Create a whitelist of trustworthy MAC addresses.
