Networks and the internet Flashcards
what is a network topology
the way a network and its connected devices are connected
what does CSMA/CA stand for
Carrier Sense Multiple Access with collision avoidance
what does data travel over when we use wifi
- a frequency (channel)
implications of using wireless networks
- as communication is done in an open space, it’s less secure
- transmission speed is lower because of traffic
- has a limited amount of bandwidth for communication and breaches of network security
- can be easily hacked
channels have a frequency range of….
22MHZ
describe the CSMA/CA without RTS/CTS
- if a device is ready to send some data, it starts and assembles the packet of data it wants to send
- asks if the channel idle
- if yes, data is transmitted
- if no, device waits a random amount of time and checks if the channel is idle again
describe the CSMA/CA with RTS CTS
- Computer with data to send listens for data signal
- If signal present, then continue to wait.
- when no signal is present, computer sends a RTS
- two computers could start transmitting simultaneously if they both detect there is no data signal
- receiver responds with a CTS
- if cts is received, start to transmit
- If CTS not received continue to wait
- receiver sends acknowledgement after all data is received
- if no acknowledgement received in reasonable time, then retransmit
the hidden node problem and how to fix it
what it is:
a wireless issue in networks where some nodes are unable to detect signals from other nodes, leading to collisions and message corruption
how it works:
- node a can see the WAP because it’s in range, node b can also see WAP
- node a cant see node b because they are out of range with each other
- if both nodes try to transmit data wirelessly, using CSMA/CA without RTS will result in data collisions
- by adding an RTS/CTS, node A doesn’t need to make any assumptions abt how many nodes there are etc, it just adds an extra layer of protection, and the WAP checks everything
what is the Wireless AccessPoint
- a hardware device that allows wireless devices to connect to a wired network using Wi-Fi or related standards.
- it bridges wireless and wired networks,
- enhance network connectivity by increasing the range and coverage area of the network
- provide flexibility in network setup and expansion, allowing for easy addition of new devices
what is a wireless router
a networking device that forwards data packets between computer networks, eg over the internet
what is a wireless network adapter/interface
- a hardware device that enables a computer or other device to connect to a wireless network
what does a WirelesssAccessPoint require access to
it requires a connection to the router, and the router requires a connection to a modem
what is a modem
a modulator demodulator - a computer hardware which converts data from a digital format into a format suitable for an analog transmission medium such as a telephone or radio (a DAC)
features of service set IDentifiers (SSIDs)
- identifies each network by a unique name
- must be used by all devices on that network
- can be set manually or automatically
- can be hidden to make it harder to detect
- can be set to broadcast a range of wireless devices in range of an access point
what do WPA and WPA2 do
- WPA and WPA2 utilize a form of authentication known as PSK
- Users must enter a password to authenticate themselves to the network.
- WPA and WPA2 dynamically generate and manage encryption keys to enhance security. these keys are periodically changed
- they use MAC (Media Access Control) address filtering, which allows or denies network access based on the unique hardware address of a device.
what is serial data transmission
a type of data transmission where bits are sent via an interface one at a time over a single wire from the source to the destination
what is parallel data transmission
where multiple bits are sent simultaneously over a number of parallel wires
disadvantages of parallel data transmission
each individual wire has different properties, there is a possibility that bits can travel at different speeds over each wires, creating the problem of skew
- parallel transmission only works over short distances
- parallel transmission can suffer from crosstalk and timing issues since each bit travels on a different wire, potentially interfering with one another and reducing overall efficiency
advantages of serial transmission over parallel
- large reduction in size and complexity of connectors in serial transmission leads to lower costs
- crosstalk will not occur, as all bits are sent on the same wire, reducing interference and allowing for longer distances., may result in corrupted words
- Serial transmission is cheaper; due to needing fewer wires / less complex hardware;
- skew wont occur as bits are sent one at a time
- serial links are more reliable over longer distances than parallel
- signal frequency can be much higher with serial because of the lack of interference at higher frequencies, resulting in a higher net data tranfer rate, even though less data is transmitted per cycle
what is bit rate
the number of bits that can be sent in a given unit of time
what is baud rate
the number of signal changes in a given period of time/in a second
baseband mode
in baseband mode, only two voltages are used
bit rate equation
bit rate of channel = baud rate x n of bits per signal
what is bandwith
- The range of frequencies that can be transmitted across a network connection;
- shared between all active users, so too many users can cause performance to decrease
what is latency
- the time delay of data to travel from source to destination
what is synchronous transmission
when receiver and transmitter are synchronised by a common clock
advantages of synchronous transmission
timing using a clock signal allows for a constant and reliable transmission for time sensitive data
- The synchronization between sender and receiver ensures that data arrives in a steady, predictable flow
- Synchronous transmission can handle larger volumes of data at higher speeds because it doesn’t need to include start and stop bits for each byte, reducing overhead.
examples of time sensitive data
real time video or voice
what is asynchronous transmission
- transmission of data where receiver and transmitter not synchronised by a clock
-one byte is sent at a time, with each character being preceded by a start bit and followed by a stop bit
examples of things that use synchronous transmission
CPU - the clock emits a signal at regular intervals and transmissions along the address, data and control bus start on a clock signal, which is shared by both receiver and sender
Purpose of the start and stop bit
- start bit - starts the receiver clock ticking
- stop bit - provides time for the recover to process the received data
what are protocol
a set of rules which govern communication
advantages of disabling SSIDs
prevents the network from appearing in the list of available networks, making it less visible to potential attackers
advantages of mac addressing
whitelisting means only approved devices can join he network
what are SSIDs
devices to identify the network
things that affect network performance
topology
- bandwidth, higher bandwidth increases performance
- choice of hardware
- wired or wireless, wired are ussually faster and more reliable
what is a wide area network
a collection of computers connected over a large geographical area, like the internet
advantages and disadvantages of asynchronous transmission
- Easier and cheaper to implement because it doesn’t require synchronization between the sender and receiver.
- Ideal for low-speed communication and can handle irregular data transmission rates
DISADVANTAGES:
- Additional start and stop bits increase the amount of data transmitted, reducing efficiency.
- Generally slower due to the need to process each byte individually and add control bits.
advantages and disadvantages of synchronous transmission
- No start and stop bits, so it is more efficient for transmitting large amounts of data
- Typically faster because data is sent in a continuous stream.
DISADVANTAGES -
- Requires synchronization between the sender and receiver, making it more complex and expensive to implement
- Initial setup and synchronization can take time, making it less suitable for small amounts of data or sporadic transmissions
relationship between bit rate and bandwidth
directly proportional
what is WIFI
- A wireless wide area network that is based on international standards.
- Used to enable devices to connect to a network wirelessly
advantages of SSIDS
- ## Using unique SSIDs reduces the likelihood of connecting to the wrong network accidentally and helps prevent unauthorized access
why is protocol important
to ensure that equipment from different suppliers can communicate
items that are covered by communication protocol
Physical connections, cabling, mode of transmission, speed, data format, error correction.
