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
