Networks (in order) Flashcards
what is synchronous transmission
In synchronous transmission, streams of bits are transferred over a communication channel at a constant rate. The transmitter and the receiver are synchronised using a common clock signal.
what is asynchronous transmission
there is no clock signal, so additional data (start and stop bits) is used to control the communication. Data is transmitted when it is available, rather than at specific intervals. This means that there can be periods of time when the transmission channel is idle.
explain the start and stop bits in asynchronous transmission
a bit is sent to signal the start of a transmission
and another bit is sent to signal the end if the transmission the end bit is the opposite to the start bit and is typically longer so the receiver has time to reset for the next communication
where is synchronous transmission often used
its often used in parallel transmission as it can send more bits per unit of time (due to no start and stop bits)
where is synchronous transition often used
its often used in parallel transmission as it can send more bits per unit of time (due to no start and stop bits)
what is serial transmission
its where data bits are sent in a sequence, one after the other, over a single wire.
what is parallel transmission
is where several bits are sent at the same time over their own dedicated wires or printed circuit tracks
whats a negative of parallel transmission
its only reliable over short distances
why is parallel transmission only good over short distances
skew, crosstalk
whats at the middle of a star network
a switch
what are topologies
The different arrangements of computer connections and devices
what is a server
server is a program on a computer that shares resources with, or provides services to, any authorised client
what are the 2 network models
client to server and peer to peer
how does a client to server model work
1) The client submits a request through a network-enabled device.
2) The network server receives and processes the request.
3) The server delivers a response to the client.
how does a peer to peer network work
each computer acts as both a server and a client—supplying and receiving files—with bandwidth and processing distributed among all members of the network
pros of peer to peer
it doesn’t cost much to set up after you have the clients
less points of failure as if one client goes down the rest of the servers normally fine
cons of a peer to peer network
physical security- its less secure as there may be many locations where the sever can be accessed so harder to monitor
back ups - individual users are likely to be responsible for backing up their own data.
pros of a client server model
easy to back up as most important files are in one location
physical security is better as a server can be monitored easily
cons of a client sever model
expensive to set up
if the sever goes down many users can be affected as opposed to just the one in a peer to peer
how are wireless packets often encrypted
using one of these WEP, WPA, or WPA2.
what does WEP stand for
WEP (Wired Equivalent Privacy)
what does WEP do
It uses a symmetric encryption algorithm, meaning the same key is used to encrypt and decrypt data. It does have some weaknesses: WEP keys are often too short and used for too long, making them easier to decipher and more accessible
what does WPA stand for
WPA (WiFi Protected Access)
what does WPA do
introduced key management, which generates a new encryption key for each data packet. Larger keys also make the encrypted messages more challenging to decrypt
what does WAP2 do
WPA2: an improvement on WPA that provides an even stronger encryption algorithm. Each message is encrypted several times, depending on the key size.
what does SSID stand for
service set identifier (SSID)
what does the SSID do
it allows a client to distinguish one network from another
The SSID often broadcast for all to see (however this can be a security risk so you can stop it from doing that it can still be found though)
what is a WAP
wireless access point
what are the 2 Frequency bands in a wireless network
2.4GHz
5.0GHz
what does CSMA/CA stand for
carrier-sense multiple access with collision avoidance
what does CSMA/CA do
CSMA/CA is a protocol used in wireless networking. It makes sure that network collisions (when two devices attempt to communicate at the same time) are avoided.
how does carrier-sense in CSMA/CA work
The first step is to listen to the channel to check for the presence of any other signals. It is at this point that a decision is made whether to send the message or to try again at a later time.
how does Collision avoidance in CSMA/CA work
Upon the detection of an existing transmission on a channel, the node that wanted to send will wait for a period of time before trying again.
whats a node
an end device, which is either sending or receiving data across the network
how does the transmission bit work in CSMA/CA
Once the channel is free, the data is sent. Then, the sender needs to receive an acknowledgement message from the receiver to verify that the data was received successfully. Otherwise, the sender will attempt to resend the message.
whats the hidden node problem
this is where a devices is trying to check if a channel is clear however it can only do in its own range, so there could be a node that’s communicating but is outside of the devices range, making it a hidden node.
what does RTS/CTS stand for
RTS- request to send
CTS- clear to send
what instructions does RTS/CTS follow
check if channel is idle:
if False:
wait random time
else:
send request to send
wait for CTS
if received:
send Msg
what does ISP stand for
internet service provider
not a question but have 4.9.3.2 Internet security left on this and need to do 4.9.4 The Transmission Control Protocol/Internet Protocol (TCP/IP) protocol but gona do that in a diffrent thing as its such a big sub topic
