Communication + Networking AQA

What services does a server provide to a client?

What services does a server provide to a client?

webpages, files, emails, databases, printing

What is the client-server network model?

where the server continuously waits for the client to make a service request

What is a peer-to-peer network model?

there is no server and all computers are connected, less expensive than client-server, each computer has different files which can be shared

What is Wi-Fi?

radio waves at a designated frequency transmitting data

Components needed for Wireless networking

wireless access point, tens of meters range, router, wireless network adapter

What is CSMA/CA on a network?

an access method that is used by wireless technology to avoid collisions between data packets

CSMA/CA protocol

node listens to the network to determine if the channel is free, if it is busy the node waits for a random period of time and rechecks, once the network is clear data is transmitted, receiver sends acknowledgment to sender, if no acknowledgment is received the data must be retransmitted

CSMA/CA with RTS/CTS protocol

before data is transmitted and after the network is clear, the node sends an RTS signal to the wireless access point and waits for a CTS signal

Ways to secure Wireless Networks

MAC Address whitelisting, turning off SSID broadcast, Encryption, passwords

What is MAC Address whitelisting?

a list that only allows devices with specified MAC Address to access the network

What are some encryption protocols that encrypt data between the adapter and access point?

WEP (Wired Equivalent Privacy) , WPA (Wifi Protected Access)

What is data communication?

the transmission of data from between devices or components

What is serial transmission?

a one bit at a time down a single wire as binary change in voltage, the voltages are converted back into binary data at the end

What is parallel transmission?

Data is transmitted several bits at a time using multiple wires between networked computers, often 8, 16, 32 or 64 bits at a time

Advantages of serial transmission

Cheaper cabling, works well over long distances

Advantages of parallel transmission

Faster than serial, more data sent at once

Disadvantages of parallel transmission

more expensive than serial, interference/crosstalk between wire can corrupt the data, over long distances the bits can desynchronise and arrive out of order

What is synchronous transmission?

a clock synchronises transmission, transmitting at the same rate as receiving, sends signals at regular intervals in a continuous stream with timing signals to keep sending and receiving clocks in time

What is asynchronous transmission?

sent in chunks with start and stop bits used to specify the beginning and end of a sequence, parity bit for error checking, slower than synchronous transmission

What is a protocol?

a set of rules that determine how devices communicate

What is Latency?

the delay in transfer between components, caused by the limitation of speed of light, medium and other processing

What is the bitrate?

the number of bits transmitted per second, baud rate x bits per signal change

What is the baudrate?

The number of signal changes per second in Hz

What is the bandwidth？

the range of frequencies at with data can be transmitted, the volume of data that can be transmitted along the medium in a given period of time

What is the relationship between bandwidth and bitrate/data capacity

the greater the bandwidth the greater the bitrate (directly proportional) and capacity of data transfer

What is a bus topology?

Where computers and other devices in a network are attached to a wire called a bus with two ends called terminators

Advantages of the bus topology

cheap to install, less cable and specific hardware than a star, easy to install more devices

Disadvantages of the bus topology

If the main cable fails the whole network fails, slow due to data collisions, less secure as all computers on the network can see all data transmissions.

What is a star network topology?

where all devices are connected to a central hub

Advantages of the star topology

better security as data is only sent to the intended recipient, if any connections fail only one node is affected, fewer collisions of data packets

Disadvantages of the star topology

expensive to install due to hardware, harder to add devices than a bus topology