4.9: section 6: communication: technology and networking

serial transmission is when bits are sent one after another over a single wire

multiple bits are sent over parallel wires simultaneously

serial can be used over long distances serial is cheaper and less complicated serial suffers from little interference at higher frequencies serial signal frequencies can be much higher serial doesnt suffer form skew or crosstalk

each byte is sent separately when its ready with a parity bit, a stop bit and a start bit.

data is sent at regular intervals timed by a clocking signal which allows for constant reliable transmission. parallel communication often uses synchronous transmission

start and stop bits are used to make clear when a new set of data has arrived

bit rate is the number of bits transferred between devices in one second

the rate of signal state change in a communication channel

a measure of the maximum capacity of a given communication channel

the time delay before a component in a computer system responds to an instruction

a set of rules relating to communication between devices that allow then to communicate

bit rate can be higher than baud rate if more than one bit is encoded into each signal bit rate= (baud rate) X (number of bits per signal)

bit rate is directly proportionate to bandwidth

one or more computers are connected to a powerful computer called a server clients have to request access and services from the server

pros: better security as all files are stored in a central location and access rights are managed by the server back ups and updates are done centrally so individual users dont have to do this manually and all devices can be simultaneously updated and backed up data and other resources can be shared

cons: expensive to install and manage professional staff required to maintain servers a d run the network if the servers go down the network goes down

all computers have equal status so they are all clients and servers

cheap to set up users share resource s easy to maintain if one computer goes down only the data stored on that computer is effected

Widley used for privacy of content as files that are illegally downloaded are impossible to trace