Unit 2

a packet is a small unit of data that being transmitted

header payload trailer

senders IP address Recievers IP address Packet number

data/part of the message

bits to show end of packet

data packets are sent through different routes so that data transfer is efficient

packets can take different routes to get to their destination this ensures message is delivered despite the unavailability of a route

data is broken down into packets each packet takes a different route a router controls the route a packet takes the packets are reassembled at the destination

when data is sent in one direction only computer to a printer

when data is sent in both directions but not at the same time walkie talkies

when data is sent in both directions at the same time broadband internet connection

one bit at a time over a single wire/channel connecting a computer through a USB connection

works well over long distances since data is fully synchronised in the correct order

transmitted at a slower rate than parallel data transmission

when several bits of data is sent down several channels/wires at the same time used in the internal circuits of a computer

works well over short distances faster than serial transmission

data can become skewed(mixed) the longer the wire, the worse it becomes

Universal Serial Bus form of serial data transmission allows both half duplex and full duplex transmission standard method for transmission of data

become industry standard is backward compatible automatically detected when plugged in no need for external power source easy to add more USB ports

only supports cable length of 5 metres early forms of USB may not be supported by computers data transfer rate is slow

interference problems due to packet switching skewing of data

it can be called even or odd one of the bits is reserved for a parity bit and the number of 1’s is counted. the even or odd parity check will make the total number of 1s even or odd

sometimes more than 1 byte it corrupted but the parity is maintained this is why other methods are needed to ensure errors are never missed

a block of data is sent and the number of 1bits are totalled horizontally and vertically. this identifies that an error has occurred and where the error is