Communication and Internet Technologies Flashcards
Data Packet
A small part of a message/data that is transmitted over a network; after transmission all the data packets are reassembled to form the original message/data
A packet of data in a unit of data contains
-packet header
-payload
-packet trailer
Packet header
the part of the data packet that contains 1-IP Addresses of the sender 2-IP Addresses of the receiver 3-includes the packet number which allows reassembly of the data packets
Packet trailer
The part of the data packet that indicates the end of the data packet and some form of error checking to ensure the data arrives error free
Payload
The actual data being carried in a data packet
Packet switching
a method of transmission in which a message is broken into many data packets which can be sent along pathways independently of each other:
-data is broken down into packets
-each packet could take a different route
-a router controls the route a packet takes
-packets may arrive out of order
-once the last packet has arrived, packets are reordered
-routing selection depends on the number of packets waiting to be processed at each node
-the shortest possible path available is always selected- this may not always be the shortest path that could be taken , since certain parts of the route may be too busy or not suitable
Advantages of packet switching
-there is no need to tie up a single communication line
-it is possible to overcome failed, busy or faulty lines by simply rerouting packets
-it is relatively easy to expand package usage
-a high data transmissions rate is possible
Disadvantages of packet switching
-packets can be lost and need to be re-sent
-the method is more prone to errors with real-time streaming
-there is a delay at the destination whilst the packets are being re-ordered
Define Serial transmission
Transfer of the data bits sequentially using a single wire
Advantages of serial transmission
-more reliable
-reduced costs & less interference as only single wire is needed
-safer transmission as it is easier to accurately collate the bits together as they are sent one at a time// less chance of the data being skewed
Disadvantages of serial transmission
-Slower transmission as data bits are only transmitted one bit at a time (sequentially) over a single wire
-additional data may need to be sent to indicate the receiving device when the data transmission has started and stopped. these are called a start bit and a stop bit
Define Parallel transmission
Transfer of data bits simultaneously using several/ multiple wires
Advantages of parallel transmission
-quicker transmission as data bits are sent simultaneously over multiple wires
Disadvantages of parallel transmission
-suitable only for short distances (approx max 5m)
-increased costs as multiple wires are needed
-more interference as multiple wires are needed that can create crosstalk
-less safe transmission as bits are sent simultaneously and errors can occur in collating them together at the receiver’s side// bits may arrive skewed
What is meant by USB
-Universal serial bus
-data transmission method
-it uses serial transmission where all bits of data are sent one at a time using a single wire
-it is a universal standard, common interface
Uses of USB
-Connect electronic devices together
-connect mouse and keyboard to a computer
-use it as a storage device using USB flash drive
Benefits of USB
-devices plugged into the computer are automatically detected and device drivers are automatically downloaded so no need to install them manually
-the connectors can only fit one way, this prevents incorrect connections being made
-USB has become the industry standard ,this means that considerable support is available to users(USB is a universal standard so it is likely to be compatible with the computer
-newer USB standards are backwards compatible with older USB standards so no additional technology is needed
-several different data transmission rates are supported
Drawbacks of USB
-The maximum cable length is presently about 5m
-the transmission speed is relatively high for a USB connection but it isn’t as high as other types of connection
How does USB use serial transmission?
for sending data externally (to and form peripherals/ between devices)
How does IC use parallel transmission
for sending data internally
Define simplex transmission
Data is sent in one direction only
Define full-duplex transmission
Data is sent in both directions at the same time
Define half-duplex transmission
Data is sent in both directions but only one direction at a time
