1.3 Data Transmission Flashcards
What are the two types of transmission?
- Serial transmission
- Parallel transmission
What is serial transmission?
Data sent bit-by-bit along the same data line.
What is parallel transmission?
All bits in bytes are sent simultaneously along separate data lines.
State 4 advantages for serial transmission.
- Cheaper and easier to setup.
- Requires only two wires rather than 8 or 16.
- Less prone to interference over long distances
- Simpler interface/circuit board.
State a disadvantage for serial transmission.
Only one bit can be transmitted at a time so transmission times can be longer.
State an advantage for parallel transmission.
Transmission can be completed in a shorter time (faster).
State 2 disadvantages for parallel transmission.
- Hardware is more expensive.
- Prone to interference over a long distance.
State 3 mode of transmission.
- Simplex
- Half-duplex
- Full-duplex
Explain simplex.
Data can travel in one direction e.g. radio.
Explain half-duplex.
Data can travel in both directions but not at the same time e.g. walkie talkie.
Explain full-duplex.
Data can travel in both directions at the same time e.g. phone.
What is multiplexing?
Allows multiple signal sources to send data along the same communication medium/wire.
What is switching?
A device forwards a packet of data towards their destination via a range of devices. It goes one step at a time to its destination.
State 7 things that a packet contains.
- Length
- Packet ID
- Source Address
- Destination Address
- Protocol
- Data
- Checksum
Explain Length.
Number of bits in the packet.
Explain Packet ID.
Unique identifier.
Explain Source address.
IP address of the device sending the packet.
Explain Destination address.
IP address of the device receiving the packet
Explain protocol.
Saying which protocol has been used to form the packet.
Explain data.
Bulk of the packet. Eventually everything else is discarded
Explain Checksum.
Validation to check data sent matched data received.
State 3 reasons why packet switches are used.
- Better security as it is very difficult to intercept.
- Makes more efficient use of data lines as there is no waiting during gaps.
- Less likely to be affected by network failure because multiple paths are used.
When does a collision occur?
When two transmissions attempt to use the same connection medium at the same time.
How are collisions dealt with? (4)
- It generates a frequency that can be detected by all connected devices.
- Devices sending data detect this frequency and are told their transmissions have failed.
- They each wait a randomly generated length of time before reattempting the transmission.
- If another collision occurs this process is repeated.
What are the two types of routing?
- Static Routing
- Dynamic Routing
What is static routing?
Each router has access to a table which tells them which path to forward data depending on the destination address.
State a disadvantage for static routing.
Although it is simple to run, it is not suitable for networks that changes often or often have devices added.
What is dynamic routing?
Each router learns the location of other devices based on monitoring sources and destination addresses of data that is forwarded.
State an advantage for dynamic routing.
(Follow up from before) This means changes to the network would be automatically identified by the router.
What is a router?
A router is a device in a network which holds information about addresses of computers in the network (or other networks).
What do routers do? (3)
- Can direct data to the correct computer
- Can direct data around a network in the most efficient way.
- Act as a gateway connecting to a larger network.
State 3 advantages of digital transmission over analogue.
- Digital transmission is preferred as it less likely to suffer from corruption.
- Can error check data.
- Can compress data and therefore transfer time is quicker.
