Parallel Transmission
All bits in a byte are sent simultaneously along seperate lines
- Faster than serial transmission
- Requires 8/16 wires
- Can only be used for short distances
Serial Transmission
Data is sent bit by bit along the same data line
- Can travel longer distances than parallel
- Requires only 2 wires
- Slow
Simplex
- Data transmission is possible in one direction only
- EG sending sound to speakers
Half Duplex
- Data transfer is possible in both directions but only one at a time
- EG walkie talkies
Full Duplex
- Data transfer is possible in both directions simulatneously
- EG video conferencing
USB
- A fast interface for connecting peripherals to computers using wired connections
- Transmit data and provide a power supply for peripheral devices
- Devices can be linked using USB, chained together through hubs
Bluetooth
- Wireless interface for connecting peripherals to computers
- Avoids needs for cables
- Devices would also need own power supply
- Devices require pairing
Multiplexor
Allows for multiple messages to be combined to that they can be sent over a data link simultaneously and then seperated again at the end
Multiplexing on multiuser computer
Allows input to the system from different terminats, then routes system output to the correct terminal
Multiplexing on WAN
Used to combine messages for transmission over the very high capacity backbone of the network
Time Division Multiplexing
Allocates small time slices alternately for data from each of the input message streams
Frequency Division Multiplexing
Sends the diffeent messages simultaneously but using different transmission frequencies
Switching
- Used to connect computers in a LAN
- Switch maintains a table with MAC addresses of devices so it can send data to the required device
- When a packet is recieved it is examined to determine the destination address and forwarded as appropriate
Router
- Device on a network that holds the addresses of a computer network
- Used to forward data packets between networks
- Contol traffic on wide area network
- Router determines destination of data packets from IP address in the packet protocol then selects approproate route
- Holds information about current transmission speeds to adjacent nodes so fastest path for transmission can be selected
TCP/IP Packet Switching
- Data is split into packets
- Each packet has a destination address
- Packets are analysed by each node
- Packets are sent down the most appropriate path
- Each node contains a routing table
- Packets may take different routes
- Packets are reassembled at the destination
Contents of a packet
- Source Address: Allow tracing of sender
- Destination Address: Allows packet to be routed to destination
- Packet number: Allows packet to be reassembled in the correct order
- Data Itself
- Tracking Information: route can be traced
- Checksum: allows checking of data for errors
Network Collsion
- Occurs when two sets of data are transmitted on the network simultaneously
- Network detects the error
- Each computer waits a random amount of time before attempting to send packet again
- Must check if channel is free and wait if not
Static Routing
- Paths and devices are programmed manually
- Simple to implement and for simple topologies
- More secure
- Unsuitable for networks which frequently have new devices added to it
- Required admin
Dynamic Routing
- Routers regularly refresh to learn about new devices and pathways
- Suitable for complex topologies
- Changes to the network would automatically be identified by the router
- Changes are not immediate
Data Transfer Rates
- How much bandwidth you need depends on what you plan on doing with your internet connection
- Not measure of speed, just how much data can fit into a transmission medium cable at any one time
Bit Rate
- Describes the data requirements of an application over time
- High bit rate means larger amount of data needs to be sent in a short time
- Video chats and live broadcasting have high bit rates
- If you dont have enough bandwidth, you could experience buffering, pixelation and time lag
Forwarding Table Columns
Destination | Cost | Go To
Routing Table Columns
Destination | Cost | Route
