Data communication basics
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The document discusses different types of communication systems and network topologies. It describes the basic components of communication systems as the data source, transmitter, transmission medium, receiver and destination. For data transmission, it explains serial transmission which transmits bits one at a time versus parallel transmission which sends all bits simultaneously. It also discusses synchronous versus asynchronous transmissions and details about start/stop bits and data transfer rates. The document concludes by describing different network topologies including bus, ring and star configurations.
Data communication basics
- 2. Every communication system has 5 basic requirements Data Source (where the data originates) Transmitter (device used to transmit data) Transmission Medium (cables or non cable) Receiver (device used to receive data) Destination (where the data will be placed) 5 Basic Components Communications Systems
- 5. Sender transmitted Data is transmitted, on a single channel, one bit at a time one after another - Much faster than parallel because of way bits processed (e.g. USB and SATA drives) Receiver received Serial Transmission 1 0 1 0 0 1 1 0
- 6. Receiver received each bit has it’s own piece of wire along which it travels - often used to send data to a printer Parallel Transmission Sender transmitted All bits are sent simultaneously 1 0 0 1 1 0 0 1
- 7. Why Not use Parallel Instead of serial? Due to inconsistencies on channels data arrives at different times Because of the way it is transmitted packet switching cannot be used The above two points makes parallel slower than serial and requires higher bandwidth. Parallel transmissions are rarely used anymore
- 8. Synchronous Transmission all data sent at once and no packet switching Asynchronous Transmission Uses stop/ start bits most common type of serial data transfer Allows packet switching Allows sharing of bandwidth (i.e. talk on phone while another person is using internet) Synchronous Vs Asynchronous Transmissions
- 9. Start and Stop Bits In the asynchronous method, each character is placed between start and stop bits ( framing ) Framing ASCII ‘A’ (41H) LSB MSB
- 10. Data Transfer Rate Rate of data transfer: bps (bits per second) Another widely used terminology for bps is baud rate For Asynchronous serial data communication, the baud rate is generally limited to 100,000bps
- 11. - simplex: One direction only Transmission Direction
- 12. Half Duplex Transmission half duplex: Both directions but only one direction at a time
- 13. Full Duplex Transmission full duplex: send and receive both directions at once
- 14. Computer Networks and Topologies
- 15. A network is a number of computers and peripheral devices connected together so as to be able to communicate (i.e. transfer data) Each device in a network is called a node. Terminals are data entry points which can also display. What is a Network?
- 16. A bus is a form of Ethernet. Nodes linked by a cable known as the bus. Bus transmits in both directions and uses CSMA/CD protocol BUS TOPOLOGY Advantages - Easy to set up and maintain failure of one node does not affect network Disadvantages Higher rate of data collision than with a bus network fails if there is any damage to the bus
- 18. Ethernet Developed at Xerox in 1976. First protocol approved as an industry standard protocol 1983 LAN protocol used on bus and star Most popular LAN protocol Inexpensive
- 19. Uses an empty data packet called a token and a special protocol called “token ring”. Packets travel around the ring in a clockwise direction. Clients require an empty token to transmit data. Advantages - no collisions because all data travels in same direction. Disadvantages - fails if an individual node in the network fails Ring Topology
- 20. All data is sent from one client to another through the server. Advantages - If one client fails no other clients are affected. Disadvantages - If central file server fails the network fails. Star Topology
Editor's Notes
- #17: Easy to add extra computers . If computer goes down it doesn’t affect rest of network