1. AS Computing F451 F451 Data Transmission

2. What data is transmitted? Phone SMS Email Radio TV Internet

3. Networks Allow communication between users Sharing of software & hardware LAN WAN

4. LAN & WAN Local Area Network Covers a small area eg. Building or single site More secure than a WAN Wide Area Network Covers wide geographical area – countries and even continents

5. Network Interface Card NIC Connects PC or peripheral to network Network Operating System

6. Other Network Hardware Routers Servers Printer Servers File Servers Email Servers Bridges Gateways

7. What do you need for a LAN? NIC Cabling Server

8. How is Data Transmitted? Binary numbers are sent as either electronic pulses or fibre optic light beams

9. Methods of Transmitting Serial Parallel

10. Serial & Parallel Transmission Serial 1 bit is transmitted at a time Single wire Parallel Many bits transmitted at a time Many wires

11. Methods of Transmission Simplex One direction Duplex Both directions simultaneously Half Duplex Both directions – one at a time

12. Handshaking Signal sent between 2 devices to ensure they are both ready to communicate 1 st Device sends a handshake signal which is acknowledged by the other device This states that each is now ready for communication

13. Bit Rates Number of bits that can be sent in 1 second. Units of Baud I bit per second = 1 Baud

14. Transmission Errors Binary numbers can be corrupted during transmission Echoing back Parity Odd & Even Check sum Part of the Transmission Protocol

15. Parity Bits 1100110 Parity Bit Even Parity 1101000 Parity Bit 1 0

16. Parity Bits 1100110 Parity Bit Odd Parity 1101000 Parity Bit 0 1

17. Checksum – Detecting Transmission Errors Bytes send in blocks Value of bytes within the block are added together That value is also sent in a byte Checksum byte is checked at receiving end If checksum is incorrect then a transmission error has occured

18. Protocols Set of rules that govern the transmission of data e.g. http or TCP/IP Logical Parts of Protocol Type of error checking used Packet size used Baud Rate Physically Parts of Protocol Cabling used Wireless or Hard wire Frequency data is sent

19. Circuit Switching Message is sent in its entirety through one predetermined route Ties up large areas of network Message packets remain in correct order Message can be more easily intercepted as it stays on the same route

20. Packet Switching A message is split into packets Each packet is sent to the destination via different routes Packets arrive at destination in different times and different order Put back into order when all packets arrive Maximises use of network Message cannot be (easily) intercepted