1. Computer Fundamentals Northern College Diploma Philip Bird

2. Computer Fundamentals Philip Bird Data Communications 0100000101000001 Parallel Faster over short distances. Data sent a byte at a time. Serial More common that parallel. Data sent a bit at a time. 01000001

3. Computer Fundamentals Philip Bird Interface Framing 0 0 1 0 0 0 0 0 1 0 1 0 0 1 0 0 0 0 1 1 1 1 Start Bit Stop Bit Parity Bit 8 Data Bits ‘A’ 8 Data Bits ‘C’

4. Computer Fundamentals Philip Bird Switching Circuit Message Packet

5. Computer Fundamentals Philip Bird Protocols, Packets and Errors Packets enable messages to be split into many smaller sections. Computers need sets of rules (protocols) on how to handle these packets – how big they should be, what to do if a transmission error occurs. TCP – is responsible for breaking up the message into datagrams, reassembling them at the other end, resending anything that gets lost, and putting things back in the right order IP – is responsible for routing individual datagrams across networks. Other protocols determine how the data is handled once it is put back into a complete message. HTTP, SMTP, POP3, FTP etc. Source IPDest IPPacket#SizeChecksumData HeaderPayload

6. Computer Fundamentals Philip Bird Network Topologies

7. Computer Fundamentals Philip Bird Northern College & JANET

8. Computer Fundamentals Philip Bird Summary Why is most data communicated in serial rather than parallel form? Why are standards so important in data communications?