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Transcript
Data Transmission
AS Computing
F451
What data is transmitted?
Phone
SMS
Email
Radio
TV
Internet
Networks
Allow communication between users
Sharing of software & hardware
LAN
WAN
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
Network Interface Card
NIC
Connects PC or peripheral to network
Network Operating System
Other Network Hardware
Routers
Servers
Printer Servers
File Servers
Email Servers
Bridges
Gateways
What do you need for a LAN?
NIC
Cabling
Server
How is Data Transmitted?
Binary numbers are sent as either electronic
pulses or fibre optic light beams
Methods of Transmitting
Serial
Parallel
Serial & Parallel Transmission
Serial
1 bit is transmitted at a time
Single wire
Parallel
Many bits transmitted at a time
Many wires
Methods of Transmission
Simplex
One direction
Duplex
Both directions simultaneously
Half Duplex
Both directions – one at a time
Handshaking
Signal sent between 2
devices to ensure
they are both ready
to communicate
1st Device sends a
handshake signal
which is
acknowledged by the
other device
This states that each
is now ready for
communication
Bit Rates
Number of bits that
can be sent in 1
second.
Units of Baud
I bit per second = 1
Baud
Transmission Errors
Binary numbers can be
corrupted during
transmission
Echoing back
Parity
Odd & Even
Check sum
Part of the
Transmission Protocol
Parity Bits
Even Parity
1 1 0 0 1 1 0 0
Parity Bit
1 1 0 1 0 0 0 1
Parity Bit
Parity Bits
Odd Parity
1 1 0 0 1 1 0 1
Parity Bit
1 1 0 1 0 0 0 0
Parity Bit
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
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
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
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