Transcript Document

INF550/NZD550
Questions
 How does 1 computer communicate with another one?
 What devices allow computers to communicate?
 How do they work?
 What mediums are used to connect computers and devices?
 What types of connections are there?
Analogue and Digital Signals
Communication Systems
 Four basic elements
 Sending and receiving devices
 Communication channel
 Connection devices
 Data transmission specifications
Switch
 Used to network multiple
computers together
 Able to determine the location of
devices connected to it so
messages are sent more efficiently
Modem
 Short for Modulator/Demodulator
 Allows computers to send
messages over the telephone lines
by converting digital signals to
analogue signals (modulation)
and back again (demodulation)
Router
 Routes data from a local area
network to another network
connection
 Allows multiple computers and
other to join the same network
 Include
 Ethernet ports for wired
connections
 Wireless antenna for wireless
connections
Device Connection Order
1.
2.
3.
4.
5.
PC or wireless device
Router
Modem
ISP (Internet Service Provider)
Internet
Physical Connections
Ethernet Cable (Twisted Pair)
 Two standard used in computing
networks
 CAT5 which can run at 100Mbps
 CAT6 which can run a 1Gbps
(1000Mpbs)
 eight strands of twisted cable
connected by an RJ45 plug.
 Industry standard in computer
networking.
Coaxial Cable
 Single solid copper core
 Historically used on computer
networks (called 10Base-T) in the
1980’s and 1990’s and has been
 Replaced by Ethernet cable due to
its higher speeds of transmission
and fragility of the network
 10Base-T was limited to 10Mpbs
 Today coaxial cable is found
delivering television signals from
antenna / satellite dish to TV unit
Fibre-Optic
 Uses light pulses to transmit data
 Capable of transmission speeds of 1




PetaByte/s (1,000,000 Gbps)
Best over limited distances
Lighter, more reliable, and less
expensive than copper type cables.
Fibre optic cables forms the backbone of the worlds communication
networks.
Government rolling out fibre (UFB)
to the majority of businesses and
home in New Zealand but will only
see speeds of up to 100Mbps.
Comparison
Wireless
Microwave
 Transmit data via electromagnetic
waves
 Used for high-volume, long
distance communications
 Must have line-of-sight
 Transmitter and receiver must be
in sight of each other
 Limit placed by curvature of the
Earth
 May experience difficulties with
severe weather eg heavy rain,
snow
Satellite
 Use communications satellites
 Must have line of sight
 Bigger footprint than microwave
transmitters as further out
 Uses broadcast transmissions
 Sends signals to many receivers at
the same time
 Used in NZ for rural broadband
 Slower than ADSL broadband

Faster than dial-up connections
Radio
 Sends data directly between




transmitters and receivers using
radio-wave frequencies
Can travel through normal office
walls
Transmitted at high speed
Can create electrical interference
Types
 Bluetooth
 Wi-Fi (Wireless Fidelity)
Infrared
 Red light
 Usually invisible to human eye
 Commonly used in remotes
 Can be used for short-distance
connections
 Needs line of sight
 One-to-one technology
 Only send between 2 devices at
one time
Comparison
Communication Channels Summary
Connection Services
 Dial-Up services
 Digital Subscriber Line (DSL)
 ADSL most widely used
 Cable
 Uses TV coaxial cable
 Satellite
 Wireless
 Fibre to home
 Cellular Services
 3G and 4G cellular networks