Network Media

1


Network Media
2
Review

• What did we do last week?
• Types of Networks
• LAN, MAN, WAN
• Four essential elements for Computer
  Communications
• Sender/Receiver
• Message
• Rules
• Confirmation

3
Physical Layer

• Objectives
• Specifications and performances of different
  types of cable.
• Unshielded twisted-pair cable (UTP).
• straight-through,
• crossover, and
• rollover cables
• Fiber-optic cable
• Wireless

4
Review - Information Transfer
Transmission Medium
Message
Encoder
Transmitter
Decoder
Receiver
Message

• Communication begins with a message, or
  information
• Message are sent across a data network by
  breaking into small chunks called packets.
• Communication uses a medium.
• The medium provides the channel over which the
  message travels from source to destination.

5
OSI Layer 1 Physical layer

• The physical layer defines the electrical,
  mechanical, procedural, and functional
  specifications
• Signal
• Connectors
• Cables

6
Physical Media Types
Physical Media
Unguided Media ( Wireless)
Fibre optic cable
Twisted Pair cable
Coaxial cable
7
What are the differences between different types
of media

• Construction
• Distance over which signal can be transported
  without being amplified
• Speed at which data transfer would happen
• Cost of media and its installation

8
Speed of Data Transfer Bandwidth

• Data rate
• transferring data per unit of time.
• Data rate determines how long it will take to
  transfer a file.
• The larger the file, the longer it takes, as
  there is more information to transfer.

9
What is basic unit of data?

• What are the basic unit of measurement in
  mks/fps system for measuring
• Length ?
• time ?
• weight ?
• Similarly, in computer communications, basic unit
  of data is
• Bit (Binary digit)

10
Bandwidth (BW) Rate of Information Transfer

• Bandwidth is the amount of information that can
  flow through a network connection in a given
  period of time.
• Measured in
• bits per second (bps).
• e.g. 100 Kilo bits per second or 100Kbps
• Analogy Road
• Wider the road, more the number of lanes possible
  and more the number of cars, it can handle

11
Bandwidth - measurement
12
Computer data cablesUnshielded Twisted Pair (UTP)

• Unshielded twisted-pair
• Consists of four pairs of colour-coded wires that
  have been twisted together and then encased in a
  flexible plastic sheath.
• Used for Local Area Networks (LAN)
• IEEE is the standards body that classifies data
  cables according to their bandwidth
• e.g., Category 5 (Cat5) cable
• Other categories include Enhanced Category 5
  (Cat5e) cable and Category 6 (Cat6).

13
Shielded twisted-pair cable (STP)

• Shielded twisted-pair cable (STP) combines the
  techniques of shielding, cancellation, and
  twisting of wires.
• Each pair of wires is wrapped in metallic foil.
• The four pairs of wires are wrapped in an overall
  metallic braid or foil.

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Fibre Optic Cabling

• Light is used to carry data
• One side send light pulses
• light / no light or
• increasing/decreasing light intensity
• Electronic circuits are used to convert light
  back to data

15
Fiber Optic Cabling - Types
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Comparing the cables
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Wireless Networks

• Signal carried in electromagnetic spectrum
• No physical wire
• Differences from wired link .
• decreased signal strength radio signal
  attenuates as it propagates through matter (path
  loss)
• interference from other sources standardized
  wireless network frequencies (e.g., 2.4 GHz)
  shared by other devices (e.g., phone) devices
  (motors) interfere
• multipath propagation radio signal reflects off
  objects ground, arriving ad destination at
  slightly different times
• . make communication across (even a point to
  point) wireless link much more difficult

18
Elements of a wireless network

• Two modes
• infrastructure mode
• base station connects mobiles hosts into wired
  network
• Ad hoc mode
• No base station

base station
mobiles hosts
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Practical -Unshielded Twisted Pair (UTP)
Straight-through Cable

• The cable that connects from the switch port to
  the computer NIC port is called a
  straight-through cable.

Hub or Switch
PC/ Router
RJ-45 connector
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Practical - Crossover cable

• The cable that connects from a switch port to
  another switch port is called a crossover cable.

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Practical - Unshielded Twisted Pair (UTP)
Rollover
Straight-through
Cross-over
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UTP Rollover Cable
Router
Terminal or a PC with terminal emulation software
Console port
Rollover cable
Com1 or Com2 serial port
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Conclusions

• Five new things you have learnt in this session
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