Media

1
Media

• Chapter 2

2
Two types of Cables

• Baseband
• Broadband

3
Baseband

• Digital signaling over one wire
• Electrical pulses or laser light
• Bi-directional allows computers to send and
  receive using one cable.
• Capable of multiplexing
• Using TDM (Time Division Multiplexing) method
  of putting multiple data streams in a single
  signal by separating the signal into many
  segments of short duration. Only changes the way
  data is transmitted.

4
Categories of Media

• Coaxial
• Twisted pair
• Fiber Optic

5
Types of Media

• Copper coaxial cable, twisted pair
• Glass fiber optic

6
Interference

• EMI
• Could come from fluorescent lights, ungrounded
  electronic equipment
• Crosstalk
• There are 8 wires in twisted pair cable. When
  electricity flows through a wire, it emanates a
  electromagnetic field. A pair of wires create a
  circuit for transmitting data via electrical
  current. If two wires are in the same electrical
  circuit, electrons flow from the negative voltage
  source to the destination along one wire and then
  the electrons flow from the destination to the
  positive voltage source along the other wire.
  If two wires within the cable are carrying a
  signal, energy from one wire can wind up in an
  adjacent wire. Thus, EMI within the cable is
  crosstalk.

7
Cancellation

• When two wires in an electrical circuit are
  placed close together, their magnetic fields are
  the exact opposite of each other. These magnetic
  fields cancel out one another. The twisting of
  the wires improves the cancellation effect.

8
Attenuation

• Cable length is specified because as a signal
  moves along the media it weakens (attenuates).

9
Coaxial Cable
10
Coaxial Cable

• Thin 10Base2
• Commonly called thinnet, thin wire, or thin
  Ethernet or cheapernet
• BNC connector
• Thick 10Base5
• Commonly called thicknet, thick wire, or thick
  Ethernet
• Transceivers and Vampire Taps

11
Twisted Pair

• Shielded Twisted Pair (STP)
• Contains eight copper wires covered in plastic
  The wires are twisted to reduce crosstalk.
• Insulated
• Reduces EMI (electromagnetic interference)
• Fairly expensive
• Uses RJ45 connectors
• Unshielded Twisted Pair (UTP)
• Commonly called Cat5
• Contains eight copper wires covered in plastic
  The wires are twisted to reduce crosstalk.
• Not insulated
• Inexpensive
• Uses RJ45 connectors

12
Twisted Pair Categories

• Cat 1 Voice-grade UTP telephone cable.
• Cat 2 Data grade transmits up to 4Mbps
• Cat 3 Data grade transmits up to 10Mbps
• Cat 4 Data grade transmits up to 16Mbps
  (often used with Token Ring)
• Cat 5 Data grade transmits up to 100Mbps
• Cat 5e Data grade transmits up to 1000 Mbps

13
Thin Coaxial Cable (10Base2)

• Max speed 10 Mbps
• Max length 185 meters
• Max nodes/segment 30
• Max segments 5 (only three can have nodes
  connected)
• Min distance b/w nodes .5 meter
• Transmission method Baseband
• Connector BNC

14
Thick Coaxial Cable (10Base5)

• Max speed 10 Mbps
• Max length 500 meters
• Max nodes/segment 100
• Min distance b/w nodes 2.5 meters
• Transmission method Baseband
• Connector Vampire tap and transceiver

15
Twisted Pair (10BaseT)

• Max speed 10 Mbps
• Max length 100 meters
• Transmission method Baseband
• Cable type Cat 3, 4, 5 UTP or STP
• Connector RJ45