Chapter 3 11

Transmission Media

Chapter 3

Chapter 3 2

Chapter Objectives

Discuss characteristics of cables List the various types of copper wired cables Discuss fiber optic cables Explain wireless transmission media

Chapter 3 3

Recall - I

Topology is a pattern of computer devices and describes the way in which these devices are connected

The disadvantages of bus topology are: Entire network gets affected if main cable breaks Terminators are required at both ends of backbone

cable Difficult to detect the faulty device Limited number of devices can be attached Heavy traffic degrades performance

Chapter 3 4

Recall - II

The advantages of ring topology are: Easier to mange as compared to Bus network Handles large volume of traffic Very reliable and offers great speed Provides a good communication over a long distance No terminators are required

Types of mesh topology are: Full mesh topology Partial mesh topology

Chapter 3 5

Characteristics of Cables Segment Length – Length of single wire Attenuation – Indicates loss of signal Bandwidth – Amount of data carried by cable Number of Segments – Maximum number of

segments in network Cost – Copper cables are cheapest, fiber optic cables

are expensive Interference susceptibility and crosstalk – Defines

concept of electronic interference on cables Crosstalk- Explains the concept of interference

generated when magnetic fields or current of one cable affects electrical currents of other cable

Chapter 3 6

Selection of cable

Analyze the present and future data transmission speed required by the application.

Determine if high density graphics are required in future.

Consider the architecture of the network to be designed.

Determine whether you want to use copper cable or fiber optic cable.

See for the dispersion of devices in the network, how widely they are spaced. (Check for the suitable price of cable.)

Check for backbone or a lobe to a LAN node.

Chapter 3 7

Types of cables Copper medium is the cheapest mode of data transfer

Types of cables

Coaxial cable Twisted pair cables

Chapter 3 8

Coaxial cable Consist of a solid copper core surrounded by an

insulator mainly made up of Poly Vinyl Chloride (PVC) or Teflon

Coaxial cables are less prone to interference (both internal and external)

Chapter 3 9

Types of Coaxial cable Coaxial cables are mainly divided into four

categories

Types of Coaxial cables

RG58 RG8 RG6 RG59

Chapter 3 10

RG58

Maximum segment length is 200 meters Interference protection is better than twisted pair

cables Offers resistance of 50 ohms BNC-T connector is used to connect this cable Used in thinnet (10BASE2) network Mostly used in changing environments Easy to add/remove devices form the network using

RG58 cable Cheapest form of coaxial cable

Chapter 3 11

RG8

Maximum segment length is 500 meters Interference protection is good compared to any

copper cable Offers resistance of 50 ohms AUI and Vampire Tap connector is used to connect

this cable Used in 10BASE5 network Expensive than RG58 Disadvantage is rigidness due to which it is only

used as a backbone

Chapter 3 12

RG6

Broadband quad-shielded cable that offers an impedance of 75 ohms

Provides lower attenuation characteristics

Useful in cable TV, CCTV and satellite dish antenna

Covers distance up to 1500 feet (450m approx)

Chapter 3 13

RG59

Solid conductor is surrounded by a foam polyethylene dielectric

Offers impedance of 75 ohm and used with BNC connector

Useful in security camera, cable TV and home theatre

Covers a distance up to 1000 feet (300m approx)

Has a higher attenuation as compared to other coaxial cables

Practical

To cut the sheath of different coaxial cables and see the different layers inside the cable.

Chapter 3 14

Chapter 3 15

Twisted Pair Cables A pair of cables twisted around each other forms a twisted

pair cable.

Twisted Pair cables

Unshielded Twisted Pair

Shielded Twisted pair

Chapter 3 16

UTP Cables - I

Pair of unshielded wires wound around each other

Cheapest form of cables available for networking purpose

Highly used in LAN environments

Easy to install Easily gets affected by EMI and

RFI

Chapter 3 17

UTP Cables - I

Maximum cable length – 100m Bandwidth – 100 Mbps Connector – RJ45 Bend Radius – 360 degree/feet Resistance – 50 ohm Signal Transmission Mode - Baseband

Chapter 3 18

UTP Cable Types-I

Cat 7

Cat 6

Cat 5e

Cat 5

Cat 4

Cat 3

Cat 2

Cat 1

UTP

Chapter 3 19

UTP cable types-II

CAT1 – telephone cable CAT2 – 4 Mbps CAT3 – 10 Mbps, 16 MHz (10 Base T) CAT4 – 16 Mbps, 20 MHz (Token Ring) CAT5 – 100 Mbps, 100 MHz (100 Base T) CAT5e – 1000 Mbps, 100 MHz (22 Gauge) CAT6 – 1000 Mbps, 250 MHz (24 Gauge) CAT6a - 10GBase – T, 500 MHz CAT7 – 10GBase – T, 600 MHz CAT7a - 40 Gigabit Ethernet ,1000 MHz

Chapter 3 20

STP Cables

Pair of wires wound around each other is placed inside a protective foil wrap

Better protection from EMI, RFI and crosstalk as compared to UTP

STP is cheaper than fiber optic cable but costlier than UTP

Chapter 3 21

Types of STP Cables

CAT5e – Operates at 350 MHz and carries data up to 1000 Mbps

150 Ohm Shielded Cable – Operates at 16 MHz

Practical

Cutting the sheath of twisted pair cable and seeing the various pairs of the cable

Chapter 3 22

Chapter 3 23

Case Study 1

The Mumbai branch of MoneyMaker bank has multiple departments, which are on different floors in the same building. Each department is interconnected using UTP cables. John, the network administrator has set up a client server environment and has used a star topology. The employees of the bank are unable to transmit data and information from one department to another in an efficient manner

Chapter 3 24

Problem

Data and information cannot be transmitted between the departments efficiently

Chapter 3 25

Suggested Solution

The problem is caused due to EMI emitted by the electrical transformers. John should use STP cables to interconnect the different departments located on each floor as STP provides better protection from EMI. The computers inside each department can be interconnected using UTP cables.

Chapter 3 26

Use CBT to explain fiber optic cable

Chapter 3 29

Fiber Optic Cable Characteristics Bandwidth – Carries large amount of data ranging

from 100 Mbps to 1 Gbps Segment Length – Transmits data signals over

larger distance (2 – 100 K.M.) Interference – No electric signals pass through

these types of cables thus providing security. Used in areas that are highly susceptible to noise, e.g. near TV towers, radio stations and electric transformer.

Chapter 3 33

Multi Mode Fiber Optic cable - II Multiple modes of light signals can be

propagated through it Transmits data over short distances Use LEDs as source of light Used to transmit two or more signals using a

single fiber Speed is less as compared to single mode

fiber optic cable Widely used now a days

Chapter 3 34

Fiber Optic Cable Connectors -I Connectors depend on the different kinds of

light emitting sources (LED and Laser) and light sensors used

Straight Tip (ST) – A popular connector used with fiber optic cables and used in gigabit Ethernets or backbone

Subscriber Connector (SC) – A type of low cost connector used in 100 Base-FX fiber optic networks and can be pushed into the device and removed by pulling out.

Chapter 3 35

Fiber Optic Cable Connectors -II Medium Interface Connector (MIC) – like SC

and are used in the FDDI architecture Sub Miniature Type A (SMA) – looks similar

to ST but uses a threaded outer shell. Fiber Jack – Attaches two fibers in snap lock

connector

Chapter 3 39

Media Comparison

Characteristics UTP STP Coaxial Cables Fiber Optic Cables

Bandwidth 10 Mbps – 100 Mbps 10 Mbps – 100 Mbps 10 Mbps 100 Mbps - 1 Gbps

Maximum cable segment 100 meters 100 meters 200 – 500 meters 2 k.m. – 100 k.m.

Interference rating Poor Better than UTP Better than twisted pair wires

Very good as compared to any other cable

Installation cost Cheap Costly than UTP Costly than twisted pair wires

Most costly to install

Bend radius 360 degrees / feet 360 degrees / feet 360 degrees / feet or 30 degrees / feet

30 degrees / feet

Security Low Low Low High

Chapter 3 40

Wireless Medium

Unguided form of transmission medium Transmitters and receivers are used to send and

receive signals Involves use of electromagnetic waves such as

microwave, infrared, radio waves etc. Wireless medium is useful in connecting large

geographical areas

Chapter 3 47

Summary – I

Networking hardware involves all peripheral devices, interface cards and other components such as cables and wires that are used to establish network connection

All cables have certain characteristics such as segment length, bandwidth, crosstalk, attenuation, interference susceptibility, cost and number of segments

Different types of medium are available for transmitting data over the network such as copper medium, fiber optic medium and wireless medium

Copper medium includes coaxial cables and twisted pair cables

Chapter 3 48

Summary – II

Twisted pair cable consists of a pair of cables that is twisted around each other

Two types twisted pair cable are STP and UTP Crosstalk is a phenomenon in which signals of one wire

interfere with the signals transmitted over the other wire To avoid crosstalk, a pair of wires wound around each

other and each pair is placed inside a protective foil wrap Types of UTP cables are Cat 1, Cat 2, Cat 3, Cat 4, Cat

5, Cat 5e, Cat 6, CAT6a and Cat 7 STP cable types include Cat 5e and 150 ohm shielded

cable

Chapter 3 49

Summary – III

Coaxial cables consist of a solid copper core that is surrounded by an insulator which is again covered by a mesh like ground wire and an outer cover known as a sheath

Thinwire or RG-58 cable is approximately 0.64 cm in diameter and is used in constantly changing environments

BNC connector is used to connect devices to the thinnet coaxial cable network

RG-8 cable is approximately 1 cm in diameter and used as a backbone cable

Chapter 3 50

Summary – IV

For RG-6 cable, the center conductor is 1.05 mm in diameter and for RG-59 cable is 0.86 mm

A fiber optic cable consists of a centre glass core that is surrounded by a glass cladding, Kevlar fibers and an outer sheath material

LEDs and lasers are used to transmit light signals through the fiber optic cables

There are two types of fiber optic cables available namely single mode and multi mode

Chapter 3 51

Summary – V

The primary types of connectors used to connect fiber cables are ST, SC, SMA, Fiber Jack and MIC

In wireless medium, signals are transmitted through air and space using radio and satellite networks