Best fit topology - LO1 part II

Compiled By Abenezer A.
MARY HELP TVET COLLEGE
Unit of Competence
Determine Best-Fit Topology
12/9/2020 1
LO1 Part II

Network Transmission media
12/9/2020 2

Transmission Media
 Transmission media is a means by which a communication
signal is carried from one system to another.
 A transmission medium can be defined as anything that can
carry information from a source to a destination.
 The transmission medium is usually free space, metallic cable
or fiber optic cable.
3

Transmission Media cont’d
4

Transmission Media cont’d
5

A. Guided Media
 Guided Transmission media uses a cabling system that
guides the data signals along a specific path.
 Guided media also known as Bounded media, which are
those that provide a conduit from one device to another,
include twisted-pair cable, coaxial cable, and fiber-optic
cable.
6

Note:
 Twisted-pair cable, coaxial cable transport signals in
the form of electric signals and fiber-optic cable
transport signals in the form of light.
7

Cable type
There are three primary types of cable used to build
LANs:
1. Coaxial
2. twisted – pair
3. fiber optic
8

Cable type cont’d
 Coaxial and twisted – pair cables are copper – based and
carry electrical signals, and fiber optic cables use glass or
plastic fibers to carry light signals.
9

1. Coaxial cable
 It contains two conductors within
the sheath.
 At the center of the cable is the
copper core that actually carries
the electrical signals.
 The core can be solid copper or
braided strands of copper.
10

1. Coaxial cable cont’d
 Surrounding the core is a layer of insulation, and surrounding that
is the second conductor, which is typically made of braided copper
mesh.
 The second conductor functions as the cable’s ground.
 Finally, the entire assembly is encased in an insulating sheath
made of PVC or Teflon.
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 There are two types of coaxial cable that have been used in
local area networking:
1. RG 8 also known as thick Ethernet
2. RG – 58 which is known as thin Ethernet
12

 These two cables are similar in construction but differ primarily in
thickness (0.405 inches for RG – 8 versus 0.195 inches for RG – 58)
and in the types of connectors they use (AUI connectors for RG – 8
and bayonet – Neill – Concelman [BNC] connectors for RG – 58).
13

 Both cable types are wired using the bus topology.
14

Note:
 Thick Ethernet and thin Ethernet are also known as 10Base5 and
10Base2, respectively.
 These abbreviations indicate that the networks on which they are
used run at 10 Mbps, use baseband transmissions, and are limited
to maximum cable length of 500 and 200 (actually 185) meters,
respectively.
15

 Coaxial cable is used today for many applications, most noticeably
cable television networks.
 It has fallen out of favor as a LAN medium due to the bus
topology’s fault – tolerance problems and the size and relative
inflexibility of the cables, which make them difficult to install and
maintain
16

2. Twisted pair cable
 Twisted pair cable wired in a star topology
is the most common type of network
medium used in LANs today.
 Most new LANs use UTP cable, but there is
also a shielded twisted pair cable (STP)
variety for use in environments more
prone to electromagnetic interference.
17

2. Twisted pair cable cont’d
 Unshielded twisted pair cable contains
eight separate copper conductors, as
opposed to the two used in coaxial
cable.
 Each conductor is a separate insulated
wire, and the eight wires are arranged
in four pairs, twisted at different rates.
18

 The twists prevent the signals on the different wire pairs from
interfering with each other ( called crosstalk) and also provides
resistance to outside interference.
 The four wire pairs are then encased in a single sheath,.
 The connectors used for twisted pair cables are called RJ – 45; they are
the same as the RJ 11 connectors used on standard telephone cables,
except that they have eight electrical contacts instead of four.
19

 Twisted pair cable has replaced coaxial cable in the data networking
world because it has several distinct advantages.
 First, because it contains eight separate wires, the cable is more
flexible than the more solidly constructed coaxial cable.
20

UTP cable grades
 Unshielded twisted pair cable comes in a variety of different grades,
called categories by the Electronics Industry Association (EIA) and
the Telecommunications Industry Association (TIA), The
Combination Being Referred To As EIA/TIA.
21

UTP cable grades cont’d
 There are Six categories of UTP
– Category 1 This refers to traditional UTP telephone cable that can carry voice but not
data transmissions. Most telephone cable prior to 1983 was Category 1 cable.
– Category 2 This category certifies UTP cable for data transmissions up to 4 megabits per
second (Mbps). It consists of four twisted pairs of copper wire.
– Category 3 This category certifies UTP cable for data transmissions up to 16 Mbps. It
consists of four twisted pairs of copper wire with three twists per foot.
consists of four twisted pairs of copper wire.
consists of four twisted pairs of copper wire.
– Category 5e -Used in networks running at speeds up to 1000 Mbps (1 gigabit per
second [Gbps]).
– Category 6-Typically, Category 6 cable consists of four pairs of 24 American Wire Gauge
(AWG) copper wires. Category 6 cables are currently the fastest standard for UTP.
12/9/2020 22

STP Cable Grades
 STP is similar in construction to UTP, except that it has only two pairs
of wires and it also has additional foil or mesh shielding around each
pair.
 The additional shielding in STP cable makes it preferable to UTP in
installations where electromagnetic interference is a problem, often
due to the proximity of electrical equipment.
23

STP Cable Grades cont’d
 Token ring STP networks use large, bulky connectors called IBM data
connectors (IDCs).
 However, most Token Ring LANs today use UTP cable.
24

Compiled By Abenezer A.12/9/2020 25

3. Fiber optic cable
 Fiber optic cable is a completely different type of network medium than
twisted pair or coaxial cable.
 Instead of carrying signals over copper conductors in the form of electrical
voltages, fiber optic cables transmit pulses of light over a glass or plastic
filament.
 Fiber optic cable is completely resistant to the electromagnetic interference
that so easily affects copper based cables.
26
Note:

Fiber optic cable cont’d
• Fiber optic cables are also much less subject to attenuation – the
tendency of a signal to weaken as it travels over a cable – than are
copper cables.
• On copper cables, signals weaken to the point of unreadability after
100 to 500 meters.
• Some fiber optic cables, but contrast, can span distances up to 120
kilometers without excessive signal degradation.
27

• Fiber optic cable is thus the medium of choice for installations that span long
distances or connect buildings on a campus.
• Fiber optic cable is also inherently more secure than copper because it is
impossible to tap into a fiber optic link without affecting normal
communication over that link.
• A fiber optic cable consists of a clear glass or clear plastic core that actually
carries the light pulses, surrounded by a reflective layer called the cladding.
• Surrounding the cladding is a plastic spacer layer, a protective layer of woven
Kevlar fibers, and an outer sheath.
28

• There are two primary types of fiber optic cable:
1. Singlemode
2. multimode
29

• With the thickness of the core and the cladding being the main difference
between them.
• The measurements of these two thicknesses are the primary specifications
used to identify each type of cable.
• Singlemode fiber typically has a core diameter of 8.3 microns, and the thickness
of the core and cladding together is 125 microns.
 This is generally referred to as 8.3/125 Singlemode fiber.
• Most of the multimode fiber used in data networking is rated as 62.5/125.
30

• Singlemode fiber is more commonly found in outdoors
installations that span long distances, such as telephone and cable
television networks.
• This type of cable is les suited to LAN installations because it is
much more expensive than multimode
31

 Multimode fiber cannot span distances as long as Singlemode and
is much cheaper.
 Fiber optic use one of two connectors, the straight tip (ST) connector
or the subscriber connector (SC).
32

Self- Check
For each of the following scenarios, specify whether the network will function
properly based on the information given. If not, explain why.
1. Twenty – five computers are connected to a 300 – meter thin Ethernet cable
segment using a bus topology.
2. Networks in two buildings 1000 meters away from each other are connected
together using Singlemode fiber optic cable with RJ – 45 connectors.
3. Fifteen computers are connected to a Token Ring network using a physical
ring topology
33

B. Unguided Media
• Unguided media transport data without using a physical
conductor.
 This type of communication is often referred to as wireless
communication.
• It uses wireless electromagnetic signals to send data.
34

B. Unguided Media cont’d
 Frequencies in the range of about 1 GHz to 40 GHz are referred to as
microwave frequencies.
 At these frequencies, highly directional beams are possible, and
microwave is quite suitable for point-to-point transmission.
35

• Frequencies in the range of 30 MHz to 1 GHz are suitable for
omnidirectional applications.
 We refer to this range as the radio range.
36

 Another important frequency range, for local applications, is the
infrared.
 This covers, roughly, from 3 x 1011 to 2 x 1014 Hz.
 For unguided media, transmission and reception are achieved by
means of an antenna.
37

Antennas
 An antenna can be defined as an electrical conductor or system of
conductors used either for radiating electromagnetic energy or for
collecting electromagnetic energy.
 For transmission of a signal, radio-frequency electrical energy from
the transmitter is converted into electromagnetic energy by the
antenna and radiated into the surrounding environment
(atmosphere, water).
38

Antennas cont’d
• For reception of a signal, electromagnetic energy impinging on the
antenna is converted into radio-frequency electrical energy and fed into
the receiver.
• An antenna will radiate power in all directions but, typically, does not
perform equally well in all directions.
• A common way to characterize the performance of an antenna is the
radiation pattern.
• An isotropic antenna radiates power in all directions equally.
39

Categories of Unguided Media
• There are three types of Unguided Media
1. Radio waves
2. Micro waves
3. Infrared
40

1. Radio waves
• Electromagnetic wave ranging in frequencies between 3
KHz and 1GHz are normally called radio waves.
• Radio waves are Omni-directional when an antenna
transmits radio waves they are propagated in all
directions.
41

1. Radio waves cont’d
• This means that sending and receiving antenna do not have to be
aligned.
• A sending antenna can send waves that can be received by any
receiving antenna.
• Radio waves particularly those waves that propagate in sky mode,
can travel long distances.
42

1. Radio waves cont’d
• This makes radio waves a good candidate for long-distance
broadcasting.
• Radio waves particularly those of low and medium frequencies can
penetrate walls.
43

2. Microwaves
• Electromagnetic waves having frequencies between 1 and 300 GHz
are called microwaves.
• Microwaves are unidirectional; when an antenna transmits
microwaves they can be narrowly focused.
44

2. Microwaves cont’d
• This means that the sending and receiving antennas need to be aligned.
• A pair of antennas can be aligned without interfering with another pair
of aligned antennas.
• Microwaves propagation is line-of-sight.
• Since the towers with the mounted antennas needs to be in direct sight
of each other, towers that are far apart need to be very tall.
45

2. Microwaves cont’d
• The curvature of the earth as well as other blocking obstacles do
not allow two short towers to communicate using microwaves.
• Repeaters are often needed for long distance communication.
• Very high frequency microwaves cannot penetrate walls.
• Parabolic dish antenna is used for this means of transmission
46

3. Infrared
• Infrared signals with frequencies ranges from 300 GHz to 400 GHz can be used
for short range communication.
• Infrared signals, having high frequencies, cannot penetrate walls.
 This helps to prevent interference between one system and another.
• Infrared Transmission in one room cannot be affected by the infrared
transmission in another room.
• There are number of computer devices which are used to send the
data through infrared medium e.g. keyboard, mice, and printers.
47

3. Infrared cont’d
• There are some manufacturers provide a special part called the IrDA
port that allows a wireless keyboard to communicate with a PC.
48

Compiled By Abenezer A.12/9/2020 49
Cont…..
Due Respect
For Your Attention

Best fit topology - LO1 part II

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