Open Elective MSE.pptx

NETWORKS
A network is a set of devices (often referred to
as nodes) connected by communication links.
A node can be a computer, printer, or any
other device capable of sending and/or
receiving data generated by other nodes on the
network.

internet: It is two or more network that can be
communicate to each other.
Internet: A collaboration of more than hundreds
of thousands of interconnected
networks.
Internetwork: The collection of two or more
networks.

Types of connections: point-to-point and multipoint

A fully connected mesh topology (five devices)

Advantages
1.The use of dedicated links guarantees.
2.A mesh topology is robust.
3.Privacy or security.
4. Point-to-point links make fault identification
and fault isolation easy.

Disadvantages
1. A mesh are related to the amount of cabling
and the number of I/O ports required.
2. Installation and reconnection are difficult.
3. The sheer bulk of the wiring can be greater
than the available space (in walls, ceilings,
or floors) can accommodate.
4. The hardware required to connect each link
(I/O ports and cable) can be prohibitively
expensive.

A star topology connecting four stations

Advantages
1. A star topology is less expensive than a mesh
topology.
2. This factor also makes it easy to install and
reconfigure
3. Far less cabling needs.
4. Robustness:
5. Easy fault identification and fault isolation.

Disadvantages
1. The dependency of the whole topology on
one single point, the hub. If the hub goes
down, the whole system is dead.
2. A star requires far less cable than a mesh,
each node must be linked to a central hub.
For this reason, often more cabling is required
in a star than in some other topologies (such
as ring or bus).
The star topology is used in local-area networks
(LANs)

A bus topology connecting three stations

Advantages
1. Ease of installation.
2. A bus uses less cabling than mesh or star
topologies.

Disadvantages
1. Difficult reconnection and fault isolation.
2. Difficult to add new devices.
3. Adding new devices may therefore require
modification or replacement of the backbone.
4. Fault or break in the bus cable stops all
transmission.

A ring topology connecting six stations

Advantages
1. Easy to install and reconfigure.
2. Fault isolation is simplified.
3. If one device does not receive a signal within
a specified period, it can issue an alarm. The
alarm alerts the network operator to the
problem and its location.

A hybrid topology:
a star backbone with three bus networks

PROTOCOLS AND STANDARDS
We define two widely used terms:
1] Protocols and
2] Standards.
Protocol, which is synonymous with rule.
Standards, which are agreed-upon rules.

Protocols
Definition:-
- Protocol is a set of rules that govern all aspect of data
communication between computers on a network.
- These rules include guidelines that regulate the
following characteristics of a network: access method,
allowed physical topologies, types of cabling, and
speed of data transfer.
- A protocol defines what, how, when it communicated.
- The key elements of a protocol are syntax, semantics
and timing.

Elements of protocol:-
i) Syntax
The structure or format of the data.
Eg. A simple protocol;
64 bits
8 bits 8 bits
Sender
address
Receiver
address
data

ii) Semantics
- Refers to the meaning of each section of bits.
- how is a particular pattern to be interpreted,
and what action is to be taken based on that
interpretation.
Eg. Does an address identify the route to be
taken or the final of the message?

iii) Timing
Refers to two characteristics:
a. When data to be sent
b. How fast it can be sent
Eg. If a sender produces data at 100 Mbps but
the receiver can process data at only 1
Mbps, the transmission will overload the
receiver and data will be largely lost.

Standards
‘A set of rules for ensuring quality'.
Standards are developed by cooperation among
standards creation committees, forums, and
government regulatory agencies.
Data communication falls into two categories:
1] De facto (by fact or by convention)
2] De jure (by law or by regulation)

Standards
Standards Creation Committees:-
a) International Standards Organization (ISO)
b) International Telecommunications Union
(ITU)
c) American National Standards Institute (ANSI)
d) Institute of Electrical and Electronics
Engineers (IEEE)
e) Electronic Industries Association (EIA)
f) Internet Engineering Task Force (IETF)

2] MAN (Metropolitan Area
Network)

A wide area network (WAN) provides long-
distance transmission of data, image, audio, and
video information over large geographic areas
that may comprise a country, a continent, or
even the whole world.

A personal area network, or PAN, is a computer
network that enables communication between
computer devices near a person.
PANs can be wired, such as USB or FireWire, or
they can be wireless, such as infrared, ZigBee,
Bluetooth and ultrawideband, or UWB.
The range of a PAN typically is a few meters.
Examples of wireless PAN, or WPAN, devices
include cell phone headsets, wireless keyboards,
wireless mice, printers, bar code scanners and
game consoles.

Transmission medium and
physical layer

Common network cable types
• Coaxial cable
• Unshielded
twisted pair
• Fiber optic

Guided Media
1] Twisted-Pair Cable
2] Coaxial Cable
3] Fiber-Optic Cable
Twisted-pair and coaxial cable use metallic (copper)
conductors that accept and transport signals in the
form of electric current. Optical fiber is a cable that
accepts and transports signals in the form of light.

Twisted-pair cable
Copper
Plastic
One of the wires is used to carry signals to
the receiver, and the other is used only as a ground
reference.

In addition to the signal sent by the
sender on one of the wires, interference (noise)
and crosstalk may affect both wires and create
unwanted signals.
If the two wires are parallel, the effect of
these unwanted signals is not the same in both
wires because they are at different locations
relative to the noise or crosstalk sources (e,g.,
one is closer and the other is farther).

UTP characteristics
• Unshielded
• Twisted (why?) pairs of insulated
conductors
• Covered by
insulating sheath

UTP categories
Category 1 Voice only (Telephone)
Category 2 Data to 4 Mbps (Localtalk)
Category 3 Data to 10Mbps (Ethernet)
Category 4 Data to 20Mbps (Token ring)
Category 5
Category 5e
Data to 100Mbps (Fast Ethernet)
Data to 1000Mbps (Gigabit Ethernet)
Category 6 Data to 2500Mbps (Gigabit Ethernet)

Categories of unshielded twisted-pair cables
Category Bandwidth Data Rate Digital/Analog Use
1 very low < 100 kbps Analog Telephone
2 < 2 MHz 2 Mbps Analog/digital T-1 lines
3 16 MHz 10 Mbps Digital LANs
6 (draft) 200 MHz 200 Mbps Digital LANs
7 (draft) 600 MHz 600 Mbps Digital LANs

 Category 5 cable, commonly referred to
as Cat 5, is a twisted pair cable for
carrying signals.
 This type of cable is used in structured cabling
for computer networks such as Ethernet.
 The cable standard provides performance of up
to 100 MHz and is suitable for most varieties
of Ethernet over twisted pair.
 Cat 5 is also used to carry other signals such
as telephony and video.
Cat 5 cable

Cat5e cable
• 1000Mbps data capacity
• For runs of up to 90 meters
• Solid core cable ideal for structural
installations (PVC or Plenum)
• Stranded cable ideal for patch cables
• Terminated with RJ-45 connectors

CAT6 or Category 6 is a description of network
cabling that consists of four twisted pair wires,
has a data rate of 10000 Mbps, and is used
in Ethernet and Gigabit Ethernet.
It additionally can support 10 Gigabit ethernet
connections over a limited
distance.(technically, 50 meters or 164 feet for
a single cable).
Cat 6 cable

Applications
Twisted-pair cables are used in telephone
lines to provide voice and data channels.
The local loop-the line that connects
subscribers to the central telephone
office---commonly consists of unshielded
twisted-pair cables.

Categories of coaxial cables
Category Impedance Use
RG-59 75 W Cable TV
RG-58 50 W Thin Ethernet
RG-11 50 W Thick Ethernet

Coaxial cables are categorized by their
radio government (RG) ratings.
Each RG number denotes a unique set of
physical specifications, including the wire
gauge of the inner conductor, the thickness
and type of the inner insulator, the
construction of the shield, and the size and
type of the outer casing.

BNC (Bayone-Neill concelman)
connectors

1] The BNC connector is used to connect
the end of the cable to a device, such as a
TV set.
2] The BNC T connector is used in Ethernet
networks to branch out to a connection to a
computer or other device.
3] The BNC terminator is used at the
end of the cable to prevent the reflection of
the signal.

Applications
Coaxial cable was widely used in analog
telephone networks where a single coaxial
network could carry 10,000 voice signals.
Later it was used in digital telephone
networks where a single coaxial cable could
carry digital data up to 600 Mbps.
However, coaxial cable in telephone networks
has largely been replaced today with fiber-
optic cable. Cable TV networks also use coaxial
cables.

A fiber-optic cable is made of glass or
plastic and transmits signals in the form
of light.
To understand optical fiber, we first need
to explore several aspects of the nature of
light.
Fiber-optic cable

 A fiber optic cable is a network cable that
contains strands of glass fibers inside an
insulated casing.
 They're designed for long distance, very high
performance data networking and
telecommunications.
 Compared to wired cables, fiber optic cables
provide higher bandwidth and can transmit data
over longer distances.
 Fiber optic cables support much of the world's
internet, cable television and telephone systems

1] The subscriber channel (SC) connector is
used for cable TV. It uses a push/pull
locking system.
2] The straight-tip (ST) connector is used for
connecting cable to networking devices. It
is more reliable than SC.
3] MT-RJ is a connector that is the same size
as RJ45.

Characteristics of Fiber Optic Cable:-
1] It can provide extremely high bandwidths in the
range from 100 Mbps to 2 Gbps because light
has a much higher frequency than light.
2] The installation of OFC is difficult and tedious.
3] The cost of OFC is more as compared to Other
cable.

Advantages of Fiber Optic Cables:-
Fiber cables offer several advantages over
traditional long-distance copper cabling.
1] Fiber optics have a higher capacity. The
amount of network bandwidth a fiber cable can
carry easily exceeds that of a copper cable with
similar thickness.
Fiber cables rated at 10 Gbps, 40 Gbps and even
100 Gbps are standard.

2] Since light can travel much longer distances
down a fiber cable without losing its strength, it
lessens the need for signal boosters.
3] Small size and light weight.
4] No electrical or electromagnetic interference.
5] Security.

Disadvantages of Fiber Optic Cables:-
1] Sophisticated plants are required for manufacturing.
2] Joining the optical fibers is a difficult Job.
3] The initial cost incurred is high.

Applications
Fiber-optic cable is often found in backbone
networks because its wide bandwidth is cost-
effective. Today, with wavelength-division
multiplexing (WDM), we can transfer data at a
rate of 1600 Gbps.
Some cable TV companies use a combination
of optical fiber and coaxial cable, thus creating
a hybrid network.
This is a cost-effective configuration since the
narrow bandwidth requirement at the user
end does not justify the use of optical fiber.

UNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic
waves without using a physical conductor.
This type of communication is often
referred to as wireless communication.

Electromagnetic spectrum for
wireless communication

Access Point
In a wireless local area network (WLAN), an
access point is a station that transmits and
receives data (sometimes referred to as
a transceiver).
An access point connects users to other users
within the network and also can serve as the
point of interconnection between the WLAN and
a fixed wire network.

Each access point can serve multiple users
within a defined network area; as people
move beyond the range of one access point,
they are automatically handed over to the
next one.
A small WLAN may only require a single
access point; the number required increases
as a function of the number of network users
and the physical size of the network.

An access point connects to a wired router,
switch, or hub via an Ethernet cable, and
projects a Wi-Fi signal to a designated area.

DIGITAL-TO-DIGITAL CONVERSION
Digital to digital conversion involves three
techniques:
1. line coding,
2. Block coding,
3.Scrambling.
Line coding is always needed; block coding
and scrambling may or may not be needed.

Line coding and decoding
Line coding is the process of converting digital
data to digital signals.

1. Unipolar scheme
All the signal levels are on one side of the time axis,
either above or below.
Unipolar NRZ (Non Return to zero) Scheme:-

 A Unipolar scheme was designed as a
non-return-to-zero (NRZ) scheme in which
the positive voltage defines bit 1 and the
zero voltage defines bit O.
 It is called NRZ because the signal does
not return to zero at the middle of the bit.
 This scheme is very costly.

2. Polar scheme
In polar schemes, the voltages are on the
both sides of the time axis.
For example, the voltage level for 0 can be
positive and the voltage level for 1 can be
negative.

I] Non-Return-to-Zero (NRZ) In polar NRZ
encoding, we use two levels of voltage
amplitude.
We can have two versions of polar NRZ:
1.NRZ-L (NRZ-Level)
2.NRZ-I, (NRZ-Invert)

 In the first variation, NRZ-L (NRZ-Level),
the level of the voltage determines
the value of the bit.
 In the second variation, NRZ-I (NRZ-
Invert), the change or lack of change in the
level of the voltage determines the value of
the bit.
 If there is no change, the bit is 0; if there
is a change, the bit is 1.

The main problem with NRZ encoding
occurs when the sender and receiver
clocks are not synchronized.
The receiver does not know when one bit
has Ended and the next bit is starting. One
solution is the return-to-zero (RZ) scheme.
Which uses three values:
 Positive,
 negative, and
 zero
 In RZ, the signal changes not between bits
but during the bit.

Disadvantage: -
 RZ encoding is that it requires two signal
changes to encode a bit and therefore
occupies greater bandwidth.
 Another problem is the complexity: RZ uses
three levels of voltage, which is more
complex to create and discern.

Manchester scheme
The idea of RZ (transition at the middle of the
bit) and the idea of NRZ-L are combined into the
Manchester scheme.
In Manchester encoding, the duration of the bit
is divided into two halves.
 The voltage remains at one level during the
first half and moves to the other level in the
second half.
 The transition at the middle of the bit
provides synchronization
III] Polar biphase

Polar biphase: Manchester and
differential Manchester schemes

Differential Manchester scheme
 Differential Manchester, combines the
ideas of RZ and NRZ-I.
 There is always a transition at the middle
of the bit, but the bit values are determined
at the beginning of the bit.
 If the next bit is 0, there is a transition; if
the next bit is 1, there is none.

In Manchester and differential
Manchester encoding, the transition
at the middle of the bit is used for
synchronization.

The Manchester scheme overcomes several
problems associated with NRZ-L,
And differential Manchester overcomes several
problems associated with NRZ-I.
1] There is no baseline wandering.
2] There is no DC component because each bit
has a positive and negative voltage
contribution.

In decoding a digital signal, the receiver
calculates a running average of the received
signal power. This average is called the
baseline.
The incoming signal power is evaluated against
this baseline to determine the value of the
data element.
A long string of Os or 1s can cause a drift in
the baseline (baseline wandering) and make it
difficult for the receiver to decode correctly. A
good line coding scheme needs to prevent
baseline wandering.
Baseline wandering

Drawback :
1] The signal rate:-
The signal rate for Manchester and
differential Manchester is double that for
NRZ. The reason is that there is
always one transition at the middle of the
bit and maybe one transition at the end of
each bit.

Unguided signals can travel from the source to
destination in several ways:
In ground propagation, radio waves travel
through the lowest portion of the
atmosphere, hugging the earth.
In sky propagation, higher-frequency radio
waves radiate upward into the ionosphere.

In line-of-sight propagation, very high-
frequency signals are transmitted in
straight lines directly from antenna to
antenna. Antennas must be directional,
facing each other, and either tall
enough or close enough together not to
be affected by the curvature of
the earth.

Radio waves :Omnidirectional antenna
Radio waves, for the most part, are omnidirectional.
When an antenna transmits radio waves, they are
propagated in all directions. This means that the
sending and receiving antennas do not have to be
aligned. A sending antenna sends waves that can
be received by any receiving antenna.

Applications
The omnidirectional characteristics of
radio waves make them useful for
multicasting, in which there is one
sender but many receivers.
AM and FM radio, television, and
cordless phones, are examples of
multicasting.

Microwaves :Unidirectional antennas

Microwaves are unidirectional. When an
antenna transmits microwave waves, they
can be narrowly focused.
This means that the sending and receiving
antennas need to be aligned.
The unidirectional property has an obvious
advantage. A pair of antennas can be aligned
without interfering with another pair of aligned
antennas.

Applications
Microwaves, due to their unidirectional
properties, are very useful when unicast
(one-to-one) communication is needed
between the sender and the receiver.
They are used in cellular phones, satellite
networks ,and wireless LANs.

Infrared waves, with frequencies from 300
GHz to 400 THz, can be used for short-
range communication.
Infrared waves, having high frequencies,
cannot penetrate walls. This advantageous
characteristic prevents interference
between one system and another; a short-
range communication system in one room
cannot be affected by another system in
the next room.
Infrared waves

Applications:
The infrared band, almost 400 THz, has an
excellent potential for data transmission. Such
a wide bandwidth can be used to transmit
digital data with a very high data rate.
Some manufacturers provide a special port
called the IrDA (The Infrared Data Association)
port that allows a wireless keyboard to
communicate with a PC.
The standard originally defined a data rate of
75 kbps for a distance up to 8 m. The recent
standard defines a data rate of 4 Mbps.

Open Elective MSE.pptx

Recommended

Recommended

More Related Content

Similar to Open Elective MSE.pptx

Similar to Open Elective MSE.pptx (20)

Recently uploaded

Recently uploaded (20)

Open Elective MSE.pptx