Multiplexing: FDM, TDM, CDM and WDM, Protocol Layering: ISO/OSI Reference Model, TCP/IP Reference Model, OSI vs TCP/IP
SnehPrasad2
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128 slides
Feb 27, 2025
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About This Presentation
Need of computer communication, Goals of communication system/Networking, Transmission Modes, Transmission Media: Guided: Twisted Pair, Coaxial and Fiber-Optic Cables, Unguided Media: Radio, VHF, Micro Waves and Satellite, Topologies: Star, Mesh, Bus etc., Multichannel Data Communication: Message, C...
Slide Content
Radio Waves
•Although there is no clear-cut demarcation
between radio waves and microwaves,
electromagnetic waves ranging in frequencies
between 3 kHz and 1 GHz are normally called
radio waves.
•Radio waves, for the most part, are omni (all)
directional. When an antenna transmits radio
waves, they are propagated in all directions.
•Although there is no clear-cut demarcation
between radio waves and microwaves,
electromagnetic waves ranging in frequencies
between 3 kHz and 1 GHz are normally called
radio waves.
•Radio waves, for the most part, are omni (all)
directional. When an antenna transmits radio
waves, they are propagated in all directions.
Radio Waves
•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.
•Radio waves, particularly those waves that
propagate in the sky mode, can travel long
distances. This makes radio waves a good
candidate for long-distance broadcasting such
as AM radio.
•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.
•Radio waves, particularly those waves that
propagate in the sky mode, can travel long
distances. This makes radio waves a good
candidate for long-distance broadcasting such
as AM radio.
Omni Directional Antenna
Radio waves are used for
multicast communications,
such as radio and television.
Radio waves are used for
multicast communications,
such as radio and television.
Microwaves
•Electromagnetic waves having frequencies
between 1 and 300 GHz are called
microwaves.
•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.
•Electromagnetic waves having frequencies
between 1 and 300 GHz are called
microwaves.
•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.
Characteristics of microwave propagation:
•Microwave propagation is line-of-sight. Since the
towers with the mounted antennas need to be in
direct sight of each other, towers that are far
apart need to be very tall.
•The curvature of the earth as well as other
blocking obstacles do not allow two short towers
to communicate by using microwaves. Repeaters
are often needed for long distance
communication.
•Very high-frequency microwaves cannot
penetrate walls. This characteristic can be a
disadvantage if receivers are inside buildings.
•Microwave propagation is line-of-sight. Since the
towers with the mounted antennas need to be in
direct sight of each other, towers that are far
apart need to be very tall.
•The curvature of the earth as well as other
blocking obstacles do not allow two short towers
to communicate by using microwaves. Repeaters
are often needed for long distance
communication.
•Very high-frequency microwaves cannot
penetrate walls. This characteristic can be a
disadvantage if receivers are inside buildings.
Unidirectional Antenna- microwave propagation
•Microwaves need unidirectional antennas that
send out signals in one direction.
•A parabolic dish antenna is based on the
geometry of a parabola: Every line parallel to the
line of symmetry (line of sight) reflects off the
curve at angles such that all the lines intersect in a
common point called the focus.
•The parabolic dish works as a funnel, catching a
wide range of waves and directing them to a
common point. In this way, more of the signal is
recovered than would be possible with a single-
point receiver.
•Microwaves need unidirectional antennas that
send out signals in one direction.
•A parabolic dish antenna is based on the
geometry of a parabola: Every line parallel to the
line of symmetry (line of sight) reflects off the
curve at angles such that all the lines intersect in a
common point called the focus.
•The parabolic dish works as a funnel, catching a
wide range of waves and directing them to a
common point. In this way, more of the signal is
recovered than would be possible with a single-
point receiver.
Parabolic Dish Antenna
Terrestrial Microwave
Satellite Communication
Geosynchronous Orbit
Infrared
•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, 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
•When we use our infrared remote control, we
do not interfere with the use of the remote by
our neighbors. However, this same
characteristic makes infrared signals useless
for long-range communication.
•In addition, we cannot use infrared waves
outside a building because the sun's rays
contain infrared waves that can interfere with
the communication.
•When we use our infrared remote control, we
do not interfere with the use of the remote by
our neighbors. However, this same
characteristic makes infrared signals useless
for long-range communication.
•In addition, we cannot use infrared waves
outside a building because the sun's rays
contain infrared waves that can interfere with
the communication.
Infrared
•Interference, in
physics, the net effect of the
combination of two or more
wave trains
moving on intersecting or coincident paths.
The effect is that of the addition of
the
amplitudes of the individual waves at each
point affected by more than one wave.
•Interference, in
physics, the net effect of the
combination of two or more
wave trains
moving on intersecting or coincident paths.
The effect is that of the addition of
the
amplitudes of the individual waves at each
point affected by more than one wave.
ANALOG AND DIGITAL
•To be transmitted, data must be transformed to
electromagnetic signals. Both data and the signals
that represent them can be either analog or digital
in form.
•Analog and Digital Data: Data can be analog or
digital. The term analog data refers to
information that is continuous; digital data
refers to information that has discrete states.
•For example, an analog clock that has hour,
minute, and second hands gives information in a
continuous form; the movements of the hands are
continuous.
•On the other hand, a digital clock that reports the
hours and the minutes will change suddenly from
8:05 to 8:06.
•To be transmitted, data must be transformed to
electromagnetic signals. Both data and the signals
that represent them can be either analog or digital
in form.
•Analog and Digital Data: Data can be analog or
digital. The term analog data refers to
information that is continuous; digital data
refers to information that has discrete states.
•For example, an analog clock that has hour,
minute, and second hands gives information in a
continuous form; the movements of the hands are
continuous.
•On the other hand, a digital clock that reports the
hours and the minutes will change suddenly from
8:05 to 8:06.
•Digital data take on discrete values. For
example, data are stored in computer memory
in the form of Os and 1s. They can be
converted to a digital signal or modulated into
an analog signal for transmission across a
medium.
•Data can be analog or digital. Analog data are
continuous and take continuous values.
•Digital data have discrete states and take
discrete values.
example, data are stored in computer memory
in the form of Os and 1s. They can be
converted to a digital signal or modulated into
an analog signal for transmission across a
medium.
•Data can be analog or digital. Analog data are
continuous and take continuous values.
•Digital data have discrete states and take
discrete values.
Analog and Digital Clocks
Comparison of analog and digital signals
Periodic and Nonperiodic Signals
.
•A periodic signal completes a pattern within a
measurable time frame, called a period, and
repeats that pattern over subsequent identical
periods. The completion of one full pattern is
called a cycle.
•A nonperiodic signal changes without
exhibiting a pattern or cycle that repeats over
time.
•In data communications, we commonly use
periodic analog signals and nonperiodic digital
signals.
.
•A periodic signal completes a pattern within a
measurable time frame, called a period, and
repeats that pattern over subsequent identical
periods. The completion of one full pattern is
called a cycle.
•A nonperiodic signal changes without
exhibiting a pattern or cycle that repeats over
time.
•In data communications, we commonly use
periodic analog signals and nonperiodic digital
signals.
Periodic Analog Signals
•The sine wave is the most fundamental form of a
periodic analog signal. When we visualize it as a
simple oscillating curve, its change over the
course of a cycle is smooth and consistent, a
continuous.
•Each cycle consists of a single arc above the time
axis followed by a single arc below it.
•A sine wave can be represented by three
parameters: the peak amplitude, the frequency,
and the phase.
•These three parameters fully describe a sine
wave.
•The sine wave is the most fundamental form of a
periodic analog signal. When we visualize it as a
simple oscillating curve, its change over the
course of a cycle is smooth and consistent, a
continuous.
•Each cycle consists of a single arc above the time
axis followed by a single arc below it.
•A sine wave can be represented by three
parameters: the peak amplitude, the frequency,
and the phase.
•These three parameters fully describe a sine
wave.
A sine wave
Sine Wave
•The peak amplitude of a signal is the absolute
value of its highest intensity, proportional to the
energy it carries.
•For electric signals, peak amplitude is normally
measured in volts. Figure shows two signals and
their peak amplitudes.
value of its highest intensity, proportional to the
energy it carries.
•For electric signals, peak amplitude is normally
measured in volts. Figure shows two signals and
their peak amplitudes.
•Period and Frequency: Period refers to the
amount of time, in seconds, a signal needs to
complete 1 cycle.
•Frequency refers to the number of periods in 1s.
• Period is the inverse of frequency, and
frequency is the inverse of period. ( T=1/f)
amount of time, in seconds, a signal needs to
complete 1 cycle.
•Frequency refers to the number of periods in 1s.
• Period is the inverse of frequency, and
frequency is the inverse of period. ( T=1/f)
•All signals are composed of three properties:
–Amplitude
–Frequency
–Phase
Signal Properties
Two signals with
the same phase
and frequency,
but
different
amplitudes
–Amplitude
–Frequency
–Phase
Signal Properties
Two signals with
the same phase
and frequency,
but
different
amplitudes
Frequency and period are the inverse of each other.
Note
Two signals
with the same
amplitude and
phase,
but
different
frequencies
Note
Two signals
with the same
amplitude and
phase,
but
different
frequencies
Units of period and frequency
The power we use at home has a frequency of 60 Hz. The period
of this sine wave can be determined as follows:
Example
The power we use at home has a frequency of 60 Hz. The period
of this sine wave can be determined as follows:
Example
The period of a signal is 100 ms. What is its frequency
in kilohertz?
Solution
First we change 100 ms to seconds, and then we calculate the
frequency from the period (1 Hz = 10
−3
kHz).
Example
in kilohertz?
Solution
First we change 100 ms to seconds, and then we calculate the
frequency from the period (1 Hz = 10
−3
kHz).
Example
Phase
•The term phase describes the position of the
waveform relative to time O. If we think of the
wave as something that can be shifted backward
or forward along the time axis, phase describes
the amount of that shift. It indicates the status of
the first cycle.
•Phase describes the position of the waveform
relative to time O.
•A phase shift of 360° corresponds to a shift of a
complete period; a phase shift of 180°
corresponds to a shift of one-half of a period; and
a phase shift of 90° corresponds to a shift of one-
quarter of a period.
•The term phase describes the position of the
waveform relative to time O. If we think of the
wave as something that can be shifted backward
or forward along the time axis, phase describes
the amount of that shift. It indicates the status of
the first cycle.
•Phase describes the position of the waveform
relative to time O.
•A phase shift of 360° corresponds to a shift of a
complete period; a phase shift of 180°
corresponds to a shift of one-half of a period; and
a phase shift of 90° corresponds to a shift of one-
quarter of a period.
Phases
Relationships between different phases
Three sine waves with the same amplitude and frequency,
but different phases
but different phases
A sine wave is offset 1/6 cycle with respect to time 0.
What is its phase in degrees and radians?
Example
Solution
We know that 1 complete cycle is 360°. Therefore,
1/6 cycle is
What is its phase in degrees and radians?
Example
Solution
We know that 1 complete cycle is 360°. Therefore,
1/6 cycle is
Wavelength
•Wavelength is another characteristic of a
signal traveling through a transmission
medium. Wavelength binds the period or the
frequency of a simple sine wave to the
propagation speed of the medium.
•Wavelength is another characteristic of a
signal traveling through a transmission
medium. Wavelength binds the period or the
frequency of a simple sine wave to the
propagation speed of the medium.
•Bandwidth: The range of frequencies contained
in a composite signal is its bandwidth. The
bandwidth is normally a difference between two
numbers. For example, if a composite signal
contains frequencies between 1000 and 5000, its
bandwidth is 5000 - 1000, or 4000.
•The bandwidth of a composite signal is the
difference between the highest and the lowest
frequencies contained in that signal.
in a composite signal is its bandwidth. The
bandwidth is normally a difference between two
numbers. For example, if a composite signal
contains frequencies between 1000 and 5000, its
bandwidth is 5000 - 1000, or 4000.
•The bandwidth of a composite signal is the
difference between the highest and the lowest
frequencies contained in that signal.
DIGITAL SIGNALS
•Information can also be represented by a
digital signal. For example, a 1 can be encoded
as a positive voltage and a 0 as zero voltage. A
digital signal with two levels.
We send 1 bit per level
•Information can also be represented by a
digital signal. For example, a 1 can be encoded
as a positive voltage and a 0 as zero voltage. A
digital signal with two levels.
We send 1 bit per level
Bit Rate:
•Most digital signals are nonperiodic, and thus
period and frequency are not appropriate
characteristics.
•Another term-bit rate (instead of frequency)-is
used to describe digital signals. The bit rate is
the number of bits sent in 1s, expressed in bits
per second (bps).
•Most digital signals are nonperiodic, and thus
period and frequency are not appropriate
characteristics.
•Another term-bit rate (instead of frequency)-is
used to describe digital signals. The bit rate is
the number of bits sent in 1s, expressed in bits
per second (bps).
•Bit Length: The bit length is the distance one
bit occupies on the transmission medium.
•Bit length =propagation speed x bit duration
Bit rate and bit interval
bit occupies on the transmission medium.
•Bit length =propagation speed x bit duration
Bit rate and bit interval
TRANSMISSION MODES
•The transmission of binary data across a link
can be accomplished in either parallel or serial
mode.
•In parallel mode, multiple bits are sent with
each clock tick.
•In serial mode, 1 bit is sent with each clock
tick.
•While there is only one way to send parallel
data, there are two subclasses of serial
transmission: asynchronous, synchronous
•The transmission of binary data across a link
can be accomplished in either parallel or serial
mode.
•In parallel mode, multiple bits are sent with
each clock tick.
•In serial mode, 1 bit is sent with each clock
tick.
•While there is only one way to send parallel
data, there are two subclasses of serial
transmission: asynchronous, synchronous
Parallel Transmission:
• Binary data, consisting of 1s and 0s, may be
organized into groups of n bits each.
•Computers produce and consume data in
groups of bits much as we conceive of and use
spoken language in the form of words rather
than letters.
•By grouping, we can send data n bits at a time
instead of 1. This is called parallel
transmission.
• Binary data, consisting of 1s and 0s, may be
organized into groups of n bits each.
•Computers produce and consume data in
groups of bits much as we conceive of and use
spoken language in the form of words rather
than letters.
•By grouping, we can send data n bits at a time
instead of 1. This is called parallel
transmission.
Parallel Transmission
Serial Transmission :
•In serial transmission one bit follows another,
so we need only one communication channel
rather than n to transmit data between two
communicating devices.
•The advantage of serial over parallel
transmission is that with only one
communication channel, serial transmission
reduces the cost of transmission over parallel
by roughly a factor of n.
•In serial transmission one bit follows another,
so we need only one communication channel
rather than n to transmit data between two
communicating devices.
•The advantage of serial over parallel
transmission is that with only one
communication channel, serial transmission
reduces the cost of transmission over parallel
by roughly a factor of n.
Serial Transmission
Asynchronous Transmission
•Asynchronous transmission is so named
because the timing of a signal is unimportant.
•Instead, information is received and translated
by agreed upon patterns.
•As long as those patterns are followed, the
receiving device can retrieve the information
without regard to the rhythm in which it is
sent.
•Asynchronous transmission is so named
because the timing of a signal is unimportant.
•Instead, information is received and translated
by agreed upon patterns.
•As long as those patterns are followed, the
receiving device can retrieve the information
without regard to the rhythm in which it is
sent.
Asynchronous Transmission
•Patterns are based on grouping the bit stream
into bytes. Each group, usually 8 bits, is sent
along the link as a unit.
• The sending system handles each group
independently, relaying it to the link whenever
ready, without regard to a timer.
•Patterns are based on grouping the bit stream
into bytes. Each group, usually 8 bits, is sent
along the link as a unit.
• The sending system handles each group
independently, relaying it to the link whenever
ready, without regard to a timer.
Asynchronous Transmission
•Without synchronization, the receiver cannot
use timing to predict when the next group will
arrive. To alert the receiver to the arrival of a
new group, therefore, an extra bit is added to
the beginning of each byte.
•This bit, usually a 0, is called the start bit. To
let the receiver know that the byte is finished,
1 or more additional bits are appended to the
end of the byte. These bits, usually Is, are
called stop bits.
use timing to predict when the next group will
arrive. To alert the receiver to the arrival of a
new group, therefore, an extra bit is added to
the beginning of each byte.
•This bit, usually a 0, is called the start bit. To
let the receiver know that the byte is finished,
1 or more additional bits are appended to the
end of the byte. These bits, usually Is, are
called stop bits.
•By this method, each byte is increased in size
to at least 10 bits, of which 8 bits is
information and 2 bits or more are signals to
the receiver.
•In asynchronous transmission, we send 1 start
bit (0) at the beginning and 1 or more stop bits
(Is) at the end of each byte. There may be a
gap between each byte.
to at least 10 bits, of which 8 bits is
information and 2 bits or more are signals to
the receiver.
•In asynchronous transmission, we send 1 start
bit (0) at the beginning and 1 or more stop bits
(Is) at the end of each byte. There may be a
gap between each byte.
Synchronous Transmission
•In synchronous transmission, the bit stream is
combined into longer "frames," which may
contain multiple bytes.
•Each byte, however, is introduced onto the
transmission link without a gap between it and
the next one.
•It is left to the receiver to separate the bit
stream into bytes for decoding purposes.
•In synchronous transmission, the bit stream is
combined into longer "frames," which may
contain multiple bytes.
•Each byte, however, is introduced onto the
transmission link without a gap between it and
the next one.
•It is left to the receiver to separate the bit
stream into bytes for decoding purposes.
Synchronous Transmission
•In other words, data are transmitted as an
unbroken string of 1s and Os, and the receiver
separates that string into the bytes, or
characters, it needs to reconstruct the
information.
•In synchronous transmission, we send bits one
after another without start or stop bits or gaps.
It is the responsibility of the receiver to group
the bits.
•In other words, data are transmitted as an
unbroken string of 1s and Os, and the receiver
separates that string into the bytes, or
characters, it needs to reconstruct the
information.
•In synchronous transmission, we send bits one
after another without start or stop bits or gaps.
It is the responsibility of the receiver to group
the bits.
Synchronous Transmission
The advantage of synchronous transmission is speed.
The advantage of synchronous transmission is speed.
Multiplexing Techniques for Communication
•Nowadays it is possible to send pictures, images, and
tweets through the internet without any superimposition
of data from one source or the other. This article
describes the techniques that make this sort of data
transfer a possible reality.
•If you want to send message from multiple source these
messages mixed and pass through single transmitted line.
How do all these message get joined together and
transmitted without getting mixed up?
•Nowadays it is possible to send pictures, images, and
tweets through the internet without any superimposition
of data from one source or the other. This article
describes the techniques that make this sort of data
transfer a possible reality.
•If you want to send message from multiple source these
messages mixed and pass through single transmitted line.
How do all these message get joined together and
transmitted without getting mixed up?
Multiplexing Techniques
•This process is done by a technique called
Multiplexing.
Multiplexing combines multiple analog
or digital signals
bound for transmission through a
single communication line or computer channel.
•This technique has been introduced to increase channel
utilization in
multicomputer communication systems and
time sharing systems and also to reduce the
communication cost.
•This process is done by a technique called
Multiplexing.
Multiplexing combines multiple analog
or digital signals
bound for transmission through a
single communication line or computer channel.
•This technique has been introduced to increase channel
utilization in
multicomputer communication systems and
time sharing systems and also to reduce the
communication cost.
Multiplexing Techniques
Types of Multiplexing
Different type of multiplexing is used in
communication. In this article, the following
three major multiplexing techniques are
discussed:
•Frequency division multiplexing (FDM)
•Wavelength division multiplexing (WDM)
•Time division multiplexing (TDM)
Different type of multiplexing is used in
communication. In this article, the following
three major multiplexing techniques are
discussed:
•Frequency division multiplexing (FDM)
•Wavelength division multiplexing (WDM)
•Time division multiplexing (TDM)
Multiplexing Techniques
Analog Multiplexing
•The analog multiplexing techniques involve signals
which are analog in nature.
•The analog signals are multiplexed according to
their frequency (FDM) or wavelength (WDM).
Digital Multiplexing
•The term digital represents the discrete bits of
information.
•Hence, the available data is in the form of frames or
packets, which are discrete.
Analog Multiplexing
•The analog multiplexing techniques involve signals
which are analog in nature.
•The analog signals are multiplexed according to
their frequency (FDM) or wavelength (WDM).
Digital Multiplexing
•The term digital represents the discrete bits of
information.
•Hence, the available data is in the form of frames or
packets, which are discrete.
Multiplexing Techniques
Frequency Division Multiplexing
•Many telephone companies uses FDM for long
distance connections to multiplex thousands of
voice signals through a coaxial cable system.
•The FDM is an analog multiplexing that
combines analog signals. Frequency division
multiplexing is applied when the bandwidth of
the link is greater than the combined bandwidth
of the signals to be transmitted.
•Many telephone companies uses FDM for long
distance connections to multiplex thousands of
voice signals through a coaxial cable system.
•The FDM is an analog multiplexing that
combines analog signals. Frequency division
multiplexing is applied when the bandwidth of
the link is greater than the combined bandwidth
of the signals to be transmitted.
•Period and Frequency: Period refers to the
amount of time, in seconds, a signal needs to
complete 1 cycle.
•Frequency refers to the number of periods in 1s.
Note that period and frequency are just one
characteristic defined in two ways.
• Period is the inverse of frequency, and
frequency is the inverse of period. ( T=1/f)
amount of time, in seconds, a signal needs to
complete 1 cycle.
•Frequency refers to the number of periods in 1s.
Note that period and frequency are just one
characteristic defined in two ways.
• Period is the inverse of frequency, and
frequency is the inverse of period. ( T=1/f)
FDM
FDM
•In this type of multiplexing, signals are
generated by sending different device-modulated
carrier frequencies, and these modulated signals
are then combined into a single signal that can
be transported by the link.
• To accommodate the modulated signal, the
carrier frequencies are separated with enough
bandwidth, and these bandwidth ranges are the
channels through which different signals travel.
•In this type of multiplexing, signals are
generated by sending different device-modulated
carrier frequencies, and these modulated signals
are then combined into a single signal that can
be transported by the link.
• To accommodate the modulated signal, the
carrier frequencies are separated with enough
bandwidth, and these bandwidth ranges are the
channels through which different signals travel.
FDM
•These channels can be separated by unused
bandwidth.
•Example
− A traditional
television transmitter,
which sends a number of channels through a
single cable uses FDM.
•These channels can be separated by unused
bandwidth.
•Example
− A traditional
television transmitter,
which sends a number of channels through a
single cable uses FDM.
Wavelength Division Multiplexing(WDM)
•Wavelength division multiplexing (WDM) is a
technology in
fiber optic communications; for
the high capacity communication systems.
• This system uses multiplexer (converge signal)
at transmitter to join signals and demultiplexer
(diverge signal) to split the signals apart, at the
receiver end.
•Wavelength division multiplexing (WDM) is a
technology in
fiber optic communications; for
the high capacity communication systems.
• This system uses multiplexer (converge signal)
at transmitter to join signals and demultiplexer
(diverge signal) to split the signals apart, at the
receiver end.
Wavelength Division Multiplexing (WDM)
•The purpose of WDM is to combine multiple
light sources into a single light source at the
multiplexer; and, at the demultiplexer the single
light is converted into multiple light sources.
•WDM is designed to use the high data rate
capability of the fiber optic cable.
•The purpose of WDM is to combine multiple
light sources into a single light source at the
multiplexer; and, at the demultiplexer the single
light is converted into multiple light sources.
•WDM is designed to use the high data rate
capability of the fiber optic cable.
Wavelength Division Multiplexing(WDM)
•Conceptually, the wavelength division multiplexing
is same as the frequency division multiplexing,
except for the transmission through the fiber optic
channels where in the multiplexing and
demultiplexing involves optical signals.
•Example
−
Optical fiber Communications use the
WDM technique, to merge different wavelengths
into a single light for the communication.
•Conceptually, the wavelength division multiplexing
is same as the frequency division multiplexing,
except for the transmission through the fiber optic
channels where in the multiplexing and
demultiplexing involves optical signals.
•Example
−
Optical fiber Communications use the
WDM technique, to merge different wavelengths
into a single light for the communication.
Wavelength Division Multiplexing(WDM)
Time-Division Multiplexing (TDM)
Time-Division Multiplexing (TDM)
•Time division multiplexing is a technique used to
transmit a signal over a single communication
channel by dividing the time frame into slots – one
slot for each message signal.
•Time-division multiplexing is primarily applied to
digital signals as well as analog signals, wherein
several low speed channels are multiplexed into
high-speed channels for transmission.
•Time division multiplexing is a technique used to
transmit a signal over a single communication
channel by dividing the time frame into slots – one
slot for each message signal.
•Time-division multiplexing is primarily applied to
digital signals as well as analog signals, wherein
several low speed channels are multiplexed into
high-speed channels for transmission.
Time-Division Multiplexing (TDM)
•Based on the time, each low-speed channel is
allocated to a specific position, where it works in
synchronized mode.
•At both the ends, i.e., the multiplexer and
demultiplexer are timely synchronized and
simultaneously switched to the next channel.
•Based on the time, each low-speed channel is
allocated to a specific position, where it works in
synchronized mode.
•At both the ends, i.e., the multiplexer and
demultiplexer are timely synchronized and
simultaneously switched to the next channel.
Types of TDM
Time division multiplexing is classifieds into two
types:
•Synchronous time-division multiplexing
•Asynchronous time-division multiplexing
Time division multiplexing is classifieds into two
types:
•Synchronous time-division multiplexing
•Asynchronous time-division multiplexing
Synchronous Time Division Multiplexing
Synchronous Time Division Multiplexing
•Synchronous time division multiplexing can be
used for both analog and digital signals.
•In synchronous TDM, the connection of input is
connected to a frame.
•If there are ‘n’ connections, then a frame is divided
into ‘n’ time slots – and, for each unit, one slot is
allocated – one for each input line.
•Synchronous time division multiplexing can be
used for both analog and digital signals.
•In synchronous TDM, the connection of input is
connected to a frame.
•If there are ‘n’ connections, then a frame is divided
into ‘n’ time slots – and, for each unit, one slot is
allocated – one for each input line.
Synchronous Time Division Multiplexing
•In this synchronous TDM sampling, the rate is
same for all the signals, and this sampling requires a
common clock signal at both the sender and receiver
end.
• In synchronous TDM, the multiplexer allocates the
same slot to each device at all times.
•In this synchronous TDM sampling, the rate is
same for all the signals, and this sampling requires a
common clock signal at both the sender and receiver
end.
• In synchronous TDM, the multiplexer allocates the
same slot to each device at all times.
Asynchronous Time-Division Multiplexing
Asynchronous Time-Division Multiplexing
•In asynchronous time-division multiplexing, the
sampling rate is different for different signals, and it
doesn’t require a common clock.
•If the devices have nothing to transmit, then their
time slot is allocated to another device.
•This type of time-division multiplexing is used in
Asynchronous Transfer Mode (ATM)networks.
•In asynchronous time-division multiplexing, the
sampling rate is different for different signals, and it
doesn’t require a common clock.
•If the devices have nothing to transmit, then their
time slot is allocated to another device.
•This type of time-division multiplexing is used in
Asynchronous Transfer Mode (ATM)networks.
SWITCHING
PROBLEM :
•Whenever we have multiple devices, we have the
problem of how to connect them to make one-to-one
communication possible.
•One solution is to make a point-to-point connection
between each pair of devices (a mesh topology) or
between a central device and every other device (a star
topology).
•These methods, however, are impractical and wasteful
when applied to very large networks.
•The number and length of the links require too much
infrastructure to be cost-efficient, and the majority of
those links would be idle most of the time.
78
PROBLEM :
•Whenever we have multiple devices, we have the
problem of how to connect them to make one-to-one
communication possible.
•One solution is to make a point-to-point connection
between each pair of devices (a mesh topology) or
between a central device and every other device (a star
topology).
•These methods, however, are impractical and wasteful
when applied to very large networks.
•The number and length of the links require too much
infrastructure to be cost-efficient, and the majority of
those links would be idle most of the time.
78
Switching
SOLUTION :
•A better solution is switching. A switched network
consists of a series of interlinked nodes, called
switches.
•Switches are devices capable of creating temporary
connections between two or more devices linked to the
switch.
•In a switched network, some of these nodes are
connected to the end systems (computers or
telephones, for example). Others are used only for
routing.
79
SOLUTION :
•A better solution is switching. A switched network
consists of a series of interlinked nodes, called
switches.
•Switches are devices capable of creating temporary
connections between two or more devices linked to the
switch.
•In a switched network, some of these nodes are
connected to the end systems (computers or
telephones, for example). Others are used only for
routing.
79
SWITCHING
80
Figure : Switched network
•The end systems (communicating devices) are labeled
A, B, C, D, and so on, and the switches are labeled I, II,
III, IV, and V. Each switch is connected to multiple links.
80
Figure : Switched network
•The end systems (communicating devices) are labeled
A, B, C, D, and so on, and the switches are labeled I, II,
III, IV, and V. Each switch is connected to multiple links.
Figure: Taxonomy of switched networks
CIRCUIT-SWITCHED NETWORKS
•A trivial circuit-switched network with four switches and four
links. Each link is divided into n (n is 3 in the figure) channels.
82
A circuit-switched network is made of a set of switches connected
by physical links, in which each link is
divided into n channels.
•A trivial circuit-switched network with four switches and four
links. Each link is divided into n (n is 3 in the figure) channels.
82
A circuit-switched network is made of a set of switches connected
by physical links, in which each link is
divided into n channels.
CIRCUIT-SWITCHED NETWORKS
Three Phases
The actual communication in a circuit-switched
network requires three phases: (i) connection setup, (ii)
data transfer, (iii) connection teardown.
83
In circuit switching, the resources need to be
reserved during the setup phase; the resources remain
dedicated for the entire duration of data transfer until
the teardown phase.
Three Phases
The actual communication in a circuit-switched
network requires three phases: (i) connection setup, (ii)
data transfer, (iii) connection teardown.
83
In circuit switching, the resources need to be
reserved during the setup phase; the resources remain
dedicated for the entire duration of data transfer until
the teardown phase.
CIRCUIT-SWITCHED NETWORKS
•Setup Phase :
•Before the two parties can communicate, a
dedicated circuit (combination of channels in
links) needs to be established.
•The end systems are normally connected through
dedicated lines to the switches, so connection
setup means creating dedicated channels between
the switches.
84
•Setup Phase :
•Before the two parties can communicate, a
dedicated circuit (combination of channels in
links) needs to be established.
•The end systems are normally connected through
dedicated lines to the switches, so connection
setup means creating dedicated channels between
the switches.
84
CIRCUIT-SWITCHED NETWORKS
Setup Phase :
•when system A needs to connect to system M, it
sends a setup request that includes the address of
system M, to switch I. Switch I finds a channel
between itself and switch IV that can be
dedicated for this purpose.
•Switch I then sends the request to switch IV,
which finds a dedicated channel between itself
and switch III. Switch III informs system M of
system A's intention at this time.
85
Setup Phase :
•when system A needs to connect to system M, it
sends a setup request that includes the address of
system M, to switch I. Switch I finds a channel
between itself and switch IV that can be
dedicated for this purpose.
•Switch I then sends the request to switch IV,
which finds a dedicated channel between itself
and switch III. Switch III informs system M of
system A's intention at this time.
85
CIRCUIT-SWITCHED NETWORKS
Setup Phase :
•In the next step to making a connection, an
acknowledgment from system M needs to be sent
in the opposite direction to system A. Only after
system A receives this acknowledgment is the
connection established.
•End-to-end addressing is required for creating a
connection between the two end systems.
86
Setup Phase :
•In the next step to making a connection, an
acknowledgment from system M needs to be sent
in the opposite direction to system A. Only after
system A receives this acknowledgment is the
connection established.
•End-to-end addressing is required for creating a
connection between the two end systems.
86
CIRCUIT-SWITCHED NETWORKS
(ii) Data Transfer Phase
•After the establishment of the dedicated circuit
(channels), the two parties can transfer data.
(iii) Teardown Phase
•When one of the parties needs to disconnect, a
signal is sent to each switch to release the
resources.
87
(ii) Data Transfer Phase
•After the establishment of the dedicated circuit
(channels), the two parties can transfer data.
(iii) Teardown Phase
•When one of the parties needs to disconnect, a
signal is sent to each switch to release the
resources.
87
CIRCUIT-SWITCHED NETWORKS
Advantages:
• The communication channel (once established) is
dedicated.
Disadvantages:
• Possible long wait to establish a connection, (10
seconds, more on long- distance or international calls.)
during which no data can be transmitted.
• More expensive than any other switching techniques,
because a dedicated path is required for each
connection.
• Inefficient use of the communication channel,
because the channel is not used when the connected
systems are not using it.
88
Advantages:
• The communication channel (once established) is
dedicated.
Disadvantages:
• Possible long wait to establish a connection, (10
seconds, more on long- distance or international calls.)
during which no data can be transmitted.
• More expensive than any other switching techniques,
because a dedicated path is required for each
connection.
• Inefficient use of the communication channel,
because the channel is not used when the connected
systems are not using it.
88
DATAGRAM NETWORKS
•In a Datagram network, there is no resource
reservation; resources are allocated on
demand. This means that there is no reserved
bandwidth on the links.
•The allocation is done on a first- come, first-
served basis.
•In a datagram network, each packet is treated
independently of all others.
89
•In a Datagram network, there is no resource
reservation; resources are allocated on
demand. This means that there is no reserved
bandwidth on the links.
•The allocation is done on a first- come, first-
served basis.
•In a datagram network, each packet is treated
independently of all others.
89
A Datagram network with four switches (routers)
DATAGRAM NETWORKS
•In this example, all four packets (or datagrams)
belong to the same message, but may travel
different paths to reach their destination.
•This is so because the links may be involved in
carrying packets from other sources and do not
have the necessary bandwidth available to carry
all the packets from A to X.
•This approach can cause the datagrams of a
transmission to arrive at their destination out of
order with different delays between the packets.
91
•In this example, all four packets (or datagrams)
belong to the same message, but may travel
different paths to reach their destination.
•This is so because the links may be involved in
carrying packets from other sources and do not
have the necessary bandwidth available to carry
all the packets from A to X.
•This approach can cause the datagrams of a
transmission to arrive at their destination out of
order with different delays between the packets.
91
DATAGRAM NETWORKS
•Packets may also be lost or dropped because of a
lack of resources. In most protocols, it is the
responsibility of an upper-layer protocol to
reorder the datagrams or ask for lost datagrams
before passing them on to the application.
•The datagram networks are sometimes referred
to as connectionless networks. The term
connectionless here means that the switch
(packet switch) does not keep information about
the connection state.
92
•Packets may also be lost or dropped because of a
lack of resources. In most protocols, it is the
responsibility of an upper-layer protocol to
reorder the datagrams or ask for lost datagrams
before passing them on to the application.
•The datagram networks are sometimes referred
to as connectionless networks. The term
connectionless here means that the switch
(packet switch) does not keep information about
the connection state.
92
DATAGRAM NETWORKS
93
•If there are no setup or teardown phases, how are
the packets routed to their destinations in a datagram
network?
• In this type of network, each switch (or packet
switch) has a routing table which is based on the
destination address.
•The routing tables are dynamic and are updated
periodically.
•The destination addresses and the corresponding
forwarding output ports are recorded in the tables.
93
•If there are no setup or teardown phases, how are
the packets routed to their destinations in a datagram
network?
• In this type of network, each switch (or packet
switch) has a routing table which is based on the
destination address.
•The routing tables are dynamic and are updated
periodically.
•The destination addresses and the corresponding
forwarding output ports are recorded in the tables.
DATAGRAM NETWORKS
94
Fig: Routing Table in a Datagram Network
94
Fig: Routing Table in a Datagram Network
DATAGRAM NETWORKS
95
Destination Address:
•Every packet in a datagram network carries a header
that contains, among other information, the destination
address of the packet.
•When the switch receives the packet, this destination
address is examined; the routing table is consulted to
find the corresponding port through which the packet
should be forwarded.
•This address, unlike the address in a virtual-circuit-
switched network, remains the same during the entire
journey of the packet.
95
Destination Address:
•Every packet in a datagram network carries a header
that contains, among other information, the destination
address of the packet.
•When the switch receives the packet, this destination
address is examined; the routing table is consulted to
find the corresponding port through which the packet
should be forwarded.
•This address, unlike the address in a virtual-circuit-
switched network, remains the same during the entire
journey of the packet.
VIRTUAL-CIRCUIT NETWORKS
96
A virtual-circuit network is a cross between a circuit-
switched network and a datagram network. It has
some characteristics of both:
1.As in a circuit-switched network, there are setup
and teardown phases in addition to the data transfer
phase.
2.Resources can be allocated during the setup phase,
as in a circuit-switched network , or on demand, as
in a datagram network.
3.As in a datagram network, data are packetized and
each packet carries an address in the header.
96
A virtual-circuit network is a cross between a circuit-
switched network and a datagram network. It has
some characteristics of both:
1.As in a circuit-switched network, there are setup
and teardown phases in addition to the data transfer
phase.
2.Resources can be allocated during the setup phase,
as in a circuit-switched network , or on demand, as
in a datagram network.
3.As in a datagram network, data are packetized and
each packet carries an address in the header.
VIRTUAL-CIRCUIT NETWORKS
97
4. As in a circuit-switched network, all packets
follow the same path established during the
connection.
5. A virtual-circuit network is normally implemented
in the data link layer, while a circuit-switched
network is implemented in the physical layer and
a datagram network in the network layer.
97
4. As in a circuit-switched network, all packets
follow the same path established during the
connection.
5. A virtual-circuit network is normally implemented
in the data link layer, while a circuit-switched
network is implemented in the physical layer and
a datagram network in the network layer.
VIRTUAL-CIRCUIT NETWORKS
98
•The network has switches that allow traffic from
sources to destinations.
• A source or destination can be a computer,
packet switch, bridge, or any other device that
connects other networks.
98
•The network has switches that allow traffic from
sources to destinations.
• A source or destination can be a computer,
packet switch, bridge, or any other device that
connects other networks.
VIRTUAL-CIRCUIT NETWORKS
99
99
VIRTUAL-CIRCUIT NETWORKS
100
Addressing:
In a virtual-circuit network, two types of
addressing are involved: global and local (virtual-
circuit identifier).
(i) Global Addressing
A source or a destination needs to have a global
address-an address that can be unique.
100
Addressing:
In a virtual-circuit network, two types of
addressing are involved: global and local (virtual-
circuit identifier).
(i) Global Addressing
A source or a destination needs to have a global
address-an address that can be unique.
VIRTUAL-CIRCUIT NETWORKS
101
(ii) Virtual-Circuit Identifier
•The identifier that is actually used for data transfer is
called the virtual-circuit identifier (VCI). A VCI,
unlike a global address, is a small number that has
only switch scope.
•It is used by a frame between two switches. When a
frame arrives at a switch, it has a VCI; when it leaves,
it has a different VCI.
101
(ii) Virtual-Circuit Identifier
•The identifier that is actually used for data transfer is
called the virtual-circuit identifier (VCI). A VCI,
unlike a global address, is a small number that has
only switch scope.
•It is used by a frame between two switches. When a
frame arrives at a switch, it has a VCI; when it leaves,
it has a different VCI.
VIRTUAL-CIRCUIT NETWORKS
102
Three Phases:
As in a circuit-switched network, a source and destination
need to go through three phases in a virtual-circuit
network: setup, data transfer, and teardown.
•In the setup phase, the source and destination use their
global addresses to help switches make table entries for
the connection.
•In the teardown phase, the source and destination inform
the switches to delete the corresponding entry.
•Data transfer occurs between these two phases.
102
Three Phases:
As in a circuit-switched network, a source and destination
need to go through three phases in a virtual-circuit
network: setup, data transfer, and teardown.
•In the setup phase, the source and destination use their
global addresses to help switches make table entries for
the connection.
•In the teardown phase, the source and destination inform
the switches to delete the corresponding entry.
•Data transfer occurs between these two phases.
VIRTUAL-CIRCUIT NETWORKS: Three
Phases
103
Data Transfer Phase :
•To transfer a frame from a source to its destination, all
switches need to have a table entry for this virtual
circuit. The table, in its simplest form, has four columns.
This means that the switch holds four pieces of
information for each virtual circuit that is already set up.
•Figure shows a frame arriving at port 1 with a VCI of
14. When the frame arrives, the switch looks in its table
to find port 1 and a VCI of 14. When it is found, the
switch knows to change the VCI to 22 and send out the
frame from port 3.
•The data transfer phase is active until the source sends
all its frames to the destination.
Phases
103
Data Transfer Phase :
•To transfer a frame from a source to its destination, all
switches need to have a table entry for this virtual
circuit. The table, in its simplest form, has four columns.
This means that the switch holds four pieces of
information for each virtual circuit that is already set up.
•Figure shows a frame arriving at port 1 with a VCI of
14. When the frame arrives, the switch looks in its table
to find port 1 and a VCI of 14. When it is found, the
switch knows to change the VCI to 22 and send out the
frame from port 3.
•The data transfer phase is active until the source sends
all its frames to the destination.
VIRTUAL-CIRCUIT NETWORKS: Three Phases
104
Figure : Switch and tables in a
virtual-circuit network
104
Figure : Switch and tables in a
virtual-circuit network
VIRTUAL-CIRCUIT NETWORKS: Three
Phases
105
Data Transfer Phase :
Figure : Source-to-destination data transfer in a virtual-circuit network
Phases
105
Data Transfer Phase :
Figure : Source-to-destination data transfer in a virtual-circuit network
REFERENCE MODELS
The OSI Reference Model:
•This model is based on a proposal developed by the
International Standards Organization (ISO) as a first
step toward international standardization of the
protocols used in the various layers.
•The model is called the ISO OSI (Open Systems
Interconnection) Reference Model because it deals
with connecting open systems—that is, systems that
are open for communication with other systems.
•The OSI model has seven layers.
The OSI Reference Model:
•This model is based on a proposal developed by the
International Standards Organization (ISO) as a first
step toward international standardization of the
protocols used in the various layers.
•The model is called the ISO OSI (Open Systems
Interconnection) Reference Model because it deals
with connecting open systems—that is, systems that
are open for communication with other systems.
•The OSI model has seven layers.
The OSI Reference Model:
Fig: The OSI reference model
Fig: The OSI reference model
The OSI Reference Model
Fig: An exchange using OSI Model
Fig: An exchange using OSI Model
The OSI Reference Model
LAYERS IN THE OSI MODEL:
Physical Layer :
•The physical layer coordinates the functions required
to carry a bit stream over a physical medium.
•It deals with the mechanical and electrical
specifications of the interface and transmission
medium.
LAYERS IN THE OSI MODEL:
Physical Layer :
•The physical layer coordinates the functions required
to carry a bit stream over a physical medium.
•It deals with the mechanical and electrical
specifications of the interface and transmission
medium.
The OSI Reference Model
LAYERS IN THE OSI MODEL:
LAYERS IN THE OSI MODEL:
The OSI Reference Model:
Data Link Layer:
•The data link layer divides the stream of bits
received from the network layer into manageable
data units called frames.
•Physical addressing. If frames are to be distributed
to different systems on the network, the data link
layer adds a header to the frame to define the sender
and/or receiver of the frame.
•Error control. The data link layer adds reliability to
the physical layer by adding mechanisms to detect
and retransmit damaged or lost frames. It also uses a
mechanism to recognize duplicate frames.
Data Link Layer:
•The data link layer divides the stream of bits
received from the network layer into manageable
data units called frames.
•Physical addressing. If frames are to be distributed
to different systems on the network, the data link
layer adds a header to the frame to define the sender
and/or receiver of the frame.
•Error control. The data link layer adds reliability to
the physical layer by adding mechanisms to detect
and retransmit damaged or lost frames. It also uses a
mechanism to recognize duplicate frames.
The OSI Reference Model:
Data Link Layer:
Data Link Layer:
The OSI Reference Model:
Network Layer :
•The network layer is responsible for the source-to-
destination delivery of a packet, possibly across
multiple networks (links).
•Whereas the data link layer oversees the delivery
of the packet between two nodes on the same
network (links), the network layer ensures that each
packet gets from its point of origin to its final
destination.
Network Layer :
•The network layer is responsible for the source-to-
destination delivery of a packet, possibly across
multiple networks (links).
•Whereas the data link layer oversees the delivery
of the packet between two nodes on the same
network (links), the network layer ensures that each
packet gets from its point of origin to its final
destination.
The OSI Reference Model:
Network Layer :
Network Layer :
The OSI Reference Model:
Network Layer :
•Logical addressing: The network layer adds a
header to the packet coming from the upper layer
that, among other things, includes the logical
addresses of the sender and receiver.
•Routing. When independent networks or links are
connected to create internetworks (network of
networks) or a large network, the connecting
devices (called routers or switches) route or switch
the packets to their final destination.
Network Layer :
•Logical addressing: The network layer adds a
header to the packet coming from the upper layer
that, among other things, includes the logical
addresses of the sender and receiver.
•Routing. When independent networks or links are
connected to create internetworks (network of
networks) or a large network, the connecting
devices (called routers or switches) route or switch
the packets to their final destination.
The OSI Reference Model:
Transport Layer :
•The transport layer is responsible for process-to-
process delivery of the entire message.
•Whereas the network layer oversees source-to-
destination delivery of individual packets, it does
not recognize any relationship between those
packets.
•The transport layer, on the other hand, ensures that
the whole message arrives intact and in order.
Transport Layer :
•The transport layer is responsible for process-to-
process delivery of the entire message.
•Whereas the network layer oversees source-to-
destination delivery of individual packets, it does
not recognize any relationship between those
packets.
•The transport layer, on the other hand, ensures that
the whole message arrives intact and in order.
The OSI Reference Model:
Transport Layer :
Transport Layer :
The OSI Reference Model:
Transport Layer :
Transport Layer :
The OSI Reference Model:
Session Layer :
The session layer is the network dialog controller. It
establishes, maintains, and synchronizes the
interaction among communicating systems.
•Dialog control. The session layer allows two
systems to enter into a dialog. It allows the
communication between two processes to take
place in either half duplex (one way at a time) or
full-duplex (two ways at a time) mode.
Session Layer :
The session layer is the network dialog controller. It
establishes, maintains, and synchronizes the
interaction among communicating systems.
•Dialog control. The session layer allows two
systems to enter into a dialog. It allows the
communication between two processes to take
place in either half duplex (one way at a time) or
full-duplex (two ways at a time) mode.
The OSI Reference Model:
Session Layer :
•Synchronization. The session layer allows a
process to add checkpoints, or synchronization
points, to a stream of data.. For example, if a
system is sending a file of 2000 pages, it is
advisable to insert checkpoints after every 100
pages to ensure that each 100-page unit is received
and acknowledged independently.
Session Layer :
•Synchronization. The session layer allows a
process to add checkpoints, or synchronization
points, to a stream of data.. For example, if a
system is sending a file of 2000 pages, it is
advisable to insert checkpoints after every 100
pages to ensure that each 100-page unit is received
and acknowledged independently.
The OSI Reference Model:
Session Layer :
Session Layer :
The OSI Reference Model:
Presentation Layer :
•The presentation layer is concerned with the syntax and
semantics of the information exchanged between two
systems.
Presentation Layer :
•The presentation layer is concerned with the syntax and
semantics of the information exchanged between two
systems.
The OSI Reference Model:
Presentation Layer :
•Translation: The information must be changed to
bit streams before being transmitted. Because
different computers use different encoding systems,
the presentation layer is responsible for
interoperability between these different encoding
methods.
•Encryption: To carry sensitive information, a
system must be able to ensure privacy.
•Compression: Data compression reduces the
number of bits contained in the information.
Presentation Layer :
•Translation: The information must be changed to
bit streams before being transmitted. Because
different computers use different encoding systems,
the presentation layer is responsible for
interoperability between these different encoding
methods.
•Encryption: To carry sensitive information, a
system must be able to ensure privacy.
•Compression: Data compression reduces the
number of bits contained in the information.
The OSI Reference Model:
Application Layer :
•The application layer enables the user, whether
human or software, to access the network.
•It provides user interfaces and support for services
such as electronic mail, remote file access and
transfer, shared database management.
•Of the many application services available, the
figure shows only three: XAOO (message-handling
services), X.500 (directory services), and File
Transfer Access Management (FTAM). The user in
this example employs XAOO to send an e-mail
message.
Application Layer :
•The application layer enables the user, whether
human or software, to access the network.
•It provides user interfaces and support for services
such as electronic mail, remote file access and
transfer, shared database management.
•Of the many application services available, the
figure shows only three: XAOO (message-handling
services), X.500 (directory services), and File
Transfer Access Management (FTAM). The user in
this example employs XAOO to send an e-mail
message.
The OSI Reference Model:
Application Layer :
Application Layer :
The OSI Reference Model:
Summary of Layers :
Summary of Layers :
2.127
Addresses in TCP/IP
Addresses in TCP/IP
2.128
Figure Relationship of layers and addresses in TCP/IP
1. MAC Addresses (Physical Address): A MAC address is
basically a local address. It will be unique locally but it is
not unique universally. The format and size of this kind of
address will further change depending on the network.
2. Logical Address(IP Addresses): The logical address is also
called the IP (Internet Protocol) address.
3. Port Address: The label that is allocated to a process is
Known as the port address.It is a 16 bit address field .
4. Specific Addresses: Specific addresses are the e-mail
addresses of the University Resource Locators(URL).
Universal Resource Locator (URL) (for eg , www.gmail.com).
Figure Relationship of layers and addresses in TCP/IP
1. MAC Addresses (Physical Address): A MAC address is
basically a local address. It will be unique locally but it is
not unique universally. The format and size of this kind of
address will further change depending on the network.
2. Logical Address(IP Addresses): The logical address is also
called the IP (Internet Protocol) address.
3. Port Address: The label that is allocated to a process is
Known as the port address.It is a 16 bit address field .
4. Specific Addresses: Specific addresses are the e-mail
addresses of the University Resource Locators(URL).
Universal Resource Locator (URL) (for eg , www.gmail.com).
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