data communication network 3

8/12/2019 data communication network 3

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Data Communications &

Networking

An Introduction


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NETWORK MODELS

Internet model (TCP/IP)

ISO-OSI Reference Model


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Layered structure example

Organization A Organization B

Postal department Network

CEO-A CEO-B

PA-A

R&D Clerk-A

Mail-man-A

PA-B

R&D Clerk-B

Mail-man-B

Mail-Box-A

Mail-Box-B


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Observations from the aboveexample

communication process is divided into number ofsub functions.

The distribution of process into more than onefunction is brought about in order to enhance theperformance at each level.

The function of the level above or above a certainlevel is transparent at each level

Modification can be performed at each levelimproving or modifying its performance much easily.

The above example is a 7 Layer Model


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Peers Each level in organization A is complemented

by a corresponding level in organization B.These level which perform the complement

function are called peers. Peers may be defined more generally as

those parties functioning at the same level

appearing to communicate each other


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Service access points

The CEO-A accesses the PA-A anddictates the letter, this boundarybetween CEO-A Layer & PA-A layer iscalled SAP.

The SAP is almost two way as in case ofPA-B of organization B handling over the

letter to CEO-B


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Hierarchy:-

according to the analysis there are 6different activities at the sender side and 6at the receiver side. For completing the taskthe activities are performed in the order iein hierarchical manner.

Services:-

Each function or layer uses services of thelayers immediately below it.


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Stack of layers

The layers which form the model are alsocalled stack of layers or layer stack.

This stack of layers is also called a protocolstack, since each layer is clearly defined aswhat services it will provide.

The rules and formats for interaction with itare well defined

L i


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Layering A vantages

Complex problems are broken into an ordered

sequence of simpler problems. Hence solving ofcomplex problem becomes easier

The modularization of layers represents the

simpler problem may be modified and implementedwithout affecting the layer above and below it

Layering approach provides a broad common

functionality which enables a wide range ofimplementers to interface to various layers instandard manner


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Internet Model (TCP/IP protocol suit)

The layered protocol stack thatdominates data communication andnetworking today is the five layerInternet model


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Physical

Data link

Network

Transport

Application

TCP/IP

Protocol Stack


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Key Points

1. Protocol architecture is the layered structure of H/Wand S/W that supports the exchange of data betweensystems and supports distributed applications such ase.mail & file transfer.

2. At each layer of protocol architecture one or moreprotocols are implemented in communicating systems.Each protocol provides a set of rules for the exchangeof data between systems.

3. Within a single machine, each layer calls upon theservices of the layer just below it


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Physical

Data link

Network

Transport

Application

A BIN1 IN2

5-4 I/f

4-3 I/f

3-2 I/f

2-1 I/f

Physical

Data link

Network

3-2 I/f

2-1 I/f

Physical

Data link

Network

3-2 I/f

2-1 I/f

Physical

Data link

Network

Transport

Application5-4 I/f

4-3 I/f

3-2 I/f

2-1 I/f

Peer to -Peer

Peer to -Peer

Peer to Peer Process


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Physical Layer

DLL

Network Layer IPv4

ARP RARP

IGMP ICMP

SCTP TCP UDP

SMTP FTP SNMP DNS HTTP

TransportLayer

Appln Layer

802.x

Wired/Wireless


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Interfaces between layers

The passing of the data and network information downthrough the layers of the sending and receiving device ismade possible by an interface between each pair ofadjacent layers

Each interface defines what information and services alayer must provide for the layer above it

A well defined interfaces and layer functions providemodularity to a network


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L5 Data H5

L4 Data H4

L3 Data H3

A B

T2 L2 Data H2

10101010110100101010 10101010110100101010

T2 L2 Data H2

L3 Data H3

L4 Data H4

L5 Data H5

An exchange using the internet model


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Physical Layer


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Physical Layer is responsible fortransmitting individual bits fromone node to the next


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Functions of Physical Layer

Physical characteristics of i/fs & media

Representation of bits

Data rates (transmission rate)

Synchronization of bits

Multiplexing

Switching

Transmission media


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Data Link Layer

The Data link layer is used for hop to hop deliveryof frames

Protocols available

802.x


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Data Link Layer is responsiblefor delivery of frames from onenode to the next


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S

LAN

LAN

R1

R2

R3

Link1

Link2 Link3 D

Data Link Layer


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Node to Node delivery


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Functions of Data Link Layer

Physical addressing

Framing

Flow control

Error Control

Access Control


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Cableend

Cableend

23

Tap

DropLine

Tap

DropLine

Tap

DropLine

45 71

T2 Data 23 71


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Network Layer

The Network layer is used for the src to destndelivery of a packets possibly across multiple

ntks. Ntk layer ensures that each packet getsfrom its point of origin to its final dstn

Only one Protocols is available

IP


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S

LAN

LAN

R1

R2

R3

Link1

Link2 Link3

Host to Host Path

D


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Physical

Data link

Network

Physical

Data link

Network

Physical

Data link

Network

Physical

Data link

Network

S R1 R2 D

Routing using the TCP/IP Layers


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Functions of Network Layer

Logical addressing

Routing

Internetworking

Packetizing

Fragmenting


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Transport Layer

The transport layer is responsible for process to processdelivery of the entire massage

Transports appln layer messages between the client &server sides of the appln

Two Protocols are available

UDP

TCP


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Transport Layer is responsiblefor sending messages (segments)

from one process to another


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Application layer

Application layer enables the user,whether Human or Software, to access the

network. It provides user interfaces andsupport for services such as e-mail,remote file access and transfer, access tothe world wide web and so on.


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Functions of the layer

Mail services.

File transfer and access

Remote login Accessing world wide web


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Messages

Segment

Packets

Frames

Bits


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Physical

Data link

Network

Transport

ApplicationProvides user access tontk resources

Ensures process toprocess delivery

Sends pkts from src to

dst

Provides hop-to-hopdelivery

T/fs bits over themedium


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Addresses in TCP/IP


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Physical

Data link

Network

Transport

ApplicationSpecfic addrbits-goa.ac.in

Port addr-1622

Logical addr 32

10.2.1.83

Physical add- 4800-1A-4B-39-4D-5D


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Physical addresses


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As we will see most local-area networks use a 48-bit (6-byte) physical address written as 12hexadecimal digits; every byte (2 hexadecimaldigits) is separated by a colon, as shown below:

07:01:02:01:2C:4BA 6-byte (12 hexadecimal digits) physical

address.


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IP addresses


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Port addresses


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As we will see a port address is a 16-bit addressrepresented by one decimal number as shown.

753A 16-bit port address representedas one single number.


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The physical addresses change from hop to hop,but the logical and port addresses usually remain thesame.

Note


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Physical Layer

Position of the physical layer


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p y y

Services


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SIGNALS

To be transmitted, data must betransformed to electromagnetic

signals.


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Analog and Digital

Analog and Digital Data

Analog and Digital Signals

Periodic and Aperiodic Signals


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Signals can be analog or digital.Analog signals can have an infinite

number of values in a range; digitalsignals can have only a limited

number of values.

Analog Signals


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Analog Signals

Sine Wave

Characteristics

Simple signal

Composite signal

1) Amplitude

Characteristics Cont


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Characteristics ContFrequency/Period

Frequency and per iod are inverses of each other.

F requency is the rate of change with respect to time.

Change in a short span of time means high

frequency. Change over a long span of time means

low frequency.



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Phase

Phase describes the position of the waveform

relative to time zero.

E l


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Example

A sine wave is offset one-sixth of a cycle with respect

to time zero. What is its phase in degrees and radians?

Solution

One complete cycle is 360 degrees. Therefore, 1/6

cycle is

(1/6) 360 = 60 degrees = 60 x 2 /360 rad = 1.046 rad

Sine wave Plots with different Characteristics


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Composite Signals


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Composite Signals

According to Four ier analysis, any composite

signal can be represented as a combination ofsimple sine waves with different f requencies,

phases, and amplitudes.


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Frequency Spectrum

The description of a signal usingfrequency domain and containing allits components is called Frequency

spectrum of that signal


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Bandwidth

Signal Bandwidth

Medium Bandwidth

data communication network 3

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