osi layers.ppt

7/28/2019 osi layers.ppt

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Advice

Person

Sales

Take

Not

Do

Please

OSI Model Layers

Application

Presentation

Session

Transport

Network

Data Link

Physical

Layer - 7

Layer - 6

Layer - 5

Layer - 4

Layer - 3

Layer - 2

Layer - 1

Upper Layer

or

Software Layer

Lower Layeror

Hardware Layer

Heart of OSI


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Application Layer

Application Layer isresponsible for providingNetworking Services to user.It also known as Desktop Layer.Identification of Services isdone using Port Numbers.

Ports are nothing but Socket i.e.Entry and Exit Point to the Layer

Total No. Ports 0

65535Reserved Ports 0 1023

Open Ports 1024 65535

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application


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Example of HTTP request

Client Web Server

http://www.iriset.ac.in


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Example of HTTP request

Client Web Server

HTTP Requesthttp:// www.iriset.ac.in

Webpage

HTTP RequestListen onPort 80

Sending HTTP ReplyWebpage

Received HTTP Replyhttp://www.iriset.ac.in

Webpage


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Example of FTP request

Client FTP Server

ftp://ftp.microsoft.com


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Example of FTP request

FTP Requestftp://ftp.microsoft.com

FTP RequestListen onPort 21

Sending FTP Reply

Received FTP Replyftp://ftp.microsoft.com

Client FTP Server


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Examples of Networking Services

Service Port No.

HTTP 80

FTP 21

SMTP 25

TELNET 23

TFTP 69


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Application

2180 25 6753 69

How data flows from Application Layer

Data

Presentation

Session

Transport

Network

Data Link

Physical


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Presentation Layer

Presentation Layer is

responsible for converting datainto standard format.

Examples : ASCII, EBCDIC, JPEG,MPEG, BMP, MIDI, WAV, MP3

Following tasks are perform atPresentation layer :

Encoding DecodingEncryption Decryption

Compression Decompression

Application

Presentation

Session

Transport

Network

Data Link

Physical

Presentation


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How data flows from Presentation Layer

Data

DataApplication

Presentation

Session

Transport

Network

Data Link

Physical


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Session Layer

Session Layer is responsible

establishing, maintaining andterminating session.

Session ID also works at SessionLayer.

Examples :

RPC Remote Procedure CallSQL Structured Query languageNFS Network File System

Application

Presentation

Session

Transport

Network

Data Link

Physical

Session


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How data flows from Session Layer

Data

Data

Data

Application

Presentation

Session

Transport

Network

Data Link

Physical


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Transport Layer

Transport Layer is

responsible for end-to-endconnectivity. It is also known asheart of OSI Layers. Followingtask are performed at TransportLayer : -

Identifying Service

Multiplexing & De-multiplexing

Segmentation

Sequencing & Reassembling

Flow Control

Error Correction

Application

Presentation

Session

Transport

Network

Data Link

Physical

Transport


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Identifying Service

Transmission Control

Protocol

Connection Oriented

Acknowledgement

Reliable

Slower Port No. 6

e.g. HTTP, FTP, SMTP

User Datagram

Protocol

Connection Less

No Acknowledgement

Unreliable

Faster Port No. 17

e.g. DNS, DHCP, TFTP

TCP UDP


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Application

Presentation

Session

Multiplexing & De-multiplexing

2180 25 6753 69

Transport

TCP - 6 UDP - 17

Network

Data Link

Physical


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Segmentation

Hello! How are you ?

Hello! How Are You ?

Hello!

How areyou ?

A B


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Hello! How Are You ?

Hello!

How areyou ?

A B

You Hello! How ? Are

Hello! How AreYou ?

youHello!

How ?are


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Hello!1/5

How2/5

Are3/5

You4/5

?5/5

Hello!

How areyou ?

A B


Hello!1/5

How2/5

Are3/5

You4/5

?5/5

Hello!1/5

How2/5

Are3/5

You4/5

?5/5

Hello!

How areyou ?


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Error Correction


Hello!1/5

How2/5

Are3/5

You4/5

?5/5

Hello!

How areyou ? Hello!1/5

Are3/5

You4/5

?5/5

Hello!1/5

Are3/5

You4/5

?5/5

Segment Missing

Hello!1/5

Are3/5

You4/5

?5/5

How2/5

How2/5

Hello! How are you ? Hello!

How areyou ?

A B


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Flow Control - Windowing

Sending

3-window

Received

3-window

Ack-Rec-3

Sending5-window

Received

4-window

A B

Ack.

Received-4

PC-A

can send 4 Segmentat a time to

PC-B


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How data flows from Transport Layer

Data

Data

Data

DataTHSegment

Application

Presentation

Session

Transport

Network

Data Link

Physical


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Network Layer

Network Layer is

responsible for providing bestpath to data to reach destination.Logical Addressing sits on thislayer. Device working on NetworkLayer is Router.

It is divided into two parts

Routed Protocols

e.g. IP, IPX, Apple Talk.

Routing Protocols

e.g. RIP, IGRP, OSPF, EIGRP

Application

Presentation

Session

Transport

Network

Data Link

Physical

Network


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Routed Protocols

Hello!

How areyou ?

192.168.1.1 192.168.1.2

A B

Segment

Segment

Source IP192.168.1.1

Destination IP192.168.1.2

Source IP192.168.1.1

Destination IP192.168.1.2

Segment

Hello!

How areyou ?


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Routing Protocols

A

www.iriset.ac.in


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How data flows from Network Layer

Data

Data

Data

Segment

Segment

NH

e.g. Router

Packet

Application

Presentation

Session

Transport

Network

Data Link

Physical


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Datalink Layer

Datalink Layer is

divided into two Sub Layers :

LLC Logical Link Control

It talks about Wan protocols e.g.PPP, HDLC, Frame-relay

MAC Media Access Control

It talks about Physical Address.It is 48 bit Addressing

i.e. 12 digit Hexadecimal No.It is also responsible for ErrorDetection

Device working on Data LinkLayer is Switch, Bridge, NIC.

Application

Presentation

Session

Transport

Network

Data Link

Physical

Data Link


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Error Detection CRC Check

Hello!

How areyou ?

Packet

Packet

Source MAC00-20-18-C0-07-71

Destination MAC00-20-18-C0-07-72

000003243422222896965543499323434349943446323111143333300000324342222289696554349932343434994344632311114Error Detected

192.168.1.100-20-18-C0-07-71

192.168.1.200-20-18-C0-07-72

A B

PC-A

CRC No. 33333

PC-BCRC No. 11114

Error DetectedFor Error Correction

Contact Source Transport layer


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Error Detection CRC Check

Packet

Packet

Source MAC00-20-18-C0-07-71


00000324342222289696554349932343434994344632311114202020000032434222228969655434993234343499434463231111420202

Source MAC00-20-18-C0-07-71


Packet

Hello!

How areyou ?

192.168.1.100-20-18-C0-07-71

192.168.1.200-20-18-C0-07-72

A B


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e.g. Switch

How data flows from Data Link Layer

Data

Data

Data

Segment

DH

Packet

DT

Application

Presentation

Session

Transport

Network

Data Link

Physical

PacketPacketFrame


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Physical Layer

Physical Layer is

responsible for electrical,mechanical or procedural checks.Data will be converted in Binarythat is 0s & 1s. Data will be in the

form of electrical pulses if it is

Coaxial or Twisted Pair cable and inthe form of Light if it is Fiber OpticCable.

Devices working at Physical Layer

are Hubs, Repeaters, Cables,Modems etc.

Application

Presentation

Session

Transport

Network

Data Link

PhysicalPhysical


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Physical Layer Example

Frame

Frame

10101010101010101010101010101010

Frame

Hello!

How areyou ?

A B01010110101010101010101011010101101010101010101010010101101010101010101010110101011010101010101010100101011010101010101010101


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How data flows from Physical Layer

Data

Data

Data

Segment

Packet

Frame

Bits

e.g. Hub

Application

Presentation

Session

Transport

Network

Data Link

Physical

l i l i


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Segment

Packet

Frame

A B

Packet

Data

Data

Data

Bits

Data

Segment

Data Encapsulation & De-capsulation

Packet

Data

Data

Data

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

PhysicalBits

DH DT

NH

THSegment

Packet

DT PacketDH DTDH

NH Segment NH

TH DataTH

Frame Packet

C i OSI i h TCP/IP L


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Application

Transport

Internet

NetworkAccess

Comparing OSI with TCP/IP Layers

OSI Layers TCP/IP Layers

Application

Presentation

Session

Transport

Network

Data Link

Physical


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ftp://ftp.microsoft.com

i f i d [ i ]


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telnet 192.168.1.150

================================

Welcome to Hyderabad Router

================================

User Access Verification

password :

Microsoft Windows 2000 [Version 5.00.2195](C) Copyright 1985-2000 Microsoft Corp.C:\>Connecting .....


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http://www.microsoft.com


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http://mail.yahoo.com

xyz

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[email protected]

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