The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers.

1. WELCOME TO OURWELCOME TO OUR
PRESENTATIONPRESENTATION
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2. SEVEN LAYERSEVEN LAYER
MODELMODEL
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3. GROUP MEMBERSGROUP MEMBERS
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4. INTRODUCTIONINTRODUCTION
International standard organization (ISO) established a committeeInternational standard organization (ISO) established a committee
in 1977 to develop an architecture for systemsin 1977 to develop an architecture for systems
communication.communication.
Open System Interconnection (OSI) reference model is theOpen System Interconnection (OSI) reference model is the
result of this effort.result of this effort.
This model allows any two different systems to communicateThis model allows any two different systems to communicate
regardless of their underlying architecture.regardless of their underlying architecture.
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5. CONT..CONT..
The OSI model describes how data flows from one computer, throughThe OSI model describes how data flows from one computer, through
a network to another computer.a network to another computer.
The OSI model is not a protocol; it is a model for understanding andThe OSI model is not a protocol; it is a model for understanding and
designing a network architecture that is flexible and robust.designing a network architecture that is flexible and robust.
The OSI model consists of seven separate but related layers, each ofThe OSI model consists of seven separate but related layers, each of
which defines a part of the process of moving information across awhich defines a part of the process of moving information across a
network.network.
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6. 6
APPLICATIONAPPLICATION
PRESENTATIONPRESENTATION
SESSIONSESSION
TRANSPORTTRANSPORT
NETWORKNETWORK
DATA LINKDATA LINK
PHYSICALPHYSICAL
APPLICATIONAPPLICATION
PRESENTATIONPRESENTATION
SESSIONSESSION
TRANSPORTTRANSPORT
NETWORKNETWORK
DATA LINKDATA LINK
PHYSICALPHYSICAL
MIDDLE LAYER
MIDDLE LAYER
HIGHER LAYER
HIGHER LAYER
Application to Application
Application to Application
Application to Application
Process to Process
LOWER LAYER
LOWER LAYER
Hop to Hop
Switch
Hop to Hop
Physical Medium
Hub and Repeater
Router
Source to Destination
Source to Destination
OSI Model's 7 LayersOSI Model's 7 Layers

7. HOST AND MEDIA LAYERHOST AND MEDIA LAYER
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8. PHYSICAL LAYERPHYSICAL LAYER
 One of the major function of the physical layer is to move data in the form of electromagnetic signals acrossOne of the major function of the physical layer is to move data in the form of electromagnetic signals across
a transmission medium.a transmission medium.
 Its responsible for movements of individual bits from one hop (Node) to next.Its responsible for movements of individual bits from one hop (Node) to next.
 Both data and the signals can be eitherBoth data and the signals can be either analoganalog oror digitaldigital..
 Transmission media work by conducting energy along a physical path which can be wired or wirelessTransmission media work by conducting energy along a physical path which can be wired or wireless
 Concerned:Concerned:
 Physical characteristics of interface and mediumPhysical characteristics of interface and medium (Transmission medium)(Transmission medium)
 Representation of bitsRepresentation of bits (stream of bits (0s or 1s) with no interpretation and encoded into signals)(stream of bits (0s or 1s) with no interpretation and encoded into signals)
 Data rateData rate (duration of a bit, which is how long it last)(duration of a bit, which is how long it last)
 Synchronization of bitsSynchronization of bits (sender and receivers clock must be synchronized)(sender and receivers clock must be synchronized)
 Line configurationLine configuration (Point-to-Point, Point-to-Multipoint)(Point-to-Point, Point-to-Multipoint)
 Physical topologyPhysical topology
 Transmission modeTransmission mode (Simplex, half duplex, full duplex)(Simplex, half duplex, full duplex)
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10101000000010111110
From data link layer
10101000000010111110
To data link layer
Physical layer
Physical layer
Transmission medium

9. DATA LINK LAYERDATA LINK LAYER (HOST TO HOST)(HOST TO HOST)
 Data link layer is responsible for moving frames from one hop (Node) to the next.Data link layer is responsible for moving frames from one hop (Node) to the next.
 Concerned:Concerned:
 FramingFraming (stream of bits into manageable data units)(stream of bits into manageable data units)
 Physical addressingPhysical addressing (MAC Address)(MAC Address)
 Flow ControlFlow Control (mechanism for overwhelming the receiver)(mechanism for overwhelming the receiver)
 Error ControlError Control (trailer, retransmission)(trailer, retransmission)
 Access ControlAccess Control (defining master device in the same link)(defining master device in the same link)
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DataH2 T2
From network layer
DataH2 T2
To network layer
To physical layer From physical layer
Data link layer Data link layer

10. NETWORK LAYERNETWORK LAYER (SOURCE TO DESTINATION)(SOURCE TO DESTINATION)
• The network layer is responsible for the delivery of individual packets from theThe network layer is responsible for the delivery of individual packets from the
source host to the destination host.source host to the destination host.
• Concerned:Concerned:
• Logical addressingLogical addressing (IP Address)(IP Address)
• RoutingRouting (Source to destination transmission between networks)(Source to destination transmission between networks)
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DataH3 Packet
From transport layer
To data link layer
DataH3 Packet
To transport layer
From data link layer
Network layer Network layer

11. TRANSPORT LAYERTRANSPORT LAYER (PROCESS TO PROCESS)(PROCESS TO PROCESS)
 The transport layer is responsible for the delivery of a message from one process toThe transport layer is responsible for the delivery of a message from one process to
anotheranother
 Concerned:Concerned:
 Service-point addressing (Port address)Service-point addressing (Port address)
 Segmentation and reassembly (Sequence number)Segmentation and reassembly (Sequence number)
 Connection control (Connectionless or connection oriented)Connection control (Connectionless or connection oriented)
 Flow control (end to end)Flow control (end to end)
 Error Control (Process to Process)Error Control (Process to Process) 11
SegmentsSegments
DataH4
From session layer
To network layer
Transport layer DataH4 DataH4
SegmentsSegments
DataH4
From session layer
From network layer
Transport layerDataH4 DataH4

12. SESSION LAYERSESSION LAYER (DIALOG INITIATION)(DIALOG INITIATION)
The session layer is responsible for dialog control and synchronizationThe session layer is responsible for dialog control and synchronization
 Concerned:Concerned:
 Dialog Control (Half Duplex/Full duplex)Dialog Control (Half Duplex/Full duplex)
 Synchronization (Synchronization points, process inline within same pageSynchronization (Synchronization points, process inline within same page))
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DataH5
From Presentation layer
To transport layer
Data Data
Syn Syn Syn
DataH5
To Presentation layer
From transport layer
Data Data
Syn Syn Syn
Session layer
Session layer

13. PRESENTATION LAYERPRESENTATION LAYER (DEPENDENCY)(DEPENDENCY)
 The presentation layer is responsible for translation, compression and encryptionThe presentation layer is responsible for translation, compression and encryption
 Concerned:Concerned:
 Translation (interoperability between different encoding system)Translation (interoperability between different encoding system)
 Encryption (Privacy schemes)Encryption (Privacy schemes)
 Compression (data compression)Compression (data compression)
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DataH6
From application layer
To session layer
DataH6
To application layer
From session layer
presentation layer
presentation layer

14. APPLICATION LAYERAPPLICATION LAYER (USER LEVEL SERVICE)(USER LEVEL SERVICE)
 The application layer is responsible for providing services to the user.The application layer is responsible for providing services to the user.
 Concerned:Concerned:
 Network virtual terminal (Software)Network virtual terminal (Software)
 File transfer, access and managementFile transfer, access and management
 Mail servicesMail services
 Directory services (access to distributed database sources for global information about variousDirectory services (access to distributed database sources for global information about various
objects and servicesobjects and services))
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DataH7
USER
(Human or Program)
To presentation layer
DataH7
Application layer
Application layer
Message Message
X.500 FTAM X.400
X.500 FTAM X.400
From presentation layer
USER
(Human or Program)

15. THE ENDTHE END
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