SUBJECT:COMPUTER

NETWORKSTOPIC:

OSI MODEL

CREATED BY:RUCHI MAURYATWINKAL PARMARSHIVALI SALUNKHE

OPEN SYSTEM INTERCONNECTION

OSI –open system interconnection model.

Conceptual model.Developed by ISO in 1984. ISO : Dedicated to defining global

communication and standards. logical framework

Introduction

7 Layers Of OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical

Top layer serve as window Interface between programme and

protocol stack.Enable to access network.

7. Application Layer

7. Application Layer

To Presentation Layer

From Presentation Layer

Network virtual terminalFile transfer , access and

managementMail services

7. Application LayerFunctions:

Also called Translation layer. concerned with syntax and semantics

of the information It can be viewed as the translator for

the network. translate data from a format into a

common format then translate the common format to

a format .Manages data-format information.

6. Presentation Layer

110011000111

H611001100011

1H6

From Application Layer To Application Layer

To Session Layer From Session Layer

6. Presentation Layer

6. Presentation LayerFunctions:

Character code TranslationData ConversionData CompressionData Encryption

hold ongoing communications (called a session) across a network.

orderly communication defines the format of the data  establish and manages the

session  reconnect the session if it

disconnects.

5. Session Layer

H5

syn syn syn

From Presentation Layer

To Transport Layer

Session Layer

From Transport Layer

To Presentation Layer

H5

syn syn syn

Session Layer

5. Session Layer

Session establishment, maintenance and termination.

Dialog Control security and access controlSynchronization

5. Session LayerFunctions:

End to end message deliveryError checking No duplication or errors are occurringMessage arrive in orderAcknowledgementRetransmits the data if error is found

4. Transport Layer

4. Transport Layer

Message acknowledgmentMessage traffic controlSession multiplexingFlow control

4. Transport LayerFunctions:

source to destination delivery.across multiple networks (links). converting logical addresses into

physical addresses.determines that how data transmits

between the network devices.Handles addressing messages for

delivery.

3. Network Layer

deciding how to route transmissions between computers

3. Network Layer

110011000111

H311001100011

1H3

From Transport Layer To Transport Layer

To Data Link Layer From Data Link Layer

Packet Packet

Logical-Physical Address Mapping Internetworking Logical AddressingRoutingPacketizingFragmentation

3. Network LayerFunctions:

provides a reliable linknode-to-node deliveryHandles special data frames

(packets)error-free transfer defines the format of data

2. Data Link Layer

Data Link layer consists of two sub-layers:1. Logical Link Control (LLC) sublayer2. Medium Access Control (MAC) sublayer

2. Data Link Layer

110011000111

H2 T211001100011

1H2 T2

From Network Layer To Network Layer

To Physical Layer From Physical Layer

Frame Frame

FramingPhysical AddressingFlow ControlError ControlAccess Control

2. Data Link LayerFunctions:

Lowest LayerTransmitting individual bitsMechanical electrical specification

1. Physical Layer

Transmission Media

110011000111

110011000111

H1 H1

Bit representationTransmission rateSynchronizingTransmission modePhysical Topology

1. Physical LayerFunctions:

Thank You !!