TOPIC:

OSI MODEL

Submitted by:

Shahreen Gul (1544-BSEE-FET-F11) Namra Afzal (1528-BSEE-FET-F11) Irum Fatima (1545-BSEE-FET-F11)

OUTLINE

Network Division of layersLayers & their functionsFormatting of data through layer

A network  is a group of two or more computer systems linked together. The link may be wire or wireless. Networks can interconnect with other networks and contain sub-networks .

NETWORKSNETWORKS

DATA COMMUNICATION

Open Systems Interconnection (OSI) is a set of internationally recognized, non-proprietary standards for networking and for operating system involved in networking functions.

THE LAYERED APPROACH TO COMMUNICATION

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data Link

1. Physical

DIVISION OF LAYERS

Upper Layers

Lower Layers

Middle Layer

7. Application

6. Presentation

5. Session

4. Transport

3. Network

2. Data Link

1. Physical

protocol is the special set of rules that end points in a telecommunication connection use when they communicate

It specify interactions between the communicating entities.

PROTOCOL

Each layer deals with one aspect of networking Layer 1 deals with the communication media

Each layer communicates with the adjacent layers In both directions Ex: Network layer communicates with:

Transport layer Data Link layer

Each layer formats the data packet Ex: Adds or deletes addresses

THE FUNCTION OF A LAYER

ROLE OF LAYERS

7. Application

6. Presentation

1. Physical

Node A

Data Out

Data In

To/from Node B

COMMUNICATION BETWEEN LAYERS

7. Application

6. Presentation

5. Session

DataEncapsulation

DataStripping

THE ROLE OF LAYERS IN POINT-TO-POINT COMMUNICATION

7. Application

1. Physical

7. Application

1.Physical

Node a Node b

The interaction between layers in the OSI model

PurposeUser application to network service interface

ExamplesFile request from serverE-mail servicesetc.

7. APPLICATION LAYER

General network accessFlow controlError recovery

APPLICATION LAYER FUNCTION

Application layer

Purpose

Formats data for exchange between points of communication

•Ex: Between nodes in a networkExample

Redirector software

•Formats for transmission to the server

6. PRESENTATION LAYER

Data translation Encryption compression

PRESENTATION LAYER FUNCTION

Presentation layer

Purpose

Dialog controller synchronization

5. SESSION LAYER

Synchronization between sender and receiverAssignment of time for transmission

•Start time•End time etc.

SESSION LAYER FUNCTION

Session layer

Purpose

Repackage proper and efficient delivery of packages

• In sequence

•Without duplication

•Error free

4. TRANSPORT LAYER

For sending data Split long messagesAssemble small messages

On receiving dataPerform the reverse Send an acknowledgment to the sender

Solve packet problemsDuring transmission and reception

TRANSPORT LAYER FUNCTION

Transport layer

Reliable process-to-process delivery of a message

Purpose

Addressing and routing the packetsExample application at the router

If the packet size is large, splits into small packets

3. NETWORK LAYER

Address translation from logical to physicalRouting of data

Based on priorityBest path at the time of transmission

Congestion control

NETWORK LAYER FUNCTION

Network layer

A routing protocol is a protocol that specifies how router communicate with each other

Enables them to select routes between any two nodes on computer network

E.g OSPF , RIP

ROUTING PROTOCOL

PurposeManages the flow of data over the physical media

Responsible for error-free transmission over the physical media

Assures error-free data submission to the Network Layer

2. DATA LINK LAYER

FramingPhysical addressFlow controlError controlAccess control

DATA LINK LAYER

Point of originPackages data for transmission over physical line

Receiving endPackages data for submission to the network layer

Deals with network transmission protocols IEEE 802. protocols

DATA LINK LAYER FUNCTION

Data link layer

Improvement to ISO ModelLogical Link Control (LLC) sub-layer

Error and flow control

Media Access Control (MAC) sub-layerApplies directly to network card communicationAccess control

DATA LINK LAYER SUBDIVISION

Network Interface Card driver

MEDIA ACCESS CONTROL APPLICATION

NETWORKSOFTWARE

NETWORKCARD

NIC Driverfacilitates data transfer

PurposeDeals with the transmission of 0s and 1s over the

physical mediaTranslation of bits into signals

ExamplePulse duration determinationTransmission synchronizationetc.

1. PHYSICAL LAYER

Physical characteristicRepresentation of bitsSynchronization of bitsPhysical topolgyTransmission mode

PHYSICAL LAYER

Encode bits into signalsCarry data from the higher layers

Decode bits into signalsCarry data from to higher layers

PHYSICAL LAYER FUNCTION

Physical layer

At each layer, additional information is added to the data packet

Trailer Packet arrival information and Some Header

Information Added at Various Layers

• Receiver’s address• Sender’s address

LAYER OPERATIONS

PACKET : GENERAL FORMAT

Header Trailer

Data

A general concept of packets serves as a prerequisite tothe understanding of the ISO-OSI model.

FORMATTING OF DATA THROUGH THE LAYERS

Application Header Presentation Header Session Header

Transport HeaderNetwork Header

Data Link Header and Trailer Physical Frame Preamble

An exchange using the OSI model

SUMMARY

Thank You