OSI REFERENCE LAYERS

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OSI REFERENCE LAYERS :

OSI REFERENCE LAYERS By K. TEJOVATHI III YEAR CSE ‘B’ Sec

CONTENTS :

CONTENTS INTRODUCTION WHAT IS OSI? OSI MODEL TYPES OF LAYERS PHYSICAL LAYER DATA LINK LAYER NETWORK LAYER TRANSPORT LAYER SESSION LAYER PRESENTATION LAYER APPLICATION LAYER CONCLUSION

What is OSI?:

What is OSI? OSI - O PEN S YSTEMS I NTERCONNECTION An open system is a set of protocol that allows any two different systems to communicate regardless of their underlying architectures. It was designed by ISO-International Organization for Standardization in late1970s. It is a seven-layer model. It is a theoretical model designed to show how a protocol stack should be implemented.

OSI MODEL:

OSI MODEL Physical layer Data link layer Network layer Transport layer 1 2 3 5 6 7 4 Application layer Session layer Presentation layer

TYPES OF LAYERS:

TYPES OF LAYERS Physical layer Data link layer Network layer Transport layer Session layer Presentation layer Application layer

PHYSICAL LAYER:

PHYSICAL LAYER The physical layer is responsible for transmitting individual bits from one node to the next Functions of physical layer: Physical characteristics of interfaces and media Representation of bits Data rate Synchronization of bits

PHYSICAL LAYER:

PHYSICAL LAYER 101010000000101111001 101010000000101111001 Physical layer Physical layer Transmission medium From data link layer To data link layer

DATA LINK LAYER:

DATA LINK LAYER The data link layer is responsible for transmitting frames from one node to the next FUNCTIONS OF DATA LINK LAYER: Framing Physical addressing Flow control Error control Access control

DATA LINK LAYER:

DATA LINK LAYER T2 Data H2 T2 Data H2 To physical layer From physical layer Data link layer Data link layer From network layer To network layer frame frame

NETWORK LAYER:

NETWORK LAYER The network layer is responsible for the delivery of packets from the original source to the final destination FUNCTIONS OF NETWORK LAYER: Logical addressing Routing

NETWORK LAYER:

NETWORK LAYER Data H3 Data H3 To data link layer From data link layer Network layer Network layer From transport layer To transport layer packet packet

TRANSPORT LAYER:

TRANSPORT LAYER The transport layer is responsible for delivery of a message from one process to another(process-to-process delivery) FUNCTIONS OF TRANSPORT LAYER: Port addressing Segmentation and reassembly Connection control Flow control Error control

TRANSPORT LAYER:

TRANSPORT LAYER Data H4 Data H4 Data H4 Data H4 Data H4 Data H4 To network layer From network layer Transport layer Transport layer From session layer To session layer segments segments

SESSION LAYER:

SESSION LAYER The session layer is the network dialog controller. It establishes, maintains,and synchronizes the interaction between communicating systems FUNCTIONS OF SESSION LAYER: Dialog control synchronization

SESSION LAYER:

SESSION LAYER H5 L5 data syn syn syn Session layer L6 data H5 L5 data syn syn syn Session layer L6 data To transport layer From transport layer From presentation layer To presentation layer

PRESENTATION LAYER:

PRESENTATION LAYER The presentation layer is concerned with the syntax and semantics of the information exchanged between two systems FUNCTONS OF PRESENTATION LAYER: Translation Encryption Compression

PRESENTATION LAYER:

PRESENTATION LAYER L6 data L7 data H6 Presentation layer Encoded ,encrypted & compressed data L6 data L7 data H6 Decoded ,decrypted & decompressed data Presentation layer To session layer From session layer From application layer To application layer

APPLICATION LAYER:

APPLICATION LAYER The application layer enables the user,whether human or software, to access the network. It provides user interfaces and support for services. FUNCTIONS OF APPLICATION LAYER: Network virtual terminal File transfer,access,and management(FTAM) Mail services Directory services

APPLICATION LAYER:

APPLICATION LAYER X.500 FTAM X.400 Application layer L7 data User X.500 FTAM X.400 Application layer L7 data User To presentation layer From presentation layer

OSI LAYERS MODEL:

OSI LAYERS MODEL

CONCLUSION:

CONCLUSION The purpose of OSI is to show how to facilitate communication between different system without regarding changes to the logic of the underlying hardware and software. It is the model for understanding and designing a network architecture that is flexible,robust and interoperable.