The document discusses the seven-layer Open Systems Interconnection (OSI) model for data communication between networked systems. It describes each layer of the OSI model including: the physical layer which deals with transmission and signaling of raw bit streams over a communication channel; the data link layer which transforms the physical layer into a reliable link; the network layer which is responsible for logical addressing and routing of packets across multiple networks; the transport layer which ensures complete and error-free delivery of message segments; the session layer which establishes and synchronizes interactions between systems; the presentation layer which formats data for transmission; and the application layer which provides user interfaces and services. Each layer uses the services of lower layers and provides services to higher layers.

1. OPEN SYSTEM
INTERCONNECTION (OSI)
MODEL
PRESENTED BY
SIMRAN KAUR

2. OSI MODEL
• OSI model is a reference tool for understanding data
communication between any two networked system.
• It divides the communication processes into 7 layers.
• Each layer performs specific functions to support the layers
above it and uses services of the layers below it.
• Each layer represents a different level of abstraction and layers
boundaries are well defined.

4. PHYSICAL LAYER
• It coordinates the functions required to transmit a bit stream
over a physical medium.
• It deals with the mechanical and electrical specifications of
interface and transmission medium.
• It defines the procedures and functions that physical devices
and interfaces have to perform for transmission to occur.

5. FUNCTIONS OF PHYSICAL LAYER
• It defines characteristics of the interface between the devices
and the transmission medium.
• It defines the type of transmission medium and transmission
rate.
• It performs synchronization of sender and receiver clocks.
• It is concerned with physical topology.
• It transmits bit stream over the communication channel

6. UNITS USED IN PHYSICAL LAYER
• Hardware used: Repeater and Hub
• Data unit: Bit stream

7. DATA LINK LAYER
• It transforms the physical layer, a raw transmission facility, to a
reliable link and is responsible for Node-to-Node delivery.
• It makes the physical layer appear error free to the upper layer
(i.e., network layer).

8. FUNCTIONS OF DATA LINK LAYER
• Framing
• Flow control
• Error control
• Access control
• Physical addressing

9. UNITS USED IN DATA LINK LAYER
• Hardware used: Bridges and Switches
• Data unit: Frames
• Protocol used: Simplex protocol, stop and wait protocol, sliding
window, HDLC, SDLC, NDP, ISDN, ARP, PSL, OSPF, NDP

10. NETWORK LAYER
• It is responsible for source to destination delivery of a packet
possibly across multiple networks (links).
• If the two systems are connected to the same link, there is
usually no need for a network layer.
• If the two systems are attached to different links with
connecting devices between networks, there is often a need of
the network layer to accomplish source to destination delivery.

11. FUNCTIONS OF NETWORK LAYER
• Logical addressing
• Routing

12. UNITS USED IN NETWORK LAYER
• Hardware used: Routers
• Data units: Packets
• Protocols used: IP(Internet Protocol), NAT(Network Address
Translation), ARP(Address Resolution Protocol), ICMP(Internet
Control Message Protocol), BGP(Border Gateway Protocol),
RARP(Reverse Address Resolution Protocol), DHCP(Dynamic
Host Configuration Protocol), BOOTP, OSPF

13. TRANSPORT LAYER
• It is responsible for source to destination delivery of the entire
message.
• It ensures that the whole message arrives intact and in order.

14. FUNCTIONS OF TRANSPORT LAYER
• Service point addressing
• Segmentation and reassembly
• Flow control
• Error control
• Connection control

15. UNITS USED IN TRANSPORT LAYER
• Hardware used: Transport gateway
• Data units: Segments
• Protocol used: TCP(Transmission Control Protocol) for
connection oriented approach and UDP(User Datagram
Protocol) for connectionless approach

16. SESSION LAYER
• It is the network dialog controller.
• It establishes, maintains and synchronizes the interaction
between communicating systems.
• It plays an important role in keeping applications data separate.

17. FUNCTIONS OF SESSION LAYER
• Dialog control
• Synchronization

18. UNITS USED IN SESSION LAYER
• Data unit: Data
• Protocol used: ADSP, ASP, ISO-SP, L2TP, F2F, PAP, PPTP, RPC,
SMPP, SDP, ZIP, RTCP

19. PRESENTATION LAYER
• It is responsible for how an application formats data to be sent
out onto the network.
• It basically allows an application to read (to understand) the
message.

20. FUNCTIONS OF PRESENTATION LAYER
• Translation
• Encryption and decryption
• Compression

21. UNITS USED IN PRESENTATION LAYER
• Data unit: Data
• Protocol used: AFP, ASCII, EBCDIC, ICA, LPP, NCP, NDR, XDR,
X.25 PAP

22. APPLICATION LAYER
• It enables the user, whether human or software, to access the
network.
• It provides user interfaces and support for services such as
electronic mail, remote file access and transfer shared database
management and other types of distributed information
services.

23. FUNCTIONS OF APPLICATION LAYER
• Network virtual terminal
• File transfer, access and management
• Mail services
• Directory services

24. UNITS USED IN APPLICATION LAYER
• Hardware used: Application Gateway
• Protocol used: HTTP, SMTP, POP3, FTP, Telnet, etc.
• Data unit: Data

25. THANK YOU!!!