The document outlines the Open Systems Interconnection (OSI) model, detailing its seven layers, each responsible for specific networking functions such as data formatting, error control, and routing. It explains how layers interact with one another and emphasizes the importance of protocols in facilitating communication between computers. The layers include physical, data link, network, transport, session, presentation, and application, with each layer adding information to data packets for effective communication.

1. TOPIC:
OSI MODEL
Submitted by:
Shahreen Gul (1544-BSEE-FET-F11)
Namra Afzal (1528-BSEE-FET-F11)
Irum Fatima (1545-BSEE-FET-F11)

2. OUTLINE
Network
Division of layers
Layers & their functions
Formatting of data through layer

3.  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

5. DATA COMMUNICATION

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

7. THE LAYERED APPROACH TO COMMUNICATION
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1. Physical

8. DIVISION OF LAYERS
Upper Layers
Lower Layers
Middle Layer
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1. Physical

9.  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

11. 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

12. ROLE OF LAYERS
7. Application
6. Presentation
1. Physical
Node A
Data Out
Data In
To/from
Node B

13. COMMUNICATION BETWEEN LAYERS
7. Application
6. Presentation
5. Session
Data
Encapsulation
Data
Stripping

14. THE ROLE OF LAYERS IN POINT-TO-POINT
COMMUNICATION
7. Application
1. Physical
7. Application
1.Physical
Node a Node b

15. The interaction between layers in the OSI model

16. Purpose
User application to network service interface
Examples
File request from server
E-mail services
etc.
7. APPLICATION LAYER

17. General network access
Flow control
Error recovery
APPLICATION LAYER FUNCTION

18. Application layer

19. Purpose
Formats data for exchange between points of
communication
•Ex: Between nodes in a network
Example
Redirector software
•Formats for transmission to the server
6. PRESENTATION LAYER

20.  Data translation
 Encryption
 compression
PRESENTATION LAYER FUNCTION

21. Presentation layer

22. Purpose
Dialog controller
synchronization
5. SESSION LAYER

23. Synchronization between sender and receiver
Assignment of time for transmission
•Start time
•End time etc.
SESSION LAYER FUNCTION

24. Session layer

25. Purpose
Repackage proper and efficient delivery of
packages
•In sequence
•Without duplication
•Error free
4. TRANSPORT LAYER

26. For sending data
Split long messages
Assemble small messages
On receiving data
Perform the reverse
Send an acknowledgment to the sender
Solve packet problems
During transmission and reception
TRANSPORT LAYER FUNCTION

27. Transport layer

28. Reliable process-to-process delivery of a message

29. Purpose
Addressing and routing the packets
Example application at the router
If the packet size is large, splits into small
packets
3. NETWORK LAYER

30. Address translation from logical to physical
Routing of data
Based on priority
Best path at the time of transmission
Congestion control
NETWORK LAYER FUNCTION

31. Network layer

32. 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

33. Purpose
Manages 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

34. Framing
Physical address
Flow control
Error control
Access control
DATA LINK LAYER

35. Point of origin
Packages data for transmission over physical line
Receiving end
Packages data for submission to the network layer
Deals with network transmission protocols
IEEE 802. protocols
DATA LINK LAYER FUNCTION

36. Data link layer

37. Improvement to ISO Model
Logical Link Control (LLC) sub-layer
Error and flow control
Media Access Control (MAC) sub-layer
Applies directly to network card communication
Access control
DATA LINK LAYER SUBDIVISION

38. Network Interface Card driver
MEDIA ACCESS CONTROL APPLICATION
NETWORK
SOFTWARE
NETWORK
CARD
NIC Driver
facilitates data
transfer

39. Purpose
Deals with the transmission of 0s and 1s over the
physical media
Translation of bits into signals
Example
Pulse duration determination
Transmission synchronization
etc.
1. PHYSICAL LAYER

40. Physical characteristic
Representation of bits
Synchronization of bits
Physical topolgy
Transmission mode
PHYSICAL LAYER

41. Encode bits into signals
Carry data from the higher layers
Decode bits into signals
Carry data from to higher layers
PHYSICAL LAYER FUNCTION

42. Physical layer

43.  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

44. PACKET : GENERAL FORMAT
Header Trailer
Data
A general concept of packets serves as a prerequisite to
the understanding of the ISO-OSI model.

45. FORMATTING OF DATA THROUGH THE LAYERS
Application Header Presentation Header Session Header
Transport HeaderNetwork Header
Data Link Header and Trailer Physical Frame Preamble

46. An exchange using the OSI model

47. SUMMARY

49. Thank You