The document discusses a technical seminar on the OSI model. It describes the seven layers of the OSI model, including the physical, data link, network, transport, session, presentation and application layers. It explains the functions of each layer and how they interact to exchange data and deliver messages from source to destination across networks.

1. A TECHNICAL
SEMINAR
ON
OSI MODEL

2.  OSI modelOSI model
 OSI LayersOSI Layers
 InteractionInteraction between layers in the OSI modelbetween layers in the OSI model
 Data Exchange Using OSI ModelData Exchange Using OSI Model
 Headers and TrailersHeaders and Trailers
 Physical LayerPhysical Layer
 Data Link LayerData Link Layer
 Network LayerNetwork Layer
 Transport LayerTransport Layer
 Session LayerSession Layer
 Presentation LayerPresentation Layer
 Application LayerApplication Layer
 Summary of LayersSummary of Layers
 ConclusionConclusion
CONTENTSCONTENTS

3. OSI Model
• OSI or Open Systems Interconnection
model is an ISO standard that covers all
aspects of network communications.
• Open system: allows different systems to
communicate regardless of their
underlying architecture or supplier
• OSI model allows complete transparency
between otherwise incompatible systems.

4. OSI Model
• OSI model consists of seven separate
layers, each defines a segment of the
process of moving information across a
network
– physical (layer 1)
– data link (layer 2)
– network (layer 3)
– transport (layer 4)
– session (layer 5)
– presentation (layer 6)
– application (layer 7)

5. SEVEN LAYERS OF THE OSI MODEL

6. Interaction between layers in the OSI model

7. Data Exchange Using OSI Model

8. Headers and Trailers I
• Each layer adds own information to the
message it receives from the layer just
above it
• On the receive side, layers strip
information added on peer layer of
transmit side before passing the message
to next higher layer
• Added “control data” is placed to the
beginning (header) or/and end of a data
packet (trailer)

9. Headers and Trailers II
• The whole package (packet or frame) is
passed to the layer just below it.
• Headers are added to the message at
layers 6, 5, 4, 3, and 2. A trailer is added
only at layer 2.
• Examples of header info: checksum,
sender/receiver address, service type

10. Physical Layer

11. Physical Layer
• Purpose: Coordinates the functions
required to transmit and receive
streams of bits, over physical
communication medium
• Major issues:
· what type of signals?
· how are bits represented by signals?
· what physical medium to use?
· interface: electrical and mechanical
· How bits are synchronized in Tx and Rx?

12. Data Link Layer

13. Node-to-node delivery

14. Data Link layer (1)
• Purpose: error-free delivery of frames
between two systems on the same
network (Node-to-Node)
Major issues:
• what information goes into header/trailer?
• how are stations addressed? Physical
Address
• how are transmission errors detected and
corrected (Error Control)

15. Data Link layer (2)
• how is transmission flow between
stations regulated? Flow Control
• how is access to “shared transmission
channel” regulated? Access Control
• For LANs, this layer has been
subdivided into two sub-layers: “logical
link control” (LLC) and “media access
control” (MAC) sub-layers

16. Data Link Layer Example

17. Network Layer

18. Source-to-destination delivery

19. Network Layer
• Purpose: source to destination delivery
of packet , possibly across multiple
networks
Major Issues:
• what info goes into header? (e.g. end-to-
end (logical) addresses: source and
destination)
• how is packet routed from source to
destination?
• regulation transmission flow between
network nodes

20. Network Layer Example

21. Network Layer Example

22. Transport layer
• Purpose: error free source to destination
delivery of (entire) messages
• how is message segmented into packets?
• how are packets reassembled into
messages?
• how are packets delivered to correct
application (port address)?
• how is the connection between source and
destination? connectionless or connection
oriented

23. Transport Layer

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

25. Session Layer

26. Presentation Layer

27. Application Layer
FTP FTPSMTP TelnetSMTPTelnet

28. Summary of Layer Functions

29. Conclusion
The International Standard
Organization created a model called
the open system interconnection,
which allows diverse system to
communicate. The seven layer OSI
model provides guidelines for the
developments universally compatible
networking protocol.