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.
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)
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
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?
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
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
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
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.