The document proposes the Open System Interconnection Model/Layer, which was proposed by the International Organization for Standardization’s SC16 committee in July 1979. The OSI model defines 7 layers for network communication: Physical, Data Link, Network, Transport, Session, Presentation, and Application layer. Each layer has a specific function and provides services to the layer above it.

1. Prepared by:
De Castro, Gilbert E.

2. Open System
Interconnection
Model/Layer was
proposed by
International
Organization for
Standardization’s
SC16 committee
(July 1979)
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3. • handles the transfer of bits from
one computer to another
• bits are actually converted into the
electrical signals that travel across
the physical circuit
• conveys the bit stream - electrical
impulse, light or radio signal --
through the network at the electrical
and mechanical level

4. • data packets are encoded and
decoded into bits
• getting data from one particular
medium to another
• formats the message into data
frames and adds a customized
header containing the hardware
destination and source address

5. • data packets are encoded and
decoded into bits
• MAC sub layer controls how a
computer on the network gains
access to the data and permission
to transmit it
• LLC layer controls frame
synchronization, flow control and
error checking

6. • responsible for transporting traffic
between devices that are not
locally attached
• provides switching and routing
technologies, creating logical paths,
known as virtual circuits, for
transmitting data from node to
node

7. • provides transparent transfer of
data between end users
• providing reliable data transfer
services to the upper layers
• controls the reliability of a given
link through flow control,
segmentation/desegmentation, and
error control
• can keep track of the segments and
retransmit those that fail.

8. • controls the dialogues
(connections) between computers
• establishes, manages and terminates
the connections between the local
and remote application
• provides for full-duplex, half-duplex,
or simplex operation, and establishes
checkpointing, adjournment,
termination, and restart procedures

9. • responsible for graceful close of
sessions, session checkpointing
and recovery

10. • establishes a context between
Application Layer entities
• provides independence from
differences in data representation
• transform data into the form that
the application layer can accept
• formats and encrypts data to be
sent across a network, providing
freedom from compatibility
problems

11. • interacts with software
applications that implement a
communicating component
• functions typically include
identifying communication
partners, determining resource
availability, and synchronizing
communication.

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14. Resources:
• http://www.webopedia.com/quick_ref/OSI_layers.asp
• http://en.wikipedia.org/wiki/OSI_model
• http://www.novell.com/info/primer/prim05.html
• http://technicals.wordpress.com/2007/10/04/osi-
model/
• http://www.cisco.com/en/US/docs/internetworking/te
chnology/handbook/Intro-to-
Internet.html#wp1020580