Overview of OSI Model
(Open System Interconnect)
OSI PROTOCOL STACK MODEL
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Network design focus on the lower
layers of the protocol stack
Central goal of network design is to
build reliable networks for application
use
Network designers are concerned with
Layers 1 through 4 or 5
OSI PROTOCOL STACK MODEL
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Seven layers:
Layer 7 – Application for user and
application data
Layer 6 – Presentation for data
formatting, encryption and character
encoding
Layer 5 –Session which negotiates and
maintains connections
OSI PROTOCOL STACK MODEL
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Layer 4 – Transport for End to end packet
sequencing and reliability
Layer 3 – Network for routing, flow control,
translations between different media types
Layer 2 – Data link (MAC) basic framing of
packets, error detection, transmission control
Layer 1-Physical for electrical and optical media,
cabling, signalling and properties
OSI PROTOCOL STACK MODEL
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TOP-DOWN DESIGN PHILOSOPHY
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Design starts at top when designing the
network - application layer
Good network design should be flexible to
support changes without wholesome
redesign
Network should be scalable, manageable
and reliable
END OF
SESSION