The OSI Reference Model
11
F I G U R E 1 . 2
The upper layers
F I G U R E 1 . 3
The lower layers
Network devices that operate at all seven layers of the OSI model include:
Network management stations
Web servers
Gateways
Network hosts
· Provides a user interface
· Presents data
· Handles processing such as encryption
· Keeps different applications'
·
data separate
Application
Presentation
Session
Transport
Network
Data Link
Physical
· Combines packets into bytes and bytes into frames
· Provides access to media using MAC address
· Performs error detection not correction
· Provides logical addressing,
·
which routers use for path determination
· Provides reliable or unreliable delivery
· Performs error correction before retransmit
· Moves bits between devices
· Specifies voltage, wire speed,
·
and pin-out of cables
Transport
Network
Data Link
Physical
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