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Determine pathways for data
Initiate data communications
Retime and retransmit data signals
Originate the flow of data
Manage data flows
Final termination point for data flow
Define the structure of layer specific PDU’s
Dictate how to accomplish layer functions
Outline the functions necessary for communications between layer
Limit the need for hardware compatibility
Require layer dependent encapsulations
Eliminate standardization among vendors
Tracks delay between end devices
Enables consistent network paths for communication
Identifies pieces of data as part of the same communication
Ensures that data pieces can be directed to the correct receiving end device
Supports error detection
Ensures ordered arrival of data
Provides delivery to correct destination
Identifies the devices on the local network
Assists intermediary devices with processing and path selection
Network
Transport
Physical
Data Link
Session
Corruption of a frame during transmission
Data reassembled at the destination
Retransmitted packets due to lost communication
A layer specific encapsulation
The destination device
An end device
An intermediate device
A media device
Network A — WAN
Network B — WAN
Network B — MAN
Network C — LAN
Network C — WAN
Network A – LAN
Manage data flows
Originate data flow
Retime and retransmit data signals
Determine pathways for data
A LAN is usually in a single geographical area.
The network is administered by a single organization.
The connection between segments in the LAN is usually through a leased connection.
The security and access control of the network are controlled by a service provider.
A LAN provides network services and access to applications for users within a common organization.
Each end of the network is generally connected to a Telecommunication Service Provider (TSP).
Piping
PDU
Streaming
Multiplexing
Encapsulation
To identify devices on the local media
To identify the hops between source and destination
To identify to the intermediary devices the best path through the network
To identify the source and destination end devices that are communicating
To identify the processes or services that are communicating within the end devices
IP phone
Laptop
Printer
Switch
File server
End
Transfer
Intermediary
Source
WAN
MAN
LAN
WLAN
Physical
Data link
Network
Transport
The destination device on the local media
The destination host address
The bits that will be transferred over the media
The source application or process creating the data
A, C, D
B, E, G, H
C, D, G, H, I, J
D, E, F, H, I, J
E, F, H, I, J
No address is added.
The physical address is added.
The logical address is added.
The process port number is added.
Path determination and packet switching
Data presentation
Reliability, flow control, and error detection
Network media control
The division of segments into packets
Physical, network, application, data link, presentation, session, transport
Application, presentation, session, transport, network, data link, physical
Application, physical, session, transport, network, data link, presentation
Presentation, data link, session, transport, network, physical, application
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