What are the OSI layers?

What are the OSI layers? For many years the OSI model (Open Systems Interconnection Model) has described the layers of information in a network, particularly the low-level transport mechanisms. From top to bottom, these are the layers and how these layers relate to your product design. 
Ethernet is physical layers: layers 1 and 2. TCP/IP (Transmission Control Protocol / Internet Protocol) is a protocol, not a network, and uses layers 3 and 4. 

Layer Name Function Example
7 Application Meaning of data HTTP
6 Presentation Building blocks of data and encryption  
5 Session Opening and closing of specific communication paths  
4 Transport Error checking TCP, UDP
3 Network Determination of data paths IP
2 Data link Data transmission, source, destination Ethernet
1 Physical Voltage levels, signal connections, wire, or fiber RJ45, fibre optique

A comparison with the ISO layers 
Let’s compare the OSI layers with a road. A man go from office to home with a taxi on the motorway.
Layer 1 (physical layer) = The roads 
Layer 2 (Data link) = Source is the office; destination is home. 
The MAC address is the unique registration number of the car. 
Layer 3 (Network) = Determination of the correct road to take; the IP address is the street address. Same address may be found in several towns. 
Layer 4 (Transport) = Error checking: is the destination correct?
Layer 5 (Session) = pay fare; handshake between source and destination 
Layer 6 (Presentation) = The taxi is one of many on the road – 1 message in the datastream 
Layer 7 (Application) = What is the purpose of travel? The passenger in the taxi is the purpose of the message, which also includes the source and destination information 

Content réference
Ethernet Military Switch RES-SCE-AC-8US
Ethernet Military Switch RESMLAC-8US-CAPS
Ethernet Military Switch RES-SCE-12MG
Ethernet Military Switch RES-SCE-8MG
Ethernet Military Switch RJSMLAC-8UG-CAPS
Ethernet Military Switch RJSMLAC-8MG-CAPS
Ethernet Military Switch RESMLAC-8US-CAPS
Ethernet Military Switch RESMLAC-8MG-CAPS
Ethernet Military Switch RESMLAC-8MG-CAPS F35
Ethernet Military Switch RESMLAC-28MG
Ethernet Military Switch RJSML-8US1/8UG1
Ethernet Military Switch RJSML-MG7F3G
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