OSI Model Facts

OSI Model Facts

The OSI model classifies and organizes the tasks that hosts perform to prepare data for transport across the network. You should be familiar with the OSI model because it is the most widely used method for understanding and talking about network communications. However, remember that it is only a theoretical model that defines standards for programmers and network administrators, not a model of actual physical layers.

Using the OSI model to discuss networking concepts has the following advantages:

• Provides a common language or reference point between network professionals
• Divides networking tasks into logical layers for easier comprehension
• Allows specialization of features at different levels
• Aids in troubleshooting
• Promotes standards interoperability between networks and devices
• Provides modularity in networking features (developers can change features without changing the entire approach)

However, you must remember the following limitations of the OSI model.

• OSI layers are theoretical and do not actually perform real functions.
• Industry implementations rarely have a layer-to-layer correspondence with the OSI layers.
• Different protocols within the stack perform different functions that help send or receive the overall message.
• A particular protocol implementation may not represent every OSI layer (or may spread across multiple layers).

To help remember the layer names of the OSI model, try the following mnemonic devices:

Layer	Name	Mnemonic (Bottom to top)	Mnemonic (Top to bottom)
Layer 7	Application	Away	All
Layer 6	Presentation	Pizza	People
Layer 5	Session	Sausage	Seem
Layer 4	Transport	Throw	To
Layer 3	Network	Not	Need
Layer 2	Data Link	Do	Data
Layer 1	Physical	Please	Processing

Have some fun and come up with your own mnemonic for the OSI model, but stick to just one so you don't get confused.

 

 

 

Credit: Testout 640-802 CCNA Notes