Classify How Applications, Devices, and Protocols Relate to the OSI Model

Classify how applications, devices, and protocols relate to the OSI model

Some common network devices and protocols and where they are implemented in the OSI model

The unofficial other OSI Layer 2.5

While not a part of the official OSI model, the term “Layer 2.5” has been used to categorize some protocols that operate between the data link layer 2 and the network layer 3. For example, Multiprotocol Label Switching (MPLS) operates on packets (layer 2) while working with IP addresses (layer 3) and uses labels to route packets differently.


In addition to standards for individual protocols in transmission, there are also interface standards for different layers to talk to the ones above or below, usually operating system specific. For example, Microsoft Winsock, and Unix’s sockets and System V Transport Layer Interface, are interfaces between applications (layers 5 and above) and the transport (layer 4). NDIS and ODI are interfaces between the media (layer 2) and the network protocol (layer 3).


X.400 An ISO and ITU standard for addressing and transporting e-mail messages.

It conforms to layer 7 of the OSI model and supports several types of transport mechanisms, including Ethernet, X.25, TCP/IP, and dial-up lines.

X.500 An ISO and ITU standard that defines how global directories should be structured. X.500 directories are hierarchical with different levels for each category of information, such as country, state, and city. X.500 supports X.400 systems.

Media Access Control Layer is one of two sublayers that make up the Data Link Layer of the OSI model. The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel.

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The MAC sublayer uses MAC protocols to ensure that signals sent from different stations across the same channel don’t collide

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Classify How Applications, Devices, and Protocols Relate to the OSI Model. (2023, Aug 02). Retrieved from

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