The OSI reference model

The open systems interconnect (OSI) reference model is illustrated in Figure 11.15. Bluetooth does not exactly resemble the model. However, we will try to relate to the different parts of the Bluetooth stack to the different parts of the OSI model.

Figure 11.15

OSI reference model and Bluetooth

The Physical layer is in charge for the electrical interface to the communications media, including modulation and channel coding. It therefore covers the radio part of the baseband.

The data link layer is in charge of transmission, framing and error control over a specific link.

The network layer is in charge of data transfer across the network, unrelated to the media and the precise topology of the network. This comprises the higher end of the link controller, setting and maintaining multiple links, and also looks after the link manger tasks.

The transport layer is in charge of reliability and multiplexing of data transfer across the network to the level that is offered by the application. Therefore, it overlaps at the high end of the LM and covers the host controller interface (HCI). The HCI facilitates actual data transfer mechanisms.

The session layer is responsible for providing management and data flow control services that are covered by the L2CAP and the lower RFCOMM/SDP ends.

The presentation layer offers a common representation for application layer data by supplementing service structure to the data units, which is the main task of RFCOMM/SDP.

The application layer manages communications between host applications.

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