OSI Layers: Description

The responsibilities of the layers of OSI are:

1. Application Layer: provides application services to the network applications such as e-mail, web, remote connection, file transfers, and database access. Other functions include: user authentication and data encryption.
2. Presentation Layer: presents the data to the upper layers by transforming data into a required format that can be accepted by the applications in the application layer.
3. Session Layer: manages the establishment, usage, and ending of the connections/sessions between the devices. It also decides how long the sessions should be, which side will transmit, when to transmit, and how long to transmit data.
4. Transport Layer: ensures that data is delivered from one end point to another without any errors. This layer implements error checking, recovery of lost packets to ensure the completeness of data transfer, and flow control.
5. Network Layer: routes data within the network. It is responsible for finding the shortest path from source to destination and route the packet through the intermediate devices such as router(s) or switch(es).
6. Data Link Layer: takes the packets from the above layers and processes them through the medium as bits.
7. Physical Layer: transmits bits from one device to another device over a physical medium (wired or wireless.)