Physical Layer

What is the Physical Layer?

The physical layer is the first layer of the OSI reference model. It is sometimes abbreviated as "PHY", derived from the first three letters of its name. The OSI model divides network protocols into the following seven layers:

1. Physical Layer: Defines the electrical, mechanical, and functional specifications required for data transmission.
2. Data Link Layer: Defines the physical communication link with the peer and the data format used in transmission.
3. Network Layer: Defines the functionality and specifications related to routing data to the destination host (node) and managing addresses within the communication path.
4. Transport Layer: Defines functionality and specifications to ensure reliable and efficient delivery of data to the destination.
5. Session Layer: Defines functionality and specifications for creating and terminating virtual communication paths (sessions) between communication programs.
6. Presentation Layer: Defines functionality and specifications for converting the format of data exchanged during communication.
7. Application Layer: Defines functionality and specifications for the exchange of application-level information.

The physical layer specifies details such as cable materials, connector shapes, and electrical signal voltages. For example, it covers Ethernet cables and interface standards like RS-232C. However, the physical layer does not concern itself with the format or content of the data being transmitted.