OSI Physical Layer Concepts

OSI Physical Layer Concepts

Although the OSI Physical layer does not define the media used, this layer is concerned with all aspects of transmitting and receiving data on the network media. Specifically, the Physical layer is concerned with transmitting and receiving bits. This layer defines several key characteristics of the physical network, including the following:

Physical structure of the network (physical topology)
Mechanical and electrical specifications for using the medium (not the medium itself)
Bit transmission encoding and timing

Although the Physical layer does not define the physical medium, it defines clear requirements that the medium must meet. These specifications differ depending on the physical medium. Ethernet for UTP, for example, has different Physical layer specifications from coaxial Ethernet (see Chapter 3, “Transmission Media”).

You learn more about network transmission media in Chapter 3. In Chapter 4, “Network Topologies and Architectures,” you learn about physical topologies.