Physical Layer of the OSI Model

The Physical layer of the OSI model is concerned with the electrical, optical, and mechanical properties of the network, including elements such as voltage, media, connector types, signal regeneration, and so forth. The physical layer doesn’t actually alter packets, but rather acts as the transmission facility over which the actual bits (1’s and 0’s) are sent. This isn’t limited to plain old copper wire – it can include optical signals, radio waves, and infrared transmissions to name but a few. Examples of equipment found at the Physical layer include network cabling, hubs, and repeaters. A number of popular Physical layer standards are listed below.

Examples of Physical layer standards:

  • High Speed Serial Interface (HSSI): High speed serial communications
  • EIA/TIA-232: Low speed serial transmissions
  • V.35: ITU-T serial transmission standard

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.