The protocols and operations of the upper OSI layers are performed in software designed by software engineers and computer scientists. For example, the services and protocols in the TCP/IP suite are defined by the Internet Engineering Task Force (IETF) in RFCs as shown in Figure 1.
The physical layer consists of electronic circuitry, media, and connectors developed by engineers. Therefore, it is appropriate that the standards governing this hardware are defined by the relevant electrical and communications engineering organizations.
There are many different international and national organizations, regulatory government organizations and private companies involved in establishing and maintaining physical layer standards. For instance, the physical layer hardware, media, encoding, and signaling standards are defined and governed by the:
- The International Organization for Standardization (ISO)
- The Telecommunications Industry Association/Electronic Industries Association (TIA/EIA)
- The International Telecommunication Union (ITU)
- The American National Standards Institute (ANSI)
- The Institute of Electrical and Electronics Engineers (IEEE)
- National telecommunications regulatory authorities including the Federal Communication Commission (FCC) in the USA and the European Telecommunications Standards Institute (ESTI).
In addition to these, there are often regional cabling standards groups such as CSA (Canadian Standards Association), CENELEC (European Committee for Electrotechnical Standardization) and JSA/JSI (Japanese Standards Association), developing local specifications.
Figure 2 lists the major contributors and some of their relevant physical layer standards.
There are four areas of the physical layer standards that standards organizations use when defining physical layer technologies:
- Physical and electrical properties of the media
- Mechanical properties (materials, dimensions, pinouts) of the connectors
- Bit representation by the signals (encoding)
- Definition of control information signals
In Figure 3, click Signals, Connectors, and Cables to see the hardware.