|  | 5.2 | Cable Specification and Termination
| 5.2.1 | Purpose of LAN media specifications
By the mid-1980s, growing pains from expansion in the field of networking were felt, especially by those companies that had instituted many different network technologies. It became increasingly difficult for networks that used different specifications and implementations to communicate with each other. An organization, called the International Organization for Standardization (ISO), researched various networks and created a network model, called the OSI Reference Model. (Note: Do not confuse the name of the model [OSI] with the name of the organization [ISO].) It was designed to help vendors create networks that would work compatibly and interoperably. By creating the OSI model, the ISO provided vendors with a set of standards. Standards are sets of rules or procedures that are either widely used, or officially specified, and that serve as the gauge or model of excellence. The OSI model standards ensured compatibility and interoperability between the various types of network technologies that were produced by the many companies around the world. The early standards that were developed for networking media were largely proprietary. They were developed for use by various companies. Eventually, many more organizations and government bodies joined the movement to regulate and specify the types of cable that could be used for specific purposes or functions. Until recently, there has been a somewhat confusing mix of standards governing networking media. Standards have ranged from fire and building codes to detailed electrical specifications. Others have focused on tests to ensure safety and performance. As you begin designing and building networks, make certain that you comply with all applicable fire codes, building codes, and safety standards. You should also follow any established performance standards in order to ensure optimal network operation and, because of the wide variety of options available today in networking media, to ensure compatibility and interoperability. Your work in this curriculum will focus on the standards for networking media that have been developed and issued by the following groups: IEEE - Institute of Electrical and Electronics Engineers UL - Underwriters Laboratories EIA - Electrical Industries Association TIA - Telecommunications Industry Association The latter two organizations, jointly, issue a list of standards that you will frequently see listed as the TIA/EIA standards. In addition to these groups and organizations, local, state, county, and national government agencies issue specifications and requirements that can impact the type of cabling that can be used in a local area network. The IEEE has outlined cabling requirements in its 802.3 and 802.5 specifications for Ethernet and Token Ring systems, and the standards for FDDI. Underwriters Laboratories issues cabling specifications that are primarily concerned with safety standards, however, they also rate twisted-pair networking media for performance. The Underwriters Laboratories established an identification program that lists markings for shielded and unshielded twisted-pair networking media in order to simplify the job of ensuring that materials used in LAN installations meet specifications.
| Web Links
| Industry Standards for Structured Cabling