been created to support ever- higher speeds, carry multimedia traffic, and ensure that organizations can purchase cabling and connectors from diverse manufacturers without risk of incompatibility. Each cabling standard includes defined tests that should be performed when cables are installed to ensure that it and all of the connectors perform to their specifications. Every new standard needs to be compatible with all lower standards. This allows applications that operated over lower-category cabling systems to operate on higher categories, as well. The biggest problems organizations face with cabling systems are that they are not always properly installed and tested to meet standards. This results in either lower-than-expected data rates or inconsistent reliability. Each of the standards specifies not only the cable itself, but all of the connections including jacks (outlets), plugs, and cross-connects in wiring closets. Cross- connects provide outlets on each floor where cabling from individual devices is connected. The floor cabling, also referred to as the horizontal plant, is connected to the riser cabling, which is the cabling connections between floors. See Figure 1-5 for an example of copper www.TechnicalPDF.com cabling in enterprises. The riser cabling is connected in the building's main wiring closet and to other buildings within a campus. www.TechnicalPDF.com Backboards in floor wiring closet where unshielded twisted pair cables are connected to LAN devices and fiber Floor2 Fiber riser cabling between floors Horizontal unshielded twisted pair Switches in wiring closets cabling on floors 1&2 Backboard Floor 1 www.TechnicalPDF.com Figure 1-5 Riser and horizontal cabling connections in a wiring closet. Standards also specify the network interface card (NIC) in printers and computers from which a cable connects the device to the jack (outlet). The Telecommunications Industry Association (TIA) rates twisted-pair cabling and connection components used inside buildings. Unshielded Twisted-Pair Copper Cabling S