The physical cabling standards upon which Ethernet is transmitted is governed by the Telecommunications Industry Association (TIA). The standards have been reflected and added to in European standards, International Organization for Standardization (ISO) authority documents.
Category 5 (was included in ANSI/TIA/EIA-568-B for informative purposes only)
Category 5 was the most common cable installed, until later installations began to use an enhanced version. It may still be the cable type most in use because it was the cable of choice during the huge infrastructure boom of the 1990s. It was designed to support frequencies of up to 100MHz. Applications include 100Base-TX, FDDI over copper, 155Mbps ATM over UTP, and, thanks to sophisticated encoding techniques, 1000Base-T Ethernet. To support 1000Base-T applications, the installed cabling system had to pass performance tests specified by TSB-95 (a Telecommunications Systems Bulletin issued in support of ANSI/TIA/EIA-568-A, which defines additional test parameters). It is no longer a recognized cable type per the ANSI/TIA-568-C standard, but for historical reference purposes, Category 5 requirements, including those taken from TSB-95, are specified in ANSI/TIA-568-C.2.
Category 5e (recognized cable type in ANSI/TIA-568-C)
Category 5e (enhanced Category 5) was introduced with the TIA/EIA-568-A-5 addendum of the cabling standard. Even though it has the same rated bandwidth as Category 5, that is, 100MHz, additional performance criteria and a tighter transmission test requirement make it more suitable for high-speed applications such as Gigabit Ethernet. Applications are the same as those for Category 5 cabling. It is now the minimum recognized cable category for data transmission in ANSI/TIA-568-C.
Category 6 (recognized cable type in ANSI/TIA-568-C)
Category 6 cabling was officially recognized with the publication of an addition to ANSI/TIA/EIA-568-B in June 2002. In addition to more stringent performance requirements as compared to Category 5e, it extends the usable bandwidth to 250MHz. Its intended use is for Gigabit Ethernet and other future high-speed transmission rates. Successful application of Category 6 cabling requires closely matched components in all parts of the transmission channel, that is, patch cords, connectors, and cable.
Category 6A or Augmented Category 6 (recognized cable type in ANSI/TIA-568-C)
Category 6A cabling was officially recognized with the publication of ANSI/TIA/EIA-568-B.2-10 in February 2008. In addition to more stringent performance requirements as compared to Category 6, it extends the usable bandwidth to 500MHz. Its intended use is for 10 Gigabit Ethernet. Like Category 6, successful application of Category 6A cabling requires closely matched components in all parts of the transmission channel, that is, patch cords, connectors, and cable.
Category 7 (recognized cable type in ISO 11801)
Category 7 is an ISO/IEC category suitable for transmission frequencies up to 1GHz. It is widely used in Europe and is gaining some popularity in the United States. It is not presently recognized in ANSI/TIA-568-C.