Category 6 cable
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Category 6 cable, commonly referred to as Cat-6, is a cable standard for Gigabit Ethernet and other network protocols that is backward compatible with the Category 5/5e and Category 3 cable standards. Compared with Cat-5 and Cat-5e, Cat-6 features more stringent specifications for crosstalk and system noise. The cable standard provides performance of up to 250 MHz and is suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), 1000BASE-T / 1000BASE-TX (Gigabit Ethernet) and 10GBASE-T (10-Gigabit Ethernet). Category 6 cable has a reduced maximum length when used for 10GBASE-T; Category 6a cable, or Augmented Category 6, is characterized to 500MHz and has improved alien crosstalk characteristics, allowing 10GBASE-T to be run for the same distance as previous protocols. Category 6 cable can be identified by the printing on the side of the cable sheath.[1]
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[edit] Category 6
Category 6 cable contains four twisted copper wire pairs, just like earlier copper cable standards. Although Cat-6 is sometimes made with 23 gauge wire, this is not a requirement; the ANSI/TIA-568-B.2-1 specification states the cable may be made with 22 to 24 AWG wire, so long as the cable meets the specified testing standards. When used as a patch cable, Cat-6 is normally terminated in 8P8C modular connectors, often incorrectly referred to as "RJ-45" electrical connectors. Cat-6 connectors are made to higher standards that help reduce noise caused by crosstalk and system interference. Attenuation, NEXT (Near End Crosstalk), and PSNEXT (Power Sum NEXT) are all significantly lower when compared to Cat-5/5e.
Some Cat-6 cables are too large and may be difficult to attach to 8P8C connectors without a special modular piece and are technically not standard compliant. If components of the various cable standards are intermixed, the performance of the signal path will be limited to that of the lowest category.
The cable is terminated in either the T568A scheme or the T568B scheme. So long as both ends of a cable are terminated using the same scheme, it doesn't matter which scheme is used; they are both straight through (pin 1 to 1, pin 2 to 2, etc) and the pairing is the same. Mixing T568A-terminated patch cords with T568B-terminated horizontal cables (or the reverse) does not produce problems in a facility. The T568B Scheme is by far the most widely used method of terminating patch cables.
Crossover is used for hub to hub, computer to computer, wherever two-way communication is necessary. All gigabit Ethernet equipment, and most new 10/100Mb equipment, supports automatic crossover, meaning that either a straight-through or crossover cable may be used for any connection. However, older equipment requires the use of a straight-through cable to connect a switch to a client device, and a crossover cable to connect a switch to a switch or a client to a client.
| Pin | Pair | Wire | Color |
|---|---|---|---|
| 1 | 3 | 1 |  white/green |
| 2 | 3 | 2 |  green |
| 3 | 2 | 1 |  white/orange |
| 4 | 1 | 2 |  blue |
| 5 | 1 | 1 |  white/blue |
| 6 | 2 | 2 |  orange |
| 7 | 4 | 1 |  white/brown |
| 8 | 4 | 2 |  brown |
| Pin | Pair | Wire | Color |
|---|---|---|---|
| 1 | 2 | 1 | white/orange |
| 2 | 2 | 2 | orange |
| 3 | 3 | 1 | white/green |
| 4 | 1 | 2 | blue |
| 5 | 1 | 1 | white/blue |
| 6 | 3 | 2 | green |
| 7 | 4 | 1 | white/brown |
| 8 | 4 | 2 | brown |
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[edit] Category 6a
The latest standard from the TIA for enhanced performance standards for twisted pair cable systems was defined in February 2008 in ANSI/TIA/EIA-568-B.2-10. Category 6a (or Augmented Category 6) is defined at frequencies up to 500 MHz—twice that of Cat 6.
Improved specifications, particularly in the area of Alien Cross-talk (AXT) as compared to Cat6 UTP which exhibited high alien noise in high frequencies.
The global cabling standard ISO/IEC 11801 will soon be extended by the addition of amendment 2. This amendment defines new specifications for Cat. 6A components and Class EA permanent links. These new global Cat. 6A / Class EA specifications require a new generation of connecting hardware offering far superior performance compared to the existing products which are based on the American TIA standard.
The most important point is a performance difference between ISO/IEC and EIA/TIA component specifications for the NEXT transmission parameter. At a frequency of 500 MHz an ISO/IEC Cat. 6A connector performs 3 dB better than a Cat. 6A connector conforming with the EIA/TIA specification. 3 dB equals 100 % increase of Near End Crosstalk noise reduction when measured in absolute magnitudes.
TIA comp. Cat. 6A ≠ ISO/IEC Cat. 6 A comp.
[edit] Maximum Length
The maximum allowed length of a Cat-6 cable is 100 meters (330 ft) when used for 10/100/1000baseT. This consists of 90 meters (300 ft) of solid "horizontal" cabling between the patch panel and the wall jack, plus 10 meters (33 ft) of stranded patch cable between each jack and the attached device. Since stranded cable has higher attenuation than solid cable, exceeding 10 meters of patch cabling will reduce the permissible length of horizontal cable.
When used for 10GbaseT, Cat-6 cable's maximum length is 55 meters (180 ft) in a favorable alien crosstalk environment, but only 37 meters (120 ft) in a hostile alien crosstalk environment such as when many cables are bundled together. 10GbaseT runs of up to 100 meters (330 ft) are permissible using Cat-6a.
[edit] Installation Caveats
Category 6 and 6a cable must be properly installed and terminated to meet specifications. Incorrect installation practices include kinking the cable or bending it with too tight a radius. Incorrect termination practices include untwisting the wire pairs or stripping the outer jacket back too far.
Shielded Category 6a cable must have the foil grounded at one end to achieve specified alien crosstalk performance. Unshielded Category 6a cable does not have this limitation, but has a larger diameter.
To ensure that an installation will meet the requirements for the network protocol it will be used for, a new installation is usually certified using a so-called cable certifier, validator or qualification tester.
[edit] Offshore Low End Cable Problem
The Communications Cable and Connectivity Association, Inc.(CCCA) cautioned that many offshore-manufactured communications cable products could present significant fire risk. In response to concerns from the industry, the CCCA commissioned an independent laboratory to analyze whether nine randomly selected offshore samples of these products met U.S. minimum requirements for performance and safety. Test results showed that none of the samples fully met all of the minimum requirements and eight of the nine samples failed to meet the National Fire Protection Association (NFPA) minimum code requirements for low flame spread and/or smoke safety requirements for installation in commercial buildings, schools and multi-tenant residences. Many of the samples failed the flame spread and smoke tests catastrophically. Because of the seriousness of these safety concerns, the CCCA plans to work in cooperation with the major leading independent telecommunications industry testing agencies to establish a new product certification program. Although details of the proposed program have not yet been established, a key component will be independent laboratory testing of structured cabling products that have been procured from point–of-sale locations.[2].
[edit] References
Details about TIA and ISO Cat 6a
10 Gb/s Over Copper: Horizontal Cabling Choices (information on cable construction and alien crosstalk mitigation)
Determining the Right Media (information on TIA TSB 155 37m versus IEEE 55m limitation)
[edit] Further reading
[edit] See also
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