Cat 5 and Cat 6 standards and some differences
 

 


Evolving Cat. 6A (Augmented) Standard

A number of wire and equipment manufacturers have developed technology and techniques which make 10 Gigs over twisted pair possible. The Telecommunications Industry Association (TIA) has formed a committee, comprised of the leading engineers from manufacturers who are working on 10G products, to develop and publish a standard for 10G network components. This committee is called TR42.7. The standard has been named Category 6 Augmented, or Cat. 6A for short.

The 6A standard being created by TR42.7 has been drafted and reviewed a couple of times. It is estimated by TIA that a completed standard may be proposed for formal adoption as early as January 2006. Several manufacturers will be ready to ship standard-compliant components and wire at the same time; some manufacturers offer those components for sale now.

Some differences between Cat. 5E/Cat. 6 ("Gig E") and Cat. 6A ("10Gig E) are as follows:

Wire construction - Both are 4 pairs twisted, but:

Cat. 5E and Cat. 6 conductors are 24 ga.
Cat. 6A conductors will be as large as 22 ga. (for lower attenuation).

Cat. 6A wire diameter will be much thicker, due to thicker insulation (to achieve lower "alien cross-talk", or cross-talk that comes from adjacent wires, NOT pairs within the same jacket).

Cat. 6A wire will be stiffer, due to a central plastic member (which holds the pairs in the optimum "lay" arrangement within the jacket).

Terminations - Jacks and patch panels will need to "spread out" the punch-downs due to thicker conductors. Each jack and patch panel maker will introduce their own solutions. It is possible that installers will need to be trained in how each manufacturer's products are intended to be terminated.

Transmission Format

10BASE/T and 100BASE/T use only pairs 1,2 and 3,6. Data is transmitted as a straight "square wave" with the voltage stepped between +1 and -1 volt. One pair is Receive, and one is Transmit.

1000BASE/T (Gig E) uses all four pairs. Each pair sends data bi-directionally. Signals are variations of sine waves; the peak voltage of each "wave" is 5 levels, which means each "baud" can contain several "bits" of data.

10,000BASE/T (10Gig E) also uses all four pairs, and each pair is bi-directional. Signals are also variations of sine waves, with 16 levels, which permits even more bits per baud. The highest frequency used is 800 Mhz.

Noise Immunity/Equalization

None of the standards for 10, 100 and 1,000BASE/T include any compensation for any kind of noise or interference. For all of these types of wiring, Far End and Near End Cross-Talk (FEXT and NEXT) are the biggest factors limiting wire performance. All FEXT and NEXT occurs when transmitted data is coupled to the receive wire within the same cable jacket. Interference from sources OUTSIDE the cable jacket is generally much lower amplitude, and insignificant in most cases.

The Category 6A standard will be much different. The DSP's (circuits which send and receive data signals over the twisted pairs) designed for 6A will be able to compensate for, and cancel out, almost all FEXT and NEXT; that is, they will be immune from interference that comes from pairs within the same 4-pair wire. Now, the most significant source of interference for 10Gig networks will be "alien" cross-talk, or interference that is of the same frequency band coming from OTHER 4-pair wires. Wires in direct contact with each other are the only significant sources for alien cross-talk. NOTE: The ability of 6A DSP's to cancel out FEXT and NEXT is the reason that 6E wire offers no advantages over regular Cat. 6 wire for 10Gig networks; the extra cross-talk margins offered by 6E wire is irrelevant.

Testing

100BASE/T testing over Cat. 5 wire was specified for frequencies up to 100 Mhz.

1000BASE/T testing over Cat. 5E wire, intended to be capable of Gig E performance, was specified for frequencies up to 350 Mhz.

10000BASE/T testing over Cat. 6 or 6A wire, intended to be capable of 10Gig E performance, has been specified for frequencies up to 500 Mhz. No testers are yet available with this capability, although several manufacturers are close to introducing their products. Not solved yet: a plan for how to test for sensitivity to alien cross-talk.

 

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