Back in 1996 there were questions about whether Category 5 was going to have sufficient bandwidth to economically support all future local area network (LAN) applications.. The ATM Forum had released its 155 Mbps over copper specification, and while the TIA Category 5 specification had barely fulfilled the performance requirement, the international Class D link performance specification did not. A debate ensued. Did it make more sense to stay with Category 5, add more sophistication into the network interface cards (NICs), and employ more complex modulation and near end crosstalk (NEXT) cancellation technology to accommodate new applications with 100 MHz? Or, should a new and higher performance level for unshielded twisted pair (UTP) cabling be specified? The IEEE had begun development of a Gigabit Ethernet specification and it was uncertain if standard Category 5 would support it. (Today it appears that while some installed Category 5 links will, Category 5e is recommended.

In addition, many suppliers had developed significantly improved production processes and techniques to minimize crosstalk and improve return loss (RL). But there was no standards-approved label that could be put on this improved cabling, except to quote ‘better headroom’, or ‘higher speed performance’. This situation was creating a great deal of confusion in the marketplace.

At a pivotal International Standards Organization (ISO) meeting in Munich in September of 1997, it was decided to concurrently develop a 200 MHz UTP Category 6 specification and 600 MHz SSTP Category 7 specification. Category 6 was on its way.

For those who would ask if Category 6 is really needed let’s compare where we were 10 years ago, where we are today, and speculate where we might be in 10 years.

When a building is put up, the essential services (plumbing, AC, heating) are expected to last the life of the building, certainly, at a minimum, 25 years. Why should any less be expected from data cabling? The cost in labor and disruption of productivity to retrofit existing buildings with new data cabling is tremendous.

Any given category of cabling can support high-speed data transmission, but the better the quality of the cabling, the cheaper the associated electronics. It is a lot easier to get 100 Mbps on Category 6 than on Category 3. The above table analogizes cabling categories and roadway quality, providing a clearer picture of the significance of media. Given the pace of networking progress, can there be any doubt that Category 5 will be insufficient to meet the demands of future LANs?

What is Category 6?

Category 6 channels have a useful bandwidth of at least 200 MHz. This means that the pair-to-pair ACR (attenuation to crosstalk ratio) will be at least 3 dB for all frequencies up to at least 200 MHz. This is also the zero Power Sum ACR point. Category 6 also has very uniform impedance and excellent RL performance. Category 6 is simply the best UTP cabling system available.

Category 6 is chiefly differentiated from Category 5 by its improved NEXT and RL performance. Good return loss is extremely important in new high-speed full duplex LAN applications. Crosstalk performance essentially controls the maximum available bandwidth since attenuation cannot be significantly improved without a large increase in conductor diameter.

The TIA TR42.5 committee is now preparing a lower cost Gigabit Ethernet hardware proposal that takes advantage of the bandwidth of Category 6 cabling.

A brief performance comparison between Category 5 and 6 based on current available draft standards is shown in the table below

Are Category 6 products available. Absolutely. Did cabling suppliers wait patiently for TIA 568A and TSB67 before shipping Category 5 products? It’s no different today. While the standards for Category 6 are being actively developed, we are not waiting for their completion. Most manufacturers have announced Category 6 cabling, connecting hardware and field test equipment. How can these manufacturers specify Category 6 performance when no Category 6 standards exist? In many cases the manufacturers state that the products offered meet the performance requirement of currently published draft standards. In some cases, a guarantee is provided that the product will meet the performance requirement of the final finished Category 6 standard when it is published. In almost all cases, you are dealing with reputable established companies with strong track records in structured cabling.

The biggest challenge facing Category 6 at this moment is a lack of interoperability. Because manufacturers have responded quickly with products in the absence of a standard, different methods to achieve NEXT connector cancellation have been used. These methods are, in most cases, incompatible with each other. For the purposes of illustration, a jack can be considered to have positive crosstalk, and a plug can have negative crosstalk. When the crosstalk is opposite in magnitude and phase, it cancels and results in a low crosstalk connection.

Because Category 6 connectors must be backward compatible with Category 5, Category 6 plugs and jacks must also have positive and negative crosstalk. But since the cancellation requirements are much more stringent for Category 6, a very tight tolerance on the components is required. For this reason, it is essential at this time to maintain one supplier’s connecting hardware throughout a given Category 6 installation.