Articles and whitepapers

19/9/2003

The Benefits of using Category 6 Cable

By John Aldous

Category 6 has finally arrived. This may seem an odd statement since 'Cat6' has been around for some considerable time, but I am actually referring to the Cat6 (Class E) defined in the recent revisions of ANSI/TIA/EIA-568-B.2-1, ISO/IEC 11801 and CENELEC EN50173-1 in 2002, which define the performance requirements of an 'Open System.' Previously, Cat6 products were essentially proprietary to each supplier and needed items such as 'personality' modules to be used with field testers.

The need for Cat6

I believe that Cat6 was developed to accommodate ever-developing computer technology, as well as the potential of Gigabit Ethernet for networking. Cable up to and including Cat5 (Cat5e), has consisted of the traditional four-pair, twisted, telephone-style type. Cat6 cable is very different in its construction. It utilises a longitudinal separator to ensure that each pair is kept a minimum distance from its neighbour. This reduces crosstalk at higher frequencies and therefore supports faster data transfer and greater signal bandwidths.

Cross-section of Cat6 cable

The cable is not the only component to change in the cabling infrastructure for buildings. The circuit design of patch panels has also changed, and has been improved to compensate for the poor transmission characteristics of the humble RJ45 connector. Patch cords, being pivotal in any system, have also been significantly affected.

The IT manager today has a choice of using either Cat5 or Cat6 cable. While there is no protocol that demands the installation of a Cat6 infrastructure, the rapid rate of change in the IT industry means that, faced with a new network, IT managers should consider future-proofing, and should consider Cat6 rather than Cat 5. The reasons for this are:

* Cat6 may be the minimum cabling required to support 10 Gigabit Ethernet.

* Cat6 supports double the bandwidth of Cat5, and so offers a better option for critical applications in the future.

* The components for Cat6 exist and are readily available. So all seems set for a smooth transition to Cat6 cabling. Sadly, as with many things in life, it is not that simple. There are a number of issues that must be taken into account.

Open market versus system solution

'Open market' means that all the constituent components for an installation actually conform to all the component specifications of the standards mentioned earlier. A 'system solution' is achieved by matching all the components so that, when connected together, they meet the Cat6 system requirements. This approach usually means that all components will be sourced from one supplier.

The advantages of the open market solution are that hardware performance will be superior - giving a large margin to the requirements for permanent links and channels, and future changes to the installation should be easier if using true open market-verified components.

It should be noted that the requirements of ANSI/TIA/EIA-568-B.2-1 dictates that all the components of the installation have open market performance, but there is no component requirement in the current edition of ISO/IEC11801 and CENELEC EN50173-1. At the time of writing, there are a small number of offerings with true component open market performance.

The advantages of the system solution are that component performance is matched - allowing a form of compensation by a superior component for a weaker colleague, and warranties/guarantees are usually made by the system supplier. The disadvantages are that usually, all the components must come from one source for a warranty to be valid, and great care must be taken to ensure that the system integrity is not compromised when making additions or changes.

The fundamental reason for this complexity is the poor performance of RJ45 connectors and patch cords. The connecting hardware must be compensated electronically due to the bad crosstalk characteristics of the RJ45 plug. Improvement of the plug and patch cord performance to eliminate crosstalk however, is not allowed by the standards because of the need for Cat6 connecting hardware to be backwardly-compatible with poorly-performing existing RJ45 plugs.

Installation

On average, Cat6 cabling architecture will cost 15-20% more than Cat5. With this is mind, possible failures, caused by the following, should be reduced wherever possible:

* Tight binding of cables at regular intervals causing return loss problems.

* Coiling of the cable at the wall outlet, thus deforming the spacer in the cable and causing return loss problems.

* Patch cords not conforming to the standards, particularly at high frequencies.

* Exceeding the minimum bend radius of the cable, causing non-conformance.

* Poorly-constructed RJ45 jacks, leading to a mismatch with the patch cord plug.

* NEXT (Near End Cross Talk).

* Return loss because of cable construction.

Conclusion

Cat6 offers a safer bet for the future by satisfying increasing speed requirements, and gives a greater margin of safety over Cat5 for the use of high-speed systems. It also supports backward compatibility with RJ45-based systems.

Possible Cat7/8 future connector

In my view, the Cat6 wiring system will be the last to use the RJ45 connector. What is needed is a high-crosstalk-performance connector that is standardised and multi-sourced. This activity is already being pursued within the standards arena, and we have already seen connection systems that have this potential from Tyco (Amp), Kerpen, Molex, RDM and Aldous Systems.

John W Aldous is Managing Director of Aldous Systems (Europe) Ltd.

www.aldoussystems.co.uk