Top Cat?

Ten Gigabit Ethernet is coming to a store near you. So predicted Alan Flatman, principal consultant at LAN Technologies, at a recent conference hosted by Siemon.

'The future of structured cabling' saw debates over the massive and speedy changes that are occurring in the industry. And, with an increase in bandwidth demand from 1 Mbit to 10 Gbit since 1980, there certainly seem to be issues to discuss.

Local area network (lan) technologies have evolved very quickly over the past two decades. Within a few years of use the market had 4 m Token Rings and 10 m thick coax Ethernet. Only ten years later, 16 m Token Rings were in place and switched Ethernet was on its way. Cat 5 copper cabling was said by Flatman to be "exhausted" by the increase in bandwidth demand, only six years into its planned 15 year life.

The first TIA standard (TIA 568) for Cat 5 cable was determined at the end of 1990, the cable emerging onto the market by mid-1991. However, early progress was less than smooth. "The published standards were not complete by the time widescale installation of the cable was taking place, and improvements were being made to these at six monthly intervals," explained Flatman.

"By the end of 1994, the level one 100 MHz testers being used on installations were only providing correct results two-thirds of the time," he continued. By late 1995, when Cat 5 cabling standards were completed, it was estimated that 40 million outlets had already been installed within Europe, and a total of 100 million worldwide.

Flatman identified the drivers to change in the market as:

• the increasing speed of applications;
  
• the introduction and alterations to electromagnetic current regulations and the European directives;
  
• technical innovation.

The main driver to decision-making in the copper cabling market today, though, was said to be the desire for 1000Base-T ie 1000 Megabit/s lan bandwidth.

Installed Cat 5 cables were said to achieve 1 Gbit/s, filtered to within 80 MHz for transmission and digitally filtered for near-end cross talk (NEXT) and echo. With this system, the costs of electronics are traded with those of cable, and the cable is left in the wall. The reduction of NEXT also produces a need to counteract far-end cross talk (FEXT) which then becomes more noticeable.

The Gigabit Ethernet Alliance recommends several options if installed cable is non-compliant with 1000Base-T transmission, including the upgrading of outlet connectors, interconnections and patch cords to Cat 5e, and the reduction of cross-connect to an interconnect. It is also recommended that all new cabling should be at least Cat 5e.

Currently, there is only one standard for Cat 5E cable (EIA 568); the enhanced standards specifications from TIA, EN and ISO which include Cat 5e are awaiting approval. "Cabling standards are progressing, and the three main bodies are working together, exchanging drafts, views and proposals to reach a more harmonised set of regulations, said Flatman.

The key proposals for change in the second editions of ISO 11 801 and EN 50 173 are to: c delete Cats 3 and 4, 150 ohm cable; c align Class D with TIA enhanced Cat 5; c Add 200 MHz Class E/Cat 6 cable; c Add 600 MHz Class F/Cat 7 cabling; c Add high bandwidth multimode fibre; c Introduce open office wiring; c Add centralised optical architecture.

The news of these proposals may strike fear into those who are just coming to terms with Cat 5 cabling, but they are said to be essential if the increasing demands for bandwidth are to be met. And with the rise in demand for interactive activities, this is sure to happen.

Cat 6 cable is similar in construction to Cat 5e cable, while offering twice the bandwidth capacity. The difference is that most Cat 6 cables have a filler that separates each pair within the cable jacket. Siemon claims to be the first company to market Cat 6 compliant connecting hardware. The company has been installing this since 1998, however the category is not due for official ratification until mid-2001.

"The IEC is developing connector standards for intermatability, interoperability and backwards-compatibility with Cat 5/5E," said Flatman, but he predicts that the "RJ-45 will not achieve the required 600 MHz performance".

The testers for this type of cabling have also caused problems in the initial installations; tester cords were found to have problems dealing with cross-talk. On investigation, Siemon found the problems initiated in transportation and installation techniques. If handled incorrectly, the twisted cable pairs open slightly, changing the capacitance, hence impedance. The addition of more copper to tighten the twist and counteract this would increase costs.

Talk of Cat 7 cable may seem extreme when the preceding Cat 6 has yet to be ratified, however bandwidth demand is growing faster than the availability of suitable products and it is claimed that Cat 7 will offer six times more capacity.

Cat 7 cable construction is different still to Cat 5e or 6; there is an overall braid or foil around all four pairs and each individual pair is also foil-wrapped. It was said not to be intended to replace Cat 6 cables but instead will be a "different system, devised specifically for Europe". The fully screened system gives high electromagnetic interference (emi) immunity and there has been large take-up of this cable throughout mainland Europe, especially Germany.

The advantage of the individually screened pairs is that they permit multiple applications over a single cable so, for example, a telephone, computer and teleconferencing can all be run on one system. There are two main markets for this: the upper-end of the home cabling market and intelligent buildings for integration of systems. John Kellow of Siemon warned though that Cat 7 cable, when on the market, is "unlikely to take off in a big way". He added: "The holy grail is to get fibre everywhere, but costing is the differential – using copper-based system is still half the price." The inclusion of pair separators in Cat 6 cables gives it a larger diameter than Cat 5, causing specific installation issues. The cable is more difficult to bend and has to be laid through a larger diameter to avoid possible bending; containment products must also be altered as a result. The termination of Cat 6 is said to be easier than Cat 5 cable, and Cat 7 termination was said by Kellow to be possible by "anyone with a set of pliers". There is no tester on the market for Cat 7 cables yet – the one "which calls itself that", says Kellow, has no interfacer.

Cat 6 cabling installations are likely to remain with the big players in the immediate future, companies that have highly skilled, warranted system suppliers.

However, with a forecast increase in training opportunities, experience in design and practice and "the wish to elevate the technology", the skills will soon be available to anyone who wishes to gain them.