Cat 6 Could Pave Way For Affordable Gigabit Ethernet to the Desktop

By investing in Category 6 cabling now, instead of Category 5E, you will build a network poised to take advantage of less expensive Gigabit Ethernet technology. That was the pitch made by Lucent Technology at the BISCI Winter Conference in Orlando, FL. There is no Cat 6 Gigabit equipment you say? Lucent brought a prototype PHY chip to the show as well.

By: John Spofford

Gigabit Ethernet hubs and network interface cards (NICs) designed specifically for Category 6 cabling will be able to use electronics that are significant less expensive than those designed for high-end Category 5 (standardized as Category 5E in TIA and upgraded Category 5 in ISO 11801).

"Replace current cabling with better cabling, i.e. Cat 6, and you have to potential to eliminate 50% of the complexity," said Luc Adriaenssens, R&D director at Bell Labs of Lucent Technologies. "It is a simple case of history repeating itself. The situation is very similar to the 100 Mbps situation in the early 1990s."

Cat 3 begat Cat 5
Early in the decade, the installed base of Cat 3 cabling could support 100 Mbps applications using expensive electronics such as 100Base-T2 or 100Base-T4, Adriaenssens explained. For new installations it proved to be far more economical to install Cat 5 cabling and use less complex 100Base-TX electronics when the time came to upgrade.

Like all new technologies, the cost of Gigabit Ethernet electronics are still very high, almost an order of magnitude more expensive than Fast Ethernet.

"There is now a huge premium to go to 1000 Base-T products," Adriaenssens said. "Very few vendors can do this technology, so there is relatively little competition. It is pretty much what the market can bear."

He estimates that approximately 50% of the cost of a Gigabit Ethernet over copper NIC card, for example, is attributable to the cost of the physical layer (PHY) chip. With an estimated 1,000,000 transistors on the PHY chip, it is roughly the size of a 486 CPU.

Of that million-transistor count, more than half is dedicated to overcoming the performance limitations of Cat 5E cabling. Use of Cat 6 cabling would eliminate this digital compensation circuitry, which in turn could dramatically reduce the cost of Gigabit Ethernet to the desktop.

Still theoretical
It is a very simple argument, but it also could be argued that Adriaenssens' point is of no practical importance. The Gigabit Ethernet over copper 1000BASE-T specification (IEEE draft 802.3ab) will not be ratified until March at the earliest. The introduction of Gigabit Ethernet equipment for Cat 5E cabling is still months away, and no standard has yet to be proposed for the use of Cat 6.

Lucent brought a prototype of a PHY chip to BISCI that has been designed to transmit Ethernet packets over Cat 6 cabling at gigabit speeds. The company's approach uses a simple extension of the Gigabit Ethernet over copper 1000BASE-T specification. Adriaenssens said that over time several flavors of Gigabit Ethernet hardware will be developed much as there are several variations of Fast Ethernet today.

But to what end?
There is a danger that Lucent is providing an answer to a question no one has asked.

"Gigabit Ethernet over copper is a noble goal to bring Gigabit to the desktop. Having a copper standard for Gigabit [Ethernet] is just going to make deployment a little easier to deal with, but it will be a long time before Gigabit is significantly deployed at the desktop," said John Armstrong, chief analyst for local-area networking hardware at the research firm Dataquest.

Armstrong contends that providing Gigabit Ethernet to the desktop is so rarely required that the media is not the constraint. "If there is an application that requires Gigabit at the desktop, and there is an IT manager that wants to deploy it, he or she will get that fiber to the desktop to make it happen."

A long way to go
For the vast majority of premises networks, any call for gigabit bandwidth to the desktop is years away. By Lucent's own numbers only half of the new Ethernet ports installed in 1998 were 100 Mbps Fast Ethernet. Although the company forecasts 100 Mbps adoption to increase to 64% this year and 74% by 2000, in terms of actual use these numbers may be overstated.

Currently most Ethernet NICs and hubs are of the 10/100 variety—capable of either 10 Mbps Ethernet or 100 Mbps Fast Ethernet operation. It makes sense to put in 100 Mbps desktop capability even if it is not immediately put to use. And, when it is put to use it will be more than enough.

"For 99 % of the transactions that occur, Fast Ethernet certainly has lots of overhead," said Armstrong.

The march of obsolescence
This sort of future proofing is precisely the point, according to Adriaenssens. Unlike a desktop PC, which is outdated when it ships, or hubs and switches that fare little better on the obsolescence curve, cabling is installed to a much longer timeline. Structured cabling plant is expected to last years, or even decades. Cable manufacturer warrantees of 15 or even 25 years are common.

Thus it makes sense to go to Cat 6 wiring for applications that will exist in the future. Adriaenssens also emphasizes that Gigabit Ethernet to the desktop is not as far away as many may think.

"Remember what information technology was like 10 to 15 years ago? A cross-country telephone conversation would often start with 'Please hurry, I'm calling long distance.' A fast PC connection was one where ASCII text would display faster than you could read it," he said.

Today people casually call any point of the world and become frustrated if an e-mailed video clip does not arrive within 30 seconds or so.

Adriaenssens proposed his simplified version of Moore's Law: "It is difficult to predict how fast applications will consume bandwidth, but every five years you can expect to add a zero to the data rate."

About BISCI
Founded in 1974 and originally known as the Building Industry Consulting Services International, BISCI is an industry association that focuses on the technical aspects of combining communication cabling designs with the process of building design. Approximately 3,000 network designers, cable technicians, contractors, and installers attended the BISCI Winter Conference.