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Wait for 10-GigE standards? Electrical requirements still not determined for cabling running high-speed applications

Communications News, April, 2004 by Robert Zahr

Many network administrators have, by today's standards, outdated cabling infrastructures installed in their facilities and are considering a higher-performance solution capable of supporting the increased bandwidth demands required for future applications. The solution most often mentioned is 1-Gigabit Ethernet.

If this is the highest-speed application that will ever be deployed on your network, then enhanced Category 5 cabling is sufficient, since it was specifically developed for an application utilizing all four UTP pairs like Gigabit Ethernet. The question, however, is will an enhanced CAT 5 solution be enough to meet your demands for the life expectancy of the cabling?

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The standard answer is to "future proof" the network infrastructure so that it will meet the demands of next-generation applications. This may not be enough justification, however, for a company to pay a 30% or more premium for a new infrastructure.

Many people also contend that Category 6 cabling is the absolute minimum cabling required to run 10-Gigabit Ethernet. While current CAT 6 solutions can run 10-GigE to a certain degree, the question is, how far?

Category 6 components being manufactured today meet the requirements established by the Telecommunications Industry Assn. (TIA)-not only for CAT 6 performance compliance, but also for interoperability between different vendors' products. A tuned system does have advantages and is proven to produce superior results.

ELECTRICAL CONSIDERATIONS REVIEWED

The objectives of the TIA/E1A CAT 6 standard committee are to develop a cabling system that is capable of supporting positive power sum attenuation to cross-talk (PSACR) up to 200 MHz. TIA agreed to specific cabling systems up to 250 MHz to accommodate electrical equipment utilizing digital signal processing techniques.

TIA/EIA has a fully released standard for the cabling that they say is needed for running high-speed applications, including 10-GigE, but the standards bodies for that particular application have yet to come up with the electrical requirements. One assumption is that when IEEE and TIA/EIA decide on the electrical requirements for 10-GigE that, at the least, today's standard compliant CAT 6 cable will support it.

The people involved in both the IEEE and TIA/ EIA committees working on the 10-GigE standard are investigating more stringent electrical requirements than were originally considered. There are also some electrical parameters that are critical for the successful deployment of this high-speed application that were never an issue when the CAT 6 standard was developed. The requirements for these new electrical parameters have to be established before the committees can guarantee that data rates of 10 Gbps can be successfully run on the cabling system.

Does this mean 10-Gigabit Ethernet cannot be run on a Category 6 cabling system? If the cablerun lengths are 55 meters or less-which must are-there is a good possibility that there will be no problems with legacy-compliant CAT 6 systems.

Objectives of the standards committees are to develop a method of deploying 10-GigE around the present electrical characteristics of CAT 6. They also are looking at additional requirements for an "augmented" CAT 6 unshielded twisted-pair system that will support 10-GigE to the full 100-meter distance specified in the cabling standard. In other words, wait for the application standard and cabling standard to be ratified before deploying 10-GigE to the full 100-meter distance.

MOVING TO CATEGORY 6

At least une application for 1-Gigabit Ethernet that already has been released was developed around the current offering of CAT 6. The methods used in this application will not work on anything less than CAT 6. As more CAT 6 installations evolve, more applications taking advantage of CAT 6 are likely to be developed.

Is a Categury 6 system with additional margin able to support 10-Gigabit Ethernet any better than one that is minimally compliant? IEEE and, in some cases, TIA/EIA decide what electrical requirements are needed fora particular application for the entire cabling channeI. These electrical requirements are designed around the cabling performance.

The application performance does not even come close to operating over the entire elcctrical limits of the cabling system because there is already sufficient margin built into a standard compliant-cabling system. Having additional margin or headroom over the standard is advantageous to prevent many installation deficiencies, but it does not increase the overall performance of the application it was designed for, nor will it result in the ability to run an application it was not intended to support. In other words, CAT 5 with additional margin is not necessarily able to support the same applications as an enhanced CAT 5 system. CAT 5e was specifically developed for higher-speed applications that could not be guaranteed to work on CAT 5.

Today, most people are just beginning to think about running 1 Gbps to the desktop. The majority of 10-Gigabit Ethernet applications over copper will probably be in data centers between switches, not to the desktop-but the trend to 1-Gigabit Ethernet to the desktop will happen.

Technology Industry

Wait for 10-GigE standards? Electrical requirements still not determined for cabling running high-speed applications

Communications News, April, 2004 by Robert Zahr

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