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Rules for playing the fast Ethernet over copper wire game.

Lans are being used for increasingly sophisticated applications," says Ralph Jacobi, president of Asymmetric Communications, a San Jose-based consulting firm. "Unix, fast processors, X-Windows and high speed graphics all take a lot of band-width. A higher native speed is needed to accommodate these applications."

As an example, Jacobi explains how a California real estate firm downloads multiple home listings including photographs to individual brokers.

"At present each one takes up to a minute, but at 100 Mb/s, this could be done in 10 seconds," he notes.

Since November, IEEE 802.3 has been studying alternative proposals for a high speed version of Ethernet that will work over standard copper building wiring. But there are several players involved and the game is complex.

KICK-OFF: According to Jack Moses, vice president of Grand Junction, Inc., Union City, Calif., the game began on September 28, 1992 when his company announced the 100 Mb/s fast Ethernet. At the same time it requested that this be included on the agenda on the next IEEE standards meeting.

On November 9, the members of 802.3 heard two technical proposals. Hewlett Packard, with the public support of AT&T Microelectronics, proposed a new MAC-level access protocol called Demand Priority Access along with the Quartet Signaling physical layer.

Sun Microsystems, SynOptics, 3Com Corp. and Grand Junction voted for retaining CSMA/CD (carrier sense multiple access with collision detection).

RULES: Without going into technical details, it appears that an industry drive toward high-speed multimedia transport lies at the bottom of the HP proposal. The existing access method does not have a fixed access time period. In other words, it is not isochronous and this makes a scaled-up version of CSMA/CD unsuitable for full motion video applications.

The same thing is true of FDDI-1, which is why FDDI-2 is being developed.

Proponents of retaining CSMA/CD say this kind of access is Ethernet and establishing access priorities based on user data content leads to a different game with different rules.

The opposing team counters by saying that in today's world, no fast data network can afford not to accommodate full-motion video.

It's worth spending a year developing a new MAC layer to achieve this, says HP. In view of AT&T's recent announcement that NCR Corp. will provide full motion video capability over its workstation networks, it may have a point.

NEW PLAYER: AT&T Paradyne entered the game with a proposal that its new carrierless amplitude/phase (CAP) modulation technology provides an ideal transport for 100 Mb/s Ethernet. No one has yet demonstrated a proven method of multi-user networking over UTP (unshielded twisted pair) wiring at this speed.

CAP is a passband modulation method that provides low-end near-end crosstalk (NEXT), a major problem when fast digital signals are transmitted over the multipair UTP cable that is used in building vertical ducts.

CALLING PLAYS: As an example of where things are headed, Intel recently announced enhancements to its 82596 high-performance, 32-bit Ethernet chip that will lead to high performance, low cost LAN solutions.

The chip uses a 32-bit data path that provides increased system performance while maximizing network throughput, says Randall Scott, Intel's connectivity general manager.

OFFICIATING: About 200 people attended the IEEE 802.3 High Speed Ethernet (HSE) study group meeting held March 22, 1993.

It was decided to pursue both 100 Mb/s Ethernet proposals. Two different work groups may be formed.

There is a strong desire on the part of equipment providers to deliver a product that operates over Category 3 UTP (the most commonly used unshielded building wire).

CAP products that can accommodate this medium will be available in the latter half of next year, notes Clete Gardenhour, business development director for AT&T Paradyne.

OUTLOOK: The industry expects more than 20 million new Ethernet nodes to be installed over the next three years. This represents a tremendous opportunity for a high-speed solution and the potential worldwide marketplace is significant (see graphic).

The goat of the HSE study group is to close invitations for technical contributions at its July meeting.

A decision on which MAC layer solution is expected at that time. Meanwhile, the game goes on.
COPYRIGHT 1993 Nelson Publishing
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Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Author:Stewart, Alan
Publication:Communications News
Date:Jun 1, 1993
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