Well, don't worry too much yet. Check this article in NetworkWorld. It stated that not all vendors experienced the same problem. One vendor, Extreme Network, has no problem transmiting over 350 meters. You better check with our beloved MRV first.
I wouldn't put money into any ATM company either because of this temporary GE setback. This problem will exist with any network protocol at HIGH SPEED. SPEED is THE problem. If you run GE at low speed, there is absolutly no problem. There are fixes for GE, for instance use better laser diode or use single-mode fiber, at extra cost of course. But today's network needs better throughput, there is no choice. With ATM, you pay other cost, for instance complexity of the network, difficulty to interface with Fast Ethernet.
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The hidden costs of Gigabit Ethernet
By Jim Duffy
Network World, 11/10/97
Arlington, Va. - Companies running Gigabit Ethernet over existing multimode
fiber could trip on a costly and troublesome distance constraint.
Vendors are trying to hush up a physical layer problem that limits Gigabit
Ethernet to 100 meters when used with existing multimode fiber, according to
Jeffries Research, in Arroyo Grande, Calif. The distance problem may force
users to replace multimode fiber used for backbones within buildings with
more expensive single-mode fiber. Analysts said that could double the price
of Gigabit Ethernet products.
''Some of those single-mode products are priced twice as high [as
multimode], said Justin Smith, an analyst with International Data Corp., a
market research firm in Framingham, Mass. ''[Price] varies a lot, but there's
definitely a significant price uplift.'' At the very least, users may have to run
new multimode fiber with higher quality lasers, said attendees at last week's
Next Generation Networks conference here.
Gigabit Ethernet is supposed to run from 260 meters to 550 meters over
multimode, which is an optimum distance for building backbones, according
to Howard Frazier, chairman of the IEEE 802.3z Gigabit Ethernet task force.
Copper, meanwhile, is intended to carry Gigabit Ethernet frames 100 meters
from wiring closet to workgroup, he said.
The distance problem occurs in 20% to 40% of installed multimode fiber,
according to the Oct. 23 issue of the Jeffries Research newsletter. The
problem was disclosed to Jeffries Research by a ''well-informed source,'' the
newsletter stated.
Ron Jeffries, president of Jeffries Research, did not return phone calls by
press time.
According to the newsletter, Gigabit Ethernet devices running at equivalent
speeds fail to operate reliably at longer distances because of a delay
characteristic in multimode fiber.
The trouble occurs when a single Gigabit Ethernet light pulse enters the fiber.
Instead of remaining a single pulse, it splits and runs down two independent
paths. At the other end of the fiber there is enough delay between the two
pulses that the information carried ''can get very screwed up,'' and
interoperability is compromised, the newsletter said.
Vendors have kept the problem quiet for fear of delaying approval of a final
Gigabit Ethernet standard and cooling market acceptance of their products,
the newsletter claimed. Vendors also may not be aware of it, according to the
newsletter, because it is a very subtle problem and Gigabit Ethernet is an
immature technology.
Nathan Walker, vice chairman of the Gigabit Ethernet Alliance and product
line manager for gigabit multilayer switching at Cisco Systems, Inc., denied
that vendors are trying to cover up the problem even though they have known
about it for three months. ''It's not that we're trying to keep it quiet. We're
trying to resolve it,'' Walker said.
Also, Jeffries' percentages on how frequently the problem occurs are suspect,
said Tony Lee, chairman of the Gigabit Ethernet Alliance and product line
manager at Extreme Networks, Inc. Extreme has not had any problem
building networks that span 350 meters over multimode fiber and has never
experienced the multimode distance limitation problem, he said.
The Gigabit Ethernet Alliance soon will post a Q&A on its Web site that
addresses the multimode fiber distance issue, Lee said. ''It's the same
problem [that crops up] with any high-speed technology over long distances,''
Lee said. Indeed, the Jeffries newsletter states that ATM is limited to 100
meters over multimode at speeds greater than 622M bit/sec. |
