From Computer Shopper: Any thoughts on how it effects MRVC? I'm thinking at worst no effect, at best anything that delays CSOC & others is great giving MRVC more time by itself & to gain share..
Gigabit Ethernet Task Force
Delays Standard
DMD Interferes With Fiber
Transmissions
by David Aubrey
Originally published in the May 1998 issue
In a move that caught both vendors and users by
surprise, the IEEE's Gigabit Ethernet task force
voted to delay ratification of the Gigabit Ethernet
specification, 802.3z, until June 1998 at the earliest.
Surprisingly, the problem stemmed from difficulty with
data transmissions over multi-mode fiber-optic cable,
a medium most early adopters of Gigabit Ethernet
have taken for granted.
The problem, dubbed Differential Mode Delay (DMD),
revolves around too much transmission "jitter."
Multimode fiber-optic cable is preferred because it
uses more than one beam of light per fiber, resulting
in increased speeds. But the use of two beams is
what causes the jitter. When the beams are
transmitted next to each other, one beam reaches the
destination before the other, forcing it to wait until the
slower beam catches up.
Bob Grow, vice chairman of the Gigabit Ethernet
Alliance, says the task force originally thought it
would have to cut Gigabit Ethernet's maximum
transmission distance from 260 meters on
62.5-micron fiber-optic cable to less than half, at only
100 meters.
But the task force has announced that a new solution
known as the "conditioned launch" is in the works.
Grow says, "In this approach, the laser sending the
data will produce a light pattern that is much more
similar to an LED than what is currently used for
Gigabit Ethernet transmissions. Since fiber-optic
cabling was designed for LED transmissions, this
should make data transfers stable enough to do
away with any distance limitation."
Gigabit Ethernet product vendors have taken the
news with mixed feelings. Some companies like Bay
Networks and Compaq Computer Corp. announced
that no Gigabit Ethernet product would ship without
the ratified 802.3z spec. In contrast, Cisco Systems
introduced Gigabit Ethernet uplinks for its Catalyst
5000 switch series and its 7500 series router family.
It also incorporated gigabit route-switching
capabilities into its NetFlow architecture.
Despite news of the delay, 3Com Corp., which has
been shipping Gigabit Ethernet switches and NICs
since last November, announced that it would likewise
continue to ship new products.
Clearly, most vendors and the alliance itself feel that
it is safe for customers to continue with their Gigabit
Ethernet installations. |
