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Re: Short haul PMDs


Dan Dove may have a handle on this number, at least for Agilent product
shipments. However, I don't believe that knowledge of this number will
help us evaluate whether our MMF/distance objectives are complete. The
more relevant figure may come from:

The percentage of <100 m 1000BASE-X links deployed (1000BASE-CX may be
included here).

Best Regards,

pat_thaler@xxxxxxxxxxx wrote:
> So, does anyone have data on what percentage of Gigabit Ethernet links
> ship with 1000BASE-CX?
> Pat
> -----Original Message-----
> From: Geoff Thompson [mailto:gthompso@xxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, August 02, 2000 4:45 PM
> To: Hakimi, Sharam (Sharam)
> Cc: stds-802-3-hssg
> Subject: RE: Short haul PMDs
> Sharam-
> I think 15 years is a slight exaggeration. 10BASE-T started as a Study
> Group in August of 1987. It was the first group to have a 100 meter
> objective.
> Before 10BASE-T there was the following:
>          10BASE5 + AUI   The AUI cable was 50 meters max
>          10BASE2 The coax was daisy-chained w/ an overall max of 185m
>          1BASE5 (StarLAN) The hub to DTE distance was 250 m
>          10BROAD36 Broadband diameter of 2800 meters
>          FOIRL 1000 meter links
> The point here is that topology has evolved as well as speed.
> We have in the recent past had a distance objective for short cables in
> 802.3z (ref: 1000BASE-CX).
> The 100 meter distance history is rooted in facilities cabling and is based
> on the (literally) cast-in-concrete distance of 90 m max from the cabling
> closet to the telecommunications outlet.
> If the prime market for an Ethernet project is not oriented to
> "in-the-wall" cabling then the 100 meter distance is not sacrosanct. The
> objective for 100 meters as approved in York was for "installed" cabling
> from ISO/IEC 11801. That means that we were talking about generic
> facilities cabling at the time, not application specific cabling.
> If we do go to application specific cabling then we have to do the
> specification in our own standard instead of referencing an outside cabling
> standard such as ISO/IEC 11801.
> Geoff
> At 11:16 AM 8/2/00 -0400, Hakimi, Sharam (Sharam) wrote:
> >During the past 15 years and through all of 802.3 distance Objectives, 100
> >meters has been the minimum and essentially the trademark of IEEE 802.3.
> >There has always been discussions that if the distance is reduced we can
> >provide less expensive PHYs, but the cost difference never justified
> >development of these PHYs . Providing 100 meter solutions does not prevent
> >anyone from using a 10, 20, 30 or other length cables as their needs
> >require. However, if time has come that the cost difference between a 100
> >meter solution and something less will  justify such development then we
> >could look at it later, but changing the objectives at this time is a BAD
> >idea in my opinion.
> >
> >Sharam Hakimi
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