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RE: Short haul PMDs


If you mean network LAN links identified to end users as 1000BASE-CX, I 
think the percentage is very close to zero.

As far as I can tell, 1000BASE-CX components are being used to build 
proprietary  links between  stackable switches for external backplanes.

These interfaces while using -CX parts, are used to connect specific 
products, are not known to the end user as -CX ports, and are not used to 
connect with products from other vendors.


At 05:20 PM 8/3/00 -0600, pat_thaler@xxxxxxxxxxx wrote:

>So, does anyone have data on what percentage of Gigabit Ethernet links
>ship with 1000BASE-CX?
>-----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
>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
>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.
>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