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RE: Distance Objectives !!!!!


I think 300 meter for MM installed base (both 50/62.5 um) may be a little
bit over ambitious, even with all the tricks we know now; namely, mode
conditioners (several types, for long-wave, and restricted launch for
short-wave), or even with the new super MM fibers, although  I did not rule
it out yet.  If we can settle on 200 meters, it is very promising.  I
believe I can show that in Montreal presentation. 

I do not have problem with SM fibers. 

Did you published the telephone number for Monday teleconference?

Ed Chang
Unisys Corporation

-----Original Message-----
From: Haile-Mariam, Atikem [mailto:ahmariam@xxxxxxx]
Sent: Friday, June 25, 1999 3:11 PM
To: 'BRIAN_LEMOFF@xxxxxxxxxxxxxxxxxxxxxxxxxx'
Cc: stds-802-3-hssg-distance@xxxxxxxx
Subject: RE: Distance Objectives !!!!!
Importance: High

With some many reflectors, I haven't had a chance to catch up!!

I haven't quite finished my research, but I propose a slight modification to
Brian's proposal:


1) At least 300 meters on MMF for installed base

2) At least 500 meters on MMF for new grades of MMF  (this would very
similar to what we developed for 802.3z in that we included additional
higher cell bandwidth fibers)

The logic for this has been discussed many times before, and so I don't want
to "rehash" it here....(Also, Bruce's ad hoc will have a lot more to say
about this in Montreal)....


3) At least 4 km's on SMF

4) At least 20 km's on SMF

The logic for 3) and 4) is as follows:

3) A "typical" RBOC utilizes/deploys networks based on a "star" topology;
with fiber running from the central office (CO) to a "drop" or building.
AT&T, (and later Bellcore), conducted studies in 1964, 1974, and 1983 that
measured min, mean, max distances from the CO to the termination point.  In
the last study, (or at least I think it is the last study), the values were
as follows:

Min: 	186 ft
Mean:	10,780 ft
Max:	114,000 ft

To each of these numbers you need to add a "typical" fiber run required to
accommodate the distribution in the drop. That value is 1,888 ft.  So mean +
distribution drop =

10,780 ft + 1,888 ft = 12, 668 ft >>>> 3.85 km >>>> ~ 4 km

Now, most people may be wondering why I would rely on such an old
study...The reason I'm using this data is that the RBOCs have not
consolidated CO's despite the ability to do so through the use of new
digital switches. (Believe me, if they had consolidated, DSL would be a lot
harder to implement than it already is...)

4) The "logic" for > 20 km's is a lot less "solid", but it goes something
like this:  

CLECs - unlike RBOCs - deploy a "ring" topology. (A ring is arguably much
more efficient since 1 CO can be used to service it). Now, depending on
where you are in relation to the CO, the link length can "very short" or
almost twice the length of the ring. (As an analogy, think of FDDI on how
you would need to "loop back" in case of a failure)...

Now for the numbers:

The average CLEC route miles is 200 km's  Based on the average number of
buildings - or buildings "passed" -  in the loop, we roughly have 50
km/building....This of course is a mis-leading statistic since not every
building is an even distance from the CO...The solution is to analyze some
of the larger CLEC and the average building/termination runs. That figure is
~20 km's.

I hope to compile a more formal presentation by next week that includes
estimates of the amount of dark fibers in these networks.


Atikem Haile-Mariam


P.S. Incidentally, I'm in full agreement with Ed in arguing that
architectures should drive link length requirements - not components. (It
just so happens, that based on what I saw in Idaho components may exist that
fit "nicely" in these architectures).

> -----Original Message-----
> From:	BRIAN_LEMOFF@xxxxxxxxxxxxxxxxxxxxxxxxxx
> [SMTP:BRIAN_LEMOFF@xxxxxxxxxxxxxxxxxxxxxxxxxx]
> Sent:	Friday, June 25, 1999 12:31 PM
> Cc:	stds-802-3-hssg-distance@xxxxxxxx
> Subject:	Distance Objectives !!!!!
>      Three days ago, I suggested a distance objective on the HSSG distance
>      reflector (the first suggestion, I believe, since Idaho). The purpose
>      of this reflector is to provide a forum for the ad hoc distance 
>      committee (all of us receiving this e-mail) to reach a consensus
> prior 
>      to the Montreal meeting.  There is a conference call Monday to reach 
>      "final" agreement.  So far, there has been no response to my
> suggested 
>      objectives.  Does this imply that we are all in agreement with them? 
>      If not, then perhaps someone who differs with me could offer a 
>      suggested alternative.  Otherwise, we will simply pick up in Montreal
>      where we left off in Idaho. 
>      -Brian Lemoff
>       HP Labs
> ______________________________ Reply Separator
> _________________________________
> Subject: Re: Discussion on the HSSG Distance reflector
> Author:  BRIAN-LEMOFF-at-om (BRIAN_LEMOFF@xxxxxxxxxxxxxxxxxxxxxxxxxx) at 
> HP-PaloAlto,mimegw2
> Date:    6/22/99 11:47 AM
>      As I understood Jonathan's kick-off message, he was proposing that we
>      have two separate objectives, the first being phrased in general
> terms 
>      such as the one he proposed, i.e. support for traditional LAN,
> support 
>      for traditional MAN, and support for WAN access.  The second, and
> more 
>      controversial objective will name the distance and fiber-type 
>      objectives.  This is probably the more important of the two, and it 
>      has not yet been discussed on this reflector!!
>      We might already have a consensus on the first objective (although 
>      there is still debate over support for the WAN), but we are nowhere 
>      near consensus on the second objective.  I would support something 
>      like the following:
>           To define physical solutions to support distances of:
>           At least 300 m on multimode fiber, including the installed base
>           At least 6 km on single mode fiber
>           At least 50km on single mode fiber
>       I am not wedded to these numbers, but I do think that some mention
> of 
>       support for the installed base should be included in this objective.
>           -Brian Lemoff
>            HP Labs
> ______________________________ Reply Separator
> _________________________________
> Subject: Discussion on the HSSG Distance reflector
> Author:  del-hanson-at-exch (del_hanson@xxxxxxxxxxxxxx) at
> HP-PaloAlto,exchgw2
> Date:    6/22/99 11:07 AM
> HSSG Distance Ad Hoc Colleagues,
> I am on vacation this week but am following my email. I have noticed that
> the dialog on the Distance reflector has died up. If this is because there
> is agreement of the restated objectives, that is great. However, by
> sending
> out an announcement of a conference call for Monday 6/28/99 at 8 AM PST
> and
> an updated summary of objectives, it was not my intent to close down
> discussions. If there are issues that need to be discussed prior to the
> call, we need to use this reflector to make them visible. Also, after the
> call we need to use the reflector to refine issues so we can go into the
> Plenary with consensus, if possible.
> Regards,
> Del Hanson