cooling door

Sun Mar 30 07:48:22 UTC 2008

>So are you envisioning ANY sort of aggregation at all?<

Yes, under most scenarios that I have considerd, there would indeed be some
nominal amount of optical gear on site, but not very much, and it certainly would
result in a considerable net reduction in overall equipment required within a
building (and a commensurate reduction in the amount of electric power consumed,
as well).

In the most "active" case, there could be a DWDM or CDWM rack in the main comms
room or building data center feeding a few high-density Ethernet switches
occupying several additional racks. From there, however, it's all home-run fiber
to optical patch panels on each floor where the LAN closets once stood, and
lateral fiber runs out to the desktops, WLAN access points and other shared
resources. Compare this to the 80 fully-equipped LAN rooms I discussed earlier
--in addition to the main building core switch and associated hierarchical
routers-- in the forty-storey building going up at Ground Zero, and the trade off
is strikingly in favor of the optical solution.

In another scenario, which we'll call the "passive" one, depending on user
density and the demand for speed, there could be absolutely no active electronics
introduced, at all, only passive splitters, at first, which could be connected
via a limited number of dark fibers to a nearby data center. These splitters
could be upgraded over time to active WDM-PONs, when necessary, which would
amount to occupying a footprint comparable to the first "active" scenario, above.

Now, I'm not suggesting that selling the Optical LAN model based on FTTD[esktop]
is something that can be achieved entirely without challenges. For starters, due
to the approach currently being used to power VoIP phones, for example,
detractors are already suggesting that fiber cannot support Power over Ethernet
(PoE), which is a standard that assumes the use of Category x UTP copper cabling
and copper-based switch ports. There are solutions for this, though, in fact
there are many solutions for this, but as in most classic chicken-and-egg
dilemmas, there's nothing out there that is currently being used on a broad basis
that one can point to. Yet.

Likewise, most economical approaches to FTTD today (or it's becoming so, very
rapidly, thanks to the economies of scale being brought about in the marketplace
at component and subystem levels thanks to the recent acceleration in residential
FTTH deployments) would demand singlemode fiber, and this would hold especially
true in cases where the collapsed backbone switch is sited beyond several hundred
meters from the user, or in another building altogether. But as things stand
today, the standards bodies and the IT managers on location who fastidiously (and
oft-times blindly) abide by TIA doctrine insist on multimode fiber -- that is,
when fiber is specified at all.

While I'm on this point, it's interesting to note that, for the sake of
maintaining backwards compatibility to the work habits and form factors of older
grades of multimode fiber (MMF), MMF has been tweaked, zorked and modified so
many times, to the point where it's overall efficacy has reached a point of
diminishing returns, IMO, that it has now surpassed its TIA copper cousin in the
number of times it has undergone incremental changes. If all of this had resulted
in MMF achieving capabiliies even half as effective as SMF, then I'd say it was
all worth it. But it hasn't. And its greatest limitation, for my purposes, at
least, is the distance for which it can be specked: For high speed applications
surpassing 1 Gbps, thd distance rating for SMF is in the tens of KILOMETERS,
wheras MMF is still being rated in the low 100s of METERS.

Frank A. Coluccio
DTI Consulting Inc.
212-587-8150 Office
347-526-6788 Mobile

On Sun Mar 30 2:41 , 'John A. Kilpatrick' <john at hypergeek.net> sent:

>
>On 3/29/08 9:53 PM, "Frank Coluccio" frank at dticonsulting.com> wrote:
>
>> There is no LAN equipment on site anymore once you've backhauled your
>> desktops directly to a central site over optical channels.
>
>So are you envisioning ANY sort of aggregation at all? I mean for this to
>be at all practical you'd have to have some sort of DWDM aggregation point
>or something, wouldn't you? And if that's the case then haven't you just
>swapped one kind of equipment for another?
>
>--
> John A. Kilpatrick
>john at hypergeek.net Email| http://www.hypergeek.net/
>john-page at hypergeek.net Text pages| ICQ: 19147504
> remember: no obstacles/only challenges
>
>