George,
You say:
>I don't see any functional difference between 30/30 and 25/25 and there is a 25 Mb/s std. for ATM on category 5 wiring, I think. I guess I see no need for sophisticated DMT signal processing to get across an office floor.<
I know.... you're testing me! <s> OK, I'll bite.
I would agree with you if all I were doing was traversing an office floor. I might even opt for Switched 10 Mbps or 100 BaseTx Ethernet. For security reasons, I might even opt for SMDS, were it not for other limitations of this protocol.
But the premise for this hypothetical model (at least implied, earlier on) was that I would be providing individualized copper-based access services to every desktop from the outside, a form of facilities-based access provider, if you will, with SONET links to the outside world.
I targeted the WTC location for two reasons:
(1) it's size and density (and the implied distribution factors that this carries), and
(2) the particular mix of tenants residing there (and the demand for data services, quotation services and financial news).
If you used 25 ATM or Ethernet riding over Cat 3 or Cat 5, you would wind up with approximately 600 "active" concentration points in each building in the way of hubs, switches, routers, repeaters, due to the floor sizes and the number of floors that exist (100 floors x 6 IDFs per floor = 600). That's a lot of equipment and real estate to support for a CLEC or ISP. The number of active device sites would actually be greater than this because many floors house multiple tenants, each with their own suites and communications infrastructures, obviously, and these would have to be supported individually for reasons of sovereignty and security.
In contrast, a DSL supported solution would only require active elements in four (4) locations to cover 100 stories for VDSL, or only one (1) racked location for ADSL, preferably on the 50th Floor. For each of these, the IDF appearances would simply be for passive cross-connects, and would result in a vastly improved architecture in terms of cost, administration and management. The only remaining fly in the ointment is that which surrounds security. Here, end users would have to fend for themselves, despite any assurances that the provider makes, reality being what it is, by employing encryption, firewalls, virus scans and other safeguards.
The reason for the seemingly high number of equipment enclosures to support standard LAN protocols derives from the constraints imposed by the ANSI/EIA/TIA 568 standard. For those lurkers who are not familiar with this standard, it lists and specifies the generic requirements for the construction and performance of structured commercial building wiring systems. In turn, LAN equipment manufacturers (NICs, hubs, switches, etc.) engineer to these specs.
Under this standard (TIA 568), all conventional LAN protocols (with the possible future exception of GE), including IBM's version of 25 ATM, are subject to a 100 Meter (328 feet) copper distance limitation (~295 feet in-wall link, and ~33 feet of patch cable and cross connect). Longer runs require regeneration or storing and forwarding, if longer runs are permitted for that protocol at all. As an access provider I would find this prohibitive to accommodate. Another detractor of using Cat 5, 25 ATM is that it at least implies that the feed is LAN-supported and administered, something that the auxiliary or individual access arrangement that I suggested would get away from, entirely.
What I've proposed for this make-believe model is similar to today's aux line that only supports a 28.8 modem or an ISDN BRI to the back of a PC. In contrast to today's "modem line," what I am suggesting is a high speed DSL line that will support vastly greater capabilities, and may be attached to a thin client, or a standard PC, with bridging to a standard TV monitor or other peripheral, as desired.
DSL Layer 1 technology can support 25 ATM convergence and carry it for up to one km or ~ 3300 feet. Ironically, this is roughly ten times the distance supported by the 25 ATM Cat 5 LAN model, and requires no repeaters or storing and forwarding. This distance is just about right to support my stated needs for in-building VDSL distribution.
Products like Orckit's Copper Trunk, for example - no, I don't hold any - would be DAVIC compliant, supporting the delivery of multi-media, internet services, market data and quotation services (Reuters, Bloomberg, Telerate, etc.), standard cable tv, VOD and new media advertising.
> I also see little need for one-way video applications in an office so I am biased toward symmetrical transmission in such an environment. <
The tenants of the WTC, as in the majority of other large structures housing financial companies, make up a mix of mainly international banks, securities firms, import/export etc. This mix is extremely demanding of quotation services, as well as CNBC, CNNfn and specialized financial news services, and worldwide CNN-like news services. Heretofore, due to price points and the economics of delivering full motion video to the desktop, quotation services and market data feeds have limited their presentations to screen-based text and columnar/ graphical reporting. Where motion video windows _do_ exist now, for newscasts and special events, say, in many cases they are kludgey patchwork assemblies of back-office Rube Goldbergs, that would fall apart in an instant were it not for the resident genius in the telco closet. Once made available at the right price, there will be many new applications involving video to the desk, IMHO.
Advertising on Madison Avenue, to keep it colloquial <s> is another example, as are the fashion industries and the entertainment industries. And lets not forget the legal professions and medicine. Yes, desktop and regular near- NTSC-grade video is going to proliferate, once the costs come down. I'm very optimistic about this.
----------------------------------
While contemplating a reply to you [ no trivial task ;-) ] I browsed through last week's copy of Telephony looking for some inspiration. In an uncanny discovery, I came across Steven Titch's (Editorial Director) full-page column inside the back cover that speaks about this very concept. It reads almost like a "proof of concept" paper, in fact.
In the Nov. 25 article titled "Master of Multimedia" on p. 64, he describes what Hong Kong Telecom Interactive Multimedia Services is doing with fiber to the building and DSL to the desk. In this instance, HK IMS is exploiting ATM to transport TCP/IP as well as VOD and MM apps, all atop DSL.
"The company is sticking to its plans for a fiber-to-the- building hardware design, using copper wire and DSL technology to carry signals short remaining distances over copper"
They're doing this in compliance with the DAVIC framework. Unfortunately, Titch doesn't get very vendor-specific in his description. I thought that some of you would be interested in this, in the event you hadn't come across it yet.
Regards, Frank |
