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To: Frank A. Coluccio who wrote (2451)12/5/1998 1:23:00 AM
From: Frank A. Coluccio  Respond to of 12823
 
All,

This Thread has been a very decent and enjoyable place to share views and discuss emerging last mile techs and ideas for a long time. It's founder knew what he was doing when he laid down the precepts in its inaugural message.

Subject 4754

I'm proud to be a part of the action here, and I enjoy the discourse I've had with each of you, as well as that which takes place between you, even when I'm only lurking.

The Last Mile is a place where I tell others to go to see an example, for themselves, of what an Internet technology board should look and behave like. Let's keep it that way.

Bravo! I say. To All of Us!

Best Regards, Frank Coluccio



To: Frank A. Coluccio who wrote (2451)12/5/1998 10:36:00 AM
From: ftth  Read Replies (1) | Respond to of 12823
 
Hi Frank, re: << ...the slide shows a slice of bandwidth associated with the DOCSIS area that is clearly labeled 5 to 42 MHz, and the remaing regions from 50 to 750 MHz going to the upper part, i.e., the digital set top box which includes the DAVIC area. >>

Right, but that's only the UPSTREAM DOCSIS path, with range as required by the DOCSIS spec; the downstream path isn't broken down by channel into service category or DOCSIS vs. DAVIC. It's hard to guess exactly what they're doing because there are several things that aren't shown, and because DOCSIS support is optional. The 2 PHY's (DOCSIS/DAVIC) aren't compatible, so channel breakdown with both DOCSIS and DAVIC is hard to just guess, as is exactly what "tool" (as they're called in the DAVIC spec) they're specifying. The words don't match the picture, as you originally indicated.

The DAVIC upstream for the bi-directional PHY on coax part of the spec is 8-26.5 MHz (which isn't shown). Downstream, DAVIC requires support to 1GHz. Few US cable plants support > 750MHz. For DAVIC there are a couple possible downstream implementations (which can coexist): 70-130 MHZ QPSK and 54-1000 MHz QAM.

My guess would be this model was driven by Time Warner and Scientific Atlanta (which was instrumental in defining DAVIC requirements) as a way to make it look like they embrace DOCSIS (half-heartedly, obviously). With this model, it would seem that a given plant could only support (for 2-way data) either DOCSIS or DAVIC OOB (but the slide shows otherwise). I can't think of a good reason why an MSO would support both upstreams, so DOCSIS is removed from consideration since it is data only, and they suceed in looking like they endorse DOCSIS when in fact it doesn't make economic sense given the rest of the model.

gotta run,
dh