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Re: What vexes VoIP users?


From: Jay Ashworth <jra () baylink com>
Date: Tue, 1 Mar 2011 22:51:49 -0500 (EST)

----- Original Message -----
From: "Scott Helms" <khelms () ispalliance net>

Let us be clear: if you're getting "digital telephone" service from a
cable television provider, it is *not* "VoIP", in the usage in which
most speakers mean that term -- "Voice Over Internet" is what they
should be saying, and cable-phone isn't that; the voice traffic rides over
a separate DOCSiS channel, protected from both the Internet and CATV
traffic on the link.

No, this incorrect. Packet Cable most certainly _is_ VOIP (a MGCP
variant to be precise until 2.0 after which it is SIP). While a few
providers, usually for non-technical reasons, did deploy an entirely
separate set of downstream and upstream interfaces that is far from the
norm. AFAIK the only top 20 MSO to do so in scale was Charter and I
don't know if they continue that today. Comcast, the largest cable
telephone provider certainly does not nor do providers need to since
any Packetcable CMTS and EMTA combo offers reliable prioritization in the
same channel(s) as the normal data path.

Indeed.  Then either Bright House is lying, their deployment was pretty 
early, or I'm nuts, cause I'm pretty certain that their early triple-
play advertising said this -- though not in so many technical words.

So of course Vonage and other VoN products will be less rugged.

As I recall, this questionably fair competitive advantage has been
looked into by ... someone. (Cablecos won't permit competing VoIP
services to utilize this protected channel, somewhere between
"generally" and "ever".)

As I said, this second channel doesn't exist in almost all cases (its
not cost effective nor needed in almost all cases). Having said that
over the top VOIP providers do suffer in comparison because they don't
get the benefit of prioritization in the local cable plant.

"Cost-effective"?

Could you expand on how the provisioning of a second virtual pipe down 
the hill to a cable box has any incremental costs at all?

Cheers,
-- jra


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