What vexes VoIP users?

Jay Ashworth jra at baylink.com
Tue Mar 1 21:33:42 CST 2011

----- Original Message -----
> From: "Michael Thomas" <mike at mtcc.com>

> On 03/01/2011 05:51 AM, Jay Ashworth wrote:
> > 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.
> >
> Er, I'm not sure what the difference you're trying to make.

Er, I'm not sure why...

> Is IP running over an L2 with a SLA any less "IP" than one
> without a SLA? That's all the DOCSIS qos is: dynamically
> creating/tearing down enhanced L2 qos channels for rtp
> to run over. It's been quite a while since I've been involved,
> but what we were working on with CableLabs certainly was
> VoIP in every respect I can think of.


I thought I was pretty clear in what I said above; I'm sorry you didn't
get it.

"What everyone is actually *selling* commercially, except for cable
providers, is *not* VoIP; it's a subset of that: VoN; Voice Over Internet;
where the IP transport *goes over the public internet*, and through 
whatever exchange points may be necessary to get from you to the 

Cable companies are selling you *one hop* (maybe 2 or 3; certainly not
12-18), over a link with bandwidth protected from whatever may be 
going on on the Internet IP link they're also selling you; and which is 
therefore guaranteed to have better quality than whatever "VoIP" service
it might be competing with."


> | 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".)
> There's is a great deal of overhead involved with the booking
> of resources for enhanced qos -- one big problem is that it
> adds quite a bit of latency to call set up. I'm sceptical at this
> point that it makes much difference for voice quality since voice
> traffic is such a tiny proportion of traffic in general -- a lot has
> changed in the last 15 years. Now video... I'm willing to believe
> that that enhanced qos still makes a difference there, but
> with youtube, netflix, etc, etc the genie isn't getting back in
> that bottle any time soon. So Moore's law is likely to have the
> final word there too making all of the docsis qos stuff ultimately
> irrelevant.

I wasn't suggesting QOS.  I was suggesting *there's a completely separate
pipe*, on non-Internet connected IP transport, carrying only the 
voice traffic, directly to a termination point, which is dedicated
from the triple-play box and nailed up.

Are you suggesting that's *not* how it's being done in production?

-- jra

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