nanog mailing list archives

Re: What vexes VoIP users?


From: Jay Ashworth <jra () baylink com>
Date: Tue, 1 Mar 2011 22:33:42 -0500 (EST)

----- Original Message -----
From: "Michael Thomas" <mike () 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.

Wow.

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 
provider.

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."

Better?

| 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?

Cheers,
-- jra


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