[kwlug-disc] [OT] Diagnosing voip and Tomato
jvj at golden.net
Mon Feb 28 19:40:43 EST 2011
On 2011-02-25 11:02, Paul Nijjar wrote:
> On Thu, Feb 24, 2011 at 10:21:52PM -0500, Insurance Squared Inc. wrote:
>> Here's where I'm puzzled. Seems like plenty of people using Voip on the
>> list. Am I the only one experiencing this problem repeatedly? Or does
>> everyone else's calls degrade as soon as the kids get home from school?
> I have mentioned this before, but our Sympatico routers are
> configurable so that our ATAs get priority bandwidth. I don't remember
> how I did this; it may have been through IP address. So if you could
> prioritize your Asterisk box's IP, you might win.
> I agree with John that the "A" in ADSL is a big pain. Fortunately we
> have not experienced much degradation, but I worry about it a fair
> - Paul
Execulink (in my case Golden.net) resells Bell's DSL and they tell me
that the service is ADSL2+.
see: various wikipedia hits on ADSL and ADSL2+ and *ITU G.992.x*
"Under good conditions the newest ADSL technology (ADSL2+) can offer
downloads at 25
Mbit/s, which is more than sufficient for most "in home"-applications
today and should be
compared to a V.90 modem's top bit rate at 56 kBit/s (0,056 Mbit/s)."
Whether ADSL or ADSL2+ , the signal format uses multiple frequencies,
above the voice band, as carriers each modulated with a combination of
phase shift and amplitude signal changes to encode as few as one or two
bits. Each of the multiple carriers is not unlike one of the two
carriers used in the 56 kBits/s modem mentioned above, one used for
upstream, one for downstream.
IMO: The DSL signal between the DSLAM has about as digital content as
an AM or FM radio signal, one carrier with amplitude or frequency shift
keying. Many forget that the transmission media whether RF or CAT5 cable
all live in an analog world. And the signals pumped over the media are
usually, except in the flat ribbon cables in one's PC are analog
signals. (The SATA standards, too, take the analog environment into
Fibre?: The days of binary on/off are long gone. Here too, wavelength
modulation (aka frequency modulation) comes into play. And the big boys
use multiple wavelengths on one fibre cable.
As for the OP's original question: I dunno. The issue may be solved with
a better downstream protocol, e.g. ADSL2+.
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