[u-u] Cheap/free VOIP home phone

Dan Astoorian djast at ecf.utoronto.ca
Tue May 26 10:09:40 EDT 2020

On Mon, 25 May 2020 13:19:24 EDT, David Gilbert writes:
> > I sometimes had calls drop after 15 minutes when I was still on
> > TekSavvy, though (although I think this is the first time I've had only
> > one side of the call drop on me).
> Yes.  It would.  What's happening is that your modem is translating the 
> ports involved in the call.  When it ages out the mapping several things 
> can happen.  An outgoing packet, for instance, can create a new mapping 
> ... and end up "originating" from a new port number... or not.  If 
> you're loosing one way, the most likely scenario is that this is 
> happening, your carrier is "accepting" that change but still sending the 
> stream to the old port.  NAT is a hack, and in most consumer devices 
> it's badly implemented.

Okay... so.

I was able to reproduce the problem by using my office VOIP line to call
my home netTALK line and staying on the call for 15 minutes.

I did this after disabling SIP ALG on my new Rogers home router, so that
apparently wasn't the issue.

I then made the netTALK device the DMZ host and rebooted it (i.e., the
netTALK device).  After doing so, I could now browse to it at either the
private (192.168.0.x) IP address or at my public IP address.  However,
the call still half-dropped after about 15 minutes.

Finally, as a control, I reconnected my TekSavvy modem and wireless
router and connected the netTALK phone through it the way it was before
the upgrade... and the symptom *still* happened, entirely eliminating my
Rogers router as the sole culprit.

I think these results narrow down the problem to one of:

a) a problem at the netTALK server end; or
b) a problem that somehow exists both for Rogers and TPIAs that use
    Rogers (is that plausible?) or
c) a problem on my netTALK device itself.

My money would be on a), given how unreliable the service has been for
me in the past.  I also think they may have made some changes on their
end recently, as a) caller ID recently seems to have arbitrarily started
working again, and b) for some reason, their web portal has suddenly
started reporting that every the call in my call history had a duration
of exactly 60 seconds (even calls going back almost 18 months).

FWIW, the configuration options for the netTALK device is very limited:
most of the options on the config page revolve around WiFi settings,
which I'm not using--I've always connected it as a wired device.  (The
only other settings are for "digit timeout (mSec)", "CallerID Type",
"Voice Volume" and "Tone volume", so this is not something I can try to
fix on the device itself.)

(Before anyone suggests it: if I Google "netTALK customer support," the
results page says "Did you mean: pull out your fingernails with a pair
of rusty pliers"?)

BTW, If anyone happens to know of a free, but not sketchy/untrustworthy,
way to test SIP from an old Android 4 phone for a >15 minute call (i.e.,
a method that doesn't involve me paying $99+tx to freephoneline.ca for a
service that might turn out not to work--like a SIP "speaking clock" or
something), I'd appreciate the pointer.


Dan Astoorian, Systems Administrator
Engineering Computing Facility
University of Toronto

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