[169538] in North American Network Operators' Group
Re: Any experience with Comcast digital voice for OOB (offlist is
daemon@ATHENA.MIT.EDU (Mark Tinka)
Sat Mar 1 16:40:17 2014
From: Mark Tinka <mark.tinka@seacom.mu>
To: nanog@nanog.org
Date: Sat, 1 Mar 2014 23:39:27 +0200
In-Reply-To: <AEA5CF7D-5C00-4638-9CBF-3F806DB98536@truenet.com>
Reply-To: mark.tinka@seacom.mu
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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On Saturday, March 01, 2014 10:20:29 PM Eric Tykwinski=20
wrote:
> I do remember though something about a modem over VoIP
> protocol being developed, something like Jay was saying
> about Faxing over VoIP, but I guess it never took off.=20
> My guess being relying on the same line as an internet
> connection would be about that smart anyways.
=46oIP (Fax over IP) is "dodgy" for a couple of key reasons:
a) Different call capabilities, during setup, of SIP
and T.30, where a portion of the segment is TDM.
b) Different FoIP modes, during setup, where one end
uses SIP and the other uses T.38, with an
inability to propagate these capabilities across
the circuit.
c) Signaling delay between initial INVITE and 200
OK, introduced due to SIP-SS7-SIP conversion.
d) TDM-IP-TDM conversions causing incorrect training
across the circuit.
e) Low-rate codecs in the transit path that are not
signaled to the end points, e.g., end points
running at g.711 while an intermediate device
runs at g.729.
My guess is modems would have the same issues.
In general, FoIP solutions have a better chance of working=20
if a circuit provisioned to transmit a fax is all-IP (or, at=20
the very least, limits the TDM-IP conversions).=20
If all else fails, scan and e-mail.
Mark.
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