Re: [hylafax-users] Fax over VoDSL PSTN emulators

["Luke McKee" <hojuruku@xxxxxxxxx>]

Lee, Andrew, and All

If you want most of the background I have it's on this forum:

http://forums.whirlpool.net.au/forum-replies.cfm?t=733376

It will probably be taken off-line in the near future because I have a
problem with the moderators for saying the part about how I gained
access to the IAD without a password was "off topic" - therefore
implies I gained access to it through illegal methods.So better the
whole thing be taken off then falsely imply I'm some kind of cracker
(i.e. defamation).

VoDSL can provide ISDN grade 64k channels with what you would think is
good QoS (CBR/VBR-rt). My site may also have complications with
improper cabling, with CAT5 cable coming out of the wall with 4 POTS
lines in it just being one example.

However a form of VoDSL called AAL2, which is what we definitely have
in play here, is capable of low bit rate codecs, a T.38 like[not same]
fax proxy (at AAL2 atm layer), silence detection, jitter buffer etc,
and the telco has paid extra for the "S" type of IAD which does have
all these features. The product manager I have been speaking to (once)
is not confirming or denying re-provisioning the service since I
stirred the pot, which is interesting and only implies something is
going on.

So I admit, if the ADSL line quality is good, the installation is
professional and the telco guarantees you get at 64k channel Voice
over DSL can be good for faxing with even mainpine boards. However if
the Telco has a policy of non-disclosure, or something goes wrong as
demonstrated they can be a nightmare to troubleshoot.

The case in Australia is that the product documentation clearly states
max supported fax speed 14.4k (same speed the HW supports using AAL2
low bitrate fax proxy), yet modem speed is higher which does support
V.34. What's the difference between V.34 fax and V.34 modem? um a
calling tone first, which we know is being detected and acted upon
that's what's different.

The device is definitely detecting fax and modem tones and doing some
change at the AAL2 layer. I will confirm in the future what exactly
this is.

If that forum goes off-line (as it probably will - less they restore
the most on topic post in it), I'm happy to mail you both PDFs.

Lee: keeping in mind it's AAL2 and the Telco has had no disclosure on
the matter for 2 weeks (Singtel Optus), should we be concerned about
the grade of service this VoATM is being provided as?

Andrew: I can see why at this point you seem it justified to allow returns of 
V.34 modem hardware if any IAD/VoATM/VoIP hardware is involved, not confirmed to be compatible with V.34 at the time of purchase - which believe me can happen, who could be forgiven for mixing up one piece of telco hardware with another, 
e.g. ISDN NTU with POTS verse VoATM, IAD with POTS. They look quiet similar!

I was going to do V.34 testing but the modem speeds magically increased to support up to 52kps from 33.6, so I think we have now got a service which can handle it  [after nagging the telco].

Maybe other Telco's can use it as a lesson to clarify exactly what grade of service they are selling so FUD wont scare customers away who are tech savvy.

Cheers,

Luke McKee


On 08/05/07, Lee Howard <
faxguy@xxxxxxxxxxxxxxxx> wrote:
> Luke McKee wrote:
>
> > It's running AAL2 (Bundled Voice over ATM PVC - CBR in this case) but
> > the device, at least from how I'm much interpreting so far doesn't
> > clearly confirm the codecs. The best case scenario is G.711 and GOOD
> > QoS.
>
>
> If this "Voice over DSL" isn't essentially VoIP in a different
> packaging, then how is QoS even a factor?
>
> On the PSTN once the CO gets the audio and digitizes it there is a
> virtual guarantee that it will reach the other end with the same timing
> and the same order as the original form.  If that guarantee does not
> exist on whatever network with which a fax user replaces the PSTN, then
> the reliability of that network for fax use will vary accordingly.
>
> Whatever the medum carrying the audio is, if it is at all possible for
> the audio to become corrupted when riding that medium, then the
> usability of that medium for traditional fax (or data) will depend on
> that possibility.
>
> Lee.
>
>