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

["Luke McKee" <hojuruku@xxxxxxxxx>]

Lee & Andrew.

Lee: Your earlier comments make sense.

ATM is a circuit switched network but in a VBR-rt mode, such as with
AAL2 how rigid to the QoS have to be to ensure V27ter and V.29 work
well?

I am willing to cement a truce with Mainpine and acknowledge if they
put the time in to read the posts here and try to provide real
answers. This issue SHOULD concern them very much..

Singtel Optus a telco in Australia is selling a service using a
ATA/IAD device called the Verilink 8104s. In the official
documentation it is stated that modems are supported up to 48k. I
can't get a V.92 modem to connect more than 33.6 though. I'll try
another brand.

I have already confirmed practically that V.34 carrier works for
modems. However the maximum supported fax rate is reported to be only
14.4k in official product documentation. I have a strong suspicion
that this could be due to a fax relay protocol like T.38 in play. AAL2
has such a relay protocol over ATM.

I did mention before with Voice over IP and T.38's limitations (at
least version 3 and less of it) is going to limit the number of
devices that support V.34 connections as it takes off - depending if
the proprietary fax modulation/demodulation software at each end of
the ATM frame relay network.

Mainpine support staff might be concerned to know that Optus are
rolling out these IADs with great earnest all across Australia. If
in-fact it is AAL2 and the fax calling tone puts the IAD into proxy
mode - therefore disabling V.34 - should the proprietary
modulation/demodulation software not have that capability or AAL2 even
support it (see the earlier posts here about T.38)

What happens if one of their customers buys a Mainpine or any other
V.34 fax board and tries to use it behind one of these IADs?

A site I know that has this right now, wasn't even aware they were
getting anything different from a normal PSTN line. I am trying to get
a proof positive for AAL2 because it looks like the Telco (after 2
weeks) doesn't seem to want to confirm or deny if AAL2 and or a fax
proxy is in use. The contract just says Voice over DSL which can mean
either AAL1/AAL2/SIP (the latter depending how loose you use the words
VoDSL).

I'm trying to help the customer with their issues with faxing. Seeing
Mainpine sales and myself might have some common ground here.  Maybe
they could lend some equipment or recommend a good external V.34 fax
modem? If V.34 modem calls work but V.34 faxing doesn't this may be a
sign that this feature is enabled in the IAD - and therefore likely to
be provisioned as AAL2. Do their labs operate in Australia or are
interested in issues that could affect Australian customers or where
other telco's are rolling out AAL2 IADs?

If the IAD is in 64k AAL1 CBR mode running 4 PVCs for each voice line
then V.34 faxing should work (one would hope).

Cheers,

Luke


On 04/05/07, Lee Howard <faxguy@xxxxxxxxxxxxxxxx> wrote:
> Luke McKee wrote:
>
> > In the real world with an ISP that claims to have good QoS how can
> > this affect faxing?
>
>
> QoS doesn't solve jitter, it just establishes priorities... so if QoS is
> identical along the whole network path and that prioritizes the
> communication that we're using then there is less of a change of jitter
> being a problem, but QoS doesn't make it impossible for jitter to
> happen.  That said, QoS really is an absolute *MUST* even for voice
> applications... otherwise every big download or big burst of network
> traffic will interfere.
>
> > If that be the case does the warnings in Lee's fax over IP
> > Howto still apply, considering it's a packet switched network (but not
> > the internet).
>
>
> My fax-over-voip document is in reference to running fax calls over VoIP
> channels.  Any time you are doing that then that document is relevant.
> In situations where you have a very well-controlled situation (like
> end-to-end communication over the loopback adapter or a point-to-point
> crossover connection between the peers) then the effects are mitigated
> by the amount of control that you have and the guarantee that you can
> make that the problematic conditions don't arise.
>
> I cannot tell you, specifically, what that telco is doing, however.
>
> Lee.

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