Re: receiving problems

On 02/19/2017 07:07 AM, Piviul wrote:
> Thank you very much Lee... do you know if the MultiTech MT5634ZBA is 
> compatible with T38 protocol?

The MT5634ZBA doesn't need to be T.38-compatible (and cannot perform 
T.38) because it is an analog modem.  The T.38 protocol would happen at 
the service provider for the analog line that goes to the modem.

> There is a way to ask to the modem if can implement the T38?

No, because it can't implement T.38.  T.38 is not performed on analog 
audio lines.  It is performed on network data connections.

> ...any way I ask to fastweb if they have implemented or can implement 
> the T38 protocol on our line...

I think that you misunderstand T.38, the way in which it would be used, 
and what its use is realistically capable of doing for fax.

T.38 occurs on network data connections.  So if you're using an analog 
modem then it will be your telco, possibly, that has the opportunity to 
do T.38.  T.38 is, essentially, an alternative to G.711 on Voice-over-IP 
channels.  So, in your case where you have an analog modem and assuming 
that there is another analog device on the remote side, the whole point 
of T.38 would be to avoid passing G.711 audio over the IP network 
portion of the path (to mitigate jitter by leveraging redundancy options 
in T.38).  That IP network path would likely reside entirely within the 
domains of the telcos involved.

I don't know if FASTWEB uses VoIP or not.  If they do, then to support 
fax they must ensure that the VoIP path using G.711 minimizes or 
eliminates jitter.  If they are not able eliminate jitter then to 
support fax they must implement T.38 along that VoIP path with a 
redundancy setting that compensates for the jitter. Furthermore, the 
T.38 gateways must be designed well-enough to be able to implement flow 
control mechanisms on the T.30 sides of the call in order to allow the 
T.38 redundancy to do its job without breaking the timings required by T.30.

> A last question... if my modem implement the T38 protocol, the voip 
> gateway support it as well do you know if there are more problems 
> sending and receiving faxes than on an analog/ISDN line?

Unless you are considering end-to-end T.38 communications where no 
analog or G.711 path exists then T.38 is merely trying to approximate 
what the PSTN would do for an end-to-end T.30 communication.  In other 
words, in any real world scenario Fax-over-IP (FoIP) will not likely 
surpass the reliability of fax operations on the PSTN, although in good 
implementations it could come very close.

Unfortunately, as time passes it's becoming more and more difficult to 
get pure PSTN communications end-to-end.  Telcos all over the world are 
leveraging VoIP to reduce costs and minimize unused capacity.  This 
makes choosing a telco quite important in fax reliability.

Thanks,

Lee.


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