IPLU / ELU32 : Fax Over IP

[GioBs]

Hi all,
On tswsp6 using ELU32 or IPLU for trunking (RI...), the codec is not automatically modified if the analog signal is a fax transmission.

I've noted the codec is selected from originating IPLU.
If the calling party has bearer capability "speech" the codec selected is the first in codec string in RIANP.
If the calling party has BC "3.1KHz" then the codec is always G.711.
This is true for extension [digital (speech) or analog with ICAT=0.... (speech) or ICAT=1... (3.1KHz)] and is true for incoming ISDN calls (BC in incoming SETUP).
I've verified this also using BC substitution in NUTRP (CNVTYP=3).

Why the codec is not modified in G.711 automatically if the calling is a fax machine presenting itself in speech? I know this is incorrect, but it happens. Don't IPLU recognize the T.30 fax procedure?
Is there any AS?

Waiting for T.38...

Thank you.

 

[parnum]

T.38 is not supported and neither is compression so you must use G.711 for fax(DRG), unless something has changed...

best parnum

 

[doktor]

Or if you want to install a fax server, it is recommended to use the OneBox (Messaging) Fax server in connection with the OneBox (Messaging) voice mail server.
OK, it takes 2 servers but you have the possibility to use Multifunction mashines (printer/copier/fax/scanner) in your company and also use the email integration so voice mails and fax mails are delivered in your personal Inbox in Microsoft Exchange (Outlook) or Lotus Notes (Domino).

For the Fax server the 4 port analog line card :
Dialogic Brooktrout TR1034 P4 4L.

///doktor

 

[GioBs]

Thank you, but I would understand because IPLU don't recognize T.30 handshake ad select the approriate codec (G.711) for fax pass through.

Suppose we have a two node (node X and node Y) mx-one tws voip network. ISDN trunks are connected in node X. A fax machine is connected to node Y, with ICAT=1....

If a remote fax machine calls through PSTN the fax machine located in node Y, the call crosses the VoIP network (IPLU - IPLU).

In this case the codec selection is done on the incoming call setup Bearer capability. ICAT of called fax extension is not important.

If the first choice codec in RIANP is g.729 and the calling BC is speech (don't correct, but it happens), fax transmission is KO.

Moreover if we have a remote voice caller that presents itself as BC 3,1KHz (it happens, for example POTS) the codec will be g.711, with bandwith waste.

Thank you

 

[parnum]

this is analogue line for fax, not even using DRG? so this has nothing to do with fax, it's about codec selection across the IPLUs between sites, the switch does not know this is a fax machine, it can be any analogue device connected, it's not an IP endpoint.

best parnum

 

[GioBs]

DSP on IPLU board should analize the analog signal ad find if it is a fax or no.