[Spce-user] T.38 to G.711a transcoding for peerings and vice versa

Hohl Matthias matthias.hohl at telematica.at
Thu Nov 15 07:26:21 EST 2018

Hello Daniel,


I believe it would be a problem on subscriber side:

>From SPCE to Peering Server with G.711a for faxing would be less problem because the transport will be with Sync-Ethernet and with direct peering connection.

But between subscriber PBX and SPCE there is often any kind of internet connection possible, and for this reason I think T.38 (leg from subscriber to SPCE) would make the things more stable like  G.711a.


So I think T.38 on subscriber side and G.711a on Peering side would be the most effective way to have successful fax services. Therefore SPCE has to transcode T.38 to G.711a for the peering or G.711a to T.38 for subscriber if the subscriber is supporting it.


I hope I descriped it now better 😊





Von: Spce-user <spce-user-bounces at lists.sipwise.com> Im Auftrag von Daniel Grotti
Gesendet: Donnerstag, 15. November 2018 12:00
An: spce-user at lists.sipwise.com
Betreff: Re: [Spce-user] T.38 to G.711a transcoding for peerings and vice versa


frankly I don't see the problem.
I would just enable t.38 anyway, in case the t38 re-negotiation fails (e.g with your peering server) the fax should go in G711, as falback.

Daniel Grotti
Head of Customer Support
Sipwise GmbH, Campus 21/Europaring F15
AT-2345 Brunn am Gebirge
Office: +43(0)130120332
Email: dgrotti at sipwise.com <mailto:dgrotti at sipwise.com> 
Website: https://www.sipwise.com

On 11/15/18 11:45 AM, Hohl Matthias wrote:



Today I got the information that A1 Telekom is not supporting T.38 in there IC network.

Only if the traffic is a Transit Call, T.38 will be supported as “Pass-Through”.

All other Fax Calls with a Reinvite to T.38 will be “not acceptable here”.


For better fax stability I want to allow T.38 for my subscribers.

Therefore I want to allow T.38 just on subscriber side. On peering side, T.38 has to be transcoded to G.711a, if the destination network is A1 Telekom. Also if a FAX comes from A1 with G.711a it should be transcoded to T.38 for our subscribers, of the subscriber support T.38.

IS it possible to implement this transcoding option in any way on the SPCE mr6.5.1? Maybe with a SEMS patch?


Would be nice if someone has an idea to solve this 😊


Mit freundlichen Grüßen,

Matthias Hohl



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