[SIPForum-discussion] FAX T.38

[Garron, James]

I would say that preferably the B-party should send the re-INVITE to T.38 if it supports that capability.  However there is nothing preventing A-party from sending the T.38 re-INVITE upon fax tone detection.  There are potential issues with the A side doing the re-INVITE, if for instance the initial codec that was negotiated was G711 then the answering terminal could begin transmitting CED-DIS before the A party initiate the switch to T.38.  This could possibly lead to NSF messages to get through or other capabilities that may not be supported (assuming here that there is SBC or gateway between the 2 terminals).

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Moh, Yee-Kuang
Sent: Tuesday, January 08, 2013 12:35 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] FAX T.38

Hi,

Good day. Wondering using Fax T.38, isn't that B-party has always send Re-INVITE T.38 upon codec negotiation? Can A-party send Re-INVITE T.38 if B-party doesn't?

Thanks in advance.

Regards
moh
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