[SIPForum-discussion] FAX T.38

[Mike Coffee]

Moh, you have received answers to your important question that were conflicting
and, in some cases, would not be helpful to you if followed.  However, if you
were to simply accept Eric's response as comprehensive and 100-percent correct,
you would be fine.

Mike Coffee
Co-Chair, FoIP Task Group
SIP Forum





"Jastak, Eric" <Eric.Jastak at adp.com> on 01/10/2013 12:38:30 PM

To:   "Moh, Yee-Kuang" <ykmoh at pccwglobal.com>, "discussion at sipforum.org"
      <discussion at sipforum.org>
cc:    (bcc: mcoffee)

Subject:  Re: [SIPForum-discussion] FAX T.38



Yes, you can configure the "sending" device (A-party) to send the re-invite.  Of
course, the B-party device needs to be able to handle an incoming re-invite for
T.38...some devices (gateways) don't handle that so well.  I've done this type
of configuration in the past with Cisco 2102 ATAs, but it's not recommended.
One of the downsides is that you can run into glare issues if both A and
B-parties send T.38 re-invites simultaneously.   This can result in failed
negotiations and, ultimately, inconsistent results.   The exact behavior depends
on the CPE and Fax gateways in the path; for example, if you fax a variety of
different voice gateways (e.g., T.38 to different carriers) you will likely end
up with an unreliable fax solution.

With that said, my advice is to stick with the T.38 recommendation that only the
receiving party (B-party) send the T.38 re-invite.

From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org]
On Behalf Of Moh, Yee-Kuang
Sent: Monday, January 07, 2013 9:35 PM
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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