[asterisk-dev] Asterisk hangups after T.38 ReInvite

Litnitchii Alexandr sasha at asterisk-support.ru
Mon Apr 2 07:29:42 MST 2007

Hi all.
I have an issue sending/receiving faxes in  next environment:
PSTN <-> Cisco (t.38 origination) <-> Mera (t.38 pass-through)
<-> Asterisk-1.4.2 (t.38 pass-through)  <-> Linksys SPA2100 (t.38 termination).
There is a detailed log with sip messages debug in attachment. The
summary of the issue is that call is answered, then Asterisk sends to
Mera INVITE with m=image in SDP. Mera answers OK also with m=image, and
some other parameters. Right after that Asterisk sends BYE to Mera, and
i cannot understand the reason for that. Is that a bug?

I can suppose here 2 reasons:

1. missing Contact: header in Mera's OK reply ( line number 601 )

2. Different T38 capability between asterisk <-> spa2100
 Our T38 capability (3856), peer T38 capability (3872), joint capability
(3872)  (line 482)

and  mera <-> asterisk
Our T38 capability = (3856), peer T38 capability (32), joint T38
capability (32) (line 632)

Unfortunately i have no access to Mera, nor Cisco. As we were told,
Cisco has next settings for our dialpeer:
fax rate 9600
fax-relay ecm disable
fax protocol t38 ls-redundancy 5 hs-redundancy 2 fallback none

I'm not sure if this is a bug of asterisk and whether i should submit a
ticket.  But sending/receiving faxes does work if we exclude asterisk
from the path and use it like
PSTN <-> Cisco (t.38 origination) <-> Mera (t.38 pass-through)
<-> DNAT Forwarding  <-> Linksys SPA2100 (t.38 termination).
Although Fax settings remain the same both at Cisco and SPA2100.

Should i provide more information regarding the issue?

I would really appreciate any suggestions.

Best Regards,

Litnitchii Alexander
"Comunicatii Libere" SRL

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