[asterisk-users] Asterisk 1.6.1.13 and T.38 faxing

[Kevin P. Fleming]

Vinícius Fontes wrote:

> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP v=0... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP o=PVG 1265107000170 1265107000170 IN IP4 10.152.0.164... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP s=-... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP p=+1 6135555555... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP c=IN IP4 10.152.0.164... OK.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP t=0 0... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP a=sqn: 0... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP a=cdsc: 1 image udptl t38... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP a=cpar: a=T38FaxVersion:0... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7589 process_sdp: Processing session-level SDP a=cpar: a=T38FaxUdpEC:t38UDPRedundancy... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7753 process_sdp: Processing media-level (audio) SDP a=rtpmap:101 telephone-event/8000... OK.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7753 process_sdp: Processing media-level (audio) SDP a=fmtp:101 0-15... UNSUPPORTED.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7753 process_sdp: Processing media-level (audio) SDP a=ptime:20... OK.
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:4653 change_t38_state: T38 state changed to 0 on channel SIP/voxip-00000000
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7932 process_sdp: We're settling with these formats: 0x8 (alaw)
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:7937 process_sdp: We have an owner, now see if we need to change this call
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:5231 update_call_counter: Updating call counter for incoming call
> [Feb  2 08:38:06] DEBUG[21032]: chan_sip.c:3172 __sip_xmit: Trying to put 'ACK sip:10.' onto UDP socket destined for 10.150.65.16:5060
> [Feb  2 08:38:06] DEBUG[21064]: app_fax.c:699 transmit_t38: Shut down T.38 on SIP/voxip-00000000
> 
> 
> Note how items like T38FaxUdpEC are listed as OK on one call and unsupported on another one. Could that be a bug? I can show the entire SIP conversations if that's necessary for debugging this.

That's not quite correct; in the second example, the T38 parameters are
being sent as 'capabilities' (a=cdsc and a=cpar) which Asterisk does not
support. The second example does not provide backwards compatibility for
SIP endpoints that do not support capability-based negotiation, whereas
the first one does.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kpfleming at digium.com
Check us out at www.digium.com & www.asterisk.org