[asterisk-users] Asterisk 11- Answer with [m=image 0 udptl t38] and Call Drop

[Salman Zafar]

Hello All,
           I am having a bit peculiar problem with Asterisk 11 for a
carrier. This carrier shares quite some information in SDP header, which
should not be the problem, however what happen is as follow:


Carrier----> (INVITE) -> *SIP Proxy -> Asterisk 11 -> Answer()* -> right
after answering call drops... Carrier send a BYE with (cause 79: service or
option not implemented).

*NOTE: Please refer to complete SIP traces attached. *
*
*
*Also Note:*
*Carrier*: 62.61.147.214
*Proxy*: 77.X.X.X:5060
*Asterisk11*: 77.X.X.X:5080

*Here is Invite SDP  from Carrier -> Proxy -> Asterisk 11*

INVITE sip:69609000 at 77.X.X.X SIP/2.0
v=0
o=AudiocodesGW 1638819008 1638818710 IN IP4 62.61.147.214
s=Phone-Call
c=IN IP4 77.X.X.X
t=0 0
m=audio 53372 RTP/AVP 8 118 18
a=rtpmap:8 PCMA/8000
a=rtpmap:118 PCMA/8000
a=gpmd:118 vbd=yes
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=ptime:20
a=sendrecv
a=rtcp:53373 IN IP4 77.X.X.X
m=image 56854 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxMaxBuffer:1024
a=T38FaxMaxDatagram:122
a=T38FaxRateManagement:transferredTCF
a=T38FaxUdpEC:t38UDPRedundancy

*SDP:After Answered by Asterisk 11*
v=0
o=root 164966782 164966782 IN IP4 77.X.X.X
s=Asterisk v11.0.1
c=IN IP4 77.X.X.X
t=0 0
m=audio 12636 RTP/AVP 18 8
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:8 PCMA/8000
a=ptime:20
a=sendrecv
*m=image 0 udptl t38*

I have tired by disabling/unloading fax modules as *I am not using* them
but no results. Secondly, also tried tweaking of udptl ever-odd nothing
worked.

The same carrier works for Asterisk 1.6.X and the only difference I have
notice so far is the above underlined line in Answered SDP -> m=image 0
udptl t38. I think if I some how do not advertise udptl here i would be
able to avoid this scenario. I have tried multiple ways to strip off SDP
from incoming INVITE at SIP Proxy level but it is not SDP wise enough.


*Note:*

In Asterisk 1.6 =>  WARNING[32671]: chan_sip.c:8833 process_sdp:
Unsupported SDP media type in offer: image 59978 udptl t38
In Asterisk 11 => WARNING[18748][C-0000002f]: chan_sip.c:10277 process_sdp:
Failed to initialize UDPTL, declining image stream


-- 
Regards

*Muhammad Salman Zafar*
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