[asterisk-users] chan_sip.c:3641 retrans_pkt: Retransmission timeout

Benoit Panizzon benoit.panizzon at imp.ch
Tue Mar 27 07:06:40 CDT 2012


We have a Genband C3 Switch and a couple of customers that operate asterisk 
PBXes connected via SIP Trunk. All of them still use some 1.6.X asterisk and 
this works fine.

One customer uses a 1.8 version and has a very strange problem:

Asterisk built by pbuilder @ nighthawk on a x86_64 
running Linux on 2012-03-06 01:51:21 UTC

When a call reaches this asterisk the call get's dropped after a couple of 
seconds with this message:

[Mar 27 13:47:35] WARNING[29806]: chan_sip.c:3641 retrans_pkt: Retransmission 
timeout reached on transmission F47F6F67 at 7f33ff47 for seqno 907689273 
(Critical Response) -- See 
Packet timed out after 6400ms with no response
[Mar 27 13:47:35] WARNING[29806]: chan_sip.c:3670 retrans_pkt: Hanging up call 
F47F6F67 at 7f33ff47 - no reply to our critical packet (see 

Well, the Wiki is not very helpfull, as the problems explained there do not 
seem to be the cause.

I sniffed the connection on the Asterisk Box itself and what I see is this 
flow of SIP messages:

C3 <=> Asterisk

=> Invite +sdp
<= 401 Unauthorized
=> Ack
=> Invite +sdp +auth
<= 100 Trying
<= 180 Ringing
<= RTP Audio
<= 200 OK +sdp
=> Ack
<=> RTP Audio
<= 200 OK +sdp
=> Ack
<= 200 OK +sdp
=> Ack
<= 200 OK +sdp
=> Ack
<= Bye
=> Ack
<= Bye
=> Ack
<= Bye
=> Ack

Well apparently the C3, from my point of view sends correct Acks to the 
Asterisk, but somehow the Asterisk ignores them.

I did try to get more information with debug and verbose level set to '99', 
but I don't see more messages

Does anyone have a clue, why acks could be not accepted by asterisk ?

The other way round (asterisk => c3) the calls work fine.


Benoit Panizzon
I m p r o W a r e   A G    -    

Zurlindenstrasse 29             Tel  +41 61 826 93 07
CH-4133 Pratteln                Fax  +41 61 826 93 02
Schweiz                         Web  http://www.imp.ch

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