A Kerio Operator customer was experiencing dropped calls. He noticed lines similar to this in the Operator Warning log and wondered if they were related to the dropped calls issue.
[30/May/2015 15:02:01] asterisk: WARNING: chan_sip.c:3841 in retrans_pkt: Retransmission timeout reached on transmission 2076517348-5062-4@BJC.BGI.E.BEE for seqno 119 (Non-critical Request) -- See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions#012Packet timed out after 31999ms with no response
Kerio Support explained what the entry means:
The warning log line is not really related to SIP registrations. In SIP all communication is confirmed by ACK messages.
What the warning actually means is that Operator send a SIP message (INVITE, REGISTER,...) but didn't receive a confirmation. All SIP messages are automatically re-sent after 1, 2, 4, 8, 16 seconds. When no confirmation arrives in 32 seconds, the referred warning line is logged. As a result, Operator might not have successfully registered, call may have not been terminated/initiated, etc.
See also What is the problem with SIP retransmits?
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© 2015-07-16 Anthony Lawrence