I have a Polycom 670/450 which does TLS/SRTP on the Internet leg of a call. An SBC receives the SRTP and decodes it to RTP to transit to our PBX.
When I place a call on hold and later resume....the RTP sequence numbers restart. I'm assuming that this confuses the SRTP decoding on the SBC and causes him to not decode or decode incorrectly.
I did some additional testing to confirm my theory. I did normal RTP instead of SRTP and we don't experience the problem.
I'm working with the SBC vendor to look at this problem, but wonder if there is anything on the phone to change the sequence number/RTP flow to not exhibit this problem.
Thanks for any input
what Software Version are you running ?
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
More data....I'm sending the SRTP to the SBC. When I look at the unencrypted side of the SBC, he's not forwarding the RTP. I think this helps prove my point that the SBC doesn't like something about the SRTP.
as this is quite complex please raise a case with Polycom support.
I got same problem. But, i solve this on different way.
Did you check type of hold option?
Changing option that (voIpProt.SIP.useRFC2543hold="0" voIpProt.SIP.useRFC3264HoldOnly="1" voIpProt.SIP.useSendonlyHold="1") can be useful for you.
I solved similar issue(no voice after resume) with following options: