CIPC using Duplicating RTP Streams

[Frantisek Opravil]

Does anybody know why Duplicating RTP Streams (rfc7198) is used for voice RTP from Cisco IP Communicator on my PC? Is it controlled by any Cisco or Windows (Lync 2013) setting? I found (using Wireshark) that the Duplicating RTP Streams are used from November 2016, aprox.

Call Recording did not work from our company CIPCs when they were using software version 8.6.5 (see https://supportforums.cisco.com/discussion/13118496/recording-voice-traffic-cisco-ip-communicator) but my tests shows that CallRecording worked even with CIPC version 8.6.5, when Duplicating RTP Streams were used.

RTMT alerts "RecordingSessionTerminatedUnexpectedly" are reported when the call recorder reports missing RTP stream. One of causes can be CIPC using sw version 8.6.5.

Most of our company CIPCs are not yet updated to version 8.6.6, but the amount of RTMT alerts "RecordingSessionTerminatedUnexpectedly", has decreased by end of year 2016 significantly, may be because the CIPCs started using Duplicating RTP Streams? (I could not check if Duplicating RTP Streams were used, the CIPCs affected are on very distant sites).

Do you have any explanation?

Thank you.

[Frantisek Opravil]

Hi all,

further analysis of the TCP dumps (output from Wireshark) during incoming phone call to my CIPC (and recorded to call recorder) shows, that my CIPC (or my PC) does not use "Duplicating RTP Streams (rfc7198)", my PC only sends all UDP packets 2 times!
I do not know its cause (virus, Windows update or side effect of some software).

However, since my PC sends all UDP packets 2 times, call recording works even with CIPC version 8.6.5.  When I was troubleshooting CallRecording from CIPC 8.6.5, TCP dumps (before Oct 2016) did not show outgoing UDP packets sent 2 times (and call recording did not work).

Regards         Frantisek Opravil