Hi, We are capturing packets for call quality monitoring purposes, and as part of the capture, we are grabbing the outbound packets from FreeSwitch. We are noticing what appears to be an odd behaviour in the RTP sequence timing where suddenly the timing will jump from the regular 160 increments to a number in the 10's of millions! See packet 38 below. Now I have no idea as to whether such a timing change is OK in RTP, and although the actual RTP stream does not appear to be affected, I do see that Wireshark believes there is a massive amount of jitter on the line when it analyses the packets, and any RTCP Sender Reports from the target device (and indeed several different target types have been tried) also report very large inter arrival jitter numbers at this point! It's the RTCP side of things that are more of interest here, as trying to get accurate results of our downstream jitter by capturing the returned RTCP packets. I believe that all the times we see this, there is however a Marker bit present! So I guess the question is whether this is expected behaviour, and if not any ideas? No. Time Source Destination Protocol Info 1 0.000000 gmtpbx02.redmatter.com sil1.magrathea.net SIP/SDP Request: INVITE sip:441277849884@sipipgw.magrathea.net, with session description 2 0.001595 sil1.magrathea.net gmtpbx02.redmatter.com SIP Status: 100 Giving a try 3 1.103160 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=0, Time=0 4 1.124816 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=1, Time=160 5 1.142758 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=2, Time=320 6 1.163702 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=3, Time=480 7 1.184239 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=4, Time=640 8 1.203259 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=5, Time=800 9 1.223456 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=6, Time=960 10 1.243953 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=7, Time=1120 11 1.264504 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=8, Time=1280 12 1.284839 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=9, Time=1440 13 1.304590 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=10, Time=1600 14 1.323589 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=11, Time=1760 15 1.344672 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=12, Time=1920 16 1.359227 sil1.magrathea.net gmtpbx02.redmatter.com SIP/SDP Status: 183 Session Progress, with session description 17 1.364522 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=13, Time=2080 18 1.377484 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53974, Time=160, Mark 19 1.383466 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=14, Time=2240 20 1.397476 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53975, Time=320 21 1.403953 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=15, Time=2400 22 1.417484 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53976, Time=480 23 1.423616 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=16, Time=2560 24 1.437474 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53977, Time=640 25 1.444930 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=17, Time=2720 26 1.457475 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53978, Time=800 27 1.463341 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=18, Time=2880 28 1.477473 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53979, Time=960 29 1.484235 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=19, Time=3040 30 1.497483 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53980, Time=1120 31 1.503415 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=20, Time=3200 32 1.517474 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53981, Time=1280 33 1.523541 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=21, Time=3360 34 1.537472 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53982, Time=1440 35 1.543428 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=22, Time=3520 36 1.557567 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53983, Time=1600 37 1.563656 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=23, Time=3680 38 1.577496 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53984, Time=130238272, Mark 39 1.584747 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=24, Time=3840 40 1.597474 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53985, Time=130238432 41 1.603871 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=25, Time=4000 42 1.617465 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53986, Time=130238432 43 1.624224 lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=26, Time=4160 44 1.637466 gmtpbx02.redmatter.com lon-avon-four.magrathea.net RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7, Seq=53987, Time=130238592 Many thanks, Neil