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<p class=MsoNormal>Hi,<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>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!<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>So I guess the question is whether this is expected
behaviour, and if not any ideas?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>No.
Time
Source
Destination
Protocol Info<o:p></o:p></p>
<p class=MsoNormal> 1 0.000000
gmtpbx02.redmatter.com sil1.magrathea.net SIP/SDP
Request: INVITE sip:441277849884@sipipgw.magrathea.net, with session
description<o:p></o:p></p>
<p class=MsoNormal> 2 0.001595
sil1.magrathea.net gmtpbx02.redmatter.com
SIP Status: 100 Giving a try<o:p></o:p></p>
<p class=MsoNormal> 3 1.103160
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=0,
Time=0 <o:p></o:p></p>
<p class=MsoNormal> 4 1.124816
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=1,
Time=160 <o:p></o:p></p>
<p class=MsoNormal> 5 1.142758
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=2,
Time=320 <o:p></o:p></p>
<p class=MsoNormal> 6 1.163702
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=3,
Time=480 <o:p></o:p></p>
<p class=MsoNormal> 7 1.184239
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=4,
Time=640 <o:p></o:p></p>
<p class=MsoNormal> 8 1.203259
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=5,
Time=800 <o:p></o:p></p>
<p class=MsoNormal> 9 1.223456
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=6,
Time=960 <o:p></o:p></p>
<p class=MsoNormal> 10 1.243953
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=7,
Time=1120 <o:p></o:p></p>
<p class=MsoNormal> 11 1.264504
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=8,
Time=1280 <o:p></o:p></p>
<p class=MsoNormal> 12 1.284839
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=9,
Time=1440 <o:p></o:p></p>
<p class=MsoNormal> 13 1.304590
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=10,
Time=1600 <o:p></o:p></p>
<p class=MsoNormal> 14 1.323589
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=11,
Time=1760 <o:p></o:p></p>
<p class=MsoNormal> 15 1.344672
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=12,
Time=1920 <o:p></o:p></p>
<p class=MsoNormal> 16 1.359227
sil1.magrathea.net gmtpbx02.redmatter.com SIP/SDP
Status: 183 Session Progress, with session description<o:p></o:p></p>
<p class=MsoNormal> 17 1.364522
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=13,
Time=2080 <o:p></o:p></p>
<p class=MsoNormal> 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 <o:p></o:p></p>
<p class=MsoNormal> 19 1.383466
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=14,
Time=2240 <o:p></o:p></p>
<p class=MsoNormal> 20 1.397476
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53975, Time=320 <o:p></o:p></p>
<p class=MsoNormal> 21 1.403953
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=15,
Time=2400 <o:p></o:p></p>
<p class=MsoNormal> 22 1.417484
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53976, Time=480 <o:p></o:p></p>
<p class=MsoNormal> 23 1.423616
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=16,
Time=2560 <o:p></o:p></p>
<p class=MsoNormal> 24 1.437474
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53977, Time=640 <o:p></o:p></p>
<p class=MsoNormal> 25 1.444930
lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP
PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=17, Time=2720 <o:p></o:p></p>
<p class=MsoNormal> 26 1.457475
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53978, Time=800 <o:p></o:p></p>
<p class=MsoNormal> 27 1.463341
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=18,
Time=2880 <o:p></o:p></p>
<p class=MsoNormal> 28 1.477473
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53979, Time=960 <o:p></o:p></p>
<p class=MsoNormal> 29 1.484235
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=19,
Time=3040 <o:p></o:p></p>
<p class=MsoNormal> 30 1.497483
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53980, Time=1120 <o:p></o:p></p>
<p class=MsoNormal> 31 1.503415
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=20,
Time=3200 <o:p></o:p></p>
<p class=MsoNormal> 32 1.517474
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53981, Time=1280 <o:p></o:p></p>
<p class=MsoNormal> 33 1.523541
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=21,
Time=3360 <o:p></o:p></p>
<p class=MsoNormal> 34 1.537472
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53982, Time=1440 <o:p></o:p></p>
<p class=MsoNormal> 35 1.543428
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=22,
Time=3520 <o:p></o:p></p>
<p class=MsoNormal> 36 1.557567
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53983, Time=1600 <o:p></o:p></p>
<p class=MsoNormal> 37 1.563656
lon-avon-four.magrathea.net gmtpbx02.redmatter.com RTP
PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=23, Time=3680 <o:p></o:p></p>
<p class=MsoNormal> 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 <o:p></o:p></p>
<p class=MsoNormal> 39 1.584747
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=24,
Time=3840 <o:p></o:p></p>
<p class=MsoNormal> 40 1.597474
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53985, Time=130238432 <o:p></o:p></p>
<p class=MsoNormal> 41 1.603871
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=25,
Time=4000 <o:p></o:p></p>
<p class=MsoNormal> 42 1.617465
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53986, Time=130238432 <o:p></o:p></p>
<p class=MsoNormal> 43 1.624224
lon-avon-four.magrathea.net gmtpbx02.redmatter.com
RTP PT=ITU-T G.711 PCMU, SSRC=0x216DE2D9, Seq=26,
Time=4160 <o:p></o:p></p>
<p class=MsoNormal> 44 1.637466
gmtpbx02.redmatter.com lon-avon-four.magrathea.net
RTP PT=ITU-T G.711 PCMU, SSRC=0x1855F3A7,
Seq=53987, Time=130238592<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Many thanks,<o:p></o:p></p>
<p class=MsoNormal>Neil<o:p></o:p></p>
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