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