Hi,
I'm experiencing a problem that I get udp checksum errors (shown in wireshark),
when I use the rtp_echo option or when I am not explicitly playing back a pcap
trace in a SIPp scenario.
The setup I'm using is that I have a load generating server (SIPp) acting as a
SIP user agent client, I also have a media server. I'm aware that wireshark may
show incorrect udp checksums on packages originating from the machine where the
capture was taken (because of the checksum offload).
I'm getting a capture on the media server and then filtering out packages
originating from the media server, and also viewing packages from SIPp load
generating server. What I seem to notice is that there is no incorrect udp
checksums in the part of the call/scenarioI where I'm explicitly playing back a
pcap trace. However:
- When I use rtp_echo we get udp checksum errors at all points where I'm not
explicitly playing back pcap trace.
- When not using rtp_echo, I still get incorrect checksum errors even though I
would be expecting no media at all.
When using rtp_echo, I've also made captured a tcpdump on media server AND load
generator at the same time. Indicating that:
- NO incorrect udp checksums on packages from media server to SIPp load
generator host.
- Incorrect udp checksums on packages from SIPp load generator to media server
(unless explicitly streaming a pcap file).
This was to rule out that media server sends udp packages with incorrect
checksum to the SIPp whichis then echoed back.
If I modify the scenario so that throughout the call, after media negotiation,
I am streaming a pcap file, I get no checksum errors at all.
Anyone knows why rtp echo seem to render udp checksum errors? Or why I'm
getting udp checksum errors even though I'm not explicitly streaming anything
at all?
Best Regards,
Daniel
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