[Serusers] nat test based on rfc1918 address in call-id field

[Richard]

Hi,

I am thinking about having more NAT test on a sip packet. Just want to find
out if it is useful.

I run into some situations that some 'smart' UAs try to detect its external
IP and put the external IP address into the sip packet. Depending on the
network and NAT firewall setup, it may or may not set the right external IP
and port in the packet. If it is not, but pretends to be on the public
internet, then there is most likely a one-way voice or no voice issue. I'd
like to be able to detect and force it to use a nat proxy. By checking these
packets, I found that the only trace is the private IP address in the
call-id header field. It will be useful to check if a RFC1918 address is
used in the call-id. I understand that it is not a thorough test for NAT,
well, just like any other NAT test.

Can someone please comment if it is a good test?

Thanks,
Richard

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