[Kamailio-Users] Doubt about nat=yes

[mayamatakeshi]

Hello,
I'm trying to understand this sample cfg:
http://voip-info.org/wiki/view/OpenSER+And+RTPProxy

This cfg is used as foundation for some of our cfg files here but nobody is
sure about exactly how some things work. So I'm trying to clear things up.
In particular, I am clueless about why there is code removing "nat=yes" from
the URI and adding it to the Contact header (actually I don't know what is
its meaning. I suppose this is a way of a client advertising that it is
behind NAT, but I couldn't find which RFC defines this):

subst_uri('/(sip:.*);nat=yes/\1/')

search_append('Contact:.*sip:[^>[:cntrl:]]*', ';nat=yes');

Is this something that always must be done when dealing with nat or it was a
particular situation that the writer of the cfg had to workaround?
I'm rewriting our cfg file (to be used with m4) and I'm trying to remove
unnecessary things.

Another thing in the cfg: in case a reinvite is issued, should not
unforce_rtp_proxy be called before force_rtp_proxy is called again? Could
this lead to having rtpproxy leaking resources?
 <http://www.kamailio.org/docs/modules/1.3.x/nathelper.html#AEN367>
regards,
mayama
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