[asterisk-dev] SIP replies to via or to ip/port (according toRFC)
Nick.Lewis at atltelecom.com
Thu Dec 17 05:10:05 CST 2009
>1) Force an rport parameter in the first Via header. The (default)
>described in paragraph A above will do the rest.
>2) Force symmetric RTP.
I think that strictly speaking it is down to the UAC behind the firewall
request RFC3581 behaviour by adding an empty rport rather than the
UAS adding it unilaterally. However I agree with this approach so that
the setting is nat=yes (rather than nat=route or nat=never) asterisk
will operate "as if" the UAC had added the rport parameter.
The situation with nat=no is more tricky - perhaps the default could be
changed to nat=never and nat=no depecated.
It may be worth having another setting nat=compliant that just does as
requires i.e. if rport is received then use both symmetric rtp and
Also we need to consider an option nat=auto that operates as per nat=yes
only for contact addresses 192.168.0.0/16 18.104.22.168/12 and 10.0.0.0/8
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