Erik Nordmark wrote:
Thus this is not a NAT that creates state with IP/port mappings based on observing data packets - it is a box which creates this state based on interaction with the SIP proxy. In essence it becomes a slave of the SIP proxy.
Yes.
Does anybody on the list know enough about SIP to say whether the above makes or does not make sense? Of course, folks could build a single box with this functionality - NAT(-PT) - SIP proxy - SIP proxy controlled IP/port mapper but you can't just have an independent SIP proxy and NAT(-PT) box do this; significant interfaces would be needed between the SIP and NAT functionality.
You can do that, but as Christian pointed out, this has severe limitations.
Hence NAT-PT by itself isn't useful here.
I would say that differently. NAT-PT by itself is not sufficient. If we want to go that route, we need a protocol to enable dialog between the SIP proxy and the NAT-PT boxes. Is there something in the MIDCOM space that could be used? - Alain.