asterisk users - Nov 2005 - General questions about register and nat traversal

My phones have some settings, which I do not understand. Maybe somebody 
can help me here:

1. NAT
Nat traversal      enabled, stun, disabled
Nat addr      stun01.sipphone.com
Nat ttl         30


I played with Nat traversal:
enabled:         the phone has NO audio, well it was just a white noise 
for incoming and outgoing calls
stun:               the phone works fine for OUTGOING calls, but for 
incoming calls, this phone and the others of the group ring. I pickup 
and hear nothing, while the other phones still ring. I can use *8# to 
get the call
disabled:   all is working, audio for in- and out-going calls, as well I 
do not "pickup" the phone call.

Why is that so?


2. Register
The fields are set in the phone to:
register port         1720
rtp port               1722

I wonder, why it does not need to have register port on 5060???  If I 
set it to 5060, no difference.

Again, why?


3. Call type is set to advanced. The other choice would be normal. What 
is the difference?

bye

Ronald Wiplinger