Actually, I find this behavior in sipphone.com two months ago. I am
using a sip phone which is behind our company NAT.

Richard Wu
Senior Engineer
ASTRI

On Fri, 2007-06-22 at 08:35 -0500, Robert Sparks wrote:
> That is an interesting, but nonstandard (and incorrect), registrar  
> behavior. Are you actually encountering that somewhere?
> 
> If the UA wants a contact bound to its address as it appears on the  
> other side of a NAT, it needs to use
> STUN to discover it and place it in the Contact in the Register request.
> 
> RjS
> 
> On Jun 21, 2007, at 9:07 PM, Richard wrote:
> 
> >
> > Suppose UA1, which is behind NAT, is registering a public SIP server.
> > UA1
> > (only necessary headers are shown)
> > REGISTER sip:serviceprovider.com
> > To: <sip:[EMAIL PROTECTED]>
> > From: <sip:[EMAIL PROTECTED]>
> > Contact: <sip:[EMAIL PROTECTED];expires=3600>
> >
> > Then UA1 receives the 200 OK response:
> > 200 OK
> > Contact: <sip:[EMAIL PROTECTED]:15060;expires=3600>
> >
> > Then UA2, which is located in other machine and is also behind NAT,
> > registers to the same public SIP server using the same AOR.
> >
> > REGISTER sip:serviceprovider.com
> > To: <sip:[EMAIL PROTECTED]>
> > From: <sip:[EMAIL PROTECTED]>
> > Contact: <sip:[EMAIL PROTECTED];expires=3600>
> >
> > Then UA2 receives the 200 OK response:
> > 200 OK
> > Contact: <sip:[EMAIL PROTECTED]:15060;expires=3500>
> > Contact: <sip:[EMAIL PROTECTED]:25060;expires=3600>
> >
> >> From UA2 point of view, it does not know which contact header it is
> > belong to.
> >
> > Another question is: would I use the contact header (with mapped  
> > public
> > address) from the register 200 OK response to put in creating INVITE
> > message instead of consulting the STUN server if the UA is behind NAT?
> >
> > Richard
> > Senior Engineer
> > ASTRI
> >
> >
> >
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> >
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> 


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