Re: SIP clients & AEBS hardware
Re: SIP clients & AEBS hardware
- Subject: Re: SIP clients & AEBS hardware
- From: james woodyatt <email@hidden>
- Date: Mon, 31 Jul 2006 15:16:13 -0700
On Jul 31, 2006, at 15:01, Mark Thomas wrote:
Any thoughts or know issue maybe ?
Short answer: probably a known issue.
SIP is not a NAT-friendly protocol. There have been various attempts
to work around the problem of NAT and SIP interop, but I haven't paid
close enough attention recently to know if one of them has settled
out as the preferred approach. Last I heard, STUN was the best
available solution, but it's an "add-on" that would need to be
integrated with SIP, and I don't know whether that integration has
sorted itself out yet.
The fact you are trying to use the "DMZ" feature of AirPort Extreme
suggests you have a SIP implementation that doesn't try to use STUN.
I'll bet it recommends you use the "DMZ" feature if you are behind a
NAT, and somebody has probably told you that AirPort Extreme has such
a feature.
AirPort Extreme does not have a "DMZ" feature.
AirPort Extreme has a feature it calls the "Default Host" mapping, in
which it will forward flows to a specific static private address if
there are no other port mappings or local services on the base
station to take the flow. It is not a "DMZ" in any sense of the term
as it's commonly used in networking. When flows are translated by
AirPort Extreme for the "Default Host" mapping, TCP and UDP source
ports on outbound flows are still floated, unlike as would happen
with a "DMZ" feature. Your SIP user agent probably doesn't like
this, but it's necessary to keep the default hosts mappings for
outbound flows separated from the AirPort's own transient local port
binds.
--
james woodyatt <email@hidden>
member of technical staff
apple computer, inc.
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