[asterisk-users] NAT solutions

[Brad Templeton]

On Thu, Jan 25, 2007 at 10:19:06PM -0800, Yuan LIU wrote:
> Asterisk1 <--> NAT1 --- { Internet } --- NAT2 <--> Asterisk2
> 
> If Asterisk1 can talk to Asterisk2 at trunk level, I'll be happy.

While I'm not sure of what tricks * plays at all levels, you
can certainly make this work if you have control of the NATs to
open ports, or if the asterisk servers know the address of their
partner and thus can keep the NAT "open" by sending keep-alives.
> 
> The way Jeff Pulver puts it, ICE has conquered the world :-)  Would love 
> to learn more.

ICE is a methodology.  You list every way you might be reached
(LAN, external addresses and addresses of outside relays) and the
other endpoint tries every way it can, ranked in order of quality,
and picks the best one.   So if you're both on the same LAN it will
see that and use it.  If you can't reach one another except through
a relay it identifies that and uses a relay.  If, of course, you have
a willing relay.

(Skype solved that last problem :-)
> 
> Is this the concept of STUN?  Does this also create latency (by adding an 
> additional leg in the route), packet loss, even jitter?
STUN is something else.  Using a relay does indeed increase latency
(and thus echo) and may increase jitter and packet loss, though latency
is the big issue.
> 
> I should have used FWD as an example.  One can't say it uses proprietary 
> clients.  Does it stay away from voice path?

It provides a relay if one is needed.  I don't know about today but
they started using jasomi boxes sold to deal with this question.