[standards-jig] Re: VoIP, JEP-0065 and UDP?
jesper at krogh.cc
Sun Jan 25 17:07:30 UTC 2004
I gmane.network.jabber.standards-jig, skrev Matthias Wimmer:
> Jesper Krogh schrieb am 2004-01-25 16:17:15:
> > I haven't seen any describtions on how that should be possible.. could
> > you describe it?=20
> Just by sending each other a UDP packet on the right ports, the
> association gets stored by the NAT router. The first packet won't get
> delivered, as the destination NAT does not yet know where to deliver it,
> but as soon as the destination host has sent the first UDP packet as
> well, both NAT routers know where to deliver incoming UDP packets.
I don't think so.. lets play the scenario.
We assume no default ports, if there were that would kill multiple
setups behind same NAT.
A sends a UDP datagram to B
a:1234 -> b
(A is sending from port 1234 to B at port 1234 ).
This package gets killed in B's nat unit but sets up a record in its
own nat to forward packages to the client coming on port 1234 to the
B:2345 -> a
(B is sending from port 2345 to A at port 2345).
This too gets killed by A's nat unit but sets up a record in it own nat
to forward packages to the client coming on port 2345 to the client.
Well, the first package should be sent successfully now.
A can send to B's port 2345 and
B can send to A's port 1234
But if you dont have a proxy, how should the ever know that it is 1234
and 2345 that's been allocated?
./Jesper Krogh, jesper at krogh.cc
Jabber ID: jesper at jabbernet.dk
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