[standards-jig] VoIP, JEP-0065 and UDP?

Matthias Wimmer m at tthias.net
Sun Jan 25 15:58:50 UTC 2004

Hi Krzysztof!

Krzysztof Szyntar schrieb am 2004-01-25 16:55:21:
> If I understand correctly, you say that it's imposible to get an answer to
> your UDP packets if you are connected through a NAT?

No that is not what I said.

> That's not quite true. Most NATs, after someone sends a UDP datagram,
> leave the port it went through open (for a minute or so) and listen
> for some result.

Right. But you do not need an external proxy for this. Two clients both
behind NAT can open their NAT each other without the need for a third

> That's why services such as ping are possible.

ping does not use UDP. Ping uses ICMP.

> So if we take advantage of this behaviour, we can definitely construct
> a UDP proxy.

Why a proxy if it is possible with the same technique without it?

Tot kijk

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