Re: Proposal: UP&P

On Mon, Mar 12, 2007 at 05:04:44PM +0000, Michael Rogers wrote:
> Matthew Toseland wrote:
> > I was
> > under the impression that the difference between port restricted and
> > symmetric was precisely this - that a symmetric NAT would allocate a
> > new port for every { source port, source IP, dest port, dest IP },
> > whereas a port restricted cone will usually reuse the port, and just
> > ignore packets coming from IPs other than ones we have sent packets to?
> 
> That sounds right, but to muddy the waters even further some people have 
> abandoned the "full cone/restricted cone/port restricted cone/symmetric" 
> terminology because it doesn't cover all possible combinations of 
> mapping and filtering behaviour - see tables 6 and 8 of the STUNT paper:
> 
> http://nutss.gforge.cis.cornell.edu/pub/imc05-tcpnat.pdf
> 
> Roughly speaking, it looks like 70% of NATs can punch UDP holes to each 
> other, and some of the 70% can punch holes to some of the remaining 30%. 
>    This is much worse than I thought - the real world success rate could 
> be anywhere between 49% and 91%, depending on the value of "some".
> 
> Port prediction works for 94% of NATs after a few retries, but it 
> requires out-of-band communication...

Out-of-band communication is possible ... sometimes. :|
> 
> Cheers,
> Michael

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