[e2e] using p2p overlays to overcome recursive NATs/realms

[Geoff Huston]

At 10:19 AM 8/02/2002 +0000, Jon Crowcroft wrote:

>so the problem with most the proposed solutions to workign around nats
>is that they really assume there are only 2 realms -
>the great unwashed internet, and the poor deprived natted user.
>
>the real situation is that packets might traverse multiple natted realms 
>(c.f. realm
>specific ip) - in this scenario, discovering the mapping involves 
>discovering a path of
>several mappings-


While I understand the ease with which such a sequence of NAT points could 
be established - either deliberately or even by accident, I wonder to what 
extent such configurations exist in the wild? My direct experience has been 
in scenarios of

(private realm) nat  (internet) (boundary servers) nat

I deliberately left out the second private realm becase, again based purely 
on observation) I rarely see true private-to-private connections

My own experience is that the more generalized case of a sequence of realms 
separated by NATs is a very rare thing indeed, and while I can see the 
possibility of a p2p service being capable of negotiating through such an 
environment, I can't help but wonder as to the extent of its deployment.


   Geoff