RE: Number of Firewall/NAT Users

["Christian Huitema" <huitema at exchange.microsoft.com>]

> If a compelling application comes along that is NAT-hostile, that
> will be interesting, but I can't imagine it's in anyone's interest
> to provoke such a conflict when there are well-known NAT-friendly 
> ways of replacing embedded IP addresses in most higher-level protocols
> that use them...

Well, NAPSTER comes pretty close. Two peers can exchange files if at
least one of them can act as a server, i.e. is not blocked by a NAT. If
both are behind NAT, they can't. The point being, NAT are only
transparent if the host behind a NAT acts as a "client", and initiates
the TCP connection. Peer-to-peer applications assume that every host can
be a server.

-- Christian Huitema