On Fri, Sep 01, 2000 at 05:30:42PM +0200, Sean Doran wrote:
> The IP header is strictly useful only for IP-handling equipment,
> on a hop-by-hop basis.   Among other things, the IP header's ttl
> field has to be decremented on a hop-by-hop basis; this field is
> simply not end-to-end.   Likewise, the odd religious goal of 
> "protecting the header" is in conflict with other network services
> that rely upon interpretations of and modifications to the diff-serv
> [ex-tos] field.

Yes, but changing the address means more complex protocols are broken.
FTP through NAT boxes only works via a special hack in the NAT.
talk through NAT boxes doesn't work to my knowledge, unless somebody 
has implemented the special hack for talk.
IRC dcc through NAT boxes ... etc etc. 

Not to talk about protocols which aren't invented yet.

NAT simply isn't part of the solutions, but of the problem.
	-is