[arin-ppml] ARIN-prop-127: Shared Transition Space for IPv4 Address Extension
spiffnolee at yahoo.com
Thu Jan 27 09:46:42 EST 2011
> > It's ironic that NAT traversal hacks can't handle NAT.
> Not really. They originally handled it pretty well, with ALG support
> making it a lot more friendly.
ALG isn't NAT. And without defining a layer-violating protocol,
(an application-agnostic application-layer gateway)
it isn't realistic for every NAT implementer to build an ALG for
every application that needs one.
> However, CPE's started utilizing uPNP
> and applications decided that it was saturated enough in the market
> to use it instead of relying on ALG support. This lead to applications
> creating non-uPNP unfriendly NAT hacks. Now they will regret it.
Even if every NAT vendor built an ALG for every new app, new
apps couldn't be deployed because of the installed base of NATs
which didn't have the ALG for the new app.
So here we are:
uPNP doesn't work for large-scale NAT, because it can't traverse
the NAT layers
ALGs aren't a solution, because there are too many applications
PCP is too late for implementation in applications and appliances
Seriously, for things that don't work beautifully through multi-layer
NAT, IPv6 is the only way to go. And if you think NAT444 is
your solution for exhaustion, you really need to do IPv6, too.
More information about the ARIN-PPML