Subject: RE: IPv6 and NAT

From: Christian Huitema <[email-masked]>
Date: Mon, 11 Sep 2000 09:05:09 -0700

> NAT was proposed as a temporary solution for the shortage of 
> IP address,
> which is solved with the IPv6 protocol. Currently I don't 
> expect IPv6 to be
> deployed soon (within 1 or 2 years). My ISP, nor many ISPs, 
> aren't promoting
> IPv6 yet, nor Microsoft provides IPv6 support for it's OSes.

Well, actually, Microsoft's support is documented at:
 * Microsoft IPv6 Tech Preview News
   http://www.microsoft.com/PressPass/press/2000/Mar00/IPv6PR.asp
 * Microsoft IPv6 Tech Preview Kit
   http://msdn.microsoft.com/downloads/sdks/platform/tpipv6.asp
 * Microsoft IPv6 white paper
   http://www.microsoft.com/technet/network/ipvers6.asp
but let's go to your actual points:

> However, some scenarios where NAT provides THE solution, are for
> * private networks that may not be exposed to the Internet   and
> * for networks that have only one IP address available to use on the
> Internet,
> while host on the private network are required to make 
> 'direct' connections
> to the Internet.

IPv6 supports "private networks that may not be exposed to the Internet"
through the use of scoped addresses, i.e. "site-local" and "link-local"
addresses. This covers most of the cases in which some dumb hosts are
allowed to connect to the network but not to the Internet. For example, if
you have a light-switch that should not be activated by remote players, that
light-switch should be configued to only use site-local and link-local
addresses. It will never receive a packet from outside the network, nor send
a packet to the outside.

I don't really understand how your hypothesis of "networks that have only
one IP address available" fit with the other statement, "for the shortage of
IP address, which is solved with the IPv6 protocol..."

-- Christian Huitema

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