Re: To address or NAT to address?

[Bill Fink <bill at wizard.nasa.atd.net>]

> At 10:09 AM 12/2/99 -0800, Charles E. Perkins wrote:
> >
> >> With this in mind I hope that the same folks who complained about
> >> increased dependencies on DNS by NATs, would be equally vocal in
> >> complaining about increased reliance on the DNS by IPv6 (which claimed
> >> to be an improvement over NATs).
> >
> >DNS is supposed to be a way to resolve domain names into IP addresses.
> >How else would one get an IP(v6) address from a domain name other
> >than by using DNS?  Am I missing something here?
> 
> The IPv6 A6 record, which I helped design, map a host name to a tuple of
> (prefix length, prefix name, binary suffix). The prefix name is a DNS name.
> In order to actually get the address, one should go read the A6 record(s)
> of the prefix, then combine prefix(es) and suffix to obtain address(es).
> The idea is to facilitate renumbering by storing the prefix(es) in exactly
> one place.
> 
> One could say that this structure implies an "increased reliance on the
> DNS", in the sense that one will need to access two records instead of one
> in order to obtain the address. In fact, we may need more than two
> transactions, if the prefix itself is built from another prefix. On the
> other hand, there are at least three ways to diminish this reliance:
> 
> 1) DNS server can provide a copy of the prefix-name's A6 record in the
> "additional information" field of responses, so that the second transaction
> can be served from the cache,
> 
> 2) In "Intranet" environments, a working set of prefixes will be present in
> the cache anyhow,
> 
> 3) In really constrained environment, network managers may choose to
> arbitrage between ease of renumbering and reliance on the DNS, and set the
> prefix length to zero, thus falling back to IPv4 like operation.
> 
> In short, this issue was discussed at length in the IPv6 working group, and
> the benefits of easy renumbering/reconfiguration were deemed to exceed the
> "extra reliance."
> -- Christian Huitema



I'm glad this idea of decoupling site prefix and internal site
address is finally getting some serious attention.  I've always
felt this was critical to the success of being able to actually
renumber a site fairly painlessly.  I'll have to check out the
details of the A6 DNS draft.  I proposed something very similar
way back in March of 1995, but it wasn't given much attention
then.  Now if we could only have an alternate stateful address
configuration method than the backwards one of DHCPv6, one that
generated an IPv6 address directly from the host's domain name
rather than from a layer 2 MAC address, we'd really be in business.
Maybe that too will come eventually.  I've included my earlier
message to the ipng e-mail list as historical perspective (my
original original message is at the very end).

						-Bill