On Jul 6, 2007, at 3:07 AM, Iljitsch van Beijnum wrote:
And from an architectural perspective, address translation is
clearly a dead end. One of the reasons we argue against NATs is
not that there aren't other major problems, it's that people
haven't managed to get the message on NATs yet.
Well, an iceberg looks very differently depending on whether you
look at it above water or below. The problem with NAT is like
almost all persisting problems: the bad consequences aren't felt in
the place where they're created.
It should be abundantly clear, being "Internet robust" is not a
requirement set by the marketplace. People want their multiplayer
games and conferencing programs to "just work"! A transition to full
IPv6 will be perilous, as it is _not_ possible to drop IPv4 support
in most environments.
Unfortunately, the NAT problem also represents a business
opportunity. This is true whether or not the solutions are condoned
by a standards body. In the case of IPv6, Teredo UDP IPv4 tunneling,
Teredo servers, and PNRP (a name service to navigate Teredo
topologies) represents an immediate solution. A solution that
introduces _more_ translations.
The ideals of end-to-end assume the "end" is "Internet robust." With
Teredo and PNRP, external services play a significant role. Will the
"end", in conjunction with extremely complex topology ever become
"Internet robust"?
How will SMTP servers vet sources of inbound messages within an IPv6
environment? Virtually every grain of sand can obtain a "new" IPv6
address. An IPv6 address may traverse any number of translation
points as well.
This complex topology spells the end of SMTP in its current form.
Perhaps SMTP could depend upon SMTP Client names or change into a
type of URI based notification process, where messages are held by an
HTTP server. The URI of the HTTP server might then replace reliance
upon SMTP Client IP address reputation. SMTP represents just one
protocol heavily dependent upon IPv4.
As IPv4 becomes constrained, IPv4 based access control improves.
Fully adopting IPv6 introduces another problem, IPv6 address access
controls.
-Doug
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