Geoff Huston <[EMAIL PROTECTED]> writes:
|Indeed. The only other factor here is that it is not entirely a clean
|substitution,
|as NATs provide an alternative product which is an imperfect substitution.
|The extent
|to which the market, over the past few years, has tended towards NATs despite
|the negative effects in both local and network domains is quickly
|becoming the dominant factor in any economic consideration of this entire
|IPv4 / IPv6 area.
IMO, to consider IPv6 even as an imperfect substitution for IPv4+NAT is to
vastly overstate IPv6 functionality. IPv6 offers absolutely nothing as a
replacement for NAT's primary function: isolation of the customer network
from the (typically business-driven) address policies of the service provider
(e.g., cost, limits on number and stability, etc.). If anything IPv6 moves
in the opposite direction by providing more invasive mechanisms than existing
DHCP leases for the provider to disrupt the customer's network. It's all well
and good to speculate that IPv6 customers won't *need* the isolation that NAT
now offers with IPv4 because of (insert your favorite fantasy about transparent
renumbering or philanthropic ISPs) but none of those dodges exist at present.
Moreover, discussion of solutions that could actually fulfill the prophesy of
rendering isolation unnecessary (e.g., source routing in its guise of locator/
identifier separation) are systematically relegated to small discussion lists
where they pose no threat of implementation.
You might be able to call IPv6 an imperfect substitution for IPv4 *without*
NAT except for the glaring problem of single-address multi-homing support.
Similarly, IPv6+NAT might be said to be an imperfect substitution for IPv4+NAT,
and is probably what we will end up with if we end up with IPv6 (as an IPv4
replacement) at all. More likely v4 and v6 will continue in parallel forever
since the upgrade costs are significant, especially when you consider the
reduced functionality.
Dan Lanciani
[EMAIL PROTECTED]
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