Re: on NAT-PT

[itojun@iijlab.net]

>The following text is an extract from
>draft-huitema-ngtrans-unmaneval-01.txt, section 3.2.1: the problem with
>address translation:
(snip)
>In short, the problem is that inserting the DNS-ALG function in a
>gateway might be beneficial in the IPv4-only to IPv6-only scenario, but
>is detrimental in the scenarios that involve dual stack hosts. Since
>there is likely to be many more dual stack hosts than IPv6 only hosts,
>this means that NAT-PT as its stands is detrimental to IPv6 transition.

	i don't think you have checked my initial posting.
	header is attached as an evidence.

itojun


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Subject: on NAT-PT
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	there are some concerns raised in the working group meeting
	with respect to NAT-PT.  it seems to me that the concerns does not
	have enough technical ground (or there are some confusions in
	understanding how NAT-PT works).  i don't see the need for revising
	NAT-PT at all.  some clarifications on the document might be nice,
	but no major re-work is needed, IMHO.

itojun


(snip)
draft-huitema-ngtrans-unmaneval-01.txt, page 4:

>This section makes an important assumption: it assumes that the NAT-
>PT acts as a bridge between two networks, one IPv6-only and the
>other IPv6-only. As a result, the DNS-ALG will translate a DNS

	"and the other IPv4-only", i suppose.

>request for a AAAA record coming from the IPv6 host into a request
>for an A record, and vice versa. The problem is that address
>translation does not know if the traffic originates from an IPv4
>only/IPv6 only node or from a dual stack node. When a dual stack
>node A wants to communicate with an IPv4 only host B, the dual stack
>host A gets either the IPv4 address of B (preferred) or an IPv6
>address which is some kind of translation of the IPv4 address of B.
>This latter situation is not wanted, because it means unnecessary
>translation between IPv4 and IPv6. This is shown in the table below.

	the answer is simple - don't use DNS-ALG if you are a dual stack node.
	use DNS-ALG as your recursive resolver only when you are IPv6 only
	node (hence you use NAT-PT translation part if the ultimate
	destionation is IPv4-only).