Subject: notes on A6 transition from AAAA
From: Alain Durand <[email-masked]>
To: [email-masked], [email-masked]
Date: Sun, 18 Mar 2001 20:05:32 -0800

Transition from AAAA to A6

    Stub resolvers that ask for AAAA in queries with the RD bit turn ON
    will be returned AAAA answers.

    Resolvers that have send queries with RD bit OFF and ask for AAAA
    will be returned whatever is available, A6 or AAAA. Note that they
    SHOULD issues A6 queries in the first place.

    The entity that in its server role received a query with the RD bit
    turn ON and process that request in its resolver role issues
    A6 queries with the RD bit turned OFF is responsible for the
    systhesis of AAAA from A6 records. This entity MUST try first A6
    then MAY try AAAA queries to process the request.

    A authoritative server that only has AAAA entries and
    is asked for an A6 record MUST NOT synthesize A6 records
    from the AAAA ones. There is no restriction on populating both
    types, but it is strongly recommended against, and in such a case,
    both RRsets MUST be identical.

    If a query does not contain EDNS indicator, then any IPv6 addresses
    contain in additional data section MUST be AAAA.

    Root and TLD zones MUST only contain A6 with prefix of 0.