I would support deprecating IPv4-compatible addresses and compaq asked for
this 2 years ago :-----) we were told no. but we did not have 6to4
either.
/jim
On Fri, 11 May 2001, Erik Nordmark wrote:
>
> > But what seems to be ambiguous is IPv4-compatible-IPv6
> > addresses. There is no reference about this except in
> > getipnodebyaddr() in RFC2553 which says that initial 12 bits
> > needs to be stripped and then query is made for the IPv4 address
> > in in-addr.arpa domain.
>
> IPv4-compatible addresses are very very very different than IPv4-mapped
> addresses. Talking about both in the same email is a source of confusion :-(
>
> IPv4-compatible addresses, just like the 6to4 addresses, are real
> IPv6 addresses i.e. they always appear in IPv6 packet headers.
> Neither one of them can be crafted by getaddrinfo etc from knowing the
> IPv4 address of the peer, because the peer might not have configured that
> IPv6 address on an interface.
> [To contrast: The IPv4-mapped are just an *encoding* of an IPv4 address in an
> sockaddr_in6 structure thus it should be semantically identical to the
> underlying IPv4 address]
>
> So IPv4-compatible addresses (6to4 addresses, "native" IPv6 address) must
> be configured on the nodes and must be retrieved from something like the DNS.
>
> > This seems to suggest that we need to have a PTR record for
> > IPv4-compatible-IPv6 addresses in in-addr.arpa domain as is the
> > case with A records (IPv4 addresses) and not IP6.INT domain.
>
> I'm aware of that optimization but it isn't clear to me that it
> is needed or desired.
>
>
> > Or does it mean that forward resolution uses AAAA records for
> > compatible addresses and in-addr.arpa domain (IPv4 address
> > reverse domain) for address -> nodename resolution.
>
> Forward uses AAAA (or A6).
>
> > Actually there is no flag similar to AI_V4MAPPED for generating
> > IPv4-compatbile-IPv6 address?? Is this a required one?
>
> There wouldn't be a need.
> The AI_V4MAPPED flag is there so that the application can specify whether
> it wants to see IPv4 addresses as AF_INET addresses or as AF_INET6 addresses
> containing an IPv4-mapped address.
>
> > Any ideas regarding IPv4-compatbile-IPv6 addresses.
>
> Perhaps we should deprecate them?
> They are only useful for automatic tunneling and 6to4 tunneling is
> essentially a superset of automatic tunneling.
>
> Erik
>
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