Re: 6to4 using ::FFFF:0000:0000/96 (mail.comcast.net AAAA record weirdness)

[David Malone <dwmalone@maths.tcd.ie>]

On Mon, Jan 28, 2008 at 11:17:47AM +0100, R?mi Despr?s wrote:
> >>1. The RFC on Basic Socket Interface Extensions for IPv6 (RFC 2553)
> >>states in its section 3.7:
> >><< Applications may use PF_INET6 sockets to open TCP connections to IPv4
> >>   nodes, or send UDP packets to IPv4 nodes, by simply encoding the
> >>   destination's IPv4 address as an IPv4-mapped IPv6 address, and
> >>   passing that address, within a sockaddr_in6 structure, in the
> >>   connect() or sendto() call. >>

> >How important is this feature in practice?  Could we deprecate it?

> IMO deprecating it would be a bad step backward!

Yes - there is a (reasonable) school of thought that says that
draft-itojun-v6ops-v4mapped-harmful missed the mark, and that it
is actally better to write server applications to use a single
socket to accept both IPv4 and IPv6 clients. You then always use
mapped addresses to represent IPv4 addresses in ACLs/firewalls/...
Deprecating this would make life harder for people who have chosen
this model of managing dual-stacked applications.

	David.