On Wednesday, April 24, 2013 07:04:55 AM S Moonesamy wrote: > Hi Simon, > > At 04:33 24-04-2013, Simon Perreault wrote: > >I'm sorry, I've read section 5 and that still doesn't make sense to me. > > I share your opinion. > > >How does that work? Is there a NAT46 in between? > > That question was never discussed within the working group. My guess > is that there would have to be a transition mechanism in between for > that to work. > > >As IPv4-mapped IPv6 addresses do not go on the wire, this still > >doesn't make sense to me! > > I should have explained it better; the IPv4-mapped IPv6 address does > not go over the wire. > > >IPv4-mapped IPv6 addresses have two uses: > > > >1) They are used internally on a single host, between a userland app > >and the kernel, to represent IPv4 addresses using an IPv6-only > >socket. The address never leaves the host. It can be considered an > >implementation detail. They are most useful when porting an > >IPv4-only app to dual-stack. Newer applications should never use > >IPv4-mapped IPv6 addresses, and it is good practice to disable them > >explicitly. > > > >2) In various signalling protocols, to represent an IPv4 address in > >an IPv6 address field. This is protocol-specific. It is used only > >for signalling, never as actual addresses in IPv6 packet headers. > > > >At this point, I'm guessing that it would be better to forget about > >IPv4-mapped IPv6 addresses, although I still don't understand > >exactly what your intent is. > > Thanks for the explanation. The intent was to ask the IPv6 > Maintenance working group to review the text. I'll follow your guess > as it makes sense to me. By the way you will be credited in the > document shepherd write-up for your feedback.
It was discussed. The case here is #2. In SPF there are various mechanisms that can be used in an SPF record to identify sources from which mail is authorized. Two of these mechanisms directly specify IP addresses. "ip4" is used to specify IPv4 addresses and "ip6" is used to specify IPv6 addresses (that's a design decision that was made in 2003, so it is what it is). The intent of the text was to communicate that if the SPF verification process (which could possibly be running in any internet networking environment you might think of) were presented with an IPv4-mapped IPv6 address, the correct way to check if that address is authorized is using the IPv4 part of the address to check against an "ip4" mechanism. I hope that clarifies the intent. If that makes sense, I would really appreciate suggestions as a better way to word it. Scott K (4408bis editor) -------------------------------------------------------------------- IETF IPv6 working group mailing list [email protected] Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
