On Wed, 12 Dec 2001, Brian E Carpenter wrote:
> > The sentence refers to:
> >
> > whether the encapsulating IPv4 address is consistent with the encapsulated
> > 2002:: address.
> >
> > 1) You cannot receive IPv6 packets from *relay* which have 2002::/16
> > prefix. If you do, someone is using 6to4 improperly. We agree on this.
>
> Actually, the relay (according to RFC 3056) is a 6to4 router that also has a
> native IPv6 interface. It certainly can source 2002: packets from its own
> site, as well as native source addresses from the native interface.
> You can apply the consistency check, but not to relayed packets with
> a native source address.
I meant relay as a box that has relay functinality. Local packets are of
course fine, and the consistancy check applies there so that is no
problem.
But the sentence IMO basically says:
"there are packets [referring to 2002 prefix] coming from relay which
must not be checked".
By referring to 2002, the consistancy check might not be performed for
_2002_ addresses (which it should not receive except for the local ones
where the check would apply), thus relays becoming a source for
inconsistant 2002 packets.
> > 2) How do you check that 3ffe:ffff::1 is consistant with an IPv4 address?
> >
> > You cannot check *consistancy* unless the addresses are of form
> > 2002:<anything at all> and <IPv4 anything at all>. Only 2002 and IPv4 can
> > be compared.
>
> Yes. 3056 says nothing different. I see no error in the 3056 text.
Ok, I guess this is one of those way of thinking issues; whether the
'consistancy check' is basically:
1)
consistancy_check(ipv6, ipv4) {
if (bits 16-47 of ipv6 equal ipv4)
return true
else
return false
}
or:
2)
consistancy_check(ipv6, ipv4) {
if prefix of ipv6 is 2002 {
if (bits 16-47 of ipv6 equal ipv4)
return true
else
return false
}
else
return true // because consistancy is not defined for non-2002
}
That is, what's the defined consistancy between native ipv6 and ipv4
addresses.
Thus skipping the consistancy check becomes a bit of a blur.
--
Pekka Savola "Tell me of difficulties surmounted,
Netcore Oy not those you stumble over and fall"
Systems. Networks. Security. -- Robert Jordan: A Crown of Swords
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