Mark Andrews marka at
Fri Nov 29 07:28:01 UTC 2013

In message <alpine.DEB.2.02.1311290622170.1157 at>, Mikael Abrahamsson writes:
> On Fri, 29 Nov 2013, Mark Andrews wrote:
> > You can hand out /48 as easily with 6rd as you can natively.
> >
> > It's only when the ISP is lazy and encodes the entire IPv4 address
> > space into 6rd thereby wasting most of the IPv6 address space being
> > used for 6rd that a /60 appears to be generous.
> You're contradicting yourself here.

What contradiction?  You need to break up the IPv6 address allocation
for both PD and 6rd.  I would say PD is slightly more complicated
than 6rd as you also want to optimise routing more with PD.  With
6rd you do the optimisation using the IPv4 addresses.

> Yes, you're right about the technical 
> solution, but it's not as easy (you need backend systems). Also, not all 
> products support the variability of subnet lengths that the standard 
> allows.

So who is shipping cr*p that claims to support RFC 5969 yet doesn't
all arbitary size 6rd domains?

The point of have a standard is so equipement from different
manufactures can work together.  A CPE device that can't accept all
legal values should be thrown in the bin.

> So if you're not mapping the entire space (actually some products only 
> allow /32 IPv6 space) 1-1 you're making the whole solution harder due to 
> complexity in your backend system plus you're limiting the amount of 
> customer gear that will support the solution.

I claim bovine excrement on customer gear.  Show me where the
6rdPrefixLen is defined to be 32?  Even with RFC 5569 it was up to
32 and the IPv4MaskLen is 0.

> -- 
> Mikael Abrahamsson    email: swmike at
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

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