user-relative names - was:[Re: Yahoo and IPv6]

Joel Maslak jmaslak at
Wed May 18 04:18:44 UTC 2011

On Tue, May 17, 2011 at 9:37 PM, <Valdis.Kletnieks at> wrote:

> Unless you end up behind a fascist firewall that actually checks that the
> EUI-64 half of the SLAAC address actually matches your MAC address - but we
> all
> know that firewalls are weak at IPv6 support, so probably nobody's actually
> doing that checking. :)

Nevermind you can change your MAC address easily on most networks, since
most don't provide any reasonable way of verifying that L2 packets are from
where they claim to be.

FWIW, Windows Vista and 7 default to using privacy addresses with SLAAC.
Even without that, today, in the IPv4 NAT world, it's pretty much possible
to uniquely identify a user nearly almost all of the time anyhow - at least
for web access.  This is thanks to browser fingerprinting - see

There's a lot of FUD about IPv6.  Yes, the addresses are longer.  But which
is easier - remembering all the intermediate layers of network translation
(likely two boxes for nearly every residential and small business user) or
an IPv6 address that is the same, regardless of whether you are another
customer on the same ISP, a public internet user, or an internal corporate
user?  Nevermind what it is like to debug IPSEC/PPTP/L2TP, SIP, or P2P
protocols with just one NAT involved.  Imagine doing that with two NAT
devices (CGN + home NAT).  If you haven't had that unfortunate pleasure,
than I envy you!  There's also no reason we should have to remember our IPv6
addresses.  Seriously.  There are about 50 protocols to name things on
networks, many of which are scope aware.  Among other things, it's why we
don't typically have to remember MAC addresses - ARP works and it works
well.  Just because bad design forced us to remember IPv4 addresses doesn't
mean our IPv6 networks should carry over that brokenness.

IPv6 is also already in widespread use (I would guess all 500 of the Fortune
500 have it somewhere on their network, albeit quite likely not
intentionally).  I use it almost daily for my Apple MobileMe account (albeit
typically tunneled over IPv4, all behind-the-scenes).  I also use it when I
stream music around my house (Bonjour will utilize IPv6, AirTunes typically
uses it).  Windows admins might be using it too (DirectAccess; MS Remote
Assistance if firewalls block connectivity then Windows will set up a direct
IPv6 link, tunneling through your firewalls and NAT...).  And Grandma very
well may be using it today (Windows "Home Groups" use IPv6).  I would guess
half of the family members of NANOG list subscribers are using IPv6 on a
daily basis - TODAY.  The danger is in ignoring what is already on your
networks.  Sure, you can't get to most websites via IPv6.  But it's being
used for plenty of useful work today, although mostly as a way around
firewalls and as isolated islands (not connected to the global IPv6

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