IPv6 delivery model to end customers

TJ trejrco at gmail.com
Sun Feb 8 22:16:32 UTC 2009

>I didn't know where to jump in in the current discussion and what I wanted
>to discuss was quite general, so I thought I'd create a new thread instead.

And the right move, IMHO! (FWIW)

>So, anyone saying IPv6 is ready for prime-time whereever IPv4 is used, has
>very simplified view of the world. Yes, IPv6 works in the classic routed
>network model where everything is statically set up (often manually), for
>example with an ISP run CPE and static/dynamic routing and a fixed /48
>issued for that customer and SWIPed. Then it's easy to delegate reverse-DNS
>etc to the customer DNS.

We would need to differentiate between the protocol being ready, and the
vendors' support of the protocol here.  
In other words, the ivory tower work is done - now it is up to the real
Oh, and yes, in that "enterprise" deployment scenario we are almost ready!

>My ideal model would be to replace the above mentioned L2 device with a
>small and simple L3 device (L3 switch) with very small TCAM (TCAM size 6-8
>times port number should be enough), where this device uses link-local with
>the CPEs (would require all customers to actually have a router at home),
>hands out prefixes via DHCPv6-PD, inserts route towards customer link-local
>address, provisions anti-spoofing ACLs on that port, logs what prefix was
>given out to each port at what time, and off we go. (Rationale for link-
>local only is to have only customer devices in "Customer IP space" and only
>ISP infrastructure in that IP-space. This is equivalent to "ip unnumbered"
>in IPv4 in my view.) I have pitched this idea in the IETF v6ops list and
>it's now included in a draft that lists different models of
>IPv6 delivery.
>As far as I know, this IPv6 L3 device doesn't exist (in the pricerange
>needed for massive residential roll-out anyhow).

While that sounds functional/useful, I would first ask - to the
residential-focused ISPs - how they currently plan (or how are they moving
towards) delivering IPv6 to their clients?

>So, in the meantime, to get IPv6 to the end customers I see two ways
>(because they need to fit into the IPv4 security model mentioned above).
>We have either 6to4 tunneling (Cisco 7600 does this very well and code for
>Linux CPEs exist already), or we try to fit IPv6 into the IPv4 security
>model. Current recommendation from the swedish "city networks association"
>(they consists mostly of entities running LANs to residential, I believe
>there are approx 400-500k ports of that in Sweden at this time) is that if
>you don't know if your network is secure against IPv6, block it at the
>ethertype level (I'll come back to the security risks later).

6to4 works just fine, assuming you and your customers are OK with tunneling
and relays ... up until there are no more public IPs.  
Then you are talking about "A+P + 6to4" or somesuch.  *EVEN MORE FUN*

>So, what is the security problem with IPv6 in an IPv4 network? Well,
>an IPv4 network where security is done via ARP inspection, DHCP snooping
>L3 ACLs. Now, insert rogue customer who announces itself via
>RA/DHCPv6 and says it's also DNS. Vista machines will get itself an IPv6
>address via RA, ask for DNS-server via DHCPv6, so if the rogue customer can
>do some NAT-PT like functionality, they are now man in the middle for all
>the IPv4 traffic (because between the customers it's IPv6 and the L2 device
>doesn't know anything about that). I don't know if this has actually been
>done, but I see no theoretical problem with it, if someone can come up with
>something, please do tell.

"RA Guard"; learn it, live it, love it.
At some point, maybe SEND/CGA as well ... but that isn't a "ready today"

>So, my view on IPv6 is that I would love to roll it out to all residential
>customers, but unfortunately all the development done for IPv4 security has
>gone unnoticed by the people developing IPv6 and now it's behind and needs
>to catch up, or pitch a different model and then get vendors to develop
>products that do this.

I think that is a bit harsh - the work hasn't gone unnoticed.  
Rather, it has not been high enough on the list of priorities and is
therefore, yes, lagging. 

>In the mean time, we do (and I encourage everybody else to do the same)
>support 6to4 and Teredo, plus we do IPv6 native in the core and peering
>where possible plus we give IPv6 to customers where we're able to securely
>(mostly transit customers and corporate customers with IPv6 capable CPEs).


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