IPv6 Wow

Nathan Ward nanog at daork.net
Mon Oct 13 03:01:54 UTC 2008

On 13/10/2008, at 3:46 PM, Daniel Senie wrote:
> At 06:05 PM 10/12/2008, Nathan Ward wrote:
>> On 13/10/2008, at 9:53 AM, Stephen Sprunk wrote:
>>> Mikael Abrahamsson wrote:
>>>> This brings up an interesting question, should we stop announcing
>>>> our 6to4 relays outside of Europe? Is there consensus in the
>>>> business how this should be done? I have heard opinions both ways.
>>> I can understand why some folks would say stop, but unfortunately
>>> Europe has the closest public 6to4 relays to the US, and our own
>>> providers don't seem to want to put any up.  That means 6to4 will
>>> break for a great many folks who _are_ trying to use IPv6 (like
>>> developers trying to get ahead of the curve and make sure their apps
>>> don't break when the transition finally happens) but whose providers
>>> haven't clued in yet.
>> I'm sure I sound like a broken record to some, but whenever I see
>> these comments I feel the need to step up and correct them, until I
>> don't see them anymore.
>> By far the biggest end users of IPv6 are non-experimenters. Real end
>> users, many of whom do not know what an IP address is.
>> 6to4 is enabled by default in Vista - any Vista machine with a non-  
>> RFC1918 address will use 6to4. It is also available in some linksys
>> routers, and is enabled by default in Apple Airport Extreme.
> Not to rain on anyone's parade, but it'd be interesting (and  
> difficult, unfortunately) to know how many Vista machines are  
> actually on non-RFC1918 addresses. Corporate users are in many cases  
> staying with XP for a while, but they're more likely to have public  
> space than most. A great many home users have a cheap NAT box that  
> provides RFC1918 addresses.
> I do wonder whether where the Vista machines on public IPs really  
> are. I also have to wonder if performance is really better when  
> those users are routed over 6to4 in Europe from, say California, or  
> whether they'd actually get better performance if they stuck in a  
> NAT box, resulting in their using IPv4 instead?

Don't worry, you're not raining on my parade if that's what you're  
concerned about. I don't like Vista/XPSP2 having 6to4, Teredo is the  
protocol designed to connect end hosts to the IPv6 network. That works  
through NAT, and is enabled by default on Vista.
6to4 should existing in CPE devices, etc. not in end hosts. Cue  
religious war.

Also, Windows boxes that are part of a domain will only try ISATAP and  
native IPv6 - they will not attempt to tunnel IPv6 over IPv4 using  
public relays (ISATAP is an internal thing).

I did a bit of stats, and roughly 95% of packets leaving an ISP's  
aggregation layer were from hosts behind NAT (look at TTL, make  
assumptions based on initial TTL). So, 6to4 is only on 5% of  
customers, assuming that % of packets and % of customers are roughly  

Here's a mini-rant I had about Teredo traffic offlist when someone  
said they had very little 6to4 traffic. I thought it was on-list.

I suspect you'll find that Teredo contributes to a very large amount  
of it, but you won't be seeing it as you don't have a local Teredo  
relay (in my understanding of your network, anyway :-)
Even then you won't see Teredo<->Teredo, or Teredo<->NonTeredo when  
NonTeredo is on another network.

An interesting way to get a rough idea of how much Teredo<->NotTeredo  
is going on is to look at the packets going to  
teredo.ipv6.microsoft.com port 3544/UDP.
Every Vista/XPSP2 Teredo client will send a UDP packet there every 30  
seconds (IIRC), and then another packet for every new NonTeredo host  
it wants to talk to. Source UDP port is generally static and unique  
for each client host, so you can get an idea for unique number of hosts.

The periodic packets are going to be 68b (of IPv4+UDP+IPv6 = 68b),  
whereas the new-connection packets are going to be at least 76b  
(IPv4+UDP+IPv6+ICMPv6+Echo Request = 76b, then there's also the ICMPv6  
Echo Request payload). Obviously you want to add 14b if you've got  
ethernet headers and what not.

If you have netflow anywhere, you should be able to ask it an  
appropriate question with the above info.

That'll tell you number of end-to-end connections there are which may  
give you some insight there.
If you've got a netflow exporter, I'd be more than happy to run stats  
over the data to figure out what amount of Teredo there is.

Nathan Ward

More information about the NANOG mailing list