Hi Lorenzo,

On 2011-06-10 06:20, Lorenzo Colitti wrote:
> On Thu, Jun 9, 2011 at 10:57 AM, Keith Moore 
> <[email protected]>wrote:
> 
>> So the existence of 6to4 is in itself a significant barrier for IPv6
>> deployment for server operators and content providers.
>>
>> non sequitur.   Existing server operators and content providers can easily
>> provide 6to4 addresses for their servers and content, which will be used in
>> preference to native v6 addresses.
>>
> 
> No. According to Geoff's data, one of the main reasons 6to4 fails is a
> firewall that blocks IPv4 protocol 41 traffic. Even if content providers
> published 6to4 addresses, those connections would still fail.

To be clear, that statistic applies to clients whose SYN packet reaches
the server, but who never respond to SYN/ACK. It's a presumption that
the problem is Protocol 41 filtering - probably correct, but there are
other possible causes.

Also, we have no possible way of knowing how many clients send SYN packets
towards a 6to4 anycast relay, but those packets are blackholed and never
reach the intended server. From the client's viewpoint, this also looks
like a missing SYN/ACK, leading to retries and eventual fallback to IPv4.

In other words, the real failure rate may be much worse than Geoff reports,
but we have no way of measuring it.
> 
> 
>> Application developers should develop using manually configured tunnels,
>> not 6to4. At least they don't have a 20% failure rate.
>>
>> How do you know?  How do you even measure the failure rate of manually
>> configured tunnels in the aggregate?
>>
> 
> In a similar way as Geoff measured 6to4 - looking at SYNs. I suspect that
> the answer will be that much fewer users have configured tunnels than 6to4,
> and that the failure rate is much lower.

Er, I'm currently on 2001:388:f000::xxxx
Do you have an algorithm that will tell you whether that is native
or a configured tunnel?

    Brian
> 
> 
>>  I don't think you can monitor that kind of traffic the way you can 6to4,
>> because the traffic patterns are much more constrained.   It's been awhile
>> since I used manually configured tunnels (from a well-known tunnel broker).
>>  But the one time I did try them, 6to4 worked better overall - lower latency
>> and lower failure rate.
>>
> 
> Please try again. You will be pleasantly surprised.
> 
> 
> 
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