[AusNOG] My Predictions for the ISP Industry

[Geoff Huston]

On 16/03/2012, at 3:05 PM, Mark Andrews wrote:

> 
> In message <20120316025931.GA86708 at atdot.dotat.org>, Mark Newton writes:
>> On Fri, Mar 16, 2012 at 01:55:20PM +1100, Paul Brooks wrote:
>> 
>>> Which means the HE figures are conservative, and there are likely to
>>> be a whole pile more people using mechanisms like 6to4 above and
>>> beyond the real tunnel figures.
>> 
>> Yeah, but a counterpoint is that 6to4 often doesn't work.
>> 
>> Check Geoff's presso at APNIC31 for the lowdown.
> 
> And neither do 6in4 tunnels, like HE offer, if they are initiated
> from the same points in the network.
> 
> Now if people wrote their applications with multi-homed support
> that didn't suck, broken 6to4 tunnels wouldn't be a major issue.
> You don't have to wait 30 seconds to try the next address.  You can
> try more than one address.  This could be multiple IPv4 addresses,
> multiple IPv6 address or a mix of IPv4 and IPv6 addresses.

Its not the broken tunnels in 6to4 that are the major problem - it's than many (15% or so, +/- 5%) edge devices use pretty tight filter rules and deny incoming protocol 41 packets. So you can send 6to4, but you receive nothing! This is, of course, a problem, because your system only detects the brokenness by waiting for a packet for ages. And your system is also unduly optimistic. It will forget that it had to fail back to IPv4 and when you head to a new dual stack site it will do this send and wait in 6to4 all over again. And again. ...

Geoff