[Outages-discussion] Wikipedia suffers global outage.

[paul e]

>> Update: Unfortunately, for many, this outage seems to have lasted
>> longer than an hour. It appears that many ISPs=92 DNS resolvers do
>> not honor the so-called Negative Cache TTL that we send (1 hour), and
>> instead use a longer value. We have circumvented this problem by
>> renaming the affected DNS record to something else.

cmadams> I'm curious: what software/settings are these "many ISPs" using
cmadams> that does this?  I've seen this mentioned before, but BIND for
cmadams> example doesn't have an option to do this IIRC.

ncache is set on the auth server for the zone, in the SOA record. It's
the 'minimum' timer, the last of the 4 timers after serial number. See
RFC 2308 for how negative caching works.

Any RFC compliant resolver should deal with this correctly. BIND does
the correct thing, both on the auth server side and as a recursive
resolver.