[2014-07-12 08:17:15 | Lars Rohrbach]
The slowness in LDAP authentication turned out to be just one of the more noticeable symptoms of the real problem, which was that our border firewall CPU load was spiking again, causing occasional dropped packets.
The root cause was some planned network scanning for security research purposes. This scanning was halted, and all services returned to normal. Scanning will later resume, rate-limited to keep resultant firewall load manageable.
Resolved as of 2014-07-11 17:00:00