A look at the throughput graph clearly showed a drop to almost zero around 12:20 UTC+2:

A temporary outage on the AMS-IX internet backbone caused an extended outage of internet traffic across Netherlands.

Quote

Dear Tech-L subscribers,

Today Wednesday 13/05/2015 at 12:20 UTC+2 an installation engineer working on the PE under maintenance in EQUINIX AM3, while testing one of the newly installed 100GE modules, accidentally placed a loop on the ISP peering VLAN.

DETAILS:

The loop caused a high CPU on all backbone and customer modules resulting in many BGP sessions dropping.
The incident lasted 10 minutes.
BGP sessions are restoring.

The situation has normalized again.