  Understanding network health is essential to improve Internet reliability.
For instance, detecting disruptions in peer and provider networks facilitates
the identification of connectivity problems. Currently this task is time
consuming for network operators. It involves a fair amount of manual
observation because operators have little visibility into other networks. In
this paper we leverage the RIPE Atlas measurement platform to monitor and
analyze network conditions. We propose a set of complementary methods to detect
network disruptions from traceroute measurements. A novel method of detecting
changes in delays is used to identify congested links, and a packet forwarding
model is employed to predict traffic paths and to identify faulty routers in
case of packet loss. In addition, aggregating results from each method allows
us to easily monitor a network and identify coordinated reports manifesting
significant network disruptions, reducing uninteresting alarms. Our
contributions consist of a statistical approach providing robust estimation for
Internet delays and the study of hundreds of thousands link delays. We present
three cases demonstrating that the proposed methods detect real disruptions and
provide valuable insights, as well as surprising findings, on the location and
impact of identified events.
