  Network failures continue to plague datacenter operators as their symptoms
may not have direct correlation with where or why they occur. We introduce 007,
a lightweight, always-on diagnosis application that can find problematic links
and also pinpoint problems for each TCP connection. 007 is completely contained
within the end host. During its two month deployment in a tier-1 datacenter, it
detected every problem found by previously deployed monitoring tools while also
finding the sources of other problems previously undetected.
