The Inter Providers Traffic Analyzer, is a tool to detect "anomalies", i.e. sudden peaks or troughs or abnormal events, in ISPs traffic at an Internet eXchange (follow referred as IX).
The reasons of these anomalies are various (physical problems on the interface, bad configurations, unexpected flows,...) but they always look like an anomalous fluctuation in bandwidth usage. For this reason the amount of bytes transmitted and received by the interfaces of the switches at the IX is the only parameter considered. Any layer 2, 3, 4 header inspection is performed.
In a "node" like an Internet eXchange a variation in the traffic intensity on a specific interface, can generate a small distribute fluctuation on all the other interfaces or a more significant fluctuation on a restricted number of interfaces. Sometimes it can be very difficult to find all the interfaces involved in a "critical event" and looking at each interface's graph can require a big amount of time.