rtt_cpt.md

RTT change detection

This document explains how we detect RTT changes for the ping measurements collected in this work.

Usage

$ python rtt_analysis.py

The script will read all the ping measurement json files in data/ and produces json files with the same names in the data/rtt_analysis/ folder according to the dir section in config. path_analysis.log will be generated for debugging uses.

Four functions are provides in localutils/changedetect.py to perform changepoint detection for time series in a standalone manner. The implementation is basically a wrapper of its original R functions provided in changepoint and changepoint.np packages. For more details of each function, please check the docstring.

One difference with the original R implementation is that the output is the beginning indexes of the segments following changepoints, instead of the index before the new segment.

Output

Each json file in data/rtt_analysis/ follows the following structure:

{
    probe id (int):{
        "epoch": list of int; timestamps for each measurement,
        "cpt_normal&MBIC": list of int; same length as "epoch" list, 1 for momement of change, otherwise 0,
        "cpt_np&MBIC": list of int; same length as "epoch" list, 1 for momement of change, otherwise 0,
        "cpt_poissom&MBIC": list of int; same length as "epoch" list, 1 for momement of change, otherwise 0,
        "min_rtt": list of float, same length as "epoch" list, rtt values of the ping measurement
    }
}