Overview

• This is an end-to-end available bandwith measurement tool that uses active packet-train probing. Available bandwidth is defined as the residual bandwidth on the path, which can be calculated as path capacity minus path load.

• Using active probing to get accurate network measurement, we need carefully tune the probing parameters: (1) probing packet size, (2) number of probing packets, and (3) initial probing gap, i.e., probing speed.

• Although all these parameters are important to get correct measurement, initial probing gap is the most important parameter to control for accurate available bandwidth measurement. The most accurate measurement is obtained when the packet-train sending rate at source equals its arriving rate at destination, where the initial packet pair gap that gives a high correlation between the packet gap changes and the competing traffic throughput on the the tight link. This IGI/PTR tool is designed based on this insight.

• IGI and PTR share the probing procedure, which is illustrated in the right figure. The main difference between them is that IGI focuses on calculating background traffic load, while PTR directly calculates packet transmission rate, to estimate end-to-end available bandwidth.