Experiments with Pathrate

Problem
The capacity of a network path is the maximum throughput that the path can provide to a traffic flow. For example, if the slowest link in a path is a 10BaseT Ethernet segment, then the capacity of the path will be 10Mbps.

The capacity of a path is an important network characteristic for many applications, including server selection, peer-to-peer networks, and congestion control. An important problem is to estimate the capacity of a path using end-to-end measurements, i.e., without any information from the path routers.

We have developed a capacity estimation tool called Pathrate. Pathrate uses a measurement methodology that is based on the dispersion of packet pairs and trains, as well as on some statistical estimation techniques. Note that Pathrate requires access at both the sender and the receiver of the path.

The tool is available at:

The project will involve the following:

1. Reading the paper on capacity estimation and Pathrate.
   • C.Dovrolis, P.Ramanathan, D.Moore, Packet Dispersion Techniques and Capacity Estimation, appeared at Infocom 2001.

2. Downloading and installing Pathrate at two Unix machines, one of which is outside the GATech campus.

3. Runing experiments with Pathrate about 70 times, uniformly distributed over the time period of one week. I will analyze the reported capacity estimates in terms ofaccuracy, and consistency. These experiments will be repeated for both paths.

4. The previous analysis uses the final capacity estimate of Pathrate. Using the results of step 3 (reported in the pathrate.log file at the receiver) I will analyze the Asymptotic Dispersion Rate (ADR) that Pathrate reports. I will try to determine if there is a correlation between the ADR and the time-of-day, by analysing the ADR variations across different runs.

Deliverables

• I will write a 5-10 page report showing the measurement methodology and summary of results, specifically, 
• Accuracy of Pathrate capacity estimates.
• Consistency of Pathrate capacity estimates.
• ADR variations across different runs.

Meeting Schedule
As and when required.