Experiments with Pathrate
| Sponsor |
Constantinos Dovrolis
dovrolis@cc.gatech.edu
318 GCATT
|
| Area |
Networks |
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:
www.pathrate.org
Here is what you need to do.
- Read the following paper on capacity estimation and Pathrate.
- Download and install Pathrate at two Unix machines.
NOTE: It is important that one of these
machines is outside the GAtech campus. For example,
you can use your undergraduate school account, if you still have
one.
- Run Pathrate about 70 times, uniformly distributed over the time
period of one week. Analyze the reported capacity estimates in terms of
accuracy (are they correct?), and consistency
(are they constant?). Repeat these experiments and analysis
for both paths (i.e., both from A to B and from B to A).
- 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) analyze the
Asymptotic Dispersion Rate (ADR) that Pathrate reports.
The ADR is an important dynamic characteristic of
network performance.
What can we learn from the ADR variations regarding the load
of the path? Is there a correlation between the ADR and the
time-of-day?
Background
Ideally you will be able to get all the background that you need
for this project from the previously mentioned paper.
Deliverables
-
Write a 5-10 page report showing your measurement methodology
and summary of results. More specifically, structure your
results in the following way:
-
Accuracy of Pathrate capacity estimates.
-
Consistency of Pathrate capacity estimates.
-
ADR variations across different runs.
Evaluation
Based on the report turned in to the sponsor of the project by the due
date.