[Tmrg] suggestions on fairness metrics to the TCP evaluation round-table

[Sándor Molnár]

Hi All,

We have recently completed a project on the fairness analysis of high 
speed transport protocols. One of our result is that we suggest a new 
performance metric (saturation time) that can be important from the 
dynamical aspects of interacting protocols. We have found that the 
short-term dynamics could have significant impacts on long-term 
fairness. We hope it is relevant to the topic of TCP evaluation 
round-table, especially to convergence time. Our results can be found in 
our downloadable technical report, see below.

The website of our project:
http://qosip.tmit.bme.hu/~sonkoly/Tcp/

The technical report can be downloaded from:
http://qosip.tmit.bme.hu/~sonkoly/Tcp/files/Technical_Report.pdf

I also included the abstract of the report.

Abstract
---------
The short-term dynamics of competing high speed TCP flows could have 
surprising impacts on their long-term fairness.  As a result, this could 
have a severe impact on the co-existence and, finally, the deployment 
feasibility of different seemingly promising proposals for the next 
generation networks. However, to our best knowledge, no root-cause 
analysis of the observation is available. This is the major motivation 
of our work.

The contribution of the paper is twofold. First, we present our 
comprehensive performance evaluation results of both inter- and 
intra-protocol fairness behavior of different TCP versions to get an 
overall view of these protocols. The analysis has revealed not only the 
equilibrium behavior but also the transient characteristics with the 
dynamic behavior. Second, we have performed a root-cause analysis to get 
a deeper understanding in the case of some of the promising TCP 
versions. This study not only fills the "black holes", the questions 
which remained unanswered in some cases but rather goes deeper and 
investigates questions which have never been asked yet. The analysis 
spans multiple dimensions: flow-level, packet-level, queueing and 
spectral analysis. Three loss-based (HighSpeed TCP, Scalable TCP and BIC 
TCP) approaches and the delay-based FAST are investigated in details 
with both dumb-bell and parking-lot topologies.

Regards,
Sandor