Behavior study of TCP over ADSL lines

Abstract : ADSL (Assymetric Digital Subscriber Line) is a transmission technology using high speed modems on shorts distances. It is usable over classical phone lines, what permit an interesting access in the scope of the Internet development : all phone's users relatively near a phone central can ask a fast access to Internet. However, ADSL has the particularity to be assymetric : the downstream bandwidth (to user) is much more important than the upstream bandwidth (to network). So, it's interesting to study the behavior of the transport protocol TCP over such physical medium.

The work contains 3 parts :
 

• Study of ADSL modems and transport protocol TCP
• Implementation of a simulator
• Simulation of throughput with variations of ADSL and TCP parameters.

Comparison with Belgacom measurements to validate the model.

The simulator

I do not have to implement a new simulator from scratch because STCP already exists. STCP is simulator of TCP over ATM realized by Sam Manthorp at EPFL. It is written in C. You can download the last version here. Note that S.Manthorp no longer work on STCP so no futher version will be released.

So, I have only added some functionnalities. The resulting code is available here.

Tool

To improve the readability of STCP config fiIe (.dat), I made a simple STCP mode for EMACS which highlights keywords and comments.
Get the file dat-mode.elc , put it where you want and add the following line to your .emacs :

(load-library "dat-mode.elc")

with the appropriate path.

krier at montefiore.ulg.ac.be