Tech Report: Congestion Avoidance and Control

Date Completed: June 2009

In this Tech Report, we start by introducing the principles of congestion control and its importance in the stability of the Internet. We then move on to provide some background information on TCP’s congestion control algorithms as well as on Explicit Congestion Notification (ECN). Afterwards, we explain the concepts behind the major Active Queue Management (AQM) mechanisms and explore their designs. We conclude the report by stating our opinion regarding “fairness” and will reinforce our position by introducing the “re-ECN” initiative.

Tech Report: IEEE 802.11 and Propagation Modeling: A Survey and a Practical Design Approach

Technical Report, Masood Khosroshahy (2007)

Abstract—Due to known difficulties of researchers in the networking domain regarding experimentation of their ideas in actual networks, network simulators have become indispensable tools for investigating and validating various ideas in all layers of the network. In this survey, we inspect the implementations of IEEE 802.11 PHY-MAC and propagation models of some of the well-known, open-source network simulators. The chosen simulators are: NS-2, OMNeT++, GloMoSim, J-Sim and JiST/SWANS. The study concentrates on the availability and implementation flexibility of MAC modes, physical layer features and propagation models. This survey could help the research community in determining the state-of-the-art of IEEE 802.11 implementations and, to the best of our knowledge, is the first such study published in the open literature. To facilitate the ongoing and future network simulator developments, we also present our design and implementation approaches in successfully developing a prototype of a detailed IEEE 802.11a PHY layer along with the propagation models.

Index Terms—IEEE 802.11, Network Simulators, Propagation Models, WiFi

Download the Tech Report.

Project: Vigenere Cipher --A Case Selected for Properly Designing a Software before Realizing It

Date Completed: December 2005

Introduction to the project:

The Vigenere cipher is a cipher based on using successively shifted alphabets, a different shifted alphabet for each of the 26 English letters.

The carried out task: Writing a program in Java that ciphers and deciphers messages. The system will take a text file, a keyword, and the desired operation (ciphering or deciphering) as inputs from its user. The output of the system consists of the creation and display of original and ciphered/deciphered files.

Here is the Report , the Presentation and the Project Files.

Project/Paper: IP Telephony

Date Completed: May 2005

Project Description:

This project builds on the work that went to the implementation part of my B.S. thesis. It covers technologies such as: Session Initiation Protocol, DiffServ QoS Architecture, SIP Network Modules Development, and Network Simulation. I have written a research paper based on the outcomes of this project with the title: “Utilizing DiffServ and SIP Contact Header for Real-time Fax Traffic Engineering”

Abstract—This paper focuses on the transmission of real-time fax in IP networks. For this purpose, the best current practices, i.e., utilization of the Session Initiation Protocol (SIP) as the signaling protocol along with ITU-T T.38 recommendation, are adopted. Two traffic engineering measures: utilization of SIP contact header and DiffServ QoS architecture, are proposed to streamline the implementation of the real-time FoIP. Network simulation results show that the proposed architecture, compared to the “Best Effort” service, has much less transmission time and jitter, and packets received are in correct sequence. Moreover, SIP contact header reduces load on network’s specialized resources. Therefore, this layout is a viable alternative for traditional PSTN fax.

Please click here to download the full paper.

Please click here to download the PowerPoint presentation of the paper.

The paper was accepted and presented at:

18th Annual Canadian Conference on Electrical and Computer Engineering, CCECE05, May 1-4, 2005, Saskatoon Inn, Saskatoon, Saskatchewan, Canada Please click here to download the conference program.

J-Sim network simulator has been utilized in this project. Please click here to download the simulation files.