News Brief: 2013-2018 summary

Most projects on this site cover the pre-PhD period. The projects done during the PhD are documented under PhD Thesis as well as under Publications. Projects after the PhD, i.e., 2013 onward, are largely undocumented due to confidentiality restrictions, as I have been working in the industry. The projects that I have worked on in this period and recently are in Big Data and Deep Learning. There are few items that I have worked on on the side and could publish:

  • Productionization of TensorSpark in yarn-cluster mode (tested in an HDP cluster): I contributed to the TensorSpark project, helping people run it in a YARN-based production environment. TensorSpark implements Downpour SGD, a Google idea. This asynchronous stochastic gradient descent (SGD) is intuitively more suitable for cloud-based Spark clusters, as your cluster workers are typically sprinkled all over the data center and you want to avoid a network bottleneck which affects few workers to slow down too much the model training. See the GitHub issue/PR for details.
  • Class Activation Map is a great tool to help fine-tune and better understand a Deep Learning model (ConvNets). I created a notebook to help with this. Tech setup: Jupyter notebook / Python / TensorFlow / VGG model / Caltech256 dataset

While the above items are developed in my own time, I used them subsequently in the projects of the companies that I have worked for at the time.

Project: A Presence-based Messaging Application

Date Completed: December 2009

Here is the Report of this project.

As per the specification, a presence-based messaging and file-exchange application has been designed and implemented. Here is the scenario:

  • Clients connect to the server and immediately declare their presence.
  • A connected client can initiate a session by sending the request to the server along with the preferred number of clients in the session.
  • The server application checks the number of available clients for the session.
  • The server application initiates a session between the clients, if preferred number of clients are available.
  • When the session is underway, participants can exchange messages and files.
  • Only the session initiator can terminate the session.

Tech Report: Peer-to-Peer Traffic

Date Completed: August 2009

This Tech Report deals with Peer-to-Peer protocols. We start by giving a brief account of history of P2P applications and then cite from some of the P2P traffic measurement studies. P2P traffic identification methods and the recent P2P traffic optimization schemes constitute the core of this report, in which we examine the state-of-the-art in this field.

Tech Report: BitTorrent

Date Completed: July 2009

BitTorrent protocol has emerged as the most popular P2P protocol over the past years. The core BitTorrent protocol has been designed and implemented by Bram Cohen in 2001.

The protocol is especially useful for distributing large popular files (like open-source operating system distributions) as its performance improves as the number of interested connected peers increases. The way in which BitTorrent operates lessens the burden (hardware costs and bandwidth resources) of servers hosting the files and distributes that burden among all the peers currently connected, reducing costs significantly for original content distributors as a result. Connected peers share the task of serving the content to newly-connected peers and a “tit-for-tat” mechanism ensures fairness among all the peers. This method of content sharing also improves redundancy in the overlay network (formed around that specific content), as a probable malfunctioning of the original content provider does not render the content unavailable. In this Tech Report, we explain the functionality of the BitTorrent protocol and its various system components.

Project/Paper: UARA in edge routers: An effective approach to user fairness and traffic shaping

Date Completed: June 2009


The ever-increasing share of the peer-to-peer (P2P) traffic flowing in the Internet has unleashed new challenges to the quality of service provisioning. Striving to accommodate the rise of P2P traffic or to curb its growth has led to many schemes being proposed: P2P caches, P2P filters, ALTO mechanisms and re-ECN. In this paper, we propose a scheme named "UARA:User/Application-aware RED-based AQM" which has a better perspective on the problem: UARA is proposed to be implemented at the edge routers providing real-time near-end-user traffic shaping and congestion avoidance. UARA closes the loopholes exploited by the P2P traffic by bringing under control the P2P users who open and use numerous simultaneous connections. In congestion times, UARA monitors the flows of each user and caps the bandwidth used by "power users" which leads to the fair usage of network resources. While doing so, UARA also prioritizes the real-time traffic of each user, further enhancing the average user quality of experience (QoE). UARA hence centralizes three important functionalities at the edge routers: (1) congestion avoidance; (2) providing user fairness; (3) prioritizing real-time traffic. The simulation results indicate that average user QoE is significantly improved in congestion times with UARA at the edge routers.

Read More

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.