This paper presents the design and implementation of the Dynamic Transport Library (DTL), a UDP-based reliable transport library, initially designed for – but not limited to – peer-to-peer applications. DTL combines many features not simultaneously covered by any other transport library including: i) Wide scope of congestion control levels starting from less-than-best-effort to high-priority, ii) Prioritization of traffic relative to other non-DTL traffic, iii) Prioritization of trac between DTL connections, iv) NAT-friendliness, v) Portability, and vi) Application level implementation. Moreover, DTL has a novel feature, namely, the ability to change the level of aggressiveness of a certain con-nection at run-time. All the features of the DTL were validated using a controlled environment as well as the Planet Lab testbed.

Paper to be published at the INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING AND NETWORKING – ICDCN, January 3-6 2012, Hong-Kong.

DTL – Dynamic Transport Library for P2P Applications

Abstract:

When evaluating Peer-to-Peer content distribution systems by means of simulation, it is of vital importance to correctly mimic the bandwidth dynamics behavior of the underlying network. In this paper, we propose a scalable and accurate flow-level network simulation model based on an evolution of the classical progressive filling algorithm which implements the max-min fairness idea. We build on top of the current state of art by applying an optimization to reduce the cost of each bandwidth allocation/deallocation operation on a node-based directed network model. Unlike other works, our evaluation of the chosen approach focuses both on efficiency and on accuracy. Our experiments show that, in terms of scalability, our bandwidth allocation algorithm outperforms existing directed models when simulating large-scale structured overlay networks. Whereas, in terms of accuracy we show that allocation dynamics of the proposed solution follow those of the NS-2 packet-level simulator by a small and nearly constant offset for the same scenarios. To the best of our knowledge, this is the first time that an accuracy study has been conducted on an improvement of the classical progressive filling algorithm.

Paper published at the 5th International ICST Conference on Performance Evaluation Methodologies and Tools, Paris, Frace, May 16-20 2011.

Accurate and Efficient Simulation of Bandwidth Dynamics for Peer-To-Peer Overlay Networks

Abstract:

In this paper we present what are, in our experience, the best practices in Peer-To-Peer(P2P) application development and how we combined them in a middleware platform called Mesmerizer. We explain how simulation is an integral part of the development process and not just an assessment tool. We then present our component-based event-driven framework for P2P application development, which can be used to execute multiple instances of the same application in a strictly controlled manner over an emulated network layer for simulation/testing, or a single application in a concurrent environment for deployment purpose. We highlight modeling aspects that are of critical importance for designing and testing P2P applications, e.g. the emulation of Network Address Translation and bandwidth dynamics. We show how our simulator scales when emulating low-level bandwidth characteristics of thousands of concurrent peers while preserving a good degree of accuracy compared to a packet-level simulator.

Paper published at the ACM Simutools 2011 Conference (industrial track), Barcelona, Spain, March 2011.

Mesmerizer: An Effective Tool for a Complete Peer-to-Peer Software Development Life-cycle