טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentFriedman Alexander
SubjectDiscouraging Selfishness in Lossy Peer-to-Peer Networks
DepartmentDepartment of Electrical Engineering
Supervisor Professor Idit Keidar
Full Thesis textFull thesis text - English Version


Abstract

We present Loss-Tolerant Selfishness Monitor (LTSM), a generic service for detecting selfish behavior in various Peer-to-Peer (P2P) applications, such as Mobile Ad-hoc Network (MANET) routing and data streaming (multicast). Resources in P2P systems are provided by the participating peer nodes themselves; each node has to contribute memory, CPU power, bandwidth, and energy. Since most nodes in a MANET are battery-powered, energy is a scarce resource in such an environment. In commercial P2P applications, nodes may exhibit selfish behavior by tampering with the P2P protocol in order to lower their cost. Consequently, it is important for such protocols to work well even when users are equipped with a selfish version of the protocol.


Unlike most previous selfishness-resistant protocols, LTSM can be used in networks subject to message loss, where selfish behavior detection is particularly challenging. For example, wireless networks, such as MANETs, inherently suffer from high packet loss rates. Furthermore, multicast systems for streaming video or audio typically use unreliable transport like UDP, since it is acceptable for some of the data to be lost.


One of our main contributions is mathematically analyzing the impact of various system parameters on the incentives for cooperation, and showing how to choose these parameters so as to ensure that full cooperation is a Nash Equilibrium, at a minimal cost.


Finally, we illustrate the applicability of LTSM in two exemplar contexts: multicast and MANET routing.