Worst-Case Nash Equilibria in Restricted Routing

  • Authors:
  • Pinyan Lu;Changyuan Yu

  • Affiliations:
  • Institute for Theoretical Computer Science, Tsinghua University, Beijing, P.R. China 100084;Institute for Theoretical Computer Science, Tsinghua University, Beijing, P.R. China 100084

  • Venue:
  • WINE '08 Proceedings of the 4th International Workshop on Internet and Network Economics
  • Year:
  • 2008

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Abstract

We study a restricted related model of the network routingproblem. There are m parallel links with possibly different speeds,between a source and a sink. And there are n users, and each user ihas a traffic of weight w i to assign to one of the links from asubset of all the links, named his/her allowable set. We analyzethe Price of Anarchy (denoted by PoA) of the system, which is theratio of the maximum delay in the worst-case Nash equilibrium andin an optimal solution. In order to better understand this model,we introduce a parameter λ for the system, and define aninstance to be λ-good if for every user, there exist a linkwith speed at least $\frac{s_{max}}{\lambda}$ in his/her allowableset. In this paper, we prove that for λ-good instances, thePrice of Anarchy is $ \Theta \big( \min\{\frac{\log \lambda m}{\log\log \lambda m}, m\}\big)$. We also show an important applicationof our result in coordination mechanism design for task schedulinggame. We propose a new coordination mechanism, Group-Makespan, forunrelated selfish task scheduling game. Our new mechanism ensuresthe existence of pure Nash equilibrium and its PoA is $O\big(\frac{\log^2 m}{\log \log m}\big)$. This result improves thebest known result of O(log2 m) by Azar, Jain and Mirrokni in[2].