A queueing system for modeling a file sharing principle

  • Authors:
  • Florian Simatos;Philippe Robert;Fabrice Guillemin

  • Affiliations:
  • INRIA Paris-Rocquencourt, Le Chesnay, France;INRIA Paris-Rocquencourt, Le Chesnay, France;Orange Labs, Lannion, France

  • Venue:
  • SIGMETRICS '08 Proceedings of the 2008 ACM SIGMETRICS international conference on Measurement and modeling of computer systems
  • Year:
  • 2008

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Abstract

We investigate in this paper the performance of a simple file sharing principle. For this purpose, we consider a system composed of N peers becoming active at exponential random times; the system is initiated with only one server offering the desired file and the other peers after becoming active try to download it. Once the file has been downloaded by a peer, this one immediately becomes a server. To investigate the transient behavior of this file sharing system, we study the instant when the system shifts from a congested state where all servers available are saturated by incoming demands to a state where a growing number of servers are idle. In spite of its apparent simplicity, this queueing model (with a random number of servers) turns out to be quite difficult to analyze. A formulation in terms of an urn and ball model is proposed and corresponding scaling results are derived. These asymptotic results are then compared against simulations.