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Timed token protocols are used to handle on the same local area network both real-time and non real-time traffic. This paper deals with the analysis of this type of protocols, giving worst case values for the throughput of non realtime traffic and the average token rotation time. The results have been obtained for synchronous traffic generated according to a generic periodic pattern, under heavy conditions for non real-time traffic. Finally, it is shown that the difference between the values obtained under worst case assumptions are close to those obtained under best case assumptions [8]; therefore, the method presented in this paper may be used to provide important guidelines so as to properly tune timed token protocol parameters for each specific network installation.

Peer-to-Peer (P2P) file sharing systems make use of a considerable percentage of Internet Service Providers (ISPs) bandwidth. This paper presents the Collaborative Locality-aware Overlay SERvice (CLOSER), an architecture that aims at lessening the usage of expensive international links by exploiting traffic locality (i.e., a resource is downloaded from the inside of the ISP whenever possible). The paper proves the effectiveness of CLOSER by analysis and simulation, also comparing this architecture with existing solutions for traffic locality in P2P systems. While savings on international links can be attractive for ISPs, it is necessary to offer some features that can be of interest for users to favor a wide adoption of the application. For this reason, CLOSER also introduces a privacy module that may arouse the users' interest and encourage them to switch to the new architecture.