Peer-to-peer (P2P) applications have the potential to improve net- work scalability and create a community in which resources are under the shared responsibility of its members. Current popular solutions target specific applications, such as file sharing and VoIP (Voice-over-IP), but important challenges prevent P2P technology from having wider acceptance in other services. Overwhelmed by interdomain traffic generated by P2P applications that build overlays asymmetric to the network topology, ISPs offer at a home user level only connections with asymmetric bandwidth. This measure efficiently hinders P2P applications. This paper introduces a new incentive model for overlay applications and ISPs to collaborate and to create at the same time a win-win situation. The approach combines two principles: (1) ISPs and P2P applications communicate to correct overlay asymmetry and (2) ISPs diminish bandwidth asymmetry by providing users additional bandwidth reserved for intradomain traffic.