This paper presents design and evaluation of an adaptive streaming mechanism from multiple senders to a single receiver in Peer-to-Peer
(P2P) networks, called P2P Adaptive Layered Streaming, or PALS. PALS is a receiver-driven mechanism. It enables a receiver peer to orchestrate quality adaptive streaming of a single, layer encoded video stream from multiple congestion controlled senders, and is able to support a spectrum of non-interactive streaming applications. The primary challenge in design of a multi-source streaming mechanism is that available bandwidth from each peer is not known a priori, and could significantly change during a session. In PALS, the receiver periodically performs quality adaptation based on aggregate bandwidth from all senders to determine (i) overall quality (i.e. number of layers) that can be collectively delivered from all senders, and more importantly (ii) specific subset of packets that should be delivered by each sender in order to gracefully cope with any sudden change in its bandwidth. Our detailed simulation-based evaluations illustrate that PALS can effectively cope with several angles of dynamics in the system including: bandwidth variations, peer participation, and partially available content at different peers. We also demonstrate the importance of coordination among senders and examine key design tradeoffs for the PALS mechanism.