Many emerging real-time applications generate layered data streams, which can be used effectively to adapt multicast real-time transmissions to heterogeneous bandwidth environments. However, these applications have not changed with regard to being sensitive to transient congestion and cannot wait a full round-trip time for sender-initiated adaptation. In this paper we propose the selective truncating internetwork protocol (STRIP) supporting layered data transfer, and capable of handling congestion at a finer level of granularity by truncating packets, i.e., stripping off less important data. STRIP inter-operates with the traditional IP infrastructure and can be introduced in a step-by-step fashion, starting where the benefits are obvious, for example with routers which are connected to bandwidth constrained links and which have a surplus of processing capacity. We describe the design and architecture of STRIP and compare it with solutions for differentiated forwarding on a per-packet basis. STRIP provides a simple mechanism that can meet the demands for real-time flows effectively by supporting low delay forwarding, avoiding data-unit reordering, and supporting various drop priorities at the same time