This paper considers the single-source and multi-source multicasting problem in wormhole-routed networks. A general trip-based model is proposed for any network having at least 2 virtual channels per physical channel. The underlying concept of this model is a node sequence called skirt, which always exists in graphs of any topology. The strength of this model is demonstrated by its capabilities: (a) the resulting routing scheme is simple, adaptive, distributed and deadlock-free; (b) the model is independent of the network topology, regular or irregular; (c) the minimum number of virtual channels required is constant as the network grows in size; and (d) it can tolerate faults easily. Using 2 virtual channels/physical channel, it is shown how to construct a single trip in faulty hypercubes and multiple trips in fault-free meshes. Simulation experimental results indicate the potential of the model to tolerate faults with very little performance degradation and to reduce multicast latency with multiple trips.