In this paper we present ToCL a thread oriented communication library specially designed to fully exploit multithreading in a multi-networked cluster environment. ToCL provides a basic set of primitives to handle zero-copy message passing between application threads spread among cluster nodes. Large messages are fragmented and sent to remote threads as single messages using multiple low-level communication subsystems. The current implementation supports both Myrinet through GM and Gigabit Ethernet through VIA but we plan to extend it to other communication subsystems
