This paper presents two advanced communication libraries, Ninf and PM. Ninf is an ongoing global network-wide computing infrastructure project which allows users to access computational resources including hardware, software and scientific data distributed across a wide area network. Computational resources are shared as Ninf remote libraries executable at a remote Ninf server. Users can build an application by calling the libraries with the Ninf Remote Procedure Call. In order to facilitate location transparency and network-wide parallelism, Ninf metaserver maintains global resource information regarding computational server and databases, allocating and scheduling coarse-grained computation for global load balancing. PM is a high-performance communication library for workstation clusters connected with Myrinet gigabit LAN card, which has a dedicated processor and on-board memory to handle a communication protocol. In order to obtain high-performance communication and support a multi-user environment, we co-designed PM, an operating system realized by a daemon process, and the run-time routine for a programming language. Several unique features, e.g., network context switching and modified ACK/NACK flow control algorithm have been developed for PM. PM for the Suns has a speed of 20 μs round trip for a user-level 8 bytes message and 38.6 Mbytes/s bandwidth for an 8 Kbytes message.