x-kernel is an experimental operating system for personal workstations that allows uniform access to resources throughout a nationwide internet: an interconnection of networks similar to the TCP/IP internet. This network is also called the National Research and Education Network (NREN). The x-kernel supports a library of protocols, and it accesses different resources with different protocol combinations. In addition, two user-level systems that give users an integrated and uniform interface to resources have been built on top of the x-kernel. These two systems-a file system and a command interpreter-hide differences among the underlying protocols.< >