It is constructed from file servers on stationary hosts and mobile clients. It has a cache storage on the client, and dynamically adapts for variety of network speeds and bandwidths includes disconnection. Then, PFS can run on variety of UNIX variants. In short, you can mount file server's disks onto your laptop computer over the network, and you can continue accessing to these files even when your computer disconnected from the network. Recently, mobile computers become small, light and powerful.
Many users can perform their work on small laptops.
These machines can also connected to networks as well as stationary machines. In a well networked environment, a mobile computer can act likes a stationary one. Users will share and use programs and data over the network. However, once it moves out to disconnected environment, it must work only with its own resources. Mobile computers connect to his network with variety of methods from fast ethernet to slow wireless modems.