We consider the problem of providing network access to hosts whose physical location clianges with time. Such hosts cannot depend on traditional forms of network connectivity and routing because their location, and hence the route to reach them, cannot be deduced from their network address. In this paper, we explore the concept of providing continuous network access to mobile computers, and present a set of IP-based protocols that achieve that goal.They are primarily targeted at supporting a campus environment with mobile computers, but also extend gracefully to accommodate hosts moving between different networks. The key feature is the dependence on ancillary machines, the Mobile Support Stations (MSSS), to track the location of the Mobile Hosts. Using a combination of caching, forwarding pointers, and timeouts, a minimal amount of state is kept in each MSS. The state information is kept in a distributed fashion; the system scales well, reacts quickly to changing topologies, and does not place an overwhelming burden on the network.
The work habits of many individuals yield file access patterns that are quite pronounced and can be regarded as defining working sets of files used for particular applications. This paper describes a client cache management technique for detecting these patterns and then exploiting them to successfully prefetch files from servers. Trace-driven simulations show the technique substantially increases file cache hit rate in a single-user environment. Successful file prefetching carries three major advantages: (1) applications run faster, (2) there is less "burst" load placed on the network, and (3) properlyloaded client caches can better survive network outa.ges. Our technique requires little extra code, and -because it is simply an augmentation of the standard LRU client cache management algorithm -is ea.sily incorporated into existing software.
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