Prioritized dispersal: a scheme for selective exploitation of redundancy in distributed systems

In distributed redundant-resource systems such as communication networks with multiple paths between nodes, there is a choice in allocating resources to tasks; this can be used for fault-tolerance, but also in order to improve performance. The allocation, however is complicated by the fact that the system state is not known and changes dynamically. Exploiting redundancy by partitioning a message into several submessages and sending them along with several "redundant" submessages along different paths, as is done by dispersal schemes, increases the load, reduces capacity and even increases delay at permissible heavy loads. We present and analyze novel "prioritized dispersal" schemes, whereby "redundant" submessages receive lower priority than the "original" submessages, and show their performance to substantially exceed that of non-prioritized schemes. This extends the beneficial applicability of selective exploitation of redundancy, whose benefits for centralized systems have been established, to distributed systems.