A unit that supports the low-level linking of several regions of a single network. In any network it is helpful to subdivide the network into a number of regions in which most traffic is between pairs of nodes within that region, with only a small amount of traffic leaving the region. A router links several regions: interregion traffic will be forwarded to the correct region but traffic addressed to a destination in the same region as the sender will not be forwarded. A router must be capable of interpreting the sender and receiver addresses in the data, and must be able to determine where to forward traffic. It must therefore be capable of interpreting the network protocol, must store tables that assist in managing the routing activity, and will probably need to store an entire packet before forwarding it. The router is designed so as to function at the lowest possible level within the protocol stack, consistent with achieving correct partitioning of the network and correct routing of traffic. Despite the complexity of the unit and the delay it introduces, large networks almost invariably include routers. See also bridge.