Interconnection router arrangements are implemented using a variety of arrangements and methods. Using one such arrangement, an interconnection network router arrangement sends data units between a set of router inputs and a set of router outputs. The interconnection network router arrangement includes a sub-switch that is capable of selectively transferring a data unit from an array of sub-switch inputs to an array of sub-switch outputs. The sub-switch has a memory circuit for storing the data unit before the data unit is transferred to a sub-switch output and a memory circuit for storing the data unit after the data unit is transferred from the sub-switch inputs and before the data unit is sent to a router output.