Router (on-chip network)
Beginner
The little intersection at each core that decides which way a piece of data goes next.
Novice
A small switch at each node of an on-chip network. It takes packets arriving from its neighbors or its own core and forwards each one toward its destination, one hop at a time.
Expert
Typically a few input buffers, a routing-computation step, an allocator and a crossbar, pipelined over one to a few cycles. Its buffer depth and flow-control scheme set how it behaves under congestion.
Explained in Dataflow and spatial meshes (Architectures).
See also: Network-on-chip (NoC), Flow control (credit-based).