Deadlock (network)
Beginner
A jam where several pieces of data each wait for space held by another, in a circle, so none can ever move.
Novice
A state in which a set of packets each hold a buffer the next one needs, forming a cycle, so none can advance. Routing rules are designed so such cycles cannot form.
Expert
Arises from cyclic channel dependencies. Avoided by restricting turns (dimension-order or turn-model routing), by virtual channels with an escape path, or, for message-level protocol deadlock, by separating request and response classes.
Explained in Dataflow and spatial meshes (Architectures).
See also: Dimension-order (XY) routing, Flow control (credit-based).