Message arbitration in a ring interconnect system based on activity indications for each node in the ring interconnect

A ring interconnect system comprises a plurality of nodes. Each node is connected to two other nodes to form a ring interconnect. Every pair of nodes is connected by an inter-node path for that pair of nodes distinct from the ring interconnect. Each of the nodes comprises a message buffer to buffer messages received from at least one device associated with the node. Each of the nodes also comprises activity level circuitry to transmit an activity indication, when a number of the messages in the message buffer is equal to or above a threshold, to each other node of the plurality of nodes via the respective inter-node paths. Each of the nodes also comprises arbitrator circuitry to receive the activity indications from each other node and from the activity level circuitry, and to allow ingress of a message from the message buffer onto the ring interconnect in dependence on the activity indications. Also provided is a method of operating a node of a ring interconnect system.