Cluster control in network systems

A device for connection as a node in a data communications network system comprising a plurality of such nodes which are interconnectable to form a plurality of ad hoc networks, wherein the device comprises control logic for implementing a cluster-based routing protocol, memory for storing routing information in accordance with said routing protocol, and communications circuitry for communication of data with other said nodes with which the device is connected in use, wherein the control logic is configured such that:

• when the device is connected as a node which is a member of a cluster, the control logic maintains cluster control information in said memory, the cluster control information being dependent on the size of at least the cluster of which that node is a member;
• when the device is connected as a node which is a member of a cluster, on connection of that node to another said node which is a member of another cluster, the control logic controls transmission to the other node, via said communications circuitry, of the cluster control information maintained in said memory, determines whether a clustering condition, dependent on the cluster control information maintained in the memory and cluster control information received from said other node via said communications circuitry, is satisfied, and if so controls communication of a clustering agreement to the other node;
• and
• if said clustering condition is satisfied and a said clustering agreement is communicated to the control logic from said other node, the control logic controls exchange of routing information with the other node to merge the two clusters of the two nodes.

A computer program product comprising a computer usable medium having embodied therein computer readable program code means for causing a processor of a device for connection as a node implementing a clusterbased routing protocol in a data communications network system comprising a plurality of such nodes which are interconnectable to form a plurality of ad hoc networks, to perform a cluster control method comprising the steps of:

• when the device is connected as node which is a member of a cluster, maintaining cluster control information dependent on the size of at least the cluster of which that node is a member;
• when the device is connected as node which is a member of a cluster, on connection of that node to another said node which is a member of another cluster, transmitting said cluster control information to the other node, determining whether a clustering condition, dependent on the cluster control information transmitted to the other node and cluster control information received from the other node, is satisfied and, if so, communicating a clustering agreement to the other node;
• and
• if said clustering condition is satisfied and a said clustering agreement is received from the other node, exchanging routing information with the other node and merging the two clusters of the two nodes.