A single communication fabric for a data processing apparatus is provided. The fabric has an interconnection network to provide a topology of data communication channels between a plurality of data-handling functional units. The interconnection network has a first interconnection domain to provide data communication between a first subset of the data-handling functional units and a second interconnection domain to provide data communication between a second subset of the data-handling functional units. The power management circuitry is arranged to control a first performance level for the first interconnection domain independently from control of a second performance level for the second interconnection domain. Machine readable instructions and a method are provided to concurrently set performance levels of two different fabric domains to respective different operating frequencies.