An integrated circuit 2 includes a plurality of transaction sources 6, 8, 10, 12, 14, 16, 18, 20 communicating via a ring-based interconnect 30 with shared caches 22, 24 each having an associated POC/POS 30, 34 and serving as a request servicing circuit. The request servicing circuits have a set of processing resources 36 that may be allocated to different transactions. These processing resources may be allocated either dynamically or statically. Static allocation can be made in dependence upon a selection algorithm. This selection algorithm may use a quality of service value/priority level as one of its input variables. A starvation ratio may also be defined such that lower priority levels are forced to be selected if they are starved of allocation for too long. A programmable mapping may be made between quality of service values and priority levels. The maximum number of processing resources allocated to each priority level may also be programmed.