A method comprises generating, using a computer, an integrated circuit layout including a plurality of data handling nodes interconnected by routing circuitry defining data packet routes between the plurality of data handling nodes; for a transaction source node configured to generate data packets associated with a data handling translation between that transaction source node and a transaction target node and having one or more routing data fields controlling routing of the data packet, detecting, using the computer, a difference between a first routing controlled by the one or more routing data fields and a selected second routing provided by the integrated circuit layout; and providing, using the computer, one or more data mapping nodes in the integrated circuit layout to map an initial value of one or more of the routing data fields of a data packet generated by the transaction source node to a mapped data value, so that the mapped data value controls routing of the data packet using the selected second routing.