An improved protocol for data transfer between a request node and a home node of a data processing network that includes a number of devices coupled via an interconnect fabric is provided that minimizes the number of response messages transported through the interconnect fabric. When congestion is detected in the interconnect fabric, a home node sends a combined response to a write request from a request node. The response is delayed until a data buffer is available at the home node and home node has completed an associated coherence action. When the request node receives a combined response, the data to be written and the acknowledgment are coalesced in the data message.