A device allocates buffer space for storing data received from another device. The other device has a credit balance corresponding to the amount of buffer space. A sending device reduces its number of credits by a cost of a packet and sends the packet. To ensure that the buffer does not overflow, the sending device spends a credit for each entry in the buffer that could be consumed by the sent data packet. When received data is added to the buffer without consuming a new entry, a response packet that returns a credit is sent to the sending device before the data is read from the buffer. Thus, the sending device is enabled to continue sending data without waiting for the buffer to be read, enabling the communication between the two devices to make more efficient use of the buffer.