In response to receiving a “Return Available PPI Credits” command from a credit-aware (CA) device, a packet engine sends a “Credit To Be Returned” (CTBR) value it maintains for that device back to the CA device, and zeroes out its stored CTBR value. The CA device adds the credits returned to a “Credits Available” value it maintains. The CA device uses the “Credits Available” value to determine whether it can issue a PPI allocation request. The “Return Available PPI Credits” command does not result in any PPI allocation or de-allocation. In another aspect, the CA device issues one PPI allocation request to the packet engine when its recorded “Credits Available” value is zero or negative. If the PPI allocation request cannot be granted, then it is buffered in the packet engine, and is resubmitted within the packet engine, until the packet engine makes the PPI allocation.