Method for verifying responses to messages using a barrier message

In a processing system comprising a plurality of data sending/receiving units, including a first data unit and a second data unit, interconnected to communicate information-containing message packets therebetween, a method verifying communication of message packets between the first and the second data units, including the steps of:

• the first data unit sending to the second data unit at least one prior message packet that requires the second data unit to send a response message packet to the first data unit;
• if, after a predetermined elapsed time since the one prior message packet was sent, the first data unit has not received the response message packet, the first data unit sending to the second data unit a barrier transaction message packet containing information that identifies the barrier transaction message packet;
• requiring second data unit, upon receipt of the barrier transaction message packet, to send the response message packet if not yet sent, and then send a barrier response message packet to the first data unit containing a copy of the information;
• whereby upon receipt of the barrier response message packet by the first data unit it is confirmed whether or not the first data unit received the response message packet.

In a processing system comprising a plurality of data sending/receiving units, including a first data unit and a second data unit, interconnected to communicate information-containing message packets therebetween, a method for verifying receipt of responses to messages sent between the first and the second data units, including the steps of:

• the first data unit,
• (a) sending to the second data unit one or more prior message packets each requiring the second data unit to send to the first data unit a corresponding response message packet, and
• (b) if, for each of the one or more prior message packets, the corresponding response message packet is not received by the first data unit, then for such each of the one or more prior message packets,
• (c) forming a barrier transaction message packet containing predetermined data,
• (d) saving a first copy of the predetermined data, and
• (e) sending the barrier transaction message packet for receipt by the second data unit;
• the second data unit,
• (a) receiving the barrier transaction message packet to form in reply a barrier response message packet containing a second copy of the predetermined data,
• (b) requiring the second data unit to send first response message packets received prior to receiving the barrier transaction message packet before sending the barrier response message packet, and
• (c) after sending the first response message packets, sending the barrier response message packet to the first data unit;
• the first data unit,
• (a) receiving the barrier response message packet,
• (b) comparing the second copy of the predetermined data contained in the barrier response message packet with the first copy of the predetermined data to determine that the barrier transaction response message packet is in response to the barrier transaction message packet and confirming whether or not the first data unit received the response message packets to the one or more prior message packets.