Large scale multi-processor system with a link-level interconnect providing in-order packet delivery
A large-scale multiprocessor system with a link-level interconnect that provides in-order packet delivery. The method comprises transmitting, over a link in the defined interconnection topology, a sequence of packets in a defined order from a first node to a second node. The second node is an intermediate node in a route between the first and third node. At the first node, the transmitted packets are stored in a buffer. In response to an error in reception, the first node retrieves packets from the buffer and re-transmits them to the second node, beginning with the packet subsequent to the last packet in the sequence correctly received by the second node and continuing through the remainder of the sequence of packets.
1 . A method of providing in-order delivery of link-level packets in a multiprocessor computer system having a large plurality of processing nodes interconnected by a defined interconnection topology, comprising:
for a network transmission between a first node and a third node of the multiprocessor computer system, transmitting, over a link in the defined interconnection topology, a sequence of packets in a defined order from a first node to a second node, the second node being an intermediate node in a route between the first and the third node;
at the first node, storing the transmitted packets in a buffer;
at the first node, receiving status information from the second node indicating the last packet in the sequence correctly received by the second node and indicating that an error in reception has been detected by the second node;
the first node, retrieving packets from the buffer and re-transmitting them to the second node, beginning with the packet subsequent to the last packet in the sequence correctly received by the second node and continuing through the remainder of the sequence of packets.
2 . The method of claim 1 , wherein the large plurality of processing nodes are connected in a Kautz topology.
3 . The method of claim 2 , wherein the Kautz topology is of degree 3.
4 . The method of claim 1 , wherein packet transmission is on a unidirectional data link from the first node to the second node and wherein acknowledgements are received on a separate unidirectional control link from the second node to the first.
5 . The method of claim 1 , wherein acknowledgements are received periodically.
6 . The method of claim 1 , wherein an error in reception is detected using a CRC code.
7 . The method of claim 1 , wherein an error in reception is detected as an illegal 10 bit code.
8 . A system for providing in-order delivery of link-level packets in a multiprocessor computer system having a large plurality of processing nodes interconnected by a defined interconnection topology, comprising:
a first node connected to a third node over a link in the defined interconnection topology;
a second node, which is an intermediate node in a route between the first node and the third node;
a buffer for storing a sequence of packets transmitted from the first node to the second node in a defined order;
status information, sent from the second node, comprising a sequence number of the last correctly received packet and a flag signaling that an error in reception has been detected by the second node,
wherein an error in reception signaled by the flag causes the first node to retrieve packets from the buffer and re-transmit them to the second node, beginning with the packet whose sequence number is subsequent to the sequence number of the last correctly received packet, and continuing through the remainder of the sequence of packets.
9 . The system of claim 8 , wherein the large plurality of processing nodes are connected in a Kautz topology.
10 . The system of claim 8 , wherein the Kautz topology is of degree 3.
11 . The system of claim 8 , wherein packet transmission is on a unidirectional data link from the first node to the second node and wherein acknowledgements are received on a separate unidirectional control link from the second node to the first.
12 . The system of claim 8 , wherein acknowledgements are received periodically.
13 . The system of claim 8 , wherein an error in reception is detected using a CRC code.
14 . The system of claim 8 , wherein an error in reception is detected as an illegal 10 bit code.