International Business Machines Corporation

Fu Chung Chang

Piyush Chaudhary

Peter H Hochschild

Steven J Martin

Jason E Goscinski

Rama Krishna Govindaraju

John Scott Houston

Kevin J Gildea

Robert Sidney Blackmore

Jay Robert Herring

Carl Alfred Bender

Donald G Grice

Leonard W Helmer, Jr

Richard A Swetz

Chulho Kim

Patricia E Heywood

Jennifer M Doxtader

Rama J Govindaraju

Jason S Houston

In order to solve the problem of the detection of the arrival of duplicate data packets in an interconnected, multinode data processing system, each data packet is provided with a field of r bits that are randomly generated for each data packet. However, one of the packets is provided with a field that is computed from the other randomly generated field entries in a checksum computation which yields a selected nonzero checksum value. A running checksum at the receiver is used to determine whether or not, after the receipt of the specified number, k, of data packets, a duplicate packet has been received.

Efficient probabilistic duplicate packet detector in computer networks

In remote direct memory access transfers in a multinode data processing system in which the nodes communicate with one another through communication adapters coupled to a switch or network, failures in the nodes or in the communication adapters can produce the phenomenon known as trickle traffic, which is data that has been received from the switch or from the network that is stale but which may have all the signatures of a valid packet data. The present invention addresses the trickle traffic problem in two situations: node failure and adapter failure. In the node failure situation randomly generated keys are used to reestablish connections to the adapter while providing a mechanism for the recognition of stale packets. In the adapter failure situation, a round robin context allocation approach is used with adapter state contexts being provided with state information which helps to identify stale packets.

Failover mechanisms in RDMA operations

In a multinode data processing system in which nodes exchange information over a network or through a switch, the mechanism which enables out-of-order data transfer via Remote Direct Memory Access (RDMA) also provides a corresponding ability to carry out broadcast operations, multicast operations, third party operations and conditional RDMA operations. In a broadcast operation a source node transfers data packets in RDMA fashion to a plurality of destination nodes. Multicast operation works similarly except that distribution is selective. In third party operations a single central node in a cluster or network manages the transfer of data in RDMA fashion between other nodes or creates a mechanism for allowing a directed distribution of data between nodes. In conditional operation mode the transfer of data is conditioned upon one or more events occurring in either the source node or in the destination node.

Third party, broadcast, multicast and conditional RDMA operations

In a multinode data processing system in which nodes exchange information over a network or through a switch, a structure and mechanism is provided within the realm of Remote Direct Memory Access (RDMA) operations in which DMA operations are present on one side of the transfer but not the other. On the side in which the transfer is not carried out in DMA fashion, transfer processing is carried out under program control; this is in contrast to the transfer on the DMA side which is characteristically carried out in hardware. Usage of these combination processes is useful in programming situations where RDMA is carried out to or from contiguous locations in memory on one side and where memory locations on the other side is noncontiguous. This split mode of transfer is provided both for read and for write operations.

Half RDMA and half FIFO operations

In a multinode data processing system in which the nodes communicate with one another through communication adapters coupled to a switch or network, a method is provided for using the Internet Protocol (IP) for transmitting large broadcast data packets without incurring the overhead normally associated with packet fragmentation. By adding an Internet Protocol (IP) header as the first header in every packet fragment in the fragmentation process, fragmented packets are able to be assembled in the IP layer without intervention at the adapter interface layer.

Interface internet protocol fragmentation of large broadcast packets in an environment with an unaccommodating maximum transfer unit

Method for third party, broadcast, multicast and conditional RDMA operations

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Rhinebeck, NY, United States of America

Fu Chung Chang