International Business Machines Corporation

Theodore E Tedijanto

Israel Cidon

John E Drake, Jr

Levent Gun

Chee-Seng Chow

Claude R Galand

Jeffrey Haskell Derby

Marc Adam Kaplan

Allen Leonid Roginsky

Roch A Guerin

Kenneth Harvey Potter, Jr

Gerald Arnold Marin

Inder Sarat Gopal

Shay Kutten

Hamid Ahmadi

John G Dudley

Jeane S Chen

Allan K Edwards

Elizabeth A Hervatic

Chandra Paul Immanuel

Richard M Doney

Anthony M Lee

Rachel A Bodner

A packet communications network in which multicast transmissions are made reliable by transmitting acknowledgements to all neighbors of every receiving node, including the source node. This allows the relinquishment of message holding buffers as soon as all near neighbors acknowledge receipt of the message after only tile longest round trip time to the nearest neighbors, rather than the round trip to the furthest destination. Moreover, highly reliable ancillary point-to-point transmission facilities can be used to retransmit multicast messages indicated as being lost by failure of acknowledgment. Finally, network partitions occurring during the multicast procedure do not necessarily lose the multicast message to the remote partitions since any node receiving the message can insure delivery to all other nodes in that partition.

Reliable multicasting over spanning trees in packet communications

Access control for a packet communications network includes a dynamic bandwidth updating mechanism which continuously monitors the mean bit rate of the signal source and the loss probability of the connection. These values are filtered to remove noise and then used to test whether the values fall within a pre-defined acceptable adaptation region in the mean bit rate, loss probability plane. Values falling outside of this region trigger bandwidth updating procedures which, in turn, result in acquiring a new connection bandwidth, and determining new filter parameters and new parameters for a leaky bucket access mechanism.

Dynamic bandwidth estimation and adaptation for packet communications

A method is disclosed for determining whether to use a preempt/resume protocol or an alternate protocol in transmitting data packets from a local system to a remote system. Each system informs the other whether it supports preempt/resume and provides the sizes of the largest low priority data packets it can send and receive. The local system always elects the alternate protocol unless both support preempt/resume. The local system then selects the lesser of (a) the largest low-priority data packet it can send and (b) the largest low-priority data packet the remote system can receive. Use of prompt/resume is initiated by the local system only where a packet of the selected size would be delayed in reaching the remote system by more than a predetermined interval.

Method of determining whether to use preempt/resume or alternate

A packet communications system utilizes a route determining mechanism by identifying principal paths between the source and the destination in the system. Principal paths are minimum hop count paths with a transmission delay less than a specified threshold. Principal path links are accepted as legs of the optimum path, if feasible, i.e., if the resulting load on the link is less than a specified principal threshold. Secondary links are accepted only if the resulting load on the link is less than a specified secondary threshold, where the secondary threshold is less than the principal threshold. All paths must also have a transmission delay less than a specified threshold. Each request for a route includes the source node, the destination node, the load required, the maximum transmission delay and, if desired, the quality of service parameters which all of the legs of the route must satisfy. A modified Bellman-Ford breadth-first search algorithm is used to identify the principal links and, using these principal link identifications, determining the optimum path.

Methods and apparatus for optimum path selection in packet transmission

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Theodore E Tedijanto