Lucent Technologies Inc.

Song Chong

Yung-Terng Wang

Ramesh Nagarajan

Donald David Shugard

David A Morano

Mark Katz

A method for controlling data packet traffic flow over a bus interconnecting two or more nodes in a data communication system, each node having a unique address associated therewith and having a respective buffer memory for temporarily holding incoming data communicated thereto, each node further being capable of multicast sending of data packets over the bus to one or more nodes having respective addresses logically associated a unique address, the method comprising: checking current available buffer memory occupancy upon receipt of a data packet, the node being capable of outputting for transmission on the bus a first flow control indicator message when the data temporarily stored in the buffer memory is above a first buffer occupancy threshold associated with data of a first priority type, and a second flow control indicator message when the data temporarily stored in the buffer memory is above a second buffer occupancy threshold, the second buffer occupancy threshold being greater than the first occupancy threshold; implementing logical flow control to prevent transmission of data packet traffic of the first priority from one or more sending nodes to two or more receive nodes logically associated with the outputting node at the priority in response to receipt of the first flow control indicator message; and, implementing physical logical flow control to prevent transmission of data packet at any data traffic priority in response to receipt of the second flow control indicator message.

Method for multi-priority, multicast flow control in a packet switch

In a switch fabric environment, which includes a buffer, packet data of different class-types from different sources is received, stored in the buffer, processed and outputted to its intended destination. As the buffer fills up, transmission from some of the data sources is stopped to avoid dropping of packets. To avoid packet loss, when the occupancy of the buffer reaches a first threshold value, further transmission of a first-class type of data is precluded from the particular source of that data then being received, while transmission from other sources of that same first-class type of data is not precluded from these other data sources until first-class type of data from such other sources is also received. Further, data of a second-class type is not precluded from being transmitted as long as the amount of data stored in the buffer remains below a second threshold, which is greater than the first threshold. When the occupancy of the buffer reaches that second threshold, further transmissions from the particular source of that second-class type of data then being received is also precluded. As data from other sources of that second-class type of data is received, further transmissions from those other sources are also precluded. A third-class type of data, however, is not precluded from transmission as long as the amount of data remains below a third threshold value, which is greater than the second threshold value. In order to avoid packet loss, when a packet from any source is received, it is stored regardless of whether transmission from the source of that packet has been precluded. Advantageously, a MAX/MIN distribution of the available bandwidth can be probabilistically achieved without packet loss.

Low-loss, fair bandwidth allocation flow control in a packet switch

Novel rate-based flow control methods operate in conjunction with a data communications network. Such networks include a plurality of interconnected nodes, wherein each node is adapted for connection to any of a plurality of sources. The sources send data to, and receive data from, the nodes. The path that data follows in traveling from a first source, through one or more nodes, to a second source, is referred to as a virtual circuit path. Each node includes a processor and an associated memory for storing a data queue of data received from sources. According to one embodiment, referred to as first-order rate-based flow control, a node allocates a data transfer rate to a source based upon the difference between the current queue length at that node and the queue threshold of that node multiplied by a gain. If an appropriate value is calculated and/or empirically determined for the gain, the closed-loop system is asymptotically stable with no persistent oscillation, irrespective of the number of node-to-node connections in a given virtual circuit path, and the round-trip delay of this virtual circuit path. First-order rate-based flow control maintains high node-to-node link utilization and low data loss.

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Middletown, NJ, United States of America

Song Chong