Abstract: The present invention provides for a computer network method and system that applies “hysteresis” to an active queue management algorithm. If a queue is at a level below a certain low threshold and a burst of packets arrives at a network node, then the probability of dropping the initial packets in the burst is recalculated, but the packets are not dropped. However, if the queue level crosses beyond a hysteresis threshold, then packets are discarded pursuant to a drop probability. Also, according to the present invention, queue level may be decreased until it becomes less than the hysteresis threshold, with packets dropped per the drop probability until the queue level decreases to at least a low threshold. In one embodiment, an adaptive algorithm is also provided to adjust the transmit probability for each flow together with hysteresis to increase the packet transmit rates to absorb bursty traffic.

Abstract: A design structure embodied in a machine readable storage medium for designing, manufacturing, and/or testing a design for caching data in a multiprocessor system is provided. The design structure includes a multiprocessor system, which includes a first processor including a first cache associated therewith, a second processor including a second cache associated therewith, and a main memory to store data required by the first processor and the second processor, the main memory being controlled by a memory controller that is in communication with each of the first processor and the second processor through a bus, wherein the second cache associated with the second processor is operable to cache data from the main memory corresponding to a memory access request of the first processor.

Abstract: Methods, computer program products, and systems for caching data in a multiprocessor system are provided. In one implementation, the method includes generating a memory access request for data, which data is required for a processor operation associated with the first processor. Responsive to the data not being cached within a first cache associated with the first processor, the method further includes snooping a second cache associated with the second processor to determine whether the data has previously been cached in the second cache, possibly as a result of a previous “low priority” request for the data by the first processor and responsive to the data being cached within the second cache associated with the second processor, passing the data from the second cache to the first processor.

Abstract: A method and system for providing a path for a new flow between a source node and a destination node in a network is disclosed. The network has a plurality of nodes and a plurality of links between the nodes. The nodes include the source node and the destination node. Each of the links is capable of including a plurality of existing flows and has a capacity. Each of the existing flows has a minimum guaranteed bandwidth. The method and system include determining a benefit for each link of a portion of the plurality of links coupled with a node of the plurality of nodes. The benefit is determined based on the capacity of the link and the minimum guaranteed bandwidth for a portion of the plurality of existing flows that is through the link, the node being a part of the path. The method and system also include selecting a link of the portion of the plurality of links to be part of the path.

Abstract: The present invention provides for a computer network method and system that applies “hysteresis” to an active queue management algorithm. If a queue is at a level below a certain low threshold and a burst of packets arrives at a network node, then the probability of dropping the initial packets in the burst is recalculated, but the packets are not dropped. However, if the queue level crosses beyond a hysteresis threshold, then packets are discarded pursuant to a drop probability. Also, according to the present invention, queue level may be decreased until it becomes less than the hysteresis threshold, with packets dropped per the drop probability until the queue level decreases to at least a low threshold. In one embodiment, an adaptive algorithm is also provided to adjust the transmit probability for each flow together with hysteresis to increase the packet transmit rates to absorb bursty traffic.

Abstract: The decision to discard or forward a packet is made by a flow control mechanism, upstream from the forwarding engine in the node of a communication network. The forwarding engine includes a switch with mechanism to detect congestion in the switch and return a binary signal B indicating congestion or no congestion. The flow control mechanism uses B and other network related information to generate a probability transmission table against which received packets are tested to determine proactively whether a packet is to be discarded or forwarded.

Abstract: A method for dynamically adjusting the flow rate of a plurality of logical pipes that share a common output queue. In accordance with the method of the present invention, a minimum flow rate and a maximum flow rate are set for each of the pipes. Next a determination is made of whether or not excess queue bandwidth exists in accordance with the output flow rate of the shared queue. The determination of whether or not excess bandwidth exists comprises comparing the output flow rate of the shared queue with a pre-determined threshold queue output value. An instantaneous excess bandwidth signal has a value of 1 if there is excess bandwidth and is otherwise 0 if there is no excess bandwidth. In an alternate embodiment, the instantaneous excess bandwidth signal for a particular pipe is logically ANDed with one or more additional excess bandwidth signals to form a composite instantaneous excess bandwidth signal.

Abstract: A method for dynamically adjusting the flow rate of a plurality of logical pipes that share a common output queue. In accordance with the method of the present invention, a minimum flow rate and a maximum flow rate are set for each of the pipes. Next a determination is made of whether or not excess queue bandwidth exists in accordance with the output flow rate of the shared queue. The determination of whether or not excess bandwidth exists comprises comparing the output flow rate of the shared queue with a pre-determined threshold queue output value. An instantaneous excess bandwidth signal has a value of 1 if there is excess bandwidth and is otherwise 0 if there is no excess bandwidth. In an alternate embodiment, the instantaneous excess bandwidth signal for a particular pipe is logically ANDed with one or more additional excess bandwidth signals to form a composite instantaneous excess bandwidth signal.

Abstract: The decision to discard or forward a packet is made by a flow control mechanism, upstream from the forwarding engine in the node of a communication network. The forwarding engine includes a switch with mechanism to detect congestion in the switch and return a binary signal B indicating congestion or no congestion. The flow control mechanism uses B and other network related information to generate a probability transmission table against which received packets are tested to determine proactively whether a packet is to be discarded or forwarded.

Abstract: A method and system for providing a path for a new flow between a source node and a destination node in a network is disclosed. The network has a plurality of nodes and a plurality of links between the nodes. The nodes include the source node and the destination node. Each of the links is capable of including a plurality of existing flows and has a capacity. Each of the existing flows has a minimum guaranteed bandwidth. The method and system include determining a benefit for each link of a portion of the plurality of links coupled with a node of the plurality of nodes. The benefit is determined based on the capacity of the link and the minimum guaranteed bandwidth for a portion of the plurality of existing flows that is through the link, the node being a part of the path. The method and system also include selecting a link of the portion of the plurality of links to be part of the path.