Alcatel Canada Inc.

Anthony Hung

Tom Edward Davis

Henry Chow

Mark William Janoska

Hossain Pezeshki-Esfahani

Srinivasan Ramaswamy

The method for servicing queues holding messages, such as ATM data packets, for subsequent processing or transmission to a resource such as a communications link having a finite processing capability comprises the steps of servicing each queue by forwarding the messages thereof to the resource at time intervals corresponding to a guaranteed service rate of the queue, provided the queue is non-empty; and, during time intervals when none of the queues have messages being forwarded to the resource in conformance with the above step, servicing the queues in accordance with a proportion of a remaining or idle resource bandwidth allocated to each queue. The method is preferably carried out by a hierarchical scheduler comprising an exhaustive sub-scheduler servicing a plurality of lower level sub-schedulers in accordance with non-equal priority levels assigned thereto; M non-work conserving shaper sub-schedulers feeding the exhaustive sub-scheduler; and N work conserving idle bandwidth sub-schedulers feeding the exhaustive sub-scheduler. In such a scheduler, a queue concurrently contends for service by one of the shaper sub-schedulers and one of the idle bandwidth sub-schedulers, wherein the shaper sub-scheduler servicing the queue has a higher priority level with respect to the exhaustive sub-scheduler than the idle bandwidth sub-scheduler servicing the same queue. The technique distributes the idle bandwidth of the resource in a way which is de-coupled from the guaranteed service rates of the queues, thereby providing a more efficient bandwidth distribution.

Two-component bandwidth scheduler having application in multi-class digital communications systems

A scheduling device for use in a packet-switched network, belonging to the class of non-work conserving or idling weighted round robin (WRR) arbiters, assigns a packet stream slots in a fixed-length time division multiple access (TDMA) frame by selecting free slots which are closest to ideal slot positions that would, if assigned, eliminate jitter or cell delay variation. The scheduler is able to simultaneously determine if a new constant bit rate connection requiring a predetermined bandwidth conforms to a leaky bucket or GCRA algorithm characterized by a peak packet or cell emission interval T&equals;1/PCR and a packet or cell delay variation time, CDVT, i.e., whether the new connection is GCRA (T, CDVT) conformant. This determination is made by comparing the quantity ME&plus;ML against the CDVT, where ME corresponds to the maximum time or distance by which any assigned slot is earlier than a corresponding ideal slot and ML corresponds to a maximum time or distance by which any assigned slot is later than a corresponding ideal slot. The scheduler can thus also carry out connection admission control (CAC) functions in an ATM network switch.

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Ottawa, Canada

Anthony Hung