Multicast and unicast scheduling for a network device
First Claim
1. A method of performing multicast and unicast scheduling in a network device, the method comprising the steps of:
- performing unicast cell scheduling each scheduling timeslot of a set of possible scheduling timeslots; and
performing multicast cell scheduling in parallel with and independent of the unicast cell scheduling during a subset of the possible scheduling timeslots.
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Abstract
A method and apparatus are provided for scheduling unicast and multicast data in an input-queued network device. According to one aspect of the present invention, a combined schedule is created by pipelined staging of multicast and unicast scheduling. Multicast cells are scheduled for transmission among multiple interfaces of a crossbar by performing a multicast cell scheduling cycle for multiple classes of service that are supported by the network device. Then, unicast cells are scheduled for transmission among the interfaces at a lower priority than the previously scheduled multicast cells by performing a unicast cell scheduling cycle for the multiple classes of service using only those interfaces that remain unmatched after completion of the multicast cell scheduling cycle.
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Citations
16 Claims
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1. A method of performing multicast and unicast scheduling in a network device, the method comprising the steps of:
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performing unicast cell scheduling each scheduling timeslot of a set of possible scheduling timeslots; and
performing multicast cell scheduling in parallel with and independent of the unicast cell scheduling during a subset of the possible scheduling timeslots. - View Dependent Claims (2, 3)
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4. A method of combining multicast and unicast scheduling in a network device comprising the steps of:
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scheduling multicast cells for transmission among a plurality of interfaces of a crossbar by performing a multicast cell scheduling cycle for a plurality of classes of service that are supported by the network device; and
scheduling unicast cells for transmission among the plurality of interfaces at a lower priority than the multicast cells scheduled by the multicast cell scheduling cycle by performing a unicast cell scheduling cycle for the plurality of classes of service using only those interfaces that remain unmatched after completion of the multicast cell scheduling cycle. - View Dependent Claims (5)
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6. A method of combining multicast and unicast scheduling comprising the steps of:
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scheduling multicast cells for transmission among a plurality of interfaces of a crossbar by performing a multicast cell scheduling cycle including a executing scheduling iterations for a plurality of classes of service that are supported by the network device and producing availability information indicative of those of the plurality of interfaces that remain available for scheduling; and
scheduling unicast cells for transmission among the plurality of interfaces at a lower priority than the multicast cells by performing a unicast cell scheduling cycle after the multicast cell scheduling cycle and using only those interfaces identified by the availability information.
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7. A method of performing multicast and unicast scheduling in a network device, the method comprising the steps of:
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during a first predetermined set of scheduling timeslots of a set of possible scheduling timeslots, performing both multicast cell scheduling and unicast cell scheduling, the multicast cell scheduling and the unicast cell scheduling operating in parallel and independent of each other; and
during a second predetermined set of scheduling timeslots of the set of possible scheduling timeslots, performing unicast cell scheduling based upon results of the multicast cell scheduling completed during a previous scheduling timeslot. - View Dependent Claims (8, 9)
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10. A method of combining multicast and unicast scheduling comprising the steps of:
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performing a multicast cell scheduling cycle during timeslot t for multicast cells that are to be transmitted across a fabric of a network device during timeslot t+n, the fabric coupling each of a plurality of input ports to each of a plurality of output ports, the multicast cell scheduling cycle including a scheduling iteration for each class of service supported by the network device and producing availability information indicative of those of the plurality of input ports and output ports that remain available for scheduling during timeslot t+n; and
performing a unicast cell scheduling cycle during timeslot t+n based upon the availability information, the unicast cell scheduling cycle scheduling unicast cells for transmission across the fabric during timeslot t+n. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A network device comprising:
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a plurality of input ports and output ports residing on a plurality of line cards;
a fabric coupled to the plurality of line cards, the fabric including a switched backplane allowing the simultaneous transfer of data among the plurality of input ports and output ports; and
a fabric configuration manager coupled to the fabric and the plurality of line cards, the fabric configuration manager including two independent schedulers, a multicast scheduler and a unicast scheduler, the multicast scheduler and the unicast scheduler operating independently and in parallel to match pairs of the plurality of ports for the transfer of multicast cells and unicast cells across the fabric, respectively, during a first predetermined set of scheduling timeslots, and during a second predetermined set of scheduling timeslots, the unicast scheduler performing unicast scheduling among those ports of the plurality of ports that remain unmatched by a prior multicast scheduling cycle.
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Specification