Scheduling of data transmission with minimum and maximum shaping of flows in a network device

1. A network device for processing data, the network device comprising:

at least one egress module for transmitting incoming data to at least one egress port;

wherein the at least one egress module comprises an egress scheduling module and multiple queues per each of the at least one egress port, wherein each of the multiple queues serve data that is attributable to a class of service;

a weight register used to store a weight value for each of the queues;

wherein the egress scheduling module uses a weighted deficit round robin (WDRR) schedule to provide a bandwidth sharing scheme where up to a weighted amount of traffic is serviced from each of the queues in each of one or more rounds;

wherein a current use count is tracked for each queue to indicate an amount of traffic serviced from the queue during each round;

wherein a weighted use limit is determined for each queue as:

weighted use limit=(weight value for the queue)×(expected maximum frame length);

and

wherein the egress scheduling module is configured to service each of the queues during each round if the current use count for the queue is less than the weighted use limit for the queue.

2. The network device of claim 1 wherein the weight value for a queue that is set to a predetermined value indicates that the queue should be serviced in a strict priority order.

3. The network device of claim 2 wherein at least a first queue of the queues has a weight value set to the predetermined value indicating that the first queue should be serviced in the strict priority order, wherein during a round, if the first queue is non-empty, then WDRR servicing to one or more other of the queues is suspended until the first queue becomes empty.

4. The network device of claim 3 wherein after WDRR servicing to one or more other of the queues has been suspended during the round when the first queue becomes non-empty, the WDRR servicing to the one or more queues is resumed when the first queue becomes empty during the round.

5. The network device of claim 1 wherein a weight value for a queue that is set to zero indicates that the queue should be serviced in strict priority order.

6. The network device of claim 1 and further comprising, for the at least one egress port, a queue management (QM) queue to provide flow control information and a system control (SC) queue to provide system control information, wherein weight values for both the QM and SC queues are set to a predetermined value indicating that the QM and SC queues should be serviced in a strict priority order.

7. The network device of claim 1 wherein each of the queues is marked as eligible for WDRR service for a next round if the current use count for the queue is less than the weighted use limit for the queue.

8. The network device of claim 1 wherein one or more of the queues is assigned to a strict priority group and does not participate in WDRR servicing if the one or more queues each has a weight value set to a predetermined value indicating that the queue should be serviced in a strict priority order.

9. A network device for processing data, the network device comprising:

at least one egress module for transmitting incoming data to at least one egress port;

wherein the at least one egress module comprises an egress scheduling module and multiple queues per each of the at least one egress port, wherein each of the multiple queues serve data that is attributable to a class of service;

a weight register used to store a weight value for each of the queues, wherein a weight value that is set to a predetermined value indicates that a corresponding queue should be serviced in a strict priority order for one or more strict priority (SP) queues;

wherein the other queues, each having a weight that is not set to the predetermined value, being in a group of WDRR queues, being serviced using a weighted deficit round robin (WDRR) schedule to provide a bandwidth sharing scheme where up to a weighted amount of traffic is serviced from each of the WDRR queues in each of one or more rounds;

wherein a current use count is tracked for each WDRR queue to indicate an amount of traffic serviced from the queue during a round;

wherein a weighted use limit is determined for each WDRR queue as:

weighted use limit=(weight value for the queue)×(expected maximum frame length);

and

wherein the egress scheduling module is configured to service each of the WDRR queue during each round if the current use count for the WDRR queue is less than the weighted use limit for the queue.

10. The network device of claim 9 wherein the egress scheduling module is configured to suspend WDRR servicing to the WDRR queues during the round when one of the SP queues becomes non-empty, and then to resume WDRR servicing to the WDRR queues during the round when the non-empty SP queue becomes empty during the round.

11. The network device of claim 9 wherein a weight value for a queue that is set to zero indicates that the queue should be serviced in a strict priority order.

12. A method for processing data, the network device comprising:

transmitting, by an egress module, incoming data to at least one egress port;

using, by an egress scheduling module, a weighted deficit round robin (WDRR) schedule to provide a bandwidth sharing scheme where up to a weighted amount of traffic is serviced from each of a plurality of queues in each of one or more rounds;

tracking a current use count for each of the queues to indicate an amount of traffic serviced from the queue during each round;

determining a weighted use limit for each queue as:

weighted use limit=(weight value for the queue)×(expected maximum frame length);

and

servicing, by the egress scheduling module, one or more of the queues during each round if the current use count for the queue is less than the weighted use limit for the queue.

13. The method of claim 12 wherein a weight value for a queue that is set to a predetermined value indicates that the queue should be serviced in strict priority order.

14. The method of claim 13 wherein at least a first queue of the queues has a weight value set to the predetermined value indicating that the first queue should be serviced in strict priority order, wherein during a round, if the first queue is non-empty, then servicing, by the egress scheduling module, to one or more other of the queues is suspended until the first queue becomes empty.

15. The method of claim 14 wherein, after WDRR servicing to one or more other of the queues has been suspended during the round when the first queue becomes non-empty, resuming the WDRR servicing to the one or more queues when the first queue becomes empty during the round.

16. The method of claim 12 wherein a weight value for a queue that is set to zero indicates that the queue should be serviced in a strict priority order.

17. The method of claim 12 and further comprising marking, by the egress scheduling module, one or more of the queues as eligible for WDRR service for a next round if the current use count for the queue is less than the weighted use limit for the queue.

18. The method of claim 12 and further comprising:

assigning at least one of the queues to a strict priority group if the at least one of the queues has a weight value set to a predetermined value indicating that the queue should be serviced in a strict priority order.