Systems for scheduling the transmission of data in a network device

Abstract

In a network device, a line card includes a first scheduler configured to perform scheduling for data units of a first type and a second scheduler that is connected in series to the first scheduler and configured to perform scheduling for data units of a second type. The schedulers may be configured in a variety of ways to achieve certain data unit flow characteristics.

1 . A system for scheduling traffic, including data units, in a network device, the system comprising:
 a first scheduler, including a plurality of queues to store the data units, configured to perform quality of service (QoS) scheduling on a per-data unit basis, and to route the traffic to an asynchronous transfer mode (ATM) scheduler, connected in series to the first scheduler, and configured to schedule and shape the routed traffic.   
     
     
         2 - 39 . (canceled) 
     
     
         40 . The system of  claim 1 , where the QoS scheduling includes weighted round robin scheduling. 
     
     
         41 . The system of  claim 1 , where the QoS scheduling includes per-data unit strict priority scheduling. 
     
     
         42 . The system of  claim 1 , where the ATM scheduler is a Segmentation and Reassembly (SAR) scheduler. 
     
     
         43 . The system of  claim 1 , where the first scheduler and the ATM scheduler are configured to operate in a plurality of modes. 
     
     
         44 . The system of  claim 43 , where,
 in a first mode of the plurality of modes, the first scheduler includes a plurality of virtual channel (VC) nodes, and the ATM scheduler includes a second plurality of queues, where each queue, of the second plurality of queues, corresponds to one of the plurality of VC nodes, each queue, of the second plurality of queues, is associated with an upper threshold, and each queue, of the second plurality of queues, is to transmit a backpressure message to the corresponding VC node when a bandwidth of the corresponding queue exceeds the upper threshold, the backpressure message instructing the corresponding VC node to stop sending the traffic to the corresponding queue, and   in a second mode of the plurality of modes, the ATM scheduler includes at least one output port including a buffer, the buffer being associated with an upper threshold, where the output port is to transmit a port backpressure message to the first scheduler when a bandwidth of the buffer exceeds the upper threshold, the port backpressure message instructing the first scheduler to stop sending the traffic to the output port.   
     
     
         45 . The system of  claim 44 , where in a third mode of the plurality of modes, the first scheduler performs non-strict priority scheduling and per-data unit strict priority scheduling, and the ATM scheduler performs round robin scheduling of traffic received from the first scheduler. 
     
     
         46 . The system of  claim 45 , where in the third mode of the plurality of modes, the first scheduler performs weighted round robin scheduling and the ATM scheduler performs round robin scheduling. 
     
     
         47 . The system of  claim 46 , where in the third mode of the plurality of modes, weights associated with the weighted round robin scheduling are based on QoS scheduling. 
     
     
         48 . The system of  claim 45 , where in the third mode of the plurality of modes, the ATM scheduler shapes the traffic routed from the first scheduler on a cell-by-cell basis. 
     
     
         49 . The system of  claim 44 , where in the first mode of the plurality of modes, each of the second plurality of queues are associated with a lower threshold, which is different than the upper threshold, and
 where each of the plurality of queues transmits a backpressure release message to the corresponding VC node, when the bandwidth of the respective queue goes below the lower threshold, the backpressure release message instructing the corresponding VC node to resume sending the traffic to the corresponding queue.   
     
     
         50 . The system of  claim 44 , where in the second mode of the plurality of modes, each of the at least one output port is associated with a lower threshold, and
 where each of the at least one output port transmits a backpressure release message to the first scheduler, when the bandwidth of the buffer goes below the lower threshold, the backpressure release message instructing the first scheduler to resume sending the traffic to the output port.   
     
     
         51 . The system of  claim 50 , where a difference between the upper threshold and the lower threshold is less than a size of an average data unit. 
     
     
         52 . A method for transmitting traffic by a network device, in a network, the method comprising:
 receiving traffic at a first scheduler of the network device, the first scheduler being configured to operate in one of multiple user configurable modes;   receiving, via the network device, a selection of a user configurable mode from the multiple user configurable modes;   scheduling, using the first scheduler, the traffic based on the selected user configurable mode;   routing, using the first scheduler, the traffic to a Segmentation and Reassembly (SAR) scheduler of the network device;   scheduling, using the SAR scheduler, the traffic based on the selected user configurable mode; and   transmitting the traffic by an output port of the network device.   
     
     
         53 . The method of  claim 52 , where
 in a first mode, of the multiple user configurable modes, the first scheduler includes a plurality of scheduler nodes, and the SAR scheduler includes a plurality of queues, where each queue, of the plurality of queues, corresponds to one of the plurality of scheduler nodes, each queue, of the plurality of queues, is associated with an upper threshold, and each queue, of the plurality of queues, is to transmit a backpressure message to the corresponding scheduler node when a bandwidth of the corresponding queue exceeds the upper threshold, the backpressure message instructing the corresponding scheduler node to stop sending the traffic to the corresponding queue,   in a second mode, of the multiple user configurable modes, the SAR scheduler includes at least one output port including a buffer, the buffer being associated with an upper threshold, where the output port transmits a port backpressure message to the first scheduler when a bandwidth of the buffer exceeds the upper threshold, the port backpressure message instructing the first scheduler to stop sending the traffic to the output port, and   in a third mode of the multiple user configurable modes, the first scheduler performs non-strict priority scheduling and per-data unit strict priority scheduling, and the SAR scheduler performs round robin scheduling of traffic received from the first scheduler.   
     
     
         54 . The method of  claim 53 , where in the first mode of the plurality of modes, each of the plurality of queues are associated with a lower threshold, which is different than the upper threshold, and
 where each of the plurality of queues transmits a backpressure release message to the corresponding scheduler node, when the bandwidth of the respective queue goes below the lower threshold, the backpressure release message instructing the corresponding scheduler node to resume sending the traffic to the corresponding queue.   
     
     
         55 . The method of  claim 53 , where in the second mode of the plurality of modes, each of the at least one output port is associated with a lower threshold, and
 where each of the at least one output port transmits a backpressure release message to the first scheduler, when the bandwidth of the buffer goes below the lower threshold, the backpressure release message instructing the first scheduler to resume sending the traffic to the output port.   
     
     
         56 . The method of  claim 55 , where a difference between the upper threshold and the lower threshold is less than a size of an average data unit. 
     
     
         57 . The method of  claim 53 , where in the first mode and the second mode, of the multiple user configurable modes, the plurality of scheduler nodes includes a plurality of Internet protocol (IP) nodes and a plurality of Virtual Channel (VC) nodes, and
 where in the third mode, of the multiple user configurable modes, a plurality of scheduler nodes includes a plurality of VC nodes and a plurality of Virtual Path (VP) nodes.   
     
     
         58 . In a network device, a line card to schedule traffic, including data units of a first type, the line card comprising:
 a first scheduler to perform quality of service (QoS) scheduling of the data units of the first type and to route all of the traffic, based on the QoS scheduling, to a second scheduler, connected in series to the first scheduler, to schedule the routed traffic, where the first scheduler and the second scheduler are configured to operate in one of three user selectable modes, selected from:   a first user selectable mode, in which the second scheduler is dominant over the first scheduler,   a second user selectable mode, in which the first scheduler is dominant over the second scheduler, and   a third user selectable mode, in which neither the first scheduler or the second scheduler is dominant.