Todd M Mansfield

US Patent:

6914881, Jul 5, 2005

Filed:

Nov 28, 2000

Appl. No.:

09/724488

Inventors:

Todd H. Mansfield - Arlington MA, US
Jeffrey L. Cooper - Gardner MA, US

Assignee:

Nortel Networks Ltd

International Classification:

H04L012/26
H04J003/14
G06F011/00
G08C015/00
G01R031/08

US Classification:

370230, 370252, 370395, 370429, 709232

Abstract:

A method and apparatus for queue selection is described below as Prioritized Continuous-Deficit Round Robin (PC-DRR) Scheduling. In PC-DRR scheduling a queue is selected as a source for the shared datapath using a modified round-robin approach, where queues are cyclically, sequentially evaluated to determine whether or not there is data stored in the queue. In PC-DRR scheduling, each queue is assigned a weight, wherein the weight corresponds to a predefined bandwidth that is allocated to the queue. Thus, the weight defines a fixed allotment of transmit opportunities that are to be allowed for the associated queue during its transmit tenure. In a preferred embodiment, a minimum permissible weight that is assigned to a queue is equal to a Maximum Packet Size. As data are drained from the queue, the weight is decreased incrementally by the amount of data sent, providing a balance. Thus the balance represents the instantaneous count of the number of output transmits that are remain for the queue within its transmit tenure.