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How Do Schedulers In Routers Work? Understanding RR, WRR, WFQ, And DRR Through Simple Examples

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Scheduling in a switch/router is a fascinating topic, and one that often confounds! There are a number of schedulers available today, which can be composed in various ways to create different types of scheduling mechanisms in a switch/router. This is independent of whether it is a hardware implementation (as in a classical router) or a software implementation (in a virtual router).

In this video, we explain the workings of some fundamental schedulers, such as Round Robin (RR), Weighted Round Robin (WRR), Generalized Processor Sharing (GPS), Weighted Fair Queueing (WFQ),  Deficit Round Robin (DRR), and Weighted Deficit Round Robin (WDRR) through one simple example that we use consistently to  explain each one of these.

We also see how they can be adapted to Class-based Weighted Fair Queueing (CB-WFQ), and Modified Deficit Round Robin (MDRR) used in modern switch/routers from various vendors.

All scheduler implementations from an ASIC/chip vendor or a system vendor are essentially variations on the above fundamental schedulers, so understanding these thoroughly goes a long way towards understanding different vendor implementations with much greater clarity!

This is part of our "Network Architecture & Design Series" of videos, intended to provide networking/telecom professionals insights into specific practical topics, so that they have a better understanding of them, and can apply the knowledge in their jobs or careers.

The intended audience is: network architects, principal architects, senior hardware/software engineers, as well as new professionals in hardware, software, chip, system design and product management, and, depending on interest, engineering management. 

The video was conceived, design, and presented by Dr. Vishal Sharma, Metanoia, Inc. - more about him is at:

This video is a presentation of Metanoia, Inc., which provides cutting-edge expertise to executive and engineering management at vendors and operators in the networking/telecom eco-system, and works closely with senior engineering and product mangement staff to develop next-generation systems and networks.

We can be reached at:

Phone: +1 650-641-0082 

Email: experts AT metanoia-inc DOT com




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