Fast Reroute, Fast Convergence, WRED and WFQ

Fast Reroute , Fast Convergence , WRED and WFQ. You may think that why Orhan is putting all these mechanisms together. I will give you an analogy. Those who participate my talks., know that I love using analogies.

Before we try to understand how these mechanisms are related with each other, let me explain what is Proactivity and Reactivity and how we use them in networking.

Proactivity is ‘ Taking an action before things happen ‘

Reactivity is ‘ Taking an action after things happen ‘

Vocabulary or Wikipedia meaning may not be like the above ones, but I will use the meaning in this way for this post.

With just few sentence if I would explain Fast Reroute , Fast Convergence , WRED and WFQ:

  • FRR : Fast Reroute or Data plane traffic protection is placing the backup route into RIB and FIB of the device BEFORE THE FAILURE, switching over the backup path when the failure happens.
  • Fast Convergence :  Tuning (Reducing) the protocol timers,  such as failure detection and propagation time to converge faster than default convergence, require all devices to react the changes as fast as possible, finding a backup path and installing it into RIB and FIB AFTER THE FAILURE.
  • WRED : Congestion avoidance technique, providing a mechanism to drop packets before queue completely gets full, so BEFORE QUEUE GETS FULL, drop some packets according to their Weight (Drop probability).
  • WFQ : Congestion Management mechanism, one of the ways to do queuing, AFTER QUEUE GETS FULL, manages which packet will get what kind of scheduling treatment.

What ever in the above definitions include BEFORE keyword, they are Proactive mechanism.

Whatever in the above definitions include AFTER, they are Reactive mechanisms.

As a network engineers we like to classify/categorize the technologies in certain way. Have a look at Push and Pull Based Mechanisms for example.

Now, I through the term ‘ Proactive and Reactive ‘ mechanism, use it or not, hope it was useful.If you liked this post and would like to see more, please let me know in the comment section below. Share your thoughts so I can continue to write similar ones.

Created by
Orhan Ergun

Orhan Ergun, CCIE/CCDE Trainer, Author of Many Networking Books, Network Design Advisor, and Cisco Champion 2019/2020/2021

He created OrhanErgun.Net 10 years ago and has been serving the IT industry with his renowned and awarded training.

Wrote many books, mostly on Network Design, joined many IETF RFCs, gave Public talks at many Forums, and mentored thousands of his students.  

Today, with his carefully selected instructors, OrhanErgun.Net is providing IT courses to tens of thousands of IT engineers. 

View profile