Routing

Hi everyone,

I am not very clear about the logic behind class based forwarding.

https://www.juniper.net/documentation/us/en/software/junos/traffic-mgmt-qfx/cos/topics/concept/cos-based-forwarding-overview-cos-config-guide.html

Based on the above link, I am guessing CBF is used  only when:

1) When a router  has per packet load balanced enabled and can reach certain destination say X through more than one next-hop. In such case, next hop will be selected based on the hashing algorithm.

If we want  to select next hop based on COS forwarding class rather than allowing hashing algorithm to choose next hop in above case, we can use class based forwarding .

Am I correct ?

Thanks !!

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Be kind!!
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Hi, 

Seems to me you complicate a bit the matter. You use CBF, when you need it. It's like PBR. 

"Class-of-service (CoS)-based forwarding (CBF) enables you to control next-hop selection based on a packet's class of service and, in particular, the value of the IP packet's precedence bits."

There are not so many nodes, where you have load-balancing. 
In case of load-balancing (just one of the cases), you get the sharing links by real-time packets, which can degrade the quality of an application. 

So you can try to apply CBF as a solution. 

WBW, 
Dmitry

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Dmitry Maksimov
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