Cisco Support Community
Community Member

QOS with threshold and buffer on switch

Hello, I know there 4 queue and with 3 threshold each one. My question what is the difference between the buffer and threshold percentage. For example if the buffer for traffic is 90% then how does the threshold apply to the buffer. Can I get example off percentage with buffer and threshold? Thanks,
Cisco Employee

Hello, Buffer means the



Buffer means the memory allocated for that queue 

Threshold means at which level will starting dropping the traffic due to congestion


let me give you an example :

lets say queue number 1 has 25% buffer allocated and this equals 25 mb

if we set threshold to 25% this means that we will start dropping traffic after reaching 25% of 25mb which is 6.25 mb


let me know if you got it or not 




Super Bronze

DisclaimerThe Author of this


The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.


For what (exactly) hardware?

In general, buffers provides the physical capacity of how many frame/packets might be queued.  Thresholds provide logical frame/packet limits.  How the two interact can vary based on hardware.

CreatePlease to create content