[j-nsp] QFX5100 / EX4300 Traffic impact of buffer re-partition.

[Alexandre Snarskii]

On Fri, Jul 02, 2021 at 03:18:51PM +0100, Cathal Mooney via juniper-nsp wrote:
> Hi,
> 
> We have some QFX5100-48S-6Q and EX4300-48T switches, on which we've 
> observed tail drops / outbound discards in our monitoring.
> 
> As a result we plan to re-partition the buffer allocation, assigning the 
> maximum space to the best-effort class as described here:
> 
> https://www.juniper.net/documentation/us/en/software/junos/traffic-mgmt-qfx/topics/example/cos-shared-buffer-allocation-lossy-ucast-qfx-series-configuring.html
> 
> I am curious about the statement that "traffic stops on /all/ ports 
> until buffer reprogramming is complete."  Does anyone have any 
> real-world experience of making this kind of change?  What kind of 

In my practice such changes on standalone switches resulted in short 
enough (<0.1sec) traffic interruptions. No idea about virtual-chassis.

> interruption to packet forwarding should we expect (we're just changing 
> the allocation for the existing default classes - not adding any new 
> ones.)  Also we have these configured in a virtual-chassis of 2 x 
> QFX5100 and 6 x ES4300, any idea on what behaviour to expect in that 
> circumstance?
> 
> Best regards,
> 
> Cathal.
> 
> 
> 
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