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

[Cathal Mooney]

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 
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.