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QFX5100 / EX4300 Traffic impact of buffer re-partition.
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.



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Re: QFX5100 / EX4300 Traffic impact of buffer re-partition. [ In reply to ]
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.
>
>
>
> _______________________________________________
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
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