[c-nsp] ASR9000 queue-limit ? ms

Pshem Kowalczyk pshem.k at gmail.com
Tue Oct 15 05:04:27 EDT 2013


The numbers should probably depend on size and loadings of your
network. The numbers below is what I use as my rule of thumb.
Without going into too much details:
1. Voice - 2-3 ms (and probably a policer around 35-40% of link size)
2. Video - up to 10 ms (assuming HD streaming, otherwise less)
3. Everything else - about 5 ms

If you don't have a lot of internet and nothing else is in the same
class - I'd probably give it slightly more (around 10ms) if the class
it's in enjoys only 1% of link bandwidth and you get to congestion
every now and then.

>From my experience - queues deeper then 10ms tend to mask some
underlying problems (like scheduler issues) and can cause significant
jitter across bigger networks (5ms here, 5ms there and by the time the
packets gets through  the network - it's too late).

I always set the values manually, to ensure similar number across
different platforms and also to make sure that a software change won't
affect them.

kind regards

On 15 October 2013 21:11, Adam Vitkovsky <adam.vitkovsky at swan.sk> wrote:
> Hi folks,
> I'm even considering whether to put this in place or whether I should relay
> on the default queue size calculation.
> I'd like to ask what values worked best for you or if there's a need to tune
> these at all?
> I'm interested in settings for these queues: Voice 10%, Video 50%, Business
> 39%, and Internet.
> My concern with the defaults is that it might happen that the ASR would
> allocate too long buffers increasing delay instead of drops during
> congestion and as Saku mentioned packet drops are essential for congestion
> signalization.
> On the other hand I don't want to set these too low to introduce unnecessary
> drops.
> adam
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