babel rtt in bird: How to set the RTT equal to the latency?

[Marek Küthe]

On Fri, 27 Oct 2023 17:35:24 +0200
Juliusz Chroboczek <jch at irif.fr> wrote:

> The recommended default values are much more conservative:
> 
>   rtt-min 10
>   rtt-max 120
> 
> This causes RTTs below 10ms to be considered as all equally good, and
> links above 120ms to all be considered as equally bad.  The result is that
> minor oscillations of the metrics of high-rtt links do not cause cost
> fluctuations, which avoids oscillations.

Thanks for the explanation! I have to admit that I didn't quite know
what the default values did before.

> It is of course possible that these values are not appropriate in your
> network; however, I fear that the extremely aggressive values that you
> describe above may cause unnecessary oscillations, especially since BIRD
> does not yet implement hysteresis on metrics.

I hope it's okay if I ask something about such an old e-mail.

I have a network where sometimes it comes to an RTT of 1ms (when nodes
are next to each other) and sometimes it comes to 300ms (Europe <->
Hong Kong). In this case I would use something like `rtt-max 300`.
Which rtt-cost would you recommend?

> 
> -- Juliusz


-- 
Marek Küthe
m.k at mk16.de
er/ihm he/him
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