[Cake] Stranger target behaviour

Kevin Darbyshire-Bryant kevin at darbyshire-bryant.me.uk
Sun Nov 1 08:21:34 EST 2015

On 01/11/15 09:47, Sebastian Moeller wrote:
> Hi there,
> On Oct 31, 2015, at 21:29 , Dave Taht <dave.taht at gmail.com> wrote:
>> The second one is from the interval >> 4, which equates to 6.2ms. I
>> note I picked that because some early data (2012) we had showed that
>> target slightly greater than cable media acquision (6ms) time was a
>> slight win, and it did not hurt to use a number more evenly divisible
>> in binary than the arbitrary 5%.
> 	Well, but should it not be 6.2ms even if no rtt is explicitly requested? Currently cake has a lot of corner-cases that are not too well documented either.
Sebastian as ever picks up on the exact source of my confusion/point.

If 'target=interval/16' is the new mantra then the defaults built in to
cake qdisc should be changed, otherwise we have the current situation
which is:  Default Interval=100ms, target=5ms.  If I specify rtt 100ms
via the joys of tc, then I have: Interval=100ms, target=6.2ms.  If I
specify a target keyword such as 'internet' which also has an interval=
100ms, then target become 5ms again.  Somewhat inconsistent.

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