[Cake] Diffserv LLT mode

Jonathan Morton chromatix99 at gmail.com
Sat Apr 21 12:44:12 EDT 2018

>> Is anyone actually using the LLT diffserv setting?
> I re-tested diffserv-llt quickly using the current head of cake and tc-adv and am confused by something:
> http://drhleny.cz/bufferbloat/cake/round5/diffserv_rrul_eg_cake_ds-llt_50mbit/index.html
> When I look at the qdisc stats for cake, there are 5 tins: Low Loss, Best Effort, Low Delay, Bulk and Net Control. Shouldn’t the Low Delay tin have its target and interval reduced to something below 5ms and 100ms? And the bulk tin has a target and interval of 5.8ms and 100.8ms(?)
> In short, I forget how diffserv-llt was supposed to work, regardless of whether or not it’s on the chopping block. No need for a history lesson if it will be removed… :)
> Improved intra-flow latency could be useful for HTTP/2 or other things, but I don’t see how the current llt mode helps most ordinary people with that, when it would only apply to flows with certain diffserv markings, and doesn’t seem to adjust the target and interval anyway…

Well, at some point the intended functionality seems to have got corrupted, though it could be put back in without difficulty.  But I'm certainly not among LLT's userbase; I put the mode in mostly as a demonstration that Cake could do it if required.  If the originators are no longer pursuing the proposal, then the mode has no reason to exist any more.

The bulk tin often gets its parameters adjusted, by virtue of the fact that its threshold is a small fraction of the total.  It happens in the other modes as well.  Don't take that as significant.

 - Jonathan Morton

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