[Cake] Cake tin behaviour - discuss....

[David P. Reed]

Question: what's the "lag under load" experienced when these two loads are filling the capacity of the bottleneck router (the DSL link)?
I'm wondering whether your cake setup is deliberately building up a big queue within the router for any of the 10 bulk/best efforts flows.
 
On Saturday, April 25, 2020 4:34pm, "Kevin Darbyshire-Bryant" <kevin at darbyshire-bryant.me.uk> said:



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> 
> > On 25 Apr 2020, at 16:25, Jonathan Morton <chromatix99 at gmail.com>
> wrote:
> >
> >> On 25 Apr, 2020, at 2:07 pm, Kevin Darbyshire-Bryant
> <kevin at darbyshire-bryant.me.uk> wrote:
> >>
> >> Download from ‘onedrive’ from 1 box, using 5 flows,
> classified as Bulk. Little other traffic going on, sits there at circa 70Mbit, no
> problem.
> >>
> >> If I started another download on another box, say 5 flows, classified as
> Best Effort, what rates would you expect the Bulk & Best effort tins to flow at?
> >
> > Approximately speaking, Cake should give the Best Effort traffic priority
> over Bulk, until the latter is squashed down to its tin's capacity. So you may
> see 5-10Mbps of Bulk and 65-70Mbps of Best Effort, depending on some short-term
> effects.
> >
> > This assumes that the Diffserv marking actually reaches Cake, of course.
> 
> Thanks Jonathan. I can assure you diffserv markings are reaching cake both egress
> & ingress due to my pet ‘act_ctinfo/connmark -savedscp’ project. 
> Amongst other monitoring methods a simple 'watch -t tc -s qdisc show dev $1’
> albeit with a slightly modified cake module & tc to report per tin traffic as a
> percentage of total & per tin % of threshold is used.
> 
> eg:
> Bulk Best Effort Video Voice
> thresh 4812Kbit 77Mbit 38500Kbit 19250Kbit
> target 5.0ms 5.0ms 5.0ms 5.0ms
> interval 100.0ms 100.0ms 100.0ms 100.0ms
> pk_delay 961us 167us 311us 164us
> av_delay 453us 78us 141us 75us
> sp_delay 51us 12us 17us 9us
> backlog 9084b 0b 0b 0b
> pkts 60618617 2006708 460725 11129
> bytes 91414263264 2453185010 636385583 5205008
> traffic% 89 0 0 0
> traftin% 1435 0 0 0
> way_inds 2703134 8957 169 111
> way_miss 922 6192 104 525
> way_cols 0 0 0 0
> drops 8442 230 37 0
> marks 5 0 0 0
> ack_drop 0 0 0 0
> sp_flows 2 3 1 3
> bk_flows 1 0 0 0
> un_flows 0 0 0 0
> max_len 66616 12112 9084 3360
> quantum 300 1514 1174 587
> 
> Your expectation is that Best Effort would exert downward pressure on Bulk traffic
> reducing bulk traffic to about bulk threshold level which is my expectation also. 
> Tin priority then host (fairness), then flow.
> 
> As you may have guessed, that’s not quite what I’m seeing but as
> I’ve managed to see the issue when using ‘flowblind’ am now much
> less inclined to point the finger at host fairness & friends. I remain confused
> why ‘bulk’ is exceeding its allocation though in what should be
> pressure from best effort but it ends up going all over the place and being a bit
> unstable. Odd.
> 
> BTW: The ‘onedrive’ client box is actually running linux.
> 
> 
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