[Cake] diffserv3 tin 2 target 50% of interval?
peteheist at gmail.com
Wed Feb 22 05:17:11 EST 2017
Hi, I’m finally getting to diffserv testing and am wondering about the tin 2 parameters of the default ‘diffserv3':
Tin 0 Tin 1 Tin 2
thresh 3125Kbit 50Mbit 12500Kbit
target 5.8ms 5.0ms 5.0ms
interval 100.8ms 100.0ms 10.0ms
Pk-delay 0us 0us 0us
Av-delay 0us 0us 0us
Sp-delay 0us 0us 0us
My understanding from the latest CoDel RFC: https://www.ietf.org/id/draft-ietf-aqm-codel-06.txt
and notes in the Overview section of this document from K. Nichols: http://www.pollere.net/Pdfdocs/noteburstymacs.pdf
are that ‘interval' should generally remain at 100ms and that ‘target' should be computed at around 5-10% of interval, and preferably closer to 5%.
In my testing, which I’ll release more results from soon, I’ve seen no significant benefit to changing target or interval from their defaults for either Wi-Fi or 100Mbit wired links. I question that lowering tin 2’s interval to 10ms provides any benefit, and in fact could very well cause undesired behavior for those using the defaults.
I could provide a spread of tests comparing ‘diffserv3' to ‘diffserv4’ for rrul at various bandwidths, but since ‘diffserv4’s tins all have standard 5/100 target and interval parameters, that seems preferable to the default of ‘diffserv3’. Is there a justification for setting the interval outside the guidelines suggested by CoDel’s authors?
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