Re: [Flent-users] [tohojo/flent] testing the behavior of small queue building non-ecn'd flows (#148)

["Toke Høiland-Jørgensen" <notifications@github.com>]

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flent-users <notifications@github.com> writes:

> HI Toke,
>
>
>> On Sep 3, 2018, at 19:37, Toke Høiland-Jørgensen <notifications@github.com> wrote:
>> 
>> flent-users <notifications@github.com> writes:
>> 
>> > Hi Dave,
>> >
>> >
>> >> On Sep 3, 2018, at 18:00, Dave Täht <notifications@github.com> wrote:
>> >> vnv 
>> >> Another rrul_v2 issue would be to correctly end up in all the queues on wifi.
>> >
>> > So in theory rrul_cs8 should do that... (it aims to just use one
>> > dscp-marked flow per class selector for a total of 8 tcp flows per
>> > direction...) In practice I believe the mapping from dscps to ACs is
>> > highly non-linear...
>> 
>> Well, not that non-linear:
>> 
>> const int ieee802_1d_to_ac[8] = {
>> IEEE80211_AC_BE,
>> IEEE80211_AC_BK,
>> IEEE80211_AC_BK,
>> IEEE80211_AC_BE,
>> IEEE80211_AC_VI,
>> IEEE80211_AC_VI,
>> IEEE80211_AC_VO,
>> IEEE80211_AC_VO
>> };
>
> Well, aren't these values according to IEEE P802.1p (https://en.wikipedia.org/wiki/IEEE_P802.1p)?
>
> PCP 	value		Priority	Acronym	Traffic types
> 1		0 (lowest)	BK		Background
> 0		1 (default)	BE		Best effort
> 2		2			EE		Excellent effort
> 3		3			CA		Critical applications
> 4		4			VI		Video, < 100 ms latency and jitter
> 5		5			VO		Voice, < 10 ms latency and jitter
> 6		6			IC		Internetwork control
> 7		7 (highest)	NC		Network control
>
> These map the 3 bit priority PCP values from VLAN tags to ACs, but
> note the dance with PCP 1 being lower than PCP 0, and more importantly
> the different interpretations about PCP 2, is it "excellent effort" or
> another BK code point?
>
> I guess the point I wanted to make is that mapping down from the 6bit
> DSCP to ACs is not very intuitive (with linear mapping being the "most
> intuitive").
>
> Anyway, I am totally fine with just using 3 bits, this is still plenty
> for priority hierarchies that I can still understand ;)

Oh, it's absolutely a mess. So much so that the IETF had to write a
whole RFC on it: https://tools.ietf.org/html/rfc8325

-Toke


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