[RPRWG] Error in rate normalization?
I am having troble interpreting the transformation of localFairRates
to a rate that can be interpreted by other stations on the ringlet
(normalized rate) and the way this is done in the draft
Either I am having a bad day in office or else, something is wrong ;)
Take a look below:
localFairRate is specified in units of:
1. localWeight * [bytes/(ageCoef * agingInterval)]
2. normCoef = localWeight * rateCoef * ageCoef
Where ageCoef and localWeight are per station/ringlet configured
parameters and agingInterval is a global setting which depend on the
link rate.
The normalization process aims to distribute the rate information in a
way that is not dependent on locally configured parameters, thus
dividing 1.(localFairRate) above by 2. (normCoef) :
We get :
3: ( localWeight * [bytes/(ageCoef * agingInterval)]) / (localWeight * rateCoef * ageCoef)
3. result when reorganized and simplified:
bytes / ( ageCoef * ageCoef * agingInterval * rateCoef)
From this I observe two things:
a) The "normalized" value still contains the effect of the local
ageCoef parameter
b) agingInterval is the same for all stations and could also be
removed from the expression by including it in normCoef:
If normCoef is rewritten as:
4. normCoef = (localWeight * rateCoef)/ ( ageCoef * agingInterval)
What we get when diving 1 by 4 is:
5. ( localWeight * [bytes/(ageCoef * agingInterval)]) / ((localWeight * rateCoef)/ ( ageCoef * agingInterval))
5. result when reorganized and simplified (this is the rate
distributed on the ring):
bytes/rateCoef
When the normalized rate is received by another station, this is
converted to a local rate by multiplying the normalized rate by
normCoef (the modified one above) as before.
Best Regards,
Fredrik
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Fredrik Davik
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