PXF4333 Datasheet, PDF (114/361 Pages) Infineon Technologies AG – ABM 3G ATM Buf fer Manager

ABM-3G
PXF 4333 V1.1
Operational Description
4.2.2.7 Guaranteed Cell Rates and WFQ Weight Factors
The total WFQ scheduler rate is calculated as follows:
GCR_WFQ = CCR_SB – ECR_RT(SB)
(24)
with CCR_SB being the configured SB rate as defined in Section 4.2.2.2 and ECR_RT(SB)
being the effective cell rate of the high priority RR scheduler in the SB.
GCR_WFQ is distributed to the queues in proportion to the queue’s relative weight factor 1/
T_WFQ.
The guaranteed cell rate for connection i is calculated according to:
GCR_i = -------------------------------------^G-----^C----^R-----^W-----^F---^Q---------------------------------------
(25)
T_WFQ(i) ×
Ã¥
1 ⁄ T_WFQ(k)
∀k ∈ Active Queues
with T_WFQ constrained internally to:
T_WFQ ≤ 2¹⁴ – 2⁶
(26)
Therefore, T_WFQmax = 16320.
The minimum guaranteed cell rate at a given GCR_WFQ is therefore:
GCR_min
=
G_-----C_-----R_{-----W-----F---Q--}
T_WFQmax
(27)
Assuming a fixed given GCR_min, then for any given GCR >= GCR_min the corresponding
T_WFQ can be calculated as:
T_WFQ=
-^G----^C-----^R-----^m----ⁱ-ⁿ----^×-----^T----^W-----^F---^Q----^m----^a---^x-
GCR
(28)
The integer function in equation above selects the next smaller value of the integer T_WFQ,
that is to say, the weight factor is higher than required and, thus, the queue is served
slightly faster in order to guarantee the rate.
Two special cases must be considered:
T_WFQ = 0 is used to assign the queue to the high priority round robin scheduler.
T_WFQ = 16383 is used to assign the queue to the low priority round robin scheduler.
T_WFQ is referred to as parameter WFQFactor in the register description “UQPT2T1/
DQPT2T1” on Page 254.
Data Sheet
114
2001-12-17