Information S14769EJ1V0IF00
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CHAPTER 6 TRANSMISSION SCHEDULER
Q.6.1
What is the relationship between the scheduler register settings (I, M, and P parameters) and the actual
transmission rate?
A.6.1
The scheduler register (I, M, and P parameters) is set in cell units. The average rate is set by I/M, which is the
valid cell transmission of I cells per M cell. For the peak rate, the valid cell interval is set as the P cell interval.
The actual transmission rate set by the scheduler register is dependent on the speed (line speed) of the PHY
device connected at the line side. The relationship between the line speed and transmission rate can be
expressed as follows:
Average rate = I/M
×
Line speed
Peak rate = Line speed/(P + 1)
Here is an example of a setting where the line speed is 155.52 Mbps.
Example Line speed = 155.52 Mbps, Average rate = 38.88 Mbps, Peak rate = 51.84 Mbps
I/M = 38.88/155.52 = 1/4
P = (155.52/51.84)
−
1 = 2
Reference:
µ
PD98409 User’s Manual 5.4.4 (4) Scheduler register
Q.6.2
Is the same cell scheduling operation performed with scheduler register settings of I/M = 1/10 and I/M = 10/100?
A.6.2
Yes.
Reference:
µ
PD98409 User’s Manual 5.4.4 (4) Scheduler register
Q.6.3
Is it possible to make the priorities of two or more shapers the same?
A.6.3
Yes. The priorities of the shapers can be made the same by setting the same value to the PRIORITY field of the
scheduler register of each shaper. If a cell transmission timing conflict between shapers of the same priority
occurs, cells are sequentially transmitted to the shapers by using a round-robin algorithm.
Reference:
µ
PD98409 User’s Manual 5.4.4 (4) Scheduler register
