Chapter 6 Transmission Scheduler; What Is The Relationship Between The Scheduler Register Settings (I, M, And P Parameters) And The Actual Transmission Rate; Is The Same Cell Scheduling Operation Performed With Scheduler Register Settings Of I/M = 1/10 And I/M = 10/100; Is It Possible To Make The Priorities Of Two Or More Shapers The Same - NEC mPD98409 Q&A

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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.

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

A.6.2

Yes.

Reference: µ PD98409 User's Manual 5.4.4 (4) Scheduler register

Q.6.3

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

CHAPTER 6 TRANSMISSION SCHEDULER

The relationship between the line speed and transmission rate can be

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