PM73487 datasheet(42/251 Pages) PMC

42 / 251 page

PM73487 QRT

PMC-Sierra, Inc.

PMC-980618

Issue 3

622 Mbps ATM Traffic Management Device

Released

Datasheet

A congestion hysteresis bit is kept for each threshold. This bit is set whenever the queue depth

exceeds the congestion limit for that threshold. This bit remains asserted until the queue depth

falls below one-half of the congestion threshold.

Figure 35 illustrates the operation of EPD/PTD.

Figure 36 shows the operation of EPD in combination with CLP-based dropping.

Figure 35. EPD/PTD Operation

Figure 36. EPD/PTD with CLP Operation

Drop these frames

Always send the last cell of each

Tail drop this frame

Time

Maximum Threshold

Queue

Depth

Congested Threshold

Congested Queue Depth

÷ 2

Cells are arriving at a rate greater than the

rate at which they are being played out.

• = End-Of-Frame (EOF) cell

•

Drop these frames

Always send the last cell of each

Tail drop this frame

Time

Maximum Threshold

Queue

Depth

Congested Threshold

Congested Queue Depth

÷ 2

Cells are arriving at a rate greater than the

rate at which they are being played out.

• = End-Of-Frame (EOF) cell

•

= Cell Loss Priority (CLP)

PM73487 Datasheet(PDF) 42 Page - PMC-Sierra, Inc

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