Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
causes congestion to be found for the limit when the queue depth is 31744. This allows a 15-bit
value to be used to store the state of each measurement except the device measurement, which has
a 1-bit value.
Per Service
Class (SC)
Per Queue
Per Channel
Per Virtual
Output (VO)
•
31 Virtual
Outputs (VOs)
Per Device
16 Service
Classes (SCs)
Figure 41. Transmit Maximum and Congested Threshold Checks
Three congestion management algorithms are available for use on a per-channel basis. In each
channel’s TX_CH_CONFIG word (refer to section 9.3.1.7 “TX_CH_CONFIG” starting on
page 189) are bits that enable EPD, CLP-based discard, and EFCI. These may be used in combi-
nation. In addition, Packet Tail Discard (PTD) is supported as a mode of the EPD operation. Fig-
ure 35 on page 30 illustrates the operation of EPD/PTD. Figure 36 on page 30 illustrates the
operation of EPD/PTD with CLP.
As described in “Transmit Resequencing Algorithm” on page 39, there is an interaction between
EPD and the resequencing algorithm. Refer to that section for a complete description.
2.6.3 Transmit Queue Service Algorithm
The transmit queue controller supports 16 SCs for each of its 31 VOs (the per-VO structure is
shown in Figure 42 on page 38). As with the receive queue controller, the transmit queue control-
ler addresses the following key issues: QoS, CDV minimization, MCR guarantee, fairness maxi-
mization, and output isolation.
36
PMC [ PMC-SIERRA, INC ]
