Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
Figure 37 shows the operation of EFCI.
EFCI Codepoints Set
Queue
Depth
From Here
To Here
Congestion Threshold
Congestion Threshold ÷ 2
Time
Time
Figure 37. EFCI Operation
The congestion limits are kept in an exponential form. The interpretation of the limits is the same
for all measurements, except the device limit. For the other measurements, the value of “0” causes
the measurement to always find congestion. The value of “1” may not be used. The value of Fh
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 16-bit value.
2.5.5 Receive Queue Service Algorithm
Each switch fabric cell time, the receive queue controller selects up to four cells for transmission
to the switch fabric. The controller supports per-channel (per-VC) queues with 64 SCs. The con-
troller addresses the following issues: QoS, Cell Delay Variation (CDV) minimization, Minimum
Cell Rate (MCR) guarantees, and fairness maximization. The flexibility of the controller ensures
that VCs receive their expected bandwidth in a timely fashion depending upon their traffic
requirements.
Run Queue Service Algorithm to
determine Service Class (SC)
Read from ring to
determine channel
Find pointer to cell from
channel linked list
Update structures with
results of transmission
Fetch cell
Send cell to fabric
Figure 38. Steps to Send a Cell to the Fabric
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PMC [ PMC-SIERRA, INC ]
