Released
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
1.3.3.3 Four Priorities
The description in the preceding sections only considered a single priority. The EPP supports four
priorities. Therefore, there are four times as many counters and queues as have been described so far ,
and this is only for unicast traffic. The four priorities can be modeled as separate planes; the input and
output queue figures shown earlier can be considered as 2-D planes. The four priorities are then four
copies of these planes, stacked next to each other in a third dimension. Figure 17 illustrates this model for
the reference counters and virtual output queues. The virtual input queues at the oEPP are not shown.
Consequently, each iEPP has 2048 request counters (4 OC-48c input channels * 128 output channels * 4
priorities) and 512 virtual output queues (128 outputs * 4 priorities). Each oEPP has 512 virtual input
queues (4 output channels * 32 ports * 4 priorities). Remember, this calculation is for the configuration of
128 ports of OC-48c. Later on we describe how the number of queues and request counters differs for
some other possible configurations.
44
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
PMC [ PMC-SIERRA, INC ]
