PM9313 datasheet(41/343 Pages) PMC

41 / 343 page

PM9311/2/3/5 ETT1™ CHIP SET

PMC-2000164

ISSUE 3

ENHANCED TT1™ SWITCH FABRIC

Released

Data Sheet

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

PMC-Sierra, Inc.

1.3.3.1

Virtual Output Queues

Ideally, the EPP/DS would have a separate VOQ which would correspond to each of the request counters.

This would mean that congestion on one VOQ would not impact any other VOQ on the same OC-48c or

any VOQs on different OC-48c channels.

In practice, the EPP is constrained by the amount of cell buffering available in the ETT1 Dataslice device

(which contains the actual cell buffers). Consequently, all four request counters that correspond to a single

output channel share a single queue, as shown in Figure 14.

The EPP only manages a single queue for each of the output channels (whether the output channel is

OC-48c or OC-192c). If the EPP is connected to four OC-48c inputs, then those four OC-48c linecards

must share the single queue used for each output. The four dotted arrows in Figure 14 show that the four

request counters for output (0,0) all map to the same VOQ for output (0,0).

PM9313 Datasheet(PDF) 41 Page - PMC-Sierra, Inc