Released
Datasheet
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATM Traffic Management Device
lar to the SC1 and SC2 classes (Q2, Q10, Q3, Q41, Q11, ..., Q7, Q15, Q2, ...).
Unicast Traffic
Multicast Traffic
Q8
Q0
Strict Priority SC1
Q9
Q1
S0 S1
Q2
Strict Priority SC2
VC
S125 S126
Timeslot-Based Priority
•
•
Cells are FIFO-Queued
within an SC
Q10
Q11
Q12
Q13
Q14
Q15
Q3
General Purpose
Weighted Round-
Robin SCs
Q4
Q5
Q6
Q7
Figure 42. Transmit Service Class (SC) Map (Per VO)
The transmit queue controller scheduler provides the following benefits:
•
•
•
QoS - the strict priority scheme among SC1, SC2, and GP SCs, and the weighted round-
robin algorithms allows satisfaction of QoS guarantees.
CDV minimization - the treatment of the strict priority SCs ensure that cells within these
SCs get timely service.
MCR guarantee - the timeslot table ensures all SCs will receive a minimum amount of
servicing (clearly, the aggregate bandwidth given to the SC1 and SC2 VCs affects the
remaining bandwidth to be divided between the GP SCs).
•
•
Fairness maximization - the weights of the SCs (1, 4, 16, or 64) allow different SCs to
support different bandwidth requirements (for example, high bandwidth SCs are assigned
64 and are serviced 64 times as often as low bandwidth SCs, which are assigned 1).
Output isolation - the cells of channels destined for different VOs are kept in separate data
structures. This helps isolate the effects of congestion on one VO from causing congestion
on another VO.
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PMC [ PMC-SIERRA, INC ]
