OmniSwitch os6900 Network Configuration Manual page 625

Configuring QoS
Profile with a Mix of Strict Priority and WRR
Unicast queues configured as Strict Priority will inherit behavior from the Strict Priority model, and
unicast queues configured as WRR will inherit behavior from the WRR model. Multicast queues will
always follow the behavior that the corresponding unicast queues are following. For example:
•
If UC7 and UC6 are Strict Priority, then the MC3 (priority 6 and 7) will also use Strict Priority.
•
If UC7 and UC6 are Weighted Round Robin, then MC3 (priority 6 and 7) will also use Weighted
Round Robin. The weight of MC3 will be the average of the weights for UC6 and UC7.
For DCB profile ETS behavior, where a Traffic Class (TC) can have more than one priority, multicast
queues will follow the corresponding unicast queue behavior. For example:
DCB Profile 1:
TC 0 ( Priority 0 -3)
TC 1 ( Priority 4 -5)
TC 2 ( Priority 6 -7)
TC 0 has UC0 through UC3 in Round Robin, so MC0 (priority 0 and 1) and MC1 (priority 2 and 3) will
also participate in the Round Robin behavior of TC 0.
Multicast Source PFC on OmniSwitch 6900
Ingress admission control on the OmniSwitch 6900 does not distinguish between unicast and multicast
traffic. Therefore, a multicast source connected to a port which is PFC aware will react to congestion
thereby pausing transmission. This will affect multicast hosts not in the congestion path.
When a multicast source is attached to a port on a OmniSwitch 6900, make sure that PFC is not enabled
for that particular priority on the ingress. This can be done by configuring the port to use DCP 8 (all prior-
ities are lossless) or for instance, DCB-1 (priority 4 and 5 are lossless, so multicast may be sent at any
other priority other than priority 4 or 5).
If multicast sources are configured to react to PFC, it will affect subscribers not in the congestion path.
OmniSwitch AOS Release 7 Network Configuration Guide June 2013
Congestion Management
page 25-17