QoS unicast and multicast traffic is supported only on the following devices, Extreme
8820, SLX 9740, SLX 9640, SLX 9540, SLX
9250, and SLX 9150.
In the Traffic Manager, QoS for unicast traffic
follows the process shown in the following figure.
QoS for unicast traffic
The input is buffered through Virtual Output Queues
(VOQ) with output port-driven scheduling.
Each ingress Traffic Manager maintains a set of eight distinct priority queues for every output port on the system. Incoming packets are enqueued to a VOQ corresponding to the destination output port and classified with an internal priority.
Packets are dequeued by an output port on the egress card when the output port is ready to send a packet.
Switch fabric messaging is used to maintain a tight coupling between ingress and egress cards.
Egress Traffic Manager dequeues packets from
appropriate VOQs by sending VOQ transmission credits to the respective ingress
traffic managers.
Consider the following when you manage multicast
traffic:
There are four fabric multicast queues
(FMQs) for multicast traffic.
The Traffic Manager maps incoming
packets to these queues based on the traffic class or drop precedence received
from the packet processor (PP).
The ingress Traffic Manager pushes
multicast traffic to the fabric by strict priority (SP) or by a mix of SP and
weighted priority.
There is a CLI to configure ingress
multicast shaping. By default, it is opened to the maximum rate of the tower.
The egress Traffic Manager maps these
multicast packets to two egress queues (EGQ).
