102 Converged Enhanced Ethernet Administrator’s Guide
53-1001761-01
Scheduling
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DRAFT: BROCADE CONFIDENTIAL
Multicast rate limit is applied to the output of each multicast receive queue. Rate limits apply
equally to ingress receive queueing (first level expansion) and egress receive queueing (second
level expansion) since the same physical receive queues are utilized. You can set policies to limit
the maximum multicast frame rate differently for each traffic class level and cap the total multicast
egress rate out of the system.
Multicast rate limiting includes the following features:
•All configuration parameters are applied globally. Multicast rate limits are applied to multicast
receive queues as frame replications are placed into the multicast expansion queues. The
same physical queues are used for both ingress receive queues and egress receive queues so
rate limits are applied to both ingress and egress queueing.
•Four explicit multicast rate limit values are supported, one for each traffic class. The rate limit
values represent the maximum multicast expansion rate in packets per second (PPS).

Creating a receive queue multicast rate-limit

Perform the following steps from Privileged EXEC mode to create the receive queue multicast
rate-limit.
1. Enter global configuration mode.
switch#configure terminal
2. Create a lower maximum multicast frame expansion rate. In this example, the rate is to 10000
PPS.
switch(config)#qos rcv-queue multicast rate-limit 10000
Example of creating a lower maximum multicast frame expansion rate to 10000pkt/s.
switch:admin>cmsh
switch>enable
switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
switch(config)#qos rcv-queue multicast rate-limit 10000
switch(config)#end
3. Enter the copy comman d to save the running-conf ig file to the start up-config file.
switch#copy running-config startup-config
Scheduling
Scheduling arbitrates among multiple queues waiting to transmit a frame. The Brocade 8000
supports both Strict Priority (SP) and Deficit Weighted Round Robin (DWRR) scheduling algorithms.
Also supported is the flexible selection of the number of traffic classes using SP-to-DWRR. When
there are multiple queues for the same traffic class, then scheduling takes these equal priority
queues into consideration.

Strict priority scheduling

Strict priority scheduling is used to facilitate support for latency-sensitive traffic. A strict priority
scheduler drains all frames queued in the highest priority queue before continuing on to service
lower priority traffic classes. A danger with this type of service is that a queue can potentially starve
out lower priority traffic classes.