Brocade Converged Enhanced Ethernet Administrator's Guide v6.1.2_cee (53-1001258-01, June 2009)

114 Converged Enhanced Ethernet Administrator’s Guide
53-1001258-01
Scheduling
8
Multicast rate limiting includes the following features:
• All configuration parameters are applied globally. Multicast rate limits are applied to multicast
receive queues as packet 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.
Creating a receive queue multicast rate-limit
Example of creating a lower maximum multicast packet 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)#exit
switch#
Scheduling
In this section:
•Strict priority scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
•Weighted round robin scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
•Traffic class scheduling policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
•Multicast queue scheduling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Scheduling arbitrates among multiple queues waiting to transmit a packet. The Brocade 8000
supports both Strict Priority (SP) and Weighted Round Robin (WRR) scheduling algorithms. Also
supported is the flexible selection of the number of traffic classes using SP-to-WRR. 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 packets 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.
Step Task Command
1 Enter global configuration mode.
switch#configure terminal
2 Create a lower maximum multicast packet
expansion rate. In this example, the rate is to
10000pkt/s.
switch(config)#qos rcv-queue
multicast rate-limit 10000