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

Table Of Contents
Converged Enhanced Ethernet Administrator’s Guide 113
53-1001258-01
Multicast rate limiting
8
Ethernet Per-Priority Pause
Ethernet Per Priority Pause (PPP) is a basic extension of the Ethernet Pause. The Pause MAC
control message is extended with eight 2-byte pause numbers and a bitmask to indicate which
values are valid. Each pause number is interpreted identically to the base Pause protocol; however
each is applied to the corresponding Ethernet priority / class level. For example, the Pause number
zero applies to priority zero, Pause number one applies to priority one, and so on. This addresses
one shortcoming of the Ethernet Pause mechanism, which is disruptive to all traffic on the link.
However, it still suffers from the other Ethernet Pause limitations.
Ethernet Per-Priority Pause includes the following features:
Everything operates exactly as in Ethernet Pause described above except there are 8
high-water and low-water thresholds for each input port. This means queue levels are tracked
per input port plus priority.
Pause On/Off can be specified independently for TX and RX directions per priority.
Pause time programmed into Ethernet MAC is a single value covering all priorities.
Both ends of a link must be configured identically for Ethernet Pause or Ethernet Per Priority
Pause because they are incompatible.
Enabling an Ethernet PPP
Example of enabling an interface 802.3x Pause flow control TX and RX.
switch:admin>cmsh
switch>enable
switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
switch(config)#interface tengigabitethernet 0/2
switch(conf-if-te-0/2)#qos flowcontrol pfc 3 tx on rx on
switch(conf-if-te-0/2)#exit
switch(config)#exit
switch#
Multicast rate limiting
Multicast rate limiting provides a mechanism to control multicast packet replication and cap the
effect of multicast traffic.
Multicast rate limit is applied to the output of each multicast receive queue. Rate limits apply
equally to ingress receive queueing (1st level expansion) and egress receive queueing (2nd level
expansion) since the same physical receive queues are utilized. You can set policies to limit the
maximum multicast packet rate differently for each traffic class level and cap the total multicast
egress rate out of the system.
Step Task Command
1 Enter global configuration mode.
switch#configure terminal
2 Specify the 10-gigabit Ethernet interface. In
this example, 0/2 is used.
switch(config)#interface
tengigabitethernet 0/2
3 Enable an Ethernet PPP on the interface. switch(conf-if-te-0/2)#qos
flowcontrol pfc 3 tx on rx on