Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 509)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 485
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Layer 2 control traffic behavior on VPLS endpoints
3
The number variable refers to the packet limits for broadcast, multicast, and unknown unicast
packets.
NOTE
When configuring global multicast-limit all multicast packets, even those that would have been
hardware forwarded, will not be sent to the CPU to be rate-limited.
CPU packet limiting
The CPU limiting feature affects the packets being flooded into VPLS endpoints as well as remote
peers. The CPU packet limiting is as follows:
• When VPLS policy parameters are configured in the MP, the LP CPU acts on those
configuration parameters and limits the number of packets of a specific type up to the
configured limit.
• Once the number of packets for a given type exceeds the limit, the LP CPU drops the packets
before flooding into the VPLS instance.
• When a packet is dropped, the drop-reason-code is incremented accordingly.
• Counters are reset and start counting the packets again after one second.
• Known unicast packets forwarded by the LP CPU are not counted as drops as those packets is
sent directly to the next hop and not flooded. This can happen in CAM full scenarios.
Interaction with VPLS CPU protection
The interaction with VPLS CPU protection is as follows:
• When the VPLS CPU protection feature is enabled, multicast and broadcast packets are
normally forwarded in hardware using a flooding entry after Source MAC Address (SA) learning.
Most of the unicast packets is forwarded in hardware as well, and packets are sent to the CPU
for flooding in a rate-limiting fashion depending upon CPU utilization.
• When VPLS CPU protection is configured along with the packet-limiting feature, the packets
with CPU protection is subjected to CPU limiting. In other words, the packets coming to the CPU
for VPLS with CPU protection may be dropped with the CPU limiting feature enabled.
Multicast traffic processing
The multicast traffic processing is as follows:
• When a multicast packet limit is configured, multicast data packets are not differentiated from
multicast protocol packets.
• All the packets is subjected to packet limitations and may be dropped when they exceed
per-second multicast packet limits.
• Multicast snooping packets and IEEE 802.1ag packets may be affected as well.
Layer 2 control traffic behavior on VPLS endpoints
This section describes the Layer 2 control traffic behavior on VPLS endpoints.