Virtual Private LAN Services
7750 SR OS Services Guide Page 433
VPLS and Rate Limiting
Traffic that is normally flooded throughout the VPLS can be rate limited on SAP ingress through
the use of service ingress QoS policies. In a service ingress QoS policy, individual queues can be
defined per forwarding class to provide shaping of broadcast traffic, MAC multicast traffic and
unknown destination MAC traffic.
MAC Move
The MAC move feature is useful to protect against undetected loops in a VPLS topology as well
as the presence of duplicate MACs in a VPLS service.
If two clients in the VPLS have the same MAC address, the VPLS will experience a high re-learn
rate for the MAC. When MAC move is enabled, the 7750 SR will shut down the SAP or spoke
SDP and create an alarm event when the threshold is exceeded.
MAC move allows sequential order port blocking. By configuration, some VPLS ports can be
configured as “non-blockable” which allows simple level of control which ports are being blocked
during loop occurrence. There are two sophisticated control mechanisms that allow blocking of
ports in a sequential order:
1. Configuration capabilities to group VPLS ports and to define the order they should be
blocked.
2. Criteria defining when individual groups should be blocked.
For the first, configuration CLI is extended by definition of “primary” and “secondary” ports. Per
default, all VPLS ports are considered “tertiary” ports unless they are explicitly declared primary
or secondary. The order of blocking will always follow a strict order starting from “tertiary” to
secondary and then primary.
The definition of criteria for the second control mechanism is the number of periods during which
the given re-learn rate has been exceeded. The mechanism is based on the “cumulative” factor for
every group of ports. Tertiary VPLS ports are blocked if the re-learn rate exceeds the configured
threshold during one period while secondary ports are blocked only when re-learn rates are
exceeded during two consecutive periods, and so forth. The retry timeout period must be larger
than the period before blocking the “highest priority port” so it sufficiently spans across the period
required to block all ports in sequence. The period before blocking the “highest priority port” is
the cumulative factor of the highest configured port multiplied by 5 seconds (the retry timeout can
be configured through the CLI).
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