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A rate-limit rule is an instance of a rate-limit profile. The same profile can be used
to create many rate-limit rules in the same hierarchy or in different rate-limit
hierarchies. The classifier group that defines the flow can use a mark rule with
color-mark profile to set the packet ToS field based on the packet color. A rate-limit
hierarchy invoked from the classifier group is one way of changing the packet color;
the rate-limit hierarchy is invoked before the classifier group runs the mark rule to
set the packet ToS.
Hierarchical Rate-Limit Actions
Every packet traversing a rate-limit hierarchy has an owner that is defined by the
last rate limit that can apply its actions to the packet; this is a configuration option.
A rate limit in the hierarchy that does not own the packet only decrements its tokens,
but cannot perform any of the following actions:
These actions become the same action if the hierarchy has only one rate limit.
Combining these actions with the additional choices to transmit or drop packets
results in the following possible actions:
Preferred packets are transmitted unconditionally. Rate limits that process packets
transmitted unconditionally always decrement their token count, if necessary,
making it negative.
Red packets cannot be transmitted unconditionally, to avoid cases where an
aggregate rate limit is oversubscribed with transmit-unconditional rates.
Color-aware uses the incoming packet color in its algorithm
Not promoting packets means that if the packet enters the rate limit as yellow
and the rate-limit then determines that it is green, the packet remains yellow. If
the rate limit determines it is red, then the packet is colored red.
Transfer ownership of the packet to the next rate limit.
Retain ownership of the packet but consume tokens from the remaining rate
limits in the hierarchy.
Exit the rate-limit hierarchy, making that rate limit the final one for the packet.
Drop Drops the packet at that rate limit in the hierarchy. The packet does not
change the state of any rate limit further down the hierarchy.
Transmit final Sets the packet color and ends the packet's traversal of the
rate-limit hierarchy at the current rate limit. The packet is forwarded and the
rate limits further down the hierarchy are not affected. Because transmit final is
based on the result of the rate limit, transmit is not an attribute of the node in
the rate-limit hierarchy. Committed packets can exit the hierarchy while
conformed and exceeded packets continue to the next rate limit.
Transmit conditional Sets the packet color to the result calculated by the rate
limit and forwards the packet to the next rate limit for processing, also
transferring ownership of the packet to the next rate limit. The next rate limit
can then set the packet color according to the state of its token buckets and apply
Chapter 5: Creating Rate-Limit Profiles
Hierarchical Rate Limits Overview
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