Profile Capped Policers - Alcatel-Lucent 7950 Quality Of Service Manual

Explicit Arbiter Rate Limits

Profile Capped Policers

Profile capped mode has been introduced to enforce an overall in-profile burst limit to the CIR
bucket for ingress undefined, ingress explicit in-profile, egress soft-in-profile and egress explicit
in-profile packets. The default behavior when profile-capped mode is not enabled is to ignore the
CIR output state when an explicit in-profile packet is handled by an ingress or egress policer. The
explicit in-profile packets will consume CIR tokens up to 2xCBS at which point the bucket stops
incrementing and the CIR output for that type of packet enters the non-conforming state.
However, the non-conforming state is ignored by the forwarding plane and the packet continues to
be handled as in-profile. Thus, the total amount of in-profile traffic can be greater than the
configured CIR.
The profile-capped mode makes two changes:
•
•
The idea is that a profile capped policer trusts the in-profile state determined at ingress
classification or egress re-classification, the initial in-profile traffic is preferentially handled with
the CIR bucket (2xCBS instead of 1xCBS used by undefined or soft-out-of-profile traffic) and the
total amount of in-profile traffic output by the policer cannot exceed the CIR (including initial in-
profile traffic).
One other aspect to consider with profile-capped mode is the effect on stat-mode behavior. As will
be seen below, each stat-mode has a fixed number of counters in the NP and Q. The mapping of
packets to a counter is also fixed by the offered packet state (profile in, profile out, undefined, soft-
in-profile and soft-out-of-profile) in conjunction with the output state of the policer. Particularly of
note is the egress policer stat-modes and the behavior of soft-in-profile (from ingress) and profile
in (reclassified at egress) packets. In the non-capped mode, soft-in-profile is considered undefined
while in capped mode it is considered to be equivalent to profile in. Another aspect that causes
issues with ingress and egress stat-modes is the fact that initially green (profile in at ingress and
egress as well as soft-in-profile at egress), packets can actually turn yellow in the policer output.
Table 37
normal (non-profile-capped) and profile-capped mode policers.
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At egress, soft-in-profile packets (packets received from ingress as in-profile) are treated
the same as explicit in-profile (unless explicitly reclassified as out-of-profile) and have an
initial policer state of in-profile
At both ingress and egress, any packet output from the policer with a non-conforming CIR
state are treated as out-of-profile (out-of-profile state is ignored for initial in-profile
packets when profile capped mode is not enabled)
demonstrates how the CIR rate and initial profile of each packet affects the output of
7950 XRS Quality of Service Guide