Users Guide

Differentiated Services 1557
them as a result of exceeding the meter. Pre-colored packets are not re-colored
to green or yellow by the meter. Yellow packets may be colored red as a result
of exceeding the meter.
Refer to RFC 2697 for further details.
Two-Rate Meter Implementation
The police-two-rate algorithm implements a two-rate Three-Color Marker
(trTCM) per RFC 2698. The trTCM algorithm is useful in situations where a
peak rate needs to be enforced separately from a committed rate. A trTCM
meters a traffic stream per the Committed Burst Size (CBS) and Peak Burst
Size (PBS) parameters and colors packets according to the Committed
Information Rate (CIR) and the Peak Information Rate (PIR). The PIR must
be greater than or equal to the CIR. The PBS must be greater than or equal to
the CBS. It is recommended that the CBS parameter be set to the largest IP
packet size that can be legally transported. In color-blind mode, a packet is
colored red if it exceeds the PIR, yellow if it exceeds the CIR, and green if it
exceeds neither.
In color-aware mode, packets may be pre-colored yellow or red based on user-
defined criteria prior to being processed by the meter. Packets that are pre-
colored yellow or red are considered for discard as if the meter had colored
them as a result of exceeding the meter. Pre-colored packets are not re-colored
to green or yellow by the meter. Yellow packets may be colored red as a result
of exceeding the meter.
Refer to RFC 2698 for further details.