Quality of Service (QoS)
©2008 Allied Telesis Inc. All rights reserved.
Software Version 5.2.1
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
39.17
Two rate three-color policing
This policing method is based that defined in RFC 2698. The principle of two-rate three-color
policing is shown in
Figure 39-8 on page 39.17
.
Figure 39-8: Two-Rate Three-Color Policer
For a given class-map, the meter monitors the token count in both buckets, and the input data
flow. Initially tokens enter both buckets until full. As the data enters a port, the meter pairs
each byte to a token in one of the buckets, then removes a token from the appropriate bucket.
Bucket C is topped up with tokens at the Committed Information Rate (CIR), and bucket P is
topped up at the Peak Information Rate (PIR).
When data enters the port at the CIR, the bucket fills at the same rate as the incoming data,
thus the token count in bucket C remains constant. Similarly, if data enters the port at the PIR,
then the token count in bucket P remains constant. You can specify the CIR and the PIR by
using either the the
police twin-rate exceed-action
command or the
mls qos aggregate-police
exceed-action
command. The function of each of these commands is explained in the section
“Configuring and Applying a Policer” on page 39.18
.
M
e
t
e
r
Bucket C
Bucket P
Two-Rate Three-Color Policing (color aware mode)
TR-TC_bucket_meter
Data packets (at data rate > CIR)
packet size > Tc
packet size > Tp
Packets marked after metering
Tokens replace used
(green) tokens at the
Committed Information
Rate (CIR)
Tokens replace used
(yellow) tokens at the
Peak Information
Rate (PIR)
green (bucket C topped up)
Yellow (bucket P topped up)
red (no token top-up))
red (no token top-up))
PBS
(maxburstsize)
= Tp for full
bucket
CBS
(maxburstsize)
= Tc for full
bucket
yellow (bucket P topped up)
red (no token top-up)
green, yellow or red
packet size TC
yellow (bucket P topped up)
yellow
green
red
green
Yellow
red
Tokens in
Bucket P = Tp
Tokens in
Bucket C = Tc