Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 990)

Quality of Service (QoS) Introduction
Software Reference for x310 Series Switches
38.18 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
Initially both buckets have their full token count. A surge of data exceeding the CIR will
begin to empty the bucket. As the data and tokens are paired, data bytes that match
tokens below the CBS level are marked green, those that are between CBS and EBS will be
marked yellow, and those that are above EBS are marked red.
Note that although the data is metered per byte, the color marking process is applied per
packet. This means that if there were only sufficient tokens available to match part of a
packet, then the whole packet would be marked red. Then, depending on the action
parameter of the
police single-rate action command, the whole packet will be either
dropped or forwarded. In either situation, the red-marked packet will leave the bucket
counts unchanged.
Two-rate Three-color Policing
This policing method is based on that defined in RFC 2698. The principle of two-rate
three-color policing is shown in
Figure 38-8 .
Figure 38-8: 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).
M
e
t
e
r
Bucket P
Tc = Tokens
in Committed
Bucket
Green tokens
enter the
Committed Bucket
CBS
(minburstsize)
Bucket C
Two-Rate Three-Color Policing (color aware mode)
TR-TC_bucket_meter
Data packets (at data rate > CIR)
Tc
packet size > Tp
Packets marked after metering
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
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
Note that although the data is metered in bytes, coloring is applied per packet.