LevelOne GTL-2691 - Manual (Page 1178)

C HAPTER 41 | Quality of Service Commands
– 1178 –
The token buckets C and E are initially full, that is, the token count
Tc(0) = BC and the token count Te(0) = BE. Thereafter, the token
counts Tc and Te are updated CIR times per second as follows:
■
If Tc is less than BC, Tc is incremented by one, else
■
if Te is less then BE, Te is incremented by one, else
■
neither Tc nor Te is incremented.
When a packet of size B bytes arrives at time t, the following happens if
srTCM is configured to operate in color-blind mode:
■
If Tc(t)-B ≥ 0, the packet is green and Tc is decremented by B down
to the minimum value of 0, else
■
if Te(t)-B ≥ 0, the packets is yellow and Te is decremented by B
down to the minimum value of 0,
■
else the packet is red and neither Tc nor Te is decremented.
When a packet of size B bytes arrives at time t, the following happens if
srTCM is configured to operate in color-aware mode:
■
If the packet has been pre-colored as green and Tc(t)-B ≥ 0, the
packet is green and Tc is decremented by B down to the minimum
value of 0, else
■
If the packet has been pre-colored as yellow or green and if
■
Te(t)-B ≥ 0, the packets is yellow and Te is decremented by B down
to the minimum value of 0, else the packet is red and neither Tc nor
Te is decremented.
The metering policy guarantees a deterministic behavior where the
volume of green packets is never smaller than what has been
determined by the CIR and BC, that is, tokens of a given color are
always spent on packets of that color. Refer to RFC 2697 for more
information on other aspects of srTCM.
E XAMPLE
This example creates a policy called “rd-policy,” uses the class command to
specify the previously defined “rd-class,” uses the set command to classify
the service that incoming packets will receive, and then uses the police
srtcm-color-blind command to limit the average bandwidth to 100,000
Kbps, the committed burst rate to 4000 bytes, the excess burst rate to
6000 bytes, to remark any packets exceeding the committed burst size,
and to drop any packets exceeding the excess burst size.
Console(config)#policy-map rd-policy
Console(config-pmap)#class rd-class
Console(config-pmap-c)#set ip dscp 3
Console(config-pmap-c)#police srtcm-color-blind 100000 4000 6000 exceed-
action 0 violate-action drop
Console(config-pmap-c)#