Configuring Srtcm; The Trtcm (Two Rate Three Color Marker) - Samsung Ubigate iBG3026 Configuration Manual

Ubigate iBG3026 Configuration Guide/Ed.00

Configuring srTCM

To enable policing using srTCM, CIR, CBS and EBS need to be configured.
CIR configuration will be mandatory and CBS and EBS parameters will be
optional. CBS will have a default value equal to 'CIR' Kbits, which means
that the default burst time will be 1 sec. EBS will have a default value of 0
Kbits.
An action corresponding to each color assigned to the packet can also be
configured. The types of actions that will be supported are 'permit',
'markdscp' and 'drop'. A DSCP value must be provided if the action type
selected is 'mark-dscp'. The configuration of actions will not be mandatory.
They will have the following default values: green packets - 'permit', yellow
packets - 'mark-dscp 0' and red packets - 'drop'. srTCM can be configured
and enabled for each 'leaf' traffic class on an interface.

The trTCM (Two Rate Three Color Marker)

The trTCM algorithm uses two rates CIR and PIR, and two burst sizes, CBS
and PBS. The trTCM is typically implemented using two token buckets, Tc of
size CBS, and Tp of size PBS. A packet is marked red if it exceeds PBS,
yellow if it exceeds CBS but not PBS, otherwise it is green. Coloring is just a
means to convey the conformance level of packets. An action can be
configured for each color. Supported actions include Permit, Mark-DSCP and
Drop.
Let the token buckets be represented by Tc(t) whose maximum capacity is
CBS bytes, and Tp(t) whose maximum capacity is PBS bytes. One token is the
equivalent of one byte. The Tc(0) is equal to CBS, and Tp(0) is equal to PBS.
Thereafter, tokens are replenished as follows. If Tc < CBS then Tc is
incremented by CIR bytes-per-second up to CBS, and if Tp < PBS then Tp is
incremented by PIR bytes-per-second up to PBS.
When packet of size B bytes arrives for policing, if Tp(t)-B < 0, then the
packet is marked red else, if Tc(t)-B < 0 then the packet is marked yellow and
Tp is decremented by B else the packet is marked green and both Tc and Tp
are decremented by B. This mode of operation is the default mode and is
known as color-blind mode.
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