Ubigate iBG2016 Configuration Guide/Ed.00© SAMSUNG Electronics Co., Ltd. 191The trTCM (Two Rate Three Color Marker)The trTCM algorithm uses two rates CIR and PIR, and two burst sizes, CBSand PBS. The trTCM is typically implemented using two token buckets, Tc ofsize 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 ameans to convey the conformance level of packets. An action can beconfigured for each color. Supported actions include Permit, Mark-DSCP andDrop.Let the token buckets be represented by Tc(t) whose maximum capacity isCBS bytes, and Tp(t) whose maximum capacity is PBS bytes. One token is theequivalent 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 isincremented by CIR bytes-per-second up to CBS, and if Tp < PBS then Tp isincremented by PIR bytes-per-second up to PBS.When packet of size B bytes arrives for policing, if Tp(t)-B < 0, then thepacket is marked red else, if Tc(t)-B < 0 then the packet is marked yellow andTp is decremented by B else the packet is marked green and both Tc and Tpare decremented by B. This mode of operation is the default mode and isknown as color-blind mode.In the color aware mode, packet is assumed to be pre-colored. In this casewhen packet of size B bytes arrives for policing, if Tp(t)-B < 0 and packetcolor is green or yellow, then the packet marked red else if Tc(t)-B < 0 andpacket color green then the packet marked yellow and Tp is decremented by Belse packet’s color is unchanged and both Tc and Tp are decremented by B.
