Chapter 25 Two Rate Three Color Marker

• Green (low loss priority level) packets are forwarded.

trTCM operates in one of two modes: color-blind or color-aware. In color-blind mode, packets are marked based on evaluating against the PIR and CIR regardless of if they have previously been marked or not. In the color-aware mode, packets are marked based on both existing color and evaluation against the PIR and CIR. If the packets do not match any of colors, then the packets proceed unchanged.

25.2.1 trTCM - Color-blind Mode

All packets are evaluated against the PIR. If a packet exceeds the PIR it is marked red. Otherwise it is evaluated against the CIR. If it exceeds the CIR then it is marked yellow. Finally, if it is below the CIR then it is marked green.

Figure 118 trTCM - Color-blind Mode

 

Exceed NO

 

 

Exceed NO

 

 

Low Packet

 

 

PIR?

 

 

 

 

CIR?

 

 

 

Loss

 

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

High Packet

 

 

 

Medium Packet

 

 

 

 

 

 

Loss

 

 

 

Loss

 

 

 

 

 

25.2.2 trTCM - Color-aware Mode

In color-aware mode the evaluation of the packets uses the existing packet loss priority. trTCM can increase a packet loss priority of a packet but it cannot decrease it. Packets that have been previously marked red or yellow can only be marked with an equal or higher packet loss priority.

Packets marked red (high packet loss priority) continue to be red without evaluation against the PIR or CIR. Packets marked yellow can only be marked red or remain yellow so they are only evaluated against the PIR. Only the packets marked green are first evaluated against the PIR and then if they don’t exceed the PIR level are they evaluated against the CIR.

Figure 119 trTCM - Color-aware Mode

 

 

 

NO

Exceed NO

 

 

 

NO

Exceed NO

 

 

 

 

 

 

 

 

Low Packet

 

 

Red?

 

 

 

 

 

 

 

Yellow?

 

 

 

 

 

 

 

Loss

 

 

 

 

 

 

 

CIR?

 

 

 

 

PIR?

 

 

 

 

 

YES

 

 

YES

 

 

 

YES

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

High Packet

High Packet

 

Medium Packet

Medium Packet

 

 

 

 

Loss

 

Loss

 

Loss

 

Loss

 

 

 

 

209

GS-3012/GS-3012F User’s Guide