ZyXEL Communications MES-3728 - TRTCM-Color-Blind Mode; TRTCM-Color-Aware Mode; Figure 127 TRTCM-Color-Blind Mode; Figure 128 TRTCM-Color-Aware Mode

Chapter 27 Differentiated Services
MES-3728 User’s Guide
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• 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.
27.2.1 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 127 TRTCM-Color-blind Mode
27.2.2 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 128 TRTCM-Color-aware Mode
Exceed
PIR?
High Packet
Loss
Exceed
CIR?
Medium Packet
Loss
NO
YES
NO
YES
Low Packet
Loss
Exceed
PIR?
High Packet
Loss
Exceed
CIR?
Medium Packet
Loss
NO
YES
NO
YES
Low Packet
Loss
High Packet
Loss
NO
YES
Red? Yellow?
Medium Packet
Loss
NO
YES