ZyXEL VMG3925-B10B User Guide - Page 152

Two Rate Three Color Marker

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Chapter 10 Quality of Service (QoS) • If there are not enough tokens in the CBS bucket, the VMG checks the EBS bucket. The packet is marked yellow if there are sufficient tokens in the EBS bucket. Otherwise, the packet is marked red. No tokens are removed if the packet is dropped. Two Rate Three Color Marker The Two Rate Three Color Marker (trTCM, defined in RFC 2698) is a type of traffic policing that identifies packets by comparing them to two user-defined rates: the Committed Information Rate (CIR) and the Peak Information Rate (PIR). The CIR specifies the average rate at which packets are admitted to the network. The PIR is greater than or equal to the CIR. CIR and PIR values are based on the guaranteed and maximum bandwidth respectively as negotiated between a service provider and client. The trTCM evaluates incoming packets and marks them with one of three colors which refer to packet loss priority levels. High packet loss priority level is referred to as red, medium is referred to as yellow and low is referred to as green. The trTCM is based on the token bucket filter and has two token buckets (Committed Burst Size (CBS) and Peak Burst Size (PBS)). Tokens are generated and added into the two buckets at the CIR and PIR respectively. 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. The following shows how tokens work with incoming packets in trTCM: • A packet arrives. If the number of tokens in the PBS bucket is less than the size of the packet (in bytes), the packet is marked red and may be dropped regardless of the CBS bucket. No tokens are removed if the packet is dropped. • If the PBS bucket has enough tokens, the VMG checks the CBS bucket. The packet is marked green and can be transmitted if the number of tokens in the CBS bucket is equal to or greater than the size of the packet (in bytes). Otherwise, the packet is marked yellow. VMG3925-B10B User's Guide 152

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Chapter 10 Quality of Service (QoS)
VMG3925-B10B User’s Guide
152
If there are not enough tokens in the CBS bucket, the VMG checks the EBS bucket. The packet is
marked yellow if there are sufficient tokens in the EBS bucket. Otherwise, the packet is marked
red. No tokens are removed if the packet is dropped.
Two Rate Three Color Marker
The Two Rate Three Color Marker (trTCM, defined in RFC 2698) is a type of traffic policing that
identifies packets by comparing them to two user-defined rates: the Committed Information Rate
(CIR) and the Peak Information Rate (PIR). The CIR specifies the average rate at which packets are
admitted to the network. The PIR is greater than or equal to the CIR. CIR and PIR values are based
on the guaranteed and maximum bandwidth respectively as negotiated between a service provider
and client.
The trTCM evaluates incoming packets and marks them with one of three colors which refer to
packet loss priority levels. High packet loss priority level is referred to as red, medium is referred to
as yellow and low is referred to as green.
The trTCM is based on the token bucket filter and has two token buckets (Committed Burst Size
(CBS) and Peak Burst Size (PBS)). Tokens are generated and added into the two buckets at the CIR
and PIR respectively.
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.
The following shows how tokens work with incoming packets in trTCM:
A packet arrives. If the number of tokens in the PBS bucket is less than the size of the packet (in
bytes), the packet is marked red and may be dropped regardless of the CBS bucket. No tokens
are removed if the packet is dropped.
If the PBS bucket has enough tokens, the VMG checks the CBS bucket. The packet is marked
green and can be transmitted if the number of tokens in the CBS bucket is equal to or greater
than the size of the packet (in bytes). Otherwise, the packet is marked yellow.