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Chapter 10 Quality of Service (QoS)
VMG4380-B10A / VMG4325-B10A User’s Guide
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The srTCM 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 srTCM is based on the token bucket filter and has two token buckets (CBS and EBS). Tokens
are generated and added into the bucket at a constant rate, called Committed Information Rate
(CIR). When the first bucket (CBS) is full, new tokens overflow into the second bucket (EBS).
All packets are evaluated against the CBS. If a packet does not exceed the CBS it is marked green.
Otherwise it is evaluated against the EBS. If it is below the EBS then it is marked yellow. If it
exceeds the EBS then it is marked red.
The following shows how tokens work with incoming packets in srTCM:
• A packet arrives. 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).
• After a packet is transmitted, a number of tokens corresponding to the packet size is removed
from the CBS bucket.
• If there are not enough tokens in the CBS bucket, the Device 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 Device 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.
Summary of Contents for VMG4325-B10A
Page 4: ...Contents Overview VMG4380 B10A VMG4325 B10A User s Guide 4 Troubleshooting 283 ...
Page 14: ...Table of Contents VMG4380 B10A VMG4325 B10A User s Guide 14 ...
Page 15: ...15 PART I User s Guide ...
Page 16: ...16 ...
Page 24: ...Chapter 1 Introducing the Device VMG4380 B10A VMG4325 B10A User s Guide 24 ...
Page 69: ...69 PART II Technical Reference ...
Page 70: ...70 ...
Page 178: ...Chapter 10 Quality of Service QoS VMG4380 B10A VMG4325 B10A User s Guide 178 ...
Page 204: ...Chapter 13 Interface Group VMG4380 B10A VMG4325 B10A User s Guide 204 ...
Page 220: ...Chapter 15 Firewall VMG4380 B10A VMG4325 B10A User s Guide 220 ...
Page 226: ...Chapter 17 Parental Control VMG4380 B10A VMG4325 B10A User s Guide 226 ...
Page 236: ...Chapter 19 Certificates VMG4380 B10A VMG4325 B10A User s Guide 236 ...
Page 240: ...Chapter 20 Log VMG4380 B10A VMG4325 B10A User s Guide 240 ...
Page 244: ...Chapter 21 Traffic Status VMG4380 B10A VMG4325 B10A User s Guide 244 ...
Page 250: ...Chapter 24 IGMP Status VMG4380 B10A VMG4325 B10A User s Guide 250 ...
Page 254: ...Chapter 25 xDSL Statistics VMG4380 B10A VMG4325 B10A User s Guide 254 ...
Page 256: ...Chapter 26 User Account VMG4380 B10A VMG4325 B10A User s Guide 256 ...
Page 262: ...Chapter 29 TR 064 VMG4380 B10A VMG4325 B10A User s Guide 262 ...
Page 266: ...Chapter 30 Time Settings VMG4380 B10A VMG4325 B10A User s Guide 266 ...
Page 272: ...Chapter 32 Logs Setting VMG4380 B10A VMG4325 B10A User s Guide 272 ...
Page 290: ...Chapter 36 Troubleshooting VMG4380 B10A VMG4325 B10A User s Guide 290 ...
Page 344: ...Appendix D Wireless LANs VMG4380 B10A VMG4325 B10A User s Guide 344 ...