User guide

QOS QoS implementation for DIFFSERV
iMG/RG Software Reference Manual (Quality of Service)
7-6
7.1.3.3.1 How metering works
The Meter device compares temporal properties of the incoming traffic stream against configured parameters.
There are two types of meter:
• Two-level meter
This meter informs whether a packet is in profile (Green) or out of profile (Red).
• Three-level meter
This informs whether a packet is completely in profile (Green), partially in profile (Yellow) or out of profile
(Red).
The meter profile consists of a collection of parameters that define how the metering of packets is to be per-
formed. There are three different meter profiles that can be used with the above meter types.
• Token bucket meter profile (used with two-level meter).
• srTCM (single rate three color marker) meter profile (used with three-level meter).
• trTCM (two rate three color marker) meter profile (used with three-level meter).
These meter profiles differ in the algorithms that they use to decide if a packet is in or out of profile. The fol-
lowing sections describe the above profiles.
7.1.3.3.2 Token bucket meter profile
A two-level meter profile called the Token bucket meter profile consists of two parameters:
• Committed information rate (CIR)
• Committed burst size (CBS)
If the packet stream's average rate is within CIR and the burst size is within CBS then the packet is marked
Green, otherwise the packet is marked Red.
7.1.3.3.3 srTCM (single rate three color marker) meter profile
A three-level meter profile named as srTCM (single rate three color marker) meter profile consists of three
parameters:
• Committed information rate (CIR)
• Committed Burst Size (CBS)
• Excess Burst Size (EBS)
If the packet stream's average rate is within CIR and the burst size is within CBS then the packet is marked
Green. If the packet stream's average rate is within CIR and the burst size is not within CBS but within
"CBS+EBS" then the packet is marked Yellow. Otherwise, the packet is marked Red.