ZyXEL Communications VMG8924-B10D - Technical Reference

Chapter 10 Quality of Service (QoS)
VMG8924-B10D/B30D User’s Guide
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10.8 Technical Reference
The following section contains additional technical information about the VMG features described in
this chapter.
IEEE 802.1Q Tag
The IEEE 802.1Q standard defines an explicit VLAN tag in the MAC header to identify the VLAN
membership of a frame across bridges. A VLAN tag includes the 12-bit VLAN ID and 3-bit user priority.
The VLAN ID associates a frame with a specific VLAN and provides the information that devices need to
process the frame across the network.
Meter Type This shows the traffic metering algorithm used in this policer.
The Simple Token Bucket algorithm uses tokens in a bucket to control when traffic can be
transmitted. Each token represents one byte. The algorithm allows bursts of up to b bytes which is
also the bucket size.
The Single Rate Three Color Marker (srTCM) is based on the token bucket filter and identifies
packets by comparing them to the Committed Information Rate (CIR), the Committed Burst Size
(CBS) and the Excess Burst Size (EBS).
The Two Rate Three Color Marker (trTCM) is based on the token bucket filter and identifies
packets by comparing them to the Committed Information Rate (CIR) and the Peak Information
Rate (PIR).
Committed
Rate
Specify the committed rate. When the incoming traffic rate of the member QoS classes is less
than the committed rate, the device applies the conforming action to the traffic.
Committed
Burst Size
Specify the committed burst size for packet bursts. This must be equal to or less than the peak
burst size (two rate three color) or excess burst size (single rate three color) if it is also configured.
This is the maximum size of the (first) token bucket in a traffic metering algorithm.
Conforming
Action
Specify what the VMG does for packets within the committed rate and burst size (green-marked
packets).
• Pass: Send the packets without modification.
• DSCP Mark: Change the DSCP mark value of the packets. Enter the DSCP mark value to use.
Non-
Conforming
Action
Specify what the VMG does for packets that exceed the excess burst size or peak rate and burst
size (red-marked packets).
• Drop: Discard the packets.
• DSCP Mark: Change the DSCP mark value of the packets. Enter the DSCP mark value to use.
The packets may be dropped if there is congestion on the network.
Available Class
Selected Class
Select a QoS classifier to apply this QoS policer to traffic that matches the QoS classifier.
Highlight a QoS classifier in the Available Class box and use the > button to move it to the
Selected Class box.
To remove a QoS classifier from the Selected Class box, select it and use the < button.
Apply Click Apply to save your changes.
Cancel Click Cancel to exit this screen without saving.
Table 52 Policer Setup: Add/Edit
LABEL DESCRIPTION