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QoS Excess Tagging 511
QoS Excess Tagging
Your system enables you to tag nonconforming excess (packets that
exceed the rate-limit criteria) with a special IEEE 802.1p tag value. This
refers to any packets marked as excess that you want to tag. By default,
excess tagging is disabled.
You can use your configuration tool (Administration Console or Web
Console) to enable or disable excess tagging and display your excess
tagging information.
If you
enable excess tagging
, you can specify an IEEE 802.1p tag value for
nonconforming excess in the range of from 0 to 7 , with 0 as the default.
(See “IEEE 802.1p” earlier in this chapter for a list of the tags and their
associated priority levels). Specifying
1 means that nonconforming excess
become background traffic.
Example of QoS
Excess Tagging
The following example shows how to use a classifier, control, and QoS
excess tagging to tag conforming QoS multicast video traffic from a
server as
Streaming Multimedia 802.1p service and tag any excess traffic
as Standard 802.1p service.
In this sample configuration:
■
The configured rate limit is 1 MByte, so when the server sends
1.5 MBytes, the upstream system knows 1 MByte is conforming and
500 Kbytes is excess.
■
The upstream system configures the classifier, control, and the
tagging, and has the QoS flow. The upstream system passes the
excess traffic with the tag of 2 (Standard priority) to the downstream
system.
■
The downstream system can prioritize traffic from this flow at layer 2,
using its default 802.1p classifier 404 (for conforming packets) and
classifier 402 (for nonconforming excess) along with the
corresponding controls 4 and 2.
For this configuration, you must enable QoS excess tagging with a tag
value of 2 in addition to defining the classifier and control.