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604 C
HAPTER
22: Q
O
S
AND
RSVP
Example: 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 to tag any excess
traffic as Standard 802.1p service.
In this sample configuration:
■
The configured rate limit is 1 MB, so when the server sends 1.5 MB,
the upstream system knows that 1 MB is conforming and 500 KB 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 packets) along with the
corresponding controls 4 and 2.
For this configuration, you must enable QoS excess tagging with a tag
value of 2 as well as define the classifier and control.
Figure 76 QoS Excess Tagging
Server
169.10.20.30
Conforming
(1 MByte)
Excess
(500 KBytes)
Conforming
Excess with
tag of 2
L3
Upstream
Switch 4007
with Multilayer Module
L3
Downstream
Switch 4007
with Multilayer Module