Cisco IE 4000, Software Configuration Manual

Page: 580 / 1066

576
Configuring QoS
Understanding QoS
Figure 78 QoS Classification Layers in Frames and Packets
These sections contain additional information about classification:

Class Maps, page 576

The match Command, page 577

Classification Based on Layer 2 CoS, page 577

Classification Based on IP Precedence, page 577

Classification Based on IP DSCP, page 578

Classification Comparisons, page 579

Classification Based on QoS ACLs, page 580

Classification Based on QoS Groups, page 580

Classification Based on VLAN IDs, page 581
Class Maps
As explained previously, you use an MQC class map to name a specific traffic flow (or class) and to isolate it from all
other traffic. A class map defines the criteria used to match against a specific traffic flow to further classify it. If you have
more than one type of traffic that you want to classify, you can create another class map and use a different name. When
you enter the
class-map command with a class-map name, the switch enters the class-map configuration mode. In this
mode, you define the match criterion for the traffic by using the match class-map configuration command. After a packet
is matched against the class-map criteria, it is acted on by the associated action specified in a policy map.
141151
Layer 2 IEEE 802.1Q and IEEE 802.1p Frame
Preamble
Start frame
delimiter
DA
Len
SA Type
TAG
2 Bytes
PT Data FCS
Layer 3 IPv4 Packet
Version
length
ToS
1 Byte
ID Offset TTL Proto FCS IP-SA IP-DA
PRI
7 6 5 4 3 2 1 0
CFI VLAN ID
Data
3 bits used for CoS
(IEEE 802.1p user priority)
IP precedence
DSCP
Standard IPv4:
MSBs called IP precedence
Flow control
for DSCP