Class Maps - Cisco IE-4000 Software Configuration Manual

Configuring QoS
Understanding QoS
Figure 78 QoS Classification Layers in Frames and Packets
Layer 2 IEEE 802.1Q and IEEE 802.1p Frame
Preamble
Layer 3 IPv4 Packet
Version
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.
Start frame
DA
delimiter
3 bits used for CoS
(IEEE 802.1p user priority)
ToS
Len
length 1 Byte
7 6 5
IP precedence
DSCP
Standard IPv4:
MSBs called IP precedence
TAG
SA Type
2 Bytes
PRI CFI
ID Offset TTL Proto
4 3 2
576
PT Data
VLAN ID
FCS IP-SA IP-DA
1 0
Flow control
for DSCP
FCS
Data