Cisco Systems A9014CFD manual Classification Based on QoS Groups, 24-11

Chapter 24 Configuring QoS

Understanding QoS

Table 24-1		Typical Traffic Classifications (continued)
			DSCP	DSCP	IP
Traffic Type			per-hop	(decimal)	Precedence	CoS
Less critical data (silver data)—noncritical, but relatively
important data.
•	Level 1		AF11	10	1	1
•	Level 2		AF12	12	1	1
			AF13	14	1	1
•	Level 3
Best-effort data (bronze data)—other traffic, including all			Default	0	0	0
noninteractive traffic, regardless of importance.
Less than best-effort data—noncritical, bandwidth-intensive
data traffic given the least preference. This is the first traffic type
to be dropped.
•	Level 1			2	0	0
•	Level 2			4	0	0
				6	0	0
•	Level 3

Classification Based on QoS Groups

A QoS group is an internal label used by the router to identify packets as a members of a specific class. The label is not part of the packet header and is restricted to the router that sets the label. QoS groups provide a way to tag a packet for subsequent QoS action without explicitly marking (changing) the packet.

A QoS group is identified at ingress and used at egress; it is assigned in an input policy to identify packets in an output policy. See Figure 24-3. The QoS groups help aggregate different classes of input traffic for a specific action in an output policy.

Figure 24-4 QoS Groups

1.Classify traffic

2.Set qos-group

Switching functions

1.Match qos-group

2.Output policy

141152

You can use QoS groups to aggregate multiple input streams across input classes and policy maps for the same QoS treatment on the egress port. Assign the same QoS group number in the input policy map to all streams that require the same egress treatment, and match to the QoS group number in the output policy map to specify the required queuing and scheduling actions.

You can also use QoS groups to identify traffic entering a particular interface if the traffic must be treated differently at the output based on the input interface.

You can use QoS groups to configure per-port, per-VLAN QoS output policies on the egress interface for bridged traffic on the VLAN. Assign a QoS group number to a VLAN on the ingress interface by configuring a per-port, per-VLAN input policy. Then use the same QoS-group number for classification at the egress. Because the VLAN of bridged traffic does not change during forwarding through the router, the QoS-group number assigned to the ingress VLAN can be used on the egress interface to identify the same VLAN.

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09		24-11