Cisco IE 4000, Руководство по настройке программного обеспечения

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579
Configuring QoS
Understanding QoS
802.1Q Tunneling CoS Mapping
The switch supports VLAN mapping from the customer VLAN-ID (C-VLAN) to a service-provider VLAN-ID (S-VLAN). For
QoS, the switch can set the service-provider CoS (S-CoS) from either the customer CoS (C-CoS) or the customer DSCP
(C-DSCP) value, and can map the inner CoS to the outer CoS for any traffic with traditional 802.1Q tunneling (QinQ) or
selective QinQ VLAN mapping. This default allows copying the customer CoS into the service provider network.
The switch supports C-CoS to S-CoS propagation for traditional QinQ and for selective QinQ on trunk ports. This is the
default behavior and does not require configuration. When you configure traditional QinQ or selective QinQ on Layer 2
trunk ports using 1-to-2 VLAN mapping, the switch also allows setting the S-CoS from C-DSCP.
For traffic entering the switch on 802.1Q tunnel ports or trunk ports configured for VLAN mapping, the switch has the
ability to examine the customer packet header and set the service-provider CoS value (S-CoS) from either the customer
CoS value or the customer DSCP value.
Configuring CoS matching on 802.1Q mapped ports is handled in this way:

On interfaces configured for 802.1Q tunneling (on tunnel or trunk ports) or selective 802.1Q (on trunk ports), the
CoS value of the VLAN tag (inner VLAN or C-VLAN) received on the interface (C-CoS) is automatically reflected in
the tunnel VLAN tag (outer VLAN or S-VLAN) by default.

The set cos policy-map class configuration commands always apply to the outer-most VLAN tag after processing
is complete, that is the S-VLAN-ID. For example, in 802.1Q tunnels, entering a set cos command changes only the
CoS value of the outer tag of the encapsulated packet.

When you configure a policy by entering the match dscp class map configuration command and you enter the set
cos policy-map class configuration command for QinQ and selective QinQ mapping interfaces, a DSCP match sets
the outer CoS of the encapsulated value.

You can set DSCP based on matching the outer VLAN.

If you enter the match cos command on interfaces configured for traditional QinQ or for selective QinQ mapping,
the match is to the outer CoS, which is the reflected inner Cos (C-CoS).
Classification Comparisons
Table 56 on page 579 shows suggested IP DSCP, IP precedence, and CoS values for typical traffic types.
Table 56 Typical Traffic Classifications
Traffic Type DSCP
per-hop DSCP
(decimal) IP
Precedence CoS
Voice-bearer—traffic in a priority queue or the queue with the
highest service weight and lowest drop priority. EF 46 5 5
Voice control—signalling traffic, related to call setup, from a
voice gateway or a voice application server. AF31 26 3 3
Video conferencing—in most networks, video conferencing over
IP has similar loss, delay, and delay variation requirements as
voice over IP traffic. AF41 34 4 4
Streaming video—relatively high bandwidth applications with a
high tolerance for loss, delay, and delay variation. Usually
considered more important than regular background
applications such as e-mail and web browsing. AF13 14 1 1