Cisco Cisco 1700 2600 3600 3700 Series VPN Module White Paper

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VSS#sh interfaces tenGigabitEthernet 1/5/4 capabilities | include QOS

QOS scheduling: rx-(8q4t), tx-(1p7q4t)

QOS queueing mode: rx-(cos,dscp), tx-(cos,dscp)

Applying Policies

Classification or policing policies are applied to the system through the Modular QoS CLI (MQC) mechanisms,

which use class maps and policy maps. Each policy map can use multiple class maps to make up a policy map,

and you can define these policy classes for different types of traffic flows.

On the Cisco Catalyst 6500, you can define up to 255 class maps per policy map, with a total of 1024 class maps

per system, implying that across the Virtual Switching System a maximum of 1024 class maps can be supported.

MQC in Cisco IOS Software allows the separation of class maps from policy maps and the separation of these

maps from the application on an interface. The initial release of software also has a limitation in that it allows for

only a limited number of interfaces to be indexed uniquely for QoS purposes. As a result, you can apply QoS

policies only on Layer 3 interfaces (SVIs, physical interfaces, port channels, etc.) and on Layer 2 Cisco

EtherChannel links.

In a Cisco Virtual Switching System, application of policies on physical Layer 2 interfaces is now supported in

12.2(33)SXI and above.

Policing

Policing is the process of inspecting whether traffic on a given port or within a VLAN has exceeded a predefined

rate. If that traffic is out of profile (that is, the rate of the traffic stream exceeds the predefined rate), either excess

data can be dropped or its priority value marked down.

Two types of policers are supported on the Cisco Catalyst 6500 Series switches: aggregate policers and microflow

policers. Although you can implement both types, they are subject to different restrictions in a Cisco Virtual

Switching System environment. The next section addresses some of these restrictions relating to policers.

Aggregate Policing

Aggregate policers limit the amount of traffic received or transmitted in or out a port. The aggregate policer applies

to all traffic on a port or VLAN that matches a specified QoS ACL. If the aggregate policer is applied to a single

interface, it counts all matching traffic (that matches the classifying ACL) coming into the interface toward the

policer. If the aggregate policer is applied to a VLAN, then all of the matching traffic coming in any of the ports in

that VLAN is counted toward the stated rate.

There are two forms of aggregate policers:

Per-interface aggregate policers: These policers are applied to an individual interface using the police command

within a policy-map class. You can apply these map classes to multiple interfaces, but the policer polices each

interface separately.

Named aggregate policers or shared aggregate: These policers are applied to a group of ports and police traffic

across all interfaces cumulatively. Name aggregates are applied using the mls qos aggregate police command.