Packet Tagging Overview

You can use the traffic-class rule in policies to tag a packet flow so that the QoS application can provide traffic-class queuing. Policies can perform both in-band and out-of-band packet tagging:

For example, an Internet service provider (ISP) provides a Broadband Remote Access Server (B-RAS) service that has both video and data components, and the ISP wants to guarantee that the video traffic gets priority treatment relative to the data traffic. The ISP’s users have a 1.5 Mbps virtual circuit (VC) terminating on a digital subscriber line access multiplexer (DSLAM). The ISP wants to allocate 800 Kbps of this link for video, if there is a video stream.

The ISP creates a classifier list to define a video packet flow, creates a policy to color the packets, and applies the policy to the interface:

host1(config)#ip classifier-list video ip any any dsfield 16host1(config)#ip classifier-list data ip any any dsfield 32host1(config)#ip policy-list colorVideoGreenhost1(config-policy-list)#classifier-group videohost1(config-policy-list-classifier-group)#color greenhost1(config-policy-list-classifier-group)#exithost1(config-policy-list)#classifier-group datahost1(config-policy-list-classifier-group)#color yellowhost1(config-policy-list-classifier-group)#exithost1(config-policy-list)#exithost1(config)#interface atm 12/1.1host1(config-if)#ip policy input colorVideoGreen statistics enabled

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