Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

Guide That Contains This Content
[+] Expand All
[-] Collapse All

    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:

    • Policies perform in-band tagging by using their respective mark rule to modify a packet header field. For example, IP policies use the mark rule to modify an IP packet heard ToS field, and Frame Relay policies use the mark-de rule to modify the DE bit.
    • Policies perform out-of-band tagging by using the traffic class or color rule. Explicit packet coloring lets you configure prioritized packet flows without having to configure a rate-limit profile. The router uses the color to queue packets for egress queue threshold dropping as described in Creating Rate-Limit Profiles.

    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

    Published: 2014-08-14