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JUNOSe 11.1.x Policy Management Configuration Guide
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:
Creating Multiple Forwarding Solutions with IP Policy Lists
By default, the router uses a single route table lookup to determine the forwarding
solution for packets. For IP policy lists only, the forward command enables you to
configure one or more unique forwarding solutions (interfaces or next-hop addresses)
that override the route table lookup. By creating a group of forwarding solutions, you
can ensure that there is a reachable solution for the packets.
You can use the order keyword to specify the order of the group of forwarding
solutions within a single forward rule. If no order value is specified, then the default
order of 100 is assigned to a solution. The router evaluates the forwarding solutions
in the group, starting at the solution with the lowest order value, and then uses the
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Packet Tagging Overview
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" on
page 77.
host1(config)#ip classifier-list video ip any any dsfield 16
host1(config)#ip classifier-list data ip any any dsfield 32
host1(config)#ip policy-list colorVideoGreen
host1(config-policy-list)#classifier-group video
host1(config-policy-list-classifier-group)#color green
host1(config-policy-list-classifier-group)#exit
host1(config-policy-list)#classifier-group data
host1(config-policy-list-classifier-group)#color yellow
host1(config-policy-list-classifier-group)#exit
host1(config-policy-list)#exit
host1(config)#interface atm 12/1.1
host1(config-if)#ip policy input colorVideoGreen statistics enabled
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