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Configuring priority marking
Overview
Priority marking sets the priority fields or flag bits of packets to modify the priority of packets. For
example, you can use priority marking to set IP precedence or DSCP for a traffic class of IP packets
to control the forwarding of these packets.
To configure priority marking to set the priority fields or flag bits for a class of packets, perform the
following tasks:
1. Configure a traffic behavior with a priority marking action.
2. Associate the traffic class with the traffic behavior.
Priority marking can be used together with priority mapping. For more information, see "Configuring
prio
rity mapping."
Color-based priority marking
Packet coloring methods
The color of a packet indicates the device's evaluation for the packet transmission priority. The
device can color a packet by using either of the following methods:
• Traffic policing
• Mapping drop precedence
Traffic policing
Traffic policing is a common traffic control technology. Traffic policing uses the token bucket
mechanism to evaluate the incoming or outgoing packets and colors the packets according to the
evaluation result. By configuring different traffic control policies for packets in different colors, you
can provide differentiated services for different traffic flows and use network resources efficiently.
The switch supports evaluating traffic by using two token buckets (bucket C and bucket E), and it
colors a packet according to the number of tokens in the token buckets.
The switch supports coloring packets by using either of the following traffic policing functions:
common CAR and aggregate CAR. For more information about coloring packets by using token
buckets and about common CAR and aggregate CAR, see "Configuring traffic policing, GTS, and
rate limit" and
"Configuring aggregate CAR."
Mapping drop precedence
Without traffic policing configured, a switch looks up the 802.1p priority of a packet in the
802.1p-to-drop priority mapping table, allocates the drop precedence value to the packet, and colors
the packet according to the drop precedence value. Drop precedence value 0 denotes green packets,
1 denotes yellow packets, and 2 denotes red packets. For more information about priority mapping
tables, see "Configuring priority mapping."
Configuring color-based priority marking
Configuring priority marking based on colors obtained through traffic policing
After traffic policing evaluates and colors packets, the switch can mark traffic with various priority
values (including DSCP values, 802.1p priority values, and local precedence values) by color.
Configure priority marking by using either of the following methods:
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