H3C Technologies H3C S6300 Series Switches - Manual (Page 69)

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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, you can associate a traffic class with a traffic behavior configured with the
priority marking action to set the priority fields or flag bits of the traffic class of packets.
Priority marking can be used together with priority mapping. For more information, see "
Configuring
priority 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 polices for packets in different colors, you can provide
differentiated services for different traffic flows and ensure that the network resources are well utilized.
The device 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 device supports coloring packets by using either of the following traffic policing features: 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 ."