Web Management Guide-R05

Table Of Contents
Chapter 9
| Class of Service
Layer 3/4 Priority Settings
– 241
Trust Mode
CoS
– Maps layer 3/4 priorities using Class of Service values. (This is the
default setting.)
DSCP
– Maps layer 3/4 priorities using Differentiated Services Code Point
values.
Web Interface
To configure the trust mode:
1.
Click Traffic, Priority, Trust Mode.
2.
Set the trust mode for any port.
3.
Click Apply.
Figure 141: Setting the Trust Mode
Mapping CoS
Priorities to Internal
DSCP Values
Use the Traffic > Priority > CoS to DSCP page to maps CoS/CFI values in incoming
packets to per-hop behavior and drop precedence values for priority processing.
Command Usage
The default mapping of CoS to PHB values is shown in Table 17 on page 242.
Enter up to eight CoS/CFI paired values, per-hop behavior and drop
precedence.
If a packet arrives with a 802.1Q header but it is not an IP packet, then the CoS/
CFI-to-PHB/Drop Precedence mapping table is used to generate priority and
drop precedence values for internal processing. Note that priority tags in the
original packet are not modified by this command.
The internal DSCP consists of three bits for per-hop behavior (PHB) which
determines the queue to which a packet is sent; and two bits for drop
precedence (namely color) which is used by Random Early Detection (RED) to
control traffic congestion.