QoS Maps Window
This window is only available for Catalyst 3550 switches and for Catalyst 2950
switches that run the enhanced software image.
It appears when you choose Device > QoS > Maps on the menu bar. You
can also click here to launch it. It
has a tab for each kind of QoS map table.
The maps tables can vary from device to device. Therefore, you begin by opening
the Host Name list and selecting the device to which the map tables will
belong.
These are the kinds of QoS map tables:
- IP Prec-DSCP (Catalyst 3550 switches only). Because DSCP values determine
which packets to drop when thresholds are exceeded in egress queues, this
mapping is required if you trust IP precedence values on any interface of
the device.
- CoS-DSCP (Catalyst 2950 and 3550 switches). This mapping is required
if you trust CoS values on any interface of the device. For Catalyst 2950
switches, you must map to standard DSCP values.
- DSCP mutation table (Catalyst 3550 switches only). This mapping is
needed only if you want to replace certain incoming DSCP values, for whatever
reason, with different values.
Unlike the other map tables, a different DSCP mutation table can be assigned
to each interface on the device, so you can have many DSCP mutation tables.
The DSCP Mutation Table tab contains a list DSCP mutation tables (empty
to start with) and these buttons:
- DSCP-CoS (Catalyst 2950 and 3550 switches). Because CoS values are
used to assign packets to egress queues, this mapping is required. For Catalyst
2950 switches, you must map from standard
DSCP values.
- Policed DSCP table (Catalyst 3550 switches
only). This mapping is required only if you want a policer to change a
DSCP value when a packet exceeds a maximum transmission rate or maximum burst
size. (The maximums are specified in the definition of the policer.)
- Min Reserves (Catalyst 3550 switches only). This table determines
how much of a buffer is allocated to each of the queues for FastEthernet interfaces.
The left column corresponds to IDs on the Minimum Reserves tab of the
Configure QoS Queues window. The right column can
contain values between 10 and 170. The ratio of each value to the sum of the
values determines the percentage of the buffer that is allocated to each queue.
Except for the DSCP Mutation Table tab, each tab contains a two-column
table with a set of values or IDs in the left column and a set of values that
these are mapped to in the right column. To change values in the right column:
- Select one or more rows.
- Click in a row to select only one row.
- Press Shift and click in contiguous rows to select contiguous
rows.
- Press Ctrl and click in noncontiguous rows to select noncontiguous
rows.
- Click Select All to select all the rows.
- To change the mapping in a single row, enter a new value in the right column.
To change the mapping in multiple rows to the same value, enter the value
in the field next to Set Selected (or use the spin buttons beside the
field), and click Set Selected.
- Click OK.
If you later want all the entries in the table to revert to their default values,
click Set Defaults.