16-14
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter 16
Configuring Tag Switching and MPLS
Configuring Tag Switching CoS
When tag switching is enabled on a hierarchical VP tunnel, the tunnel can only be used for tag switching.
Because hierarchical VP tunnels support only four service classes, both TVCs and ATM Forum VCs map
to the same service classes. Therefore, both ATM Forum VCs and TVCs cannot coexist in a hierarchical
VP tunnel. The relative weights assigned to the service classes depend on which is active (either tag
switching or ATM Forum). The class weights change whenever a hierarchical VP tunnel is toggled
between ATM Forum and tag switching. By default, a hierarchical VP tunnel comes up as an ATM
Forum port.
Table 16-3
and
Table 16-4
list the TBR classes and ATM Forum service category mappings for
hierarchical VP tunnels.
Configuring the Service Class and Relative Weight
Each service class is assigned a relative weight. These weights are configurable and range from 1 to 15.
To configure the service class and relative weight on a specific interface, perform the following steps,
beginning in global configuration mode:
ABR
4
1
UBR
5
1
1.
Even though the CBR service category is mapped to service
class 2, all of the CBR VCs are rate scheduled only, and therefore
they are not WRR scheduled.
Table 16-2 ATM Forum Class Mapping for Physical Ports
ATM Forum Service
Category
Service Class
Relative Weight
Table 16-3 Service Class to Weight Mapping for Hierarchical VP Tunnels
TBR Class
Service Class
Relative Weight
TBR_1 (WRR_1)
1
1
TBR_2 (WRR_2)
2
2
TBR_3 (WRR_3)
3
3
TBR_4 (WRR_4)
4
4
Table 16-4 ATM Forum Service Category Mapping for Hierarchical VP Tunnels
ATM Forum Service
Category
Service Class
Relative Weight
VBR-RT
1
8
VBR-NRT
2
1
ABR
3
1
UBR
4
1