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ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter16 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 c lasses, 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 VPtunnel is toggled
between ATM Forum and tag switching. By default, a hierarchical VP tunnel comes up as an ATM
Forum port.
Table16-3 and Ta ble 16 -4 list the TBR classes and ATM Forum service category mappings for
hierarchical VPtunnels.
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
class2, all of the CBR VCs are rate scheduled only, and therefore
they are not WRR scheduled.
Table16-2 ATM Forum Class Mapping for Physical Ports
ATM For um Se rvic e
Category Service Class Relative Weight
Table16-3 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
Table16-4 ATM Forum Service Category Mapping for Hierarchical VP Tunnels
ATM For um Se rvic e
Category Service Class Relative Weight
VBR-RT 1 8
VBR-NRT 2 1
ABR 3 1
UBR 4 1