Calculating The Scheduler Class Weights - Cisco Catalyst 8540 MSR Configuration Manual

Chapter 25 Configuring ATM Router Module Interfaces

Calculating the Scheduler Class Weights

Scheduling is part of the per hop behavior and the scheduler is the mechanism that ultimately provides
the QoS guarantees as it operates on the outgoing traffic.
There are eight scheduler classes available on the switch module controlling the enhanced ATM router
module. These are labeled 1 to 8 and shown in
Figure 25-12 Current Scheduler Class Weight Diagram
Broute-VC 0
MPLS_Control
MPLS_Premium
MPLS_S tandard
MPLS_A vailable
Broute-VC 1
Broute-VC 2
Broute-VC 3
Figure 25-12
of CBR, VBR, and UBR are mapped to scheduler classes 2, 3, and 5, respectively. The LSIPCs, which
are internal control VCs, are mapped to scheduler class 4. That leaves four remaining scheduler classes
for IP QoS traffic from other Layer 3 modules. Traffic from other Layer 3 modules is sent to the
enhanced ATM router module via internal broute VC's. The four broute VCs each map to one of the
remaining scheduler classes, as shown in
Only the broute VCs from XPIF based interface modules can terminate on the classes 1, 6, 7, and 8. IP
Note
QoS is not supported on EPIF based modules so, all broute VCs from EPIF based Fast Ethernet, Gigabit
Ethernet, and the original ATM route module go to scheduler class 4 only.
The broute VC 0 maps to class-default traffic and goes to scheduler class 1. The other broute VCs
correspond to non-default classes and can map to any scheduler class among 6, 7, and 8. The four broute
VCs with scheduler classes 1, 6, 7, and 8 correspond to the maximum of four output policy maps that
can be configured per interface, one of which must be the default.
The priority among the scheduler classes is decided by the weights assigned to the classes. The class
with the highest weight is serviced more often than other classes, thereby offering differential service.
OL-7396-01
Output VC Scheduler
weight
8
4
2
2
15
LSIPC
2
8
8
8
shows the mapping between the traffic types and the scheduler classes. The traffic classes
Figure 25-12.
Scheduler
class weight
1
A
2 15
3 8
4
16
5 4
6
B
7 C
8 D
Figure 25-12.
ATM Switch Router Software Configuration Guide
Configuring VC Bundling with IP and ATM QoS
Output VC
weight
15
CBR
8
VBR-rt
4
VBR-nrt
2
UBR
25-47