Cisco Systems OL-7396-01 Threshold Group for TBR Classes

16-17
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter16 Configuring Tag Switching and MPLS
Threshold Group for TBR Classes
Threshold Group for TBR Classes
A threshold group utilizes the memory efficiently among VCs of a particular traffic type. Each threshold
group is programmed with a dynamic memory allocation profile that maps into the needs of the
connections of a particular service class. There are 16 threshold groups (0 to 15) available on the ATM
switch router. Each threshold group has a set of eight regions, and each region has a set of thresholds.
When these thresholds are exceeded, cells are dropped to maintain the integrity of the shared memory
resource.
Each ATM Forum service category is mapped into a distinct threshold group. All the connections in a
particular service category map into one threshold group. Similarly, all the Tag Bit Rate (TBR) classes
have best effort traffic and the service differentiation comes mainly by giving different weights. Each of
the TBR classes map into four different threshold groups whose parameters are the same as the
unspecified bit rate (UBR) threshold group.
Table16-5 shows the th reshold group parameters mapped to the connections in all of the T BR classes
for the Catalyst 8540 MSR.
Table16-6 shows the th reshold group parameters mapped to the connections in all of the T BR classes
for the Catalyst 8510 MSR and LightStream 1010 ATM switch routers.
Each threshold group is divided into eight regions. Each region has a set of thresholds that are calculat ed
from the corresponding threshold group parameters given in Tab le 16-5 . The threshold group might be
in any one of the regions depending on the fill level (cell occupancy) of that group. And that region is
used to derive the set of thresholds which apply to all the connections in that group.
Table16-5 Threshold Group Parameters for TVCs (Catalyst8540 MSR)
Group
Maximum
Cells
Maximum
Queue
Limit
Minimum
Queue Limit
Mark
Threshold
Discard
Threshold Use
7 131,071 511 31 25% 87% TBR_1
8 131,071 511 31 25% 87% TBR_2
9 131,071 511 31 25% 87% TBR_3
10 131,071 511 31 25% 87% TBR_3
Table16-6 Threshold Group Parameters for TVCs (Catalyst8510 MSR and LightStream 1010)
Group
Maximum
Cells
Maximum
Queue
Limit
Minimum
Queue Limit
Mark
Threshold
Discard
Threshold Use
7 65,535 511 31 25% 87% TBR_1
8 65,535 511 31 25% 87% TBR_2
9 65,535 511 31 25% 87% TBR_3
10 65,535 511 31 25% 87% TBR_3