Cabletron Systems SmartCell 6A000 User Manual

SmartCell 6A000 User Guide   4-23

Switch Administration

Traffic Management  

Class of Service Queue Allocation Guidelines

The following are recommended settings for the Min and Max thresholds for the class of service queues under specific 
sustained traffic conditions. Use these settings as guidelines for threshold settings:

CBR — fewer than 100 connections on a port: Min = 50, Max = 1000

CBR — more than 100 connections on a port: Min = 100, Max = 1000

rt-VBR — bandwidth utilization less than 20%: Min = 10, Max = 1000*

rt-VBR — bandwidth utilization more than 20 %: Min = 100, Max = 4000*

Nrt-VBR — for port B4 (CPU): Min = 100, Max = 4000

Nrt-VBR — for all other ports: Min = 10, Max = 1000

UBR — Min = 32, Max = 16,000

* Use the show cacstats command to view bandwidth utilization.

4.6.4

EFCI, EPD, and RM Thresholds

To control switch congestion, the SmartCell 6A000 implements standard resource management cell (RM-cell) 
marking, explicit forward congestion indicator cell marking (with backward RM cell marking), and early packet 
discard (EPD). These congestion control schemes are triggered when the number of cells within shared memory 
reaches user definable thresholds. Use the

 command to view and set these thresholds.

For example, enter the 

 command.

SmartCell ZX # show switchtrafficcongestion

Switch Traffic Congestion Parameters

============================================================================

Queue 1 EFCI Threshold                  : 4096 cells

Queue 2 EFCI Threshold                  : 4096 cells

Queue 3 EFCI Threshold                  : 4096 cells

Queue 4 EFCI Threshold                  : 4096 cells

Low EPD Threshold                       : 10922 cells

High EPD Threshold                      : 21845 cells

Switch Discard Threshold                : 30508 cells

RM Cell Marking Enable                  : ON

EFCI Cell Marking Enable                : ON

SmartCell ZX # 

EFCI thresholds are set on a per class of service queue basis, while EPD thresholds are set with respect to the total 
amount of shared buffer space being used by all classes of service. 

For most types of traffic, EPD triggering is tied to the low EPD threshold. Signaling traffic, however, is tied to the high 
EPD threshold to assure that signaling packets are discarded only when congestion is most severe. 

Use the

 command to change thresholds for EFCI and EPD and to enable or disable 

RM and EFCI cell marking.

Along with EFCI and backward RM cell marking, the SmartCell 6A000 uses standard RM cell marking. The switch 
discard threshold (

) corresponds to total shared buffer utilization and represents the 

point at which the switch considers itself congested and starts marking RM cells.

The switch discard threshold is not user configurable and is shown only for information.

For information on troubleshooting congestion problems, see Chapter 5, "Troubleshooting."