Cabletron Systems 9A100 - Manual (Page 64)

4-22 SmartSwitch 9A100 User Guide
Traffic Management Switch Administration
Quality of Service Queue Allocation Guidelines
The following values are recommended settings for the Min and Max thresholds for the QoS queues under specific
sustained traffic conditions. Use the settings in Table 4-3 as guidelines for threshold settings.
* Use the show cacstats command to view bandwidth utilization.
4.6.3 EFCI, EPD, and RM Thresholds
To control switch congestion, the SmartSwitch 9A100 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
switchtrafficcongestion commands to view and set these thresholds.
For example, enter the show switchtrafficcongestion command.
SmartSwitch # 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
SmartSwitch #
EFCI thresholds are set on a per-QoS-queue basis, while EPD thresholds are set with respect to the total amount of
shared buffer 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; this assures that signaling packets are discarded only when congestion is most severe.
Use the set switchtrafficcongestion command to change thresholds for EFCI and EPD and to enable or disable
RM and EFCI cell marking.
Table 4-3 Settings for QoS queues
QoS Queue Recommended 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