Weight Command History; Usage Guidelines For The Weight Command; High Watermark And Low Watermark Default Values - Cisco 10000 Series Configuration Manual

Chapter 15 Oversubscribing Physical and Virtual Links

weight Command History

Cisco IOS Release
Release 12.3(7)XI1
Release 12.2(28)SB
Release 12.2(31)SB2

Usage Guidelines for the weight Command

On the PRE2, for the weight command to be fully effective, use the queue-depth command to set the
segmentation and reassembly (SAR) line card queue depth for each VC interface queue above the VC
weight.

High Watermark and Low Watermark Default Values

On ATM line cards, the SAR mechanism has a queue for each PVC. Each PVC queue has two thresholds
associated with it called the high watermark and low watermark. These watermarks define the number
of cells the queue can hold.
The high and low watermark settings define the depth of the PVC interface queue on the line card.
Table 15-3
on the ATM VC rate.
Table 15-3
VC Rate (bps)
0 to 18,999
19,000 to 40,999
41,000 to 99,999
100,000 to 622,000
Table 15-4
based on the ATM VC rate.
Table 15-4
VC Rate (bps)
0 to 18,999
The behavior of the high watermark threshold and the low watermark threshold depends on whether the
atm pxf queuing mode or the no atm pxf queuing mode is configured. In atm pxf queuing mode, the high
watermark is a threshold that triggers a flow-off signal and the low watermark is a threshold that triggers
a flow-on signal. The high watermark is the maximum number of cells that can be in the PVC queue for
the ATM SAR mechanism before a flow-off signal is sent to the PXF. With the exception of priority
OL-7433-09
Description
The weight command was introduced on the PRE2.
This command was integrated in Cisco IOS Release 12.2(28)SB for the
PRE2.
This command was introduced on the PRE3.
lists the default high and low watermark values for ATM variable bit rate (VBR) VCs, based
Default Watermark Values for ATM VBR VCs
Low Watermark
48
64
128
224
lists the default high and low watermark values for ATM unspecified bit rate (UBR) VCs,
Default Watermark Values for ATM UBR VCs
Low Watermark
224
High Watermark
56
72
144
240
High Watermark
240
Cisco 10000 Series Router Quality of Service Configuration Guide
How the Router Determines VC Weights
15-25