5-201/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Multicast Cells
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Shaping Rates
When you configure an OPTimum trunk, all VCCs are shaped at the shaping rate
defined for the OPTimum logical port. All VPs are shaped according to the shaping
rate configured for each VP on the Tunnel VP Shaping Rate tab in the OPTimum trunk
LPort configuration.
Collective bandwidth for all CBR VCC circuits provisioned over the VP-shaped
OPTimum trunk should be less than the configured shaping rate, otherwise control
traffic may be dropped due to shaping and the trunk will go down.
See Chapter 3, “Configuring CBX or GX Logical Ports,” for information about
configuring OPTimum trunks and virtual UNIs.
QoS Classes for VP Shaping
VP shaping is performed on all QoS classes. QoS support is provided within the
logical port (OPTimum trunk or Virtual UNI) by priority scheduling in decreasing
order of priority: CBR, VBR-RT, VBR-NRT, ABR/UBR.
Each QoS class has two configurable thresholds – a discard threshold, and a CLP0+1
threshold. The eight thresholds (two per service class) are configured on a per card
basis. See the section on configuring VP shaping attributes in the Switch Module
Configuration Guide
for CBX 3500, CBX 500, GX 550, and B-STDX 9000 for information
about the default VP shaping threshold values.
The discard threshold is used for EPD or CLP1 discards in the same manner as
described in per-VC flow control. Per-VC queuing is not performed; there is no
“fair share” bandwidth allocation among the VCs sharing a logical port.
Multicast Cells
All multicast cells are placed into a single queue. There is one queue per IOM.
Multicast cells are discarded when the ATM FCP multicast queue length reaches a
certain threshold. You can configure this threshold for each installed IOM.
Multicast cells are dequeued at the assigned multicast cells shaping rate. This rate is
configurable using Navis EMS-CBGX. See Table 6-1 on page 6-4 for more
information about configuring the Multicast Rate attribute.
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