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1/19/05
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Per-VC Traffic Shaping
Beta Draft Confidential
Per-VC Traffic Shaping
You can configure the ATM FCP to perform traffic shaping by turning off the control
loop for VCs on a trunk or UNI port that is managed by the ATM FCP. For any
direction of data flow, you configure the output logical port that will perform shaping
to terminate CCRM cells. In addition, you need to configure the connected logical port
(for shaping on a trunk) to not generate RM cells (the No Loop option). For a UNI port
to perform traffic shaping, the connected CPE should not generate CCRM cells back
to the FCP. See
for information about configuring RM cell
termination settings.
VCs are shaped at their ICR. Because control loops are disabled, the ACR will stay at
the ICR if non-real time bandwidth is available.
See
“ICR and ICR Constant” on page 5-13
for a description of the ICR calculation.
ATM FCP Queues
The ATM FCP provides per-VC queueing. Per-VC queuing provides independent
buffer allocation to each VC, thereby isolating congestion on one VC from other VCs.
Each per-VC queue has two configurable thresholds:
•
Local congestion threshold
•
Local discard threshold
The local congestion and discard thresholds for a specific VC are obtained by
indexing the congestion and discard profile tables with the MCR class of the VC. The
MCR class of the VC is obtained from its MCR (or SCR for VBR-NRT circuits). See
“MCR Class Mappings” on page D-4
for information about MCR classes.
For information on downloading the tables using Navis EMS-CBGX, see
“Downloading Buffer Threshold and Rate Profile Tables” on page 6-8
.
In addition to the local thresholds, each port on an FCP-enabled IOM is assigned the
following:
•
Global congestion threshold
•
Global discard threshold
•
Global cell loss priority 0+1 (CLP0+1) threshold
You can configure these global thresholds as ATM FCP attributes for a logical port.
The EFCI attribute sets the global congestion threshold, the Discard attribute sets the
global discard threshold, and the CLP0+1 attribute sets the global cell loss priority
0+1 threshold. See
for details about configuring these
attributes.
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