Cisco cBR 8 Configuration Guide

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For DS service flows, the required bandwidth is the minimum reservation rate, as specified in the DOCSIS
service flow QoS parameters.
In each of the above calculations, SGAC does not account for the PHY overhead. DOCSIS overhead is counted
only in the UGS and UGS-AD flows. To estimate the fraction of bandwidth available, the calculation must
account for the PHY and DOCSIS overhead, and also the overhead incurred to schedule DOCSIS maintenance
messages. SGAC applies a correction factor of 80% to the raw data rate to calculate the total available
bandwidth.
For the DS and US flow in bonded channels, the maximum reserved bandwidth is the bandwidth defined
for the SGAC threshold values. This value is indicated in kbps.
Note
Enabling SGAC Check
A fiber node configured on the CMTS represents one or more matching physical fiber nodes in the HFC plant.
The CMTS uses the fiber node configuration to identify the DOCSIS downstream service group (DS-SG) and
DOCSIS upstream Service Group (US-SG) of the physical fiber nodes in the plant. The Service Group
information is compared with MAC Domain channel configuration to automatically calculate the MAC Domain
downstream and upstream service groups (MD-DS-SGs and MD-US-SGs respectively) within the MAC
Domains.
Under each Fiber node, use the following procedure to enable SGAC check for an application type and any
service flow of the specified application type, which is admitted to a service group.
Before You Begin
Fairness Across DOCSIS Interfaces feature should always be enabled and the bandwidth percentage configured
on each bonding group should be kept minimal to allow flexible adjustment of reservable bandwidth.
Restrictions
SGAC is supported only on the downstream.
Procedure
PurposeCommand or Action
Enables privileged EXEC mode.enable
Step 1
Example:
Router> enable
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Enter your password if prompted.
Enters global configuration mode.configureterminal
Example:
Router# configure terminal
Step 2
Cisco cBR Series Converged Broadband Routers Quality of Services Configuration Guide for Cisco IOS XE Fuji
16.7.x
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Service Group Admission Control
Enabling SGAC Check

Cisco cBR 8 Specifications

General

Brand	Cisco
Model	cBR 8
Category	Network Router
Language	English