Sgac And Downstream Bandwidth Utilization; Categorization Of Service Flows - Cisco cBR 8 Configuration Manual

Service Group Admission Control
SGAC enables you to provide a reasonable guarantee about the Quality of Service (QoS) to subscribers at the
time of call admission, and to enable graceful degradation of services when resource consumption approaches
critical levels. SGAC reduces the impact of unpredictable traffic demands in circumstances that would otherwise
produce degraded QoS for subscribers.
Note SGAC begins graceful degradation of service when either a critical threshold is crossed, or when bandwidth
is nearly consumed on the Cisco CMTS, depending on the resource being monitored.
SGAC enables you to configure thresholds for each resource on the Cisco CMTS. These thresholds are
expressed in a percentage of maximum allowable resource utilization. Alarm traps may be sent each time a
threshold is crossed for a given resource.
For downstream (DS) channels, you can configure the bandwidth allocation with thresholds for each fiber
node.

SGAC and Downstream Bandwidth Utilization

SGAC allows you to control the bandwidth usage for various DOCSIS traffic types or application types. The
application types are defined by the user using a CLI to categorize the service flow.

Categorization of Service Flows

The SGAC feature allows you to allocate the bandwidth based on the application types. Flow categorization
allows you to partition bandwidth in up to eight application types or buckets. The composition of a bucket is
defined by the command-line interface (CLI), as is the definition of rules to categorize service flows into one
of these eight application buckets. Various attributes of the service flow may be used to define the rules.
For flows created by PacketCable, the following attributes may be used:
• The priority of the Packetcable gate associated with the flow (high or normal)
For flows created by PacketCable MultiMedia (PCMM), the following attributes may be used:
• Priority of the gate (0 to 7)
• Application type (0 to 65535)
All flows use the following attribute type:
• Service class name
Before a service flow is admitted, it is passed through the categorization routine. Various attributes of the
service flow are compared with the user-configured rules. Based on the match, the service flow is labeled
with application type, from 1 to 8. The bandwidth allocation is then performed per application type.
Before a service flow is admitted, it is categorized based on its attributes. The flow attributes are compared
against CLI-configured rules, one bucket at a time. If a match is found for any one of the rules, the service
flow is labeled for that bucket, and no further check is performed.
Bucket 1 rules are scanned first and bucket 8 rules are scanned last. If two different rules match two different
buckets for the same service flow, the flow gets categorized under the first match. If no match is found, the
flow is categorized as Best Effort (BE) and the bucket with best effort rule is labelled to the flow. By default,
the BE bucket is bucket 8.
Cisco cBR Series Converged Broadband Routers Quality of Services Configuration Guide for Cisco IOS XE Fuji
SGAC and Downstream Bandwidth Utilization
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