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Cisco CMTS Feature Guide, Release 12.3BC
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Title Pages
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Preface
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Admission Control for the Cisco Cable Modem Termination System
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Cable Duplicate MAC Address Reject for the Cisco CMTS
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Cable Interface Bundling and Virtual Interface Bundling for the Cisco CMTS
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Cable Monitor and Intercept Features on the Cisco CMTS
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COPS Engine Operation on the Cisco CMTS
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DHCP, ToD, and TFTP Services for the Cisco Cable Modem Termination System
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DOCSIS 1.1 for the Cisco CMTS
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DOCSIS 2.0 A-TDMA Services on the Cisco CMTS
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EtherChannel on the Cisco Cable Modem Termination System
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Flap List Troubleshooting for the Cisco CMTS
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Maximum CPE or Host Parameters for the Cisco Cable Modem Termination System
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N+1 Redundancy for the Cisco Cable Modem Termination System
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PacketCable and PacketCable Multimedia for the Cisco CMTS
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Point-to-Point Protocol over Ethernet Support on the Cisco CMTS
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Service Flow Admission Control for the Cisco CMTS
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Service Flow Mapping to MPLS-VPN on the Cisco CMTS
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Spectrum Management and Advanced Spectrum Management for the Cisco CMTS
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Telco Return for the Cisco CMTS
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Time-of-Day Server for the Cisco CMTS
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Unique Device Identifier Retrieval for the Cisco CMTS
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Upstream Scheduler Mode for the Cisco CMTS
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Glossary
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Feedback
Table Of Contents
Service Flow Admission Control for the Cisco CMTS
Prerequisites for Service Flow Admission Control
Restrictions for Service Flow Admission Control
Information About Service Flow Admission Control
Overview of Service Flow Admission Control for the Cisco CMTS
Service Flow Admission Control and Cisco Universal Broadband Routers
Service Flow Admission Control on the Cisco uBR10012 Universal Broadband Router
Service Flow Admission Control on the Cisco uBR7246VXR Universal Broadband Router
Service Flow Admission Control and Memory Requirements for the Cisco CMTS
Service Flow Admission Control and Cisco CMTS Resources
Service Flow Admission Control and CPU Utilization
Service Flow Admission Control and Memory Utilization
Service Flow Admission Control and Upstream or Downstream Bandwidth Utilization
Categorization of Service Flows
Thresholds for Upstream or Downstream Bandwidth
Exclusive and Non-Exclusive Bandwidth Thresholds
Comparing Service Flow Admission Control with Prior Admission Control
How to Configure, Monitor and Troubleshoot Service Flow Admission Control
Enabling Service Flow Admission Control for Event Types
Configuring Service Flow Admission Control Based on CPU Utilization
Configuring Service Flow Admission Control Based on Memory Resources
Defining Rules for Service Flow Categorization
Naming Application Buckets for Service Flow Admission Control
Setting Downstream and Upstream Application Thresholds
Precedence of These Configuration Commands
Preempting High-Priority Emergency 911 Calls
Calculating Upstream and Downstream Bandwidth Utilization
Bandwidth Validity Checks for Service Flow Admission Control
Displaying Application Buckets for Service Flow Admission Control
Displaying Service Flow Reservation Levels
Displaying SFAC Configuration and Status
Debugging Service Flow Admission Control for Different Event Types
Debugging Service Flow Admission Control for CPU Resources
Debugging Service Flow Admission Control for Memory Resources
Debugging Service Flow Admission Control for Downstream Bandwidth
Debugging Service Flow Admission Control for Upstream Throughput
Debugging Flow Categorization for Service Flow Admission Control
Configuration Examples for Service Flow Admission Control
Example of SFAC Configuration Commands
Example of Service Flow Admission Control for Downstream Traffic
Service Flow Admission Control for the Cisco CMTS
Revised: February 5, 2007, OL-1467-08
Cisco IOS Release 12.3(21)BC introduces Service Flow Admission Control (SFAC) on the Cisco Cable Modem Termination System. Service Flow Admission Control is supported on the Cisco uBR10012 router with Performance Routing Engines 1 and 2 (PRE1 and PRE2) modules, and the Cisco uBR7246VXR router. This document describes the concepts, advantages, configuration and monitoring capabilities of Service Flow Admission Control on the Cisco CMTS.
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Admission Control is a widely-used term that applies to similarly named features for additional Cisco products and technologies.
One earlier version of Admission Control is introduced in Cisco IOS Release 12.3(13a)BC, and is described in the following document:
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http://www.cisco.com/en/US/docs/cable/cmts/feature/guide/ufg_adm.html
Another distinct version of Admission Control is supported for the Cisco uBR7114 universal broadband router in Cisco IOS 12.1 EC software. This earlier Admission Control feature sets the percentage of upstream channel capacity allowable for the given upstream. Refer to the following document:
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http://www.cisco.com/en/US/docs/cable/cmts/ubr7100/configuration/guide/scg71ovr.html
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Additional References" section on page 16-43.
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
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Prerequisites for Service Flow Admission Control
Service Flow Admission Control requires the following:
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Restrictions for Service Flow Admission Control
SFAC in Cisco IOS Release 12.3(21)BC follows these general factors when implementing on the Cisco CMTS:
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Information About Service Flow Admission Control
This section describes DOCSIS 1.1 concepts and configuration options supported on the Cisco CMTS for Service Flow Admission Control.
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Overview of Service Flow Admission Control for the Cisco CMTS
SFAC on the Cisco CMTS is a mechanism that gracefully manages service flow admission requests when one or more resources are not available to process and support the incoming service request. Lack of such a mechanism not only causes the new request to fail with unexpected behavior but could potentially cause the flows that are in progress to have quality related problems. SFAC monitors such resources constantly, and accepts or denies requests depending on the resource availability.
SFAC 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. SFAC reduces the impact of unpredictable traffic demands in circumstances that would otherwise produce degraded QoS for subscribers.
SFAC uses two event types for resource monitoring and management—cable modem registration and dynamic service (voice call) requests. When either of these two events occurs on the Cisco CMTS, SFAC verifies that the associated resources conform to the configured limits prior to admitting and supporting the service call request.
SFAC is not a mechanism to apply QOS to the traffic flows. Scheduling and queuing are some of the mechanisms used for implementing the QOS. The QOS is applied on per packet basis. SFAC checks are performed before the flow is admitted.
SFAC in Cisco IOS Release 12.3(21)BC monitors the following resources on the Cisco CMTS.
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SFAC enables you to configure major and minor 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 minor or major threshold is crossed for a given resource.
For system-level resources, such as CPU and memory utilization, you can configure critical thresholds in addition to the major and minor thresholds. When a critical threshold is crossed, further service requests are gracefully declined until the associated resource returns to a lower threshold level.
For upstream (US) and downstream (DS) channels, you can configure the bandwidth allocation with exclusive and non-exclusive thresholds. These thresholds can be configured for specified DOCSIS traffic types.
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This section provides additional information about SFAC with the following topics:
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Service Flow Admission Control and Cisco Universal Broadband Routers
Service Flow Admission Control on the Cisco uBR10012 Universal Broadband Router
Cisco IOS Release 12.3(21)BC supports Service Flow Admission Control on the Cisco uBR10012 router and all broadband processing engines.
Service Flow Admission Control on the Cisco uBR7246VXR Universal Broadband Router
Cisco IOS release 12.3(21)BC supports Service Flow Admission Control on the Cisco uBR7246VXR router.
Service Flow Admission Control and Memory Requirements for the Cisco CMTS
Service Flow Admission Control for the Cisco CMTS is a powerful feature that maintains Quality of Service (QoS) on the Cisco CMTS and enforces graceful degradation in service when attempted consumption exceeds resource availability.
Additional memory is required in the Cisco universal broadband router to maintain and store information about various scheduling types, the distribution of upstream or downstream traffic, and associated resource check processes. For complete information about memory requirements and Cisco IOS Release 12.3(21)BC, refer to the corresponding release notes for your product:
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http://www.cisco.com/en/US/docs/cable/cmts/ubr10012/release/notes/12_3bc/ubr10k_123bc_rn.html
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http://www.cisco.com/en/US/docs/cable/cmts/ubr7200/release/notes/12_3bc/123BCu72.html
Service Flow Admission Control and Cisco CMTS Resources
Service Flow Admission Control with Cisco IOS Release 12.3(21)BC implements graceful QoS policies for the following resources of the Cisco CMTS:
System-Level Resources—Impact All Cisco CMTS Functions
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Bandwidth-Level Resources—Impact Traffic Per Interface or Per Port
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Cisco IOS release 12.3(21)BC supports the following resources for the following Cisco CMTS routers:
Cisco uBR10012 Router Resources
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Cisco uBR7246VXR Router Resources with the Cisco MC28U
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Cisco uBR7246VXR Router Resources without the Cisco MC28U
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For additional information, refer to the "How to Configure, Monitor and Troubleshoot Service Flow Admission Control" section on page 16-9.
Service Flow Admission Control and CPU Utilization
CPU utilization is defined and monitored either as a five-second or a one-minute average. Both averages cannot be configured at the same time for any given resource. For CPU utilization, you can set minor, major, and critical threshold levels.
For additional information, refer to the "Configuring Service Flow Admission Control Based on CPU Utilization" section on page 16-12.
Service Flow Admission Control and Memory Utilization
Service Flow Admission Control can define up to three different memory options on the Cisco CMTS:
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Memory resources are similar to CPU utilization, in that you can set minor, major, and critical threshold levels. Memory-based Service Flow Admission Control is supported for memory on the main CPU in Cisco IOS Release 12.3(21)BC, and not for the broadband processing engine line card memory.
For additional information, refer to the "Configuring Service Flow Admission Control Based on Memory Resources" section on page 16-13.
Service Flow Admission Control and Upstream or Downstream Bandwidth Utilization
Service Flow Admission Control 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 SFAC 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:
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For flows created by PacketCable MultiMedia (PCMM), the following attributes may be used:
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The scheduling type for Upstream flows uses the following attribute type:
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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.
Thresholds for Upstream or Downstream Bandwidth
SFAC monitors upstream or downstream bandwidth consumption with minor, major, and critical thresholds. SFAC generates alarm traps when bandwidth consumption crosses minor and major thresholds. For additional information, refer to the "How to Configure, Monitor and Troubleshoot Service Flow Admission Control" section on page 16-9.
Exclusive and Non-Exclusive Bandwidth Thresholds
In addition to minor and major thresholds, SFAC also allows configuration of exclusive or non-exclusive thresholds.
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When the traffic usage exceeds the exclusive threshold, SFAC checks if there is any non-exclusive bandwidth available. Any new service request is permitted only if sufficient non-exclusive bandwidth is available.
Comparing Service Flow Admission Control with Prior Admission Control
The prior Admission Control feature on the Cisco CMTS was introduced in Cisco IOS Release 12.3(13a)BC. This prior version of Admission Control allows you to set minor, major, exclusive and non-exclusive thresholds. This topic lists changes introduced for SFAC in Cisco IOS Release 12.3(21)BC, and identifies which part of the functionality is changed and which functionality is preserved.
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How to Configure, Monitor and Troubleshoot Service Flow Admission Control
This section describes the following configuration, monitoring and troubleshooting procedures for the Service Flow Admission Control (SFAC) feature. Configuration procedures are optional, given default configurations are enabled in Cisco IOS Release 12.3(21)BC. This section presents a sequence of procedures for non-default configurations, monitoring and debugging procedures that apply in default or non-default operations of Service Flow Admission Control.
Primary Configurations for Service Flow Admission Control
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This procedure sets the events that trigger the Admission Control checks on the Cisco CMTS.
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This procedure configures threshold levels for CPU utilization. When threshold levels are crossed during an Admission Control check, an alarm is generated or the service is gracefully declined, depending on the level crossed.
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This procedure configures memory resource types and associated threshold levels for Admission Control on the Cisco CMTS.
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This procedure describes how to configure service flow rules on the Cisco CMTS. This procedure changes default global service flow rule rules. By default, Cisco IOS Release 12.3(21)BC enables the definition of service flows according to application or traffic type, with bucket assignments for a standard set of service flow applications.
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This procedure enables you to assign alpha-numeric names to six of the eight application buckets that Service Flow Admission Control supports.
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This procedure sets downstream and upstream applications thresholds for Service Flow Admission Control on the Cisco CMTS.
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This procedure enables you to override the default Emergency 911 call preemption functions described in the "Comparing Service Flow Admission Control with Prior Admission Control" section on page 16-8.
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Provides guidelines for calculating requirements and potential configurations of Service Flow Admission Control and related thresholds and settings.
Monitoring and Troubleshooting Commands for Service Flow Admission Control
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Provides guidelines for performing validation of configuration and operation.
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Describes how to display the application types configured and active.
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Describes how to display the reservation levels configured and active.
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Describes how to display service flows, application categorizations, and bandwidth consumption status.
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Describes how to debug event type classifications.
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Describes how to debug CPU resource configurations.
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Describes how to debug downstream bandwidth settings and operation.
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Describes how to debug upstream throughput settings and operation.
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Describes how to enable and use debug and show commands for service flow categorization settings.
Enabling Service Flow Admission Control for Event Types
Service Flow Admission Control can be enabled for one or more of the following events. At least one of these events must be configured for Service Flow Admission Control on the Cisco CMTS prior to the configuration of any additional settings:
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Perform these steps to configure either or both event types on the Cisco CMTS.
Prerequisites
Service Flow Admission Control requires that event types, traffic types and CMTS resource thresholds be configured and enabled on the Cisco CMTS. Refer also to the "Prerequisites for Service Flow Admission Control" section on page 16-2.
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Examples
The following example in global configuration mode enables both event types on the Cisco CMTS:
Router(config)# cable admission-control event cm-registration
Router(config)# cable admission-control event dynamic-service
What to Do Next
Once configured, event types and Service Flow Admission Control event activity on the Cisco CMTS can be reviewed using the following two commands:
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If the resources to be monitored and managed by Service Flow Admission Control are not yet configured on the Cisco CMTS, refer to the additional procedures in this document for information about their configuration.
Configuring Service Flow Admission Control Based on CPU Utilization
Service Flow Admission Control allows you to configure minor, major and critical thresholds for CPU utilization. The thresholds are specified as percentage of CPU utilization. When the an event such as cable modem registration or dynamic service takes place, and the CPU utilization is greater than the major or minor threshold, an alarm is generated. If it is greater than the critical threshold, the new service is gracefully declined.
Service Flow Admission Control enforces threshold levels in one of two ways. The Cisco CMTS supports both enforcement methods, but both cannot be configured at the same time.
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Prerequisites
Refer to the "Prerequisites for Service Flow Admission Control" section on page 16-2.
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Configuring Service Flow Admission Control Based on Memory Resources
Three different memory resource options can be configured on the Cisco CMTS:
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Memory-based Service Flow Admission Control is supported for memory on the main CPU in Cisco IOS Release 12.3(21)BC, and not for the broadband processing engine line card memory. As with CPU utilization, you can set minor, major, and critical threshold levels.
Prerequisites
Refer to the "Prerequisites for Service Flow Admission Control" section on page 16-2.
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Defining Rules for Service Flow Categorization
This procedure describes how to configure service flow categorization rules on the Cisco CMTS. This flexible procedure changes default global service flow rules with variations of the cable application type include command.
By default, Cisco IOS Release 12.3(21)BC enables the definition of service flows according to application or traffic type, with bucket assignments for a standard set of service flow applications.
Any one or several of these steps or commands may be used, in nearly any combination, to set or re-configure SFAC on the Cisco CMTS.
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Examples
The following example maps high-priority PacketCable service flows into application bucket 5.
Router(config)# cable application-type 5 include packetcable priorityThe following example maps normal PacketCable service flows into application bucket 1.
Router(config)# cable application-type 1 include packetcable normalThe following example maps the specified bucket number with PCMM service flow with a priority of 7, then maps an application identifier of 152 for the same bucket number:
Router(config)# cable application-type 2 include pcmm priority 7Router(config)# cable application-type 2 include pcmm app-id 152The following example maps both UGS and UGS-AD into bucket number 1:
Router(config)# cable application-type 1 include scheduling-type ugsRouter(config)# cable application-type 1 include scheduling-type ugs-adThe following example maps the Best Effort CIR flows to bucket 3:
Router(config)# cable application-type 3 include BETroubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
When rules for Service Flow Admission Control are enabled on the Cisco CMTS, which is the default, those rules can be overridden or re-configured with the steps in this procedure. Once rules are enabled, the application buckets can be named or renamed with the procedure in the "Naming Application Buckets for Service Flow Admission Control" section on page 16-19.
Otherwise, refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Naming Application Buckets for Service Flow Admission Control
This procedure enables you to assign alpha-numeric names to six of the eight application buckets that Service Flow Admission Control supports. The default bucket identifiers range from 1 to 8.
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Examples
The following example illustrates the use of descriptive names instead of numeration for the associated buckets:
Router(config)# cable application-type 2 name videoRouter(config)# cable application-type 3 name gamingThe change made with this procedure is displayed with the show application-buckets command.
Troubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
The change made with this procedure is displayed with the show application-buckets command.
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Setting Downstream and Upstream Application Thresholds
This procedure sets downstream and upstream applications thresholds for Service Flow Admission Control on the Cisco CMTS. This procedure extends the previous Admission Control commands from earlier Cisco IOS releases to support additional applications in Service Flow Admission Control. The settings in this procedure may be applied in either global or per-interface mode for downstream and upstream applications, and may also be applied in per-upstream fashion if desired.
Precedence of These Configuration Commands
Service Flow Admission Control based on bandwidth can be configured at the interface or global level. For upstream bandwidth, SFAC can be configured at the per-upstream level as well.
For downstream channels, the interface-level thresholds have higher precedence over the global thresholds configured. For upstream ports, the port-level thresholds have higher precedence over interface-level thresholds; and the interface-level thresholds have higher precedence over global thresholds.
As such, if you configure both global and interface-level downstream thresholds, the interface-level thresholds are effective for that interface. In similar fashion, if you configure port-level settings and the interface-level upstream thresholds, the port-level thresholds are effective on that port. The remaining ports, with no port-level thresholds in place, use the interface-level upstream thresholds.
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Examples
The following example illustrates the sequence of steps used when setting downstream and upstream application thresholds for the specified bucket in global configuration mode:
Router> enable
Router# configure terminal
Router(config)# cable admission-control ds-bandwidth bucket-no 1 minor 15 major 25 exclusive 30 non-exclusive 15
Router(config)# cable admission-control us-bandwidth bucket-no 1 minor 10 major 20 exclusive 30 non-exclusive 10
Troubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Preempting High-Priority Emergency 911 Calls
You may configure SFAC rules and thresholds so that the high-priority voice (911) traffic receives an exclusive share of bandwidth. Because the average call volume for Emergency 911 traffic may not be very high, the fraction of bandwidth reserved for Emergency 911 calls may be small. In the case of regional emergency, the call volume of Emergency 911 calls may surge. In this case, it may be necessary to preempt some of the normal voice traffic to make room for surging Emergency 911 calls.
The Cisco CMTS software preempts one or more normal-priority voice flows to make room for the high-priority voice flows. SFAC provides the command-line interface (CLI) to enable or disable this preemption ability.
SFAC preemption logic follows the following steps:
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This preemption is effective only for PacketCable high-priority flows.
When an upstream or downstream low-priority service flow is chosen for preemption, the corresponding service flow for the same voice call in the opposite direction gets preempted as well.
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Examples
The following example disables then restores Emergency 911 call preemption on the Cisco CMTS.
Router> enableRouter# configure terminalRouter(config)# cable admission-control preempt priority-voiceRouter(config)# no cable admission-control preempt priority-voiceRouter(config)# Ctrl^ZRouter#Troubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Calculating Upstream and Downstream Bandwidth Utilization
The Service Flow Admission Control feature maintains a counter for every US and DS channel, and this counter stores the current bandwidth reservation. Whenever a service request is made to create a new service flow, Service Flow Admission Control estimates the bandwidth needed for the new flow, and adds it to the counter. The estimated bandwidth is computed as follows:
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In each of the above calculations, Service Flow Admission Control 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. Service Flow Admission Control applies a correction factor of 80% to the raw data rate to calculate the total available bandwidth.
Example
The following example describes how the bandwidth calculations are performed for US voice calls.
Consider an US channel with voice calls generated using a G711 codec:
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If you configure 70% threshold for UGS traffic on this channel, the bandwidth allocated to voice becomes 8.192 * 0.7, or 5.7344 Mbps. At 92.8 Kbps per call, this allows 62 calls. For 99% threshold, the number of calls permitted increases to 87.
Note that the 80% correction factor is an approximation to account for all the overhead. The exact correction needed depends on several factors, such as raw data rate, PHS option, FEC options, and so forth.
Because UGS packets are a fixed size, the calculation of UGS data rate requirements is straightforward. For other flow types, where the packet size is variable, the actual usage of the channel cannot be predicted. In this example, when the threshold is 99% and the channel is carrying only the voice calls, the scheduler limitation may activate before the Service Flow Admission Control threshold that is set, and no calls may be scheduled after 85 calls.
As a result, the Service Flow Admission Control feature does not guarantee the accuracy of the bandwidth estimation.
Bandwidth Validity Checks for Service Flow Admission Control
Service Flow Admission Control is based on and monitors multiple resources on the Cisco CMTS. You can configure major, minor, exclusive and non-exclusive thresholds for various traffic types. To prevent circumstances in which some Service Flow Admission Control configurations are inconsistent, Service Flow Admission Control first validates the attempted configuration, and if an error is found, Service Flow Admission Control prints an error message and the configuration is not set.
Before setting the threshold limits for a given resource on the Cisco CMTS, Service Flow Admission Control configuration should follow these important guidelines to ensure a valid configuration:
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Implicit Bandwidth
You may choose not to assign any explicit thresholds to certain buckets. In this case, these buckets assume implicit thresholds. In the previous example, if you do not configure any thresholds for buckets 5-8, then those bukets assume implicit thresholds. Because 60% bandwidth is already reserved by buckets 1-4, buckets 5-8 can share the remaining 40% bandwidth. This 40% bandwidth is treated in a non-exclusive manner. This information displays in supporting show commands.
Oversubscription
Oversubscription of a given resource on the Cisco CMTS may be encountered in one of the following ways:
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Effective bandwidth = current reservation - oversubscribed bandwidth
For example, referring to the starting scenario with voice and data both given 50% bandwidth, if the data usage reaches 70%, the data bucket oversubscription totals 20%. That is, the effective bandwidth for the data bucket = 70 - 20 = 50%.
Therefore, while calculating the available bandwidth for voice, full 50% bandwidth is considered available. Note that in this example, if you allow voice utilization to reach 50%, the total reservation becomes 120%. At present the Cisco CMTS platforms do not allow total reservation to exceed 100% of the available bandwidth for downstream channels; only upstream channels may exceed 100% reservation.
Displaying Application Buckets for Service Flow Admission Control
Cisco IOS Release 12.3(21)BC introduces the show application-buckets command to display default or customized Service Flow Admission Control settings and status on the Cisco CMTS. This command displays the bucket number and bucket name, if the latter is configured, and the associated rules for each bucket. When multiple rules are applied to one bucket, the rules display in order of priority for that bucket.
Prerequisites
This procedure presumes that SFAC is configured and operational on the Cisco CMTS.
SUMMARY STEPS
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Examples
The following example illustrates sample output of the show cable application-type command.
Router# show cable application-typeFor bucket 1, Name PktCablePacketcable normal priority gatesPacketcable high priority gatesFor bucket 2, Name PCMM-VidPCMM gate app-id = 30For bucket 3, Name GamingPCMM gate app-id = 40For bucket 4, NameFor bucket 5, NameFor bucket 6, NameFor bucket 7, NameFor bucket 8, Name HSDBest-effort (CIR) flowsTroubleshooting Tips
Service Flow Admission Control supports show and debug commands for troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Displaying Service Flow Reservation Levels
Cisco IOS Release 12.3(21)BC introduces a new command to display service flows, application categorizations, and bandwidth consumption on the Cisco CMTS.
Prerequisites
This procedure presumes that SFAC is configured and operational on the Cisco CMTS.
SUMMARY STEPS
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Examples
The following example illustrates sample output and status of the Service Flow Admission Control feature, and the show interface cable admission-control reservation { downstream | upstream } port-no command.
Router# show interface cable 5/1/1 admission-control reservation downstream.SfId Mac Address Bucket Bucket Name State Current Reserv4 0000.cad6.f052 8 act 088 0000.cad6.f052 8 act 20006 0000.cad6.eece 8 act 021 0000.cad6.eece 8 act 20008 0000.cad6.eebe 8 act 024 0000.cad6.eebe 8 act 200010 0000.cadb.30a6 8 act 027 0000.cadb.30a6 8 act 2000Displaying SFAC Configuration and Status
Cisco IOS Release 12.3(21)BC supports an enhanced command to display service flows, application categorizations, and bandwidth consumption status on the Cisco CMTS.
Prerequisites
This procedure presumes that SFAC is configured and operational on the Cisco CMTS.
SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates further information for the Service Flow Admission Control feature. This example displays threshold levels and current reservation per bucket, and the oversubscribed bandwidth per bucket. Cisco IOS indicates implicitly calculated threshold with asterisk.
Router# show cable admission-control interface cable 5/1/1 upstream 0Interface Cable5/1/1Upstream Bit Rate (bits per second) = 4096000Resource - Upstream Bandwidth-----------------------------Bucket Names Minor # of Major # of Excls # of Non-Ex Curr. Curr. Conf # ofNo Level Times Level Times Level Times Level Resv Ovrsb Level Rejec1 5 1312 7 1262 45 0 0 31 0 I 362 0 0 0 0 0 0 6* 0 0 I 03 0 0 0 0 0 0 6* 0 0 I 04 0 0 0 0 0 0 6* 0 0 I 05 0 0 0 0 0 0 6* 0 0 I 06 0 0 0 0 0 0 6* 0 0 I 07 0 0 0 0 0 0 6* 0 0 I 08 5 31 7 29 49 11 5 79 25 I 0Troubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Debugging Service Flow Admission Control for Different Event Types
Cisco IOS Release 12.3(21)BC supports the debugging of service flow events for SFAC on the Cisco CMTS.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates the enablement and displays of the debug cable admission-control event command.
Router# debug cable admission-control event*Sep 12 23:15:22.867: Entering admission control check on PRE and it's a cm-registration*Sep 12 23:15:22.867: Admission control event check is TRUEWhat to Do Next
If Service Flow Admission Control checks fail for the event types, refer to the following sections for additional information about events and configuration:
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Debugging Service Flow Admission Control for CPU Resources
Cisco IOS Release 12.3(21)BC supports the debugging of CPU resources configured for SFAC on the Cisco CMTS.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates the enablement and displays of the debug cable admission-control cpu command.
Router# debug cable admission-control cpu*Sep 12 23:08:53.255: CPU admission control check succeeded*Sep 12 23:08:53.255: System admission control check succeeded*Sep 12 23:08:53.255: CPU admission control check succeeded*Sep 12 23:08:53.255: System admission control check succeededWhat to Do Next
If Service Flow Admission Control checks fail for the CPU resources, refer to the followingsections for additional information about CPU utilization thresholds, events and configuration:
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Debugging Service Flow Admission Control for Memory Resources
Cisco IOS Release 12.3(21)BC supports the debugging of memory resources configured for SFAC on the Cisco CMTS.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates the enablement and displays of the debug cable admission-control memory command.
Router# debug cable admission-control memory*Sep 12 23:08:53.255: CPU admission control check succeeded*Sep 12 23:08:53.255: System admission control check succeeded*Sep 12 23:08:53.255: CPU admission control check succeeded*Sep 12 23:08:53.255: System admission control check succeededWhat to Do Next
If Service Flow Admission Control checks fail for memory resources, refer to the following sections for additional information about memory thresholds, events and configuration:
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Debugging Service Flow Admission Control for Downstream Bandwidth
Cisco IOS Release 12.3(21)BC supports the debugging of downstream bandwidth resources configured for SFAC on the Cisco CMTS.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates the enablement and displays of the debug cable admission-control ds-bandwidth command.
Router# debug cable admission-control ds-bandwidthOct 8 23:29:11: Failed to allocate DS bandwidth forCM 0007.0e01.1db5 in adding a new service entryWhat to Do Next
If debug commands reveal issues with Service Flow Admission Control settings for the downstream, refer to the following sections for additional information about throughput thresholds, events and configuration:
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Debugging Service Flow Admission Control for Upstream Throughput
Cisco IOS Release 12.3(21)BC supports the debugging of upstream bandwidth resources configured for SFAC on the Cisco CMTS.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
The following example illustrates the enablement and displays of the debug cable admission-control us-bandwidth command.
Router# debug cable admission-control us-bandwidthRouter#Oct 8 23:29:11: Failed to allocate US bandwidth forCM 0007.0e01.9b45 in adding a new service entryWhat to Do Next
If debug commands reveal issues with Service Flow Admission Control checks for the upstream, refer to the following sections for additional information about throughput thresholds, events and configuration:
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Debugging Flow Categorization for Service Flow Admission Control
Cisco IOS Release 12.3(21)BC introduces a new debug command that accounts for the bucket-flow scheme of Service Flow Admission Control. This debug command displays service flow categorization results—when a service flow is classified, the debug command displays the application by which it was categorized, along with which rule is matched.
Prerequisites
Default or manual configuration of the following procedure is required for using this debug command, with additional SFAC settings presumed, according to your requirements.
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SUMMARY STEPS
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DETAILED STEPS
Examples
Below is a shortened example of the information displayed when the debug cable admission-control flow-categorization command is enabled on the Cisco CMTS. This command displays interface-level information.
Router# debug cable admission-control flow-categorizationint ca 5/1/1 sfid 55 identified as video pcmm priority 6 matched.Troubleshooting Tips
Service Flow Admission Control supports debug and show commands for monitoring and troubleshooting functions on the Cisco CMTS. Refer to the following procedures:
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What to Do Next
Refer to additional non-default procedures in this document, or to the following procedures for monitoring or troubleshooting Service Flow Admission Control on the Cisco CMTS:
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Configuration Examples for Service Flow Admission Control
This section describes solutions-level examples of the Service Flow Admission Control feature on the Cisco CMTS. This section illustrates the functioning of Service Flow Admission Control in default or non-default but properly operational configurations. This section presumes the proper use of configuration and monitoring procedures and commands described elsewhere in this document.
This section contains the following examples to illustrate Service Flow Admission Control:
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Example of SFAC Configuration Commands
In this section of configuration examples, the following SFAC parameters are set on the Cisco CMTS:
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The following configuration commands enable these settings:
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cable application-type 1 include packetcable normalcable application-type 1 include packetcable prioritycable application-type 1 name PktCable•
cable application-type 8 name HSDcable application-type 8 include best-effort•
cable application-type 2 name PCMM-Vidcable application-type 2 include pcmm app-id 35•
Router# show cable application-typeFor bucket 1, Name PktCablePacketcable normal priority gatesPacketcable high priority gatesFor bucket 2, Name PCMM-VidPCMM gate app-id = 30For bucket 3, Name GamingPCMM gate app-id = 40For bucket 4, NameFor bucket 5, NameFor bucket 6, NameFor bucket 7, NameFor bucket 8, Name HSDBest-effort (CIR) flowsThese above configuration examples might be omitted or changed, but the remaining examples in this section presume the above configurations.
Example of Service Flow Admission Control for Downstream Traffic
This example presumes that you have configured the rules according to the commands illustrated at the start of this section. All the voice flows in bucket 1. All the CIR data flows are categorized in bucket 8.
This example illustrates a sample configuration for Service Flow Admission Control with downstream traffic. In this example, if voice traffic exceeds 30% bandwidth consumption, additional voice flows are denied.
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The following Cisco IOS command implements this configuration:
Router(config)# cable admission-control ds-bandwidth bucket-no 1 minor 15 major 25 exclusive 30In this example, the voice flows are rejected when the bandwidth usage of the flows exceeds 30%.
In addition, you can allow for some flexibility by allowing flows to exceed their exclusive share, and to consume up to 50% of the total downstream throughput (30% + 20%). The following command accomplishes this:
Router(config)# cable admission control downstream bucket-no 1 minor 15 major 25 exclusive 30 non-exclusive 20With this previous command, the bucket 1 flows are rejected when the voice usage exceeds 50% (30% + 20%).
Similarly you can configure data thresholds as follows:
Router(config)# cable admission control bucket-no 8 minor 15 major 25 exclusive 50 non-exclusive 10With the configuration commands as above, the following multi-stage scenario illustrates how the lending and borrowing of throughput is achieved in the presence of multiple traffic classes.
Stage I—Initial Throughput Allocations
Assume downstream throughput distribution is as follows:
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Table 15-1 summarizes this throughput disribution:
Stage 2—Voice Traffic Exceeds 30% Exclusive Throughput
Now assume conditions change as follows:
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Table 15-2 summarizes this throughput distribution:
Step 3—Bandwidth Consumption Increases by 10%
Now assume that data throughput usage increases by 10% for a new consumption total of 60%, and voice usage remains same. This consumes all remaining non-exclusive bandwidth from Best Effort.
Table 15-3 summarizes this throughput distribution:
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Additional References
The following topics provide references related to Service Flow Admission Control for the Cisco CMTS in Cisco IOS Release 2.3(21a)BC or later releases.
Related Documents
Cisco IOS Commands for the Cisco CMTS
Cisco Broadband Cable Command Reference Guide
http://www.cisco.com/en/US/docs/ios/cable/command/reference/cbl_book.html
DOCSIS 1.1 Operations for the Cisco CMTS
DOCSIS 1.1 for the Cisco CMTS
http://www.cisco.com/en/US/docs/cable/cmts/feature/guide/ufg_docs.html
CISCO-CABLE-ADMISSION-CTRL-MIB for the Cisco Cable Modem Termination System
Cisco CMTS Universal Broadband Router MIB Specifications Guide
http://www.cisco.com/en/US/docs/cable/cmts/mib/reference/guide/ubrmib3.html
Standards
CableLabs™ DOCSIS 1.1 specifications
CableLabs™ PacketCable specifications
CableLabs™ PacketCable MultiMedia specifications
http://www.cablelabs.com/packetcable/specifications/multimedia.html
MIBs
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Cisco CMTS Universal Broadband Router MIB Specifications Guide
http://www.cisco.com/en/US/docs/cable/cmts/mib/reference/guide/mibv5ubr.html
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To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
Technical Assistance
