Table Of Contents
Dynamic Bandwidth Sharing on the Cisco CMTS Router
Prerequisites for CMTS Dynamic Bandwidth Sharing
Restrictions for CMTS Dynamic Bandwidth Sharing
Information About CMTS Dynamic Bandwidth Sharing
DBS for Wideband and Modular Cable Interfaces
How to Configure CMTS Dynamic Bandwidth Sharing
Configuring DBS for a Modular Cable Interface
Configuring DBS for a Wideband Cable Interface
Verifying Configuration of DBS
Configuration Examples for CMTS Dynamic Bandwidth Sharing
Configuring DBS on a Modular Cable Interface: Example
Configuring DBS on a Wideband Cable Interface: Example
Feature Information for CMTS Dynamic Bandwidth Sharing
Dynamic Bandwidth Sharing on the Cisco CMTS Router
Revised: May 12, 2009First Published: February 25, 2008The Cable Modem Termination Service (CMTS) new feature enables dynamic bandwidth sharing (DBS) on modular cable and wideband cable interfaces.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To see a list of the releases in which each feature is supported, see the "Feature Information for CMTS Dynamic Bandwidth Sharing" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required
Contents
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Prerequisites for CMTS Dynamic Bandwidth Sharing
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Prerequisites for CMTS Dynamic Bandwidth Sharing
Table 1 shows the hardware compatibility prerequisites for the Dynamic Bandwidth Sharing on the Cisco CMTS Router feature.
Restrictions for CMTS Dynamic Bandwidth Sharing
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Information About CMTS Dynamic Bandwidth Sharing
DBS can be enabled on wideband or modular cable interfaces. The benefits of DBS are:
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DBS for Wideband and Modular Cable Interfaces
Prior to DOCSIS 3.0 standards, cable service flows were associated with a single cable interface, which in turn corresponded to a physical downstream on a line card. Under DOCSIS 3.0 standards, cable service flows can be associated with more than one downstream channel. Dynamic bandwidth sharing (DBS) is the dynamic allocation of bandwidth for wideband (WB) and modular cable (MC) interfaces sharing the same downstream channel. The bandwidth available to each WB, MC, or narrowband channel is not a fixed value—it depends on the configuration and the traffic load on the WB or MC. DBS enables high burst rates with DOCSIS 2.0 cable modems as well as DOCSIS 3.0 cable modems. The DBS feature continues working across line card and performance routing engine (PRE) switchovers with no loss of functionality.
DBS Configuration
Dynamic bandwidth sharing is achieved using a new type of modality called a link queue. Link queues represent a specific share of bandwidth on a particular channel. Link queues are only used to calculate the effective bandwidth of a channel, and such link queues are activated and deactivated according to the state of activity on a specific channel.
Dynamic bandwidth sharing and static bandwidth allocations are configured at the WB or MC interface level. By default, bandwidth for a WB or MC channel is statically allocated. When DBS is enabled on an interface, the static bandwidth percentage is converted to a committed information rate (CIR) value for the corresponding link queue. The interface CIR value represents the guaranteed portion of the interface bandwidth and is used for admission control of the service flows with minimum reserved rate. When DBS is enabled, you can also specify the remaining ratio value of the excess bandwidth for the link queue. If DBS is enabled and no bandwidth percentage is specified, no bandwidth is reserved for the WB or MC interface and the interface is effectively in protocol down state where link queues are not created.
Dynamic bandwidth sharing does not preclude static bandwidth configuration. If a static portion of bandwidth is configured on any radio frequency (RF) channel that one or more DBS-enabled channel utilizes, that portion is subtracted from the RF link's CIR. Therefore, such a portion is always reserved and is not available to dynamic WB or MC interfaces.
How to Configure CMTS Dynamic Bandwidth Sharing
This section contains the following procedures:
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Configuring DBS for a Modular Cable Interface
To configure DBS for an MC interface use the cable dynamic-bw-sharing command in interface configuration mode.
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SUMMARY STEPS
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DETAILED STEPSConfiguring DBS for a Wideband Cable Interface
To configure DBS for a wideband cable interface use the cable dynamic-bw-sharing command in interface configuration mode for WB cable.
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SUMMARY STEPS
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DETAILED STEPSVerifying Configuration of DBS
To verify the configuration of the CMTS DBS, use the show commands described below.
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Router# show pxf cable controller modular-cable 1/0/0 rf-channel 3 link-queuesLink ID is 32259link next_send: 0x00000000 channel number: 0temporary bgbw: 0x00000000 reserved bgbw: 0x00000000col.6 link bandwidth mult: 55778 shift: 18col.7 link bandwidth mult: 55778 shift: 18link aggregate cir: 0x00000000 aggregate eir: 0x00000000bw reclaimed/trunc eir: 0/0 link cir_max: 0xFFFFlink cir_sum: 70 link eir_sum: 2link bw_sum: 0 act. link q num: 0Link Queues :QID CIR(act/conf) EIR MIR WB Chan. Status420 13107/13107 1/1 65535/65535 0 Inactive423 32768/32768 1/1 65535/65535 2 Inactive•
Modular cable interface
Router(config)# interface modular-cable 1/0/0:1...Router(config-if)# cable dynamic-bw-sharing...Router# show pxf cpu queue modular-cable 1/0/0:1Link Queues :QID CIR(act/conf) EIR MIR RF Chan. Status420 19661/19661 1/1 65535/65535 0 InactiveWideband cable interface
Router(config)# interface wideband-cable 1/0/0:0...Router(config-if)# cable dynamic-bw-sharing...Router# show pxf cpu queue wideband-cable 1/0/0:0Link Queues :QID CIR(act/conf) EIR MIR RF Chan. Status419 32768/32768 1/1 65535/65535 0 Inactive566 19661/19661 1/1 65535/65535 1 InactiveEnabling DBS Debug
To enable specific DBS debug output, use the debug cr10k-rp dbs-queue command as shown in the following example:
Router# debug cr10k-rp dbs-queueCR10K RP debug dynamic BG link queue setup debugging is on
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Configuration Examples for CMTS Dynamic Bandwidth Sharing
This section provides the following configuration examples:
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Configuring DBS on a Modular Cable Interface: Example
In the following example, DBS is enabled on modular cable interface 1. Because DBS is enabled, the percent value is converted to a committed information rate (CIR) of 45, which means the modular cable channel is guaranteed 45 percent of the bandwidth. The ratio of excess bandwidth is assigned a value of 22, which means that if there is excess bandwidth available, a remaining ratio of 22 can be assigned to the MC channel.
configure terminalinterface modular-cable 1/0/0:1shutdowncable dynamic-bw-sharingno shutdowncable rf-bandwidth-percent 45 remaining ratio 22Configuring DBS on a Wideband Cable Interface: Example
In the following example, DBS is enabled on wideband channel 0. Because DBS is enabled, the percent value is converted to a CIR value of 50, which means the wideband cable channel is guaranteed 50 percent of the bandwidth. The excess-value is assigned a value of 5, which means that if there is excess bandwidth available, a remaining ratio of 5 can be assigned to the wideband channel.
configure terminalinterface wideband-cable 1/0/0:0shutdowncable dynamic-bw-sharingno shutdowncable rf-channel 10 bandwidth-percent 50 remaining ratio 5Where to Go Next
For further information on the commands required to configure, maintain, and troubleshoot Cisco uBR10012 universal broadband router and Cisco cable modems, see the Cisco IOS CMTS Cable Command Reference at: http://www.cisco.com/en/US/docs/ios/cable/command/reference/cmts_cable_cref_wrapper.html.
Additional References
The following sections provide references related to the CMTS Dynamic Bandwidth Sharing.
Related Documents
Cisco IOS CMTS cable commands
See the Cisco IOS CMTS Cable Command Reference at: http://www.cisco.com/en/US/docs/ios/cable/command/reference/cmts_cable_cref_wrapper.html
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Feature Information for CMTS Dynamic Bandwidth Sharing
Table 2 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
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