Dynamic Bandwidth Sharing on the Cisco CMTS Router

First Published: February 25, 2008

Last Updated: November 29, 2010

The Cable Modem Termination System (CMTS) enables dynamic bandwidth sharing (DBS) on modular cable (MC), integrated cable (IC), and wideband (WB) cable interfaces.

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Contents

Prerequisites for Dynamic Bandwidth Sharing

Table below shows the hardware compatibility prerequisites for the Dynamic Bandwidth Sharing on the Cisco CMTS Router feature.

Table 1 Cable Hardware Compatibility Matrix for Dynamic Bandwidth Sharing

CMTS Platform

Processor Engine

Cable Interface Line Cards

Cisco uBR10012 Universal Broadband Router

Cisco IOS Release 12.3(23)BC1 and later releases

  • PRE2

Cisco IOS Release 12.2(33)SCB and later releases

  • PRE4

Cisco IOS Release 12.2(33)SCH and later releases

  • PRE5

Cisco IOS Release 12.2(33)SCB and later releases

  • Cisco uBR10-MC5X20S/U/H

Cisco IOS Release 12.2(33)SCC and later releases

  • Cisco UBR-MC20X20V

Cisco IOS Release 12.2(33)SCE and later releases

  • Cisco uBR-MC3GX60V1

Cisco uBR7225VXR Universal Broadband Router

Cisco IOS Release 12.2(33)SCD and later releases

  • NPE-G2

Cisco IOS Release 12.2(33)SCD and later releases

  • Cisco uBR-MC88V

Cisco uBR7246VXR Universal Broadband Routers

Cisco IOS Release 12.2(33)SCD and later releases

  • NPE-G2

Cisco IOS Release 12.2(33)SCD and later releases

  • Cisco uBR-MC88V
1 Cisco uBR-MC3GX60V cable interface line card is not compatible with PRE2.

Restrictions for Dynamic Bandwidth Sharing

  • The bandwidth sharing state of a modular, integrated, or wideband cable interface can be changed only when the interface is administratively shutdown.

Information About Dynamic Bandwidth Sharing

The following sections provide information on DBS:

DBS for Modular, Integrated, and Wideband 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.

DBS is the dynamic allocation of bandwidth for MC, IC, and WB cable interfaces sharing the same downstream channel. The bandwidth available to each MC, IC, WB cable, or narrowband channel is not a fixed value—it depends on the configuration and the traffic load on the MC, IC, or WB cable.

The available bandwidth for data traffic is calculated using the following formula: Actual Line Rate – (Bandwidth used by MAC Management Messages [MMM] + Bandwidth loss due to DOCSIS header)

The bandwidth required by MMM depends on the CMTS configuration. The maximum bandwidth reserved for MMM is 4 percent (if the MMM uses less than 4 percent of bandwidth, the remaining unused bandwidth is available for the data traffic).

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 and static bandwidth allocations are configured at the MC, IC, or WB cable interface level. By default, bandwidth for an MC, IC, or WB cable 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 interface. 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 interface. If DBS is enabled and no bandwidth percentage is specified, no bandwidth is reserved for the MC, IC, or WB cable interface and the interface is effectively in protocol down state.

Dynamic bandwidth sharing does not preclude static bandwidth configuration. If a static portion of bandwidth is configured on any RF channel that one or more DBS-enabled channel utilizes, that portion is subtracted from the CIR value of the RF link. Therefore, such a portion is always reserved and is not available to dynamic MC, IC, or WB cable interfaces.


Note

Starting with Cisco IOS Release 12.2(33)SCE, the DBS mode is enabled by default, on the WB/MC/IC interfaces. To disable the DBS mode, configure the no cable dynamic-bw-sharing command.

How to Configure Dynamic Bandwidth Sharing

This section contains the following procedures:

Configuring DBS for a Modular Cable Interface

To configure DBS for an MC interface on the Cisco uBR10012 router, use the cable dynamic-bw-sharing command in interface configuration mode.


Note
The interface must be administratively shutdown before DBS can be configured on the MC interface.
     Command or ActionPurpose
    Step 1enable


    Example: 
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2configure terminal


    Example: 
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3interface modular-cable slot /subslot /port :nb-channel-number


    Example: 
    Router(config)# interface modular-cable 1/0/0:1
     

    Configures a modular cable interface.

    • slot —Chassis slot number of the cable interface line card.

    Cisco uBR10012 router: The valid range for line card is from 5 to 8 and slots 1 and 3 can be used for SIPs.

    • subslot —(Cisco uBR10012 only) Secondary slot number of the cable interface line card. Valid subslots are 0 or 1.
    • port —Downstream port number.

    Cisco uBR10012 router: The valid range is from 0 to 4 (depending on the cable interface).

    • nb-channel-number—Narrowband channel number.
     
    Step 4shutdown


    Example: 
    Router(config-if)# shutdown
     

    Shuts down the interface selected in Step 3 prior to configuring dynamic bandwidth sharing.

     
    Step 5[no] cable dynamic-bw-sharing


    Example: 
    Router(config-if)# cable dynamic-bw-sharing
     

    Enables dynamic bandwidth sharing (DBS) on the modular cable interface.

    Use the no form of this command to enable static bandwidth sharing (SBS) on the interface.

    Note    Starting with Cisco IOS Release 12.2(33)SCE, the DBS mode is enabled by default, on the WB, MC, and IC interfaces. To disable the DBS mode, configure the no cable dynamic-bw-sharing command.
     
    Step 6 no shutdown


    Example: 
    Router(config-if)# no shutdown
     

    Enables the interface on which dynamic bandwidth sharing is configured.

     
    Step 7 cable rf-bandwidth-percentpercent-value [ remaining ratio excess-value ]


    Example: 
    Router(config-if)# cable rf-bandwidth-percent 45 remaining ratio 22
     

    Enables either static or dynamic bandwidth sharing for modular cable interfaces. The default percent-value is 0. The percent-value range is 1–96.

    • If dynamic bandwidth sharing is enabled, the remaining ratio option is available. The bandwidth percentage is converted to a committed information rate (CIR) value for the corresponding interface.
    • The excess value - argument specifies the ratio of the excess bandwidth that can be allocated to the modular cable channel. The default excess value - is 1. The excess value - range is 1–100.
     

    Configuring 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.


    Note

    The interface must be administratively shutdown before DBS can be configured on the wideband cable interface.

       Command or ActionPurpose
      Step 1enable


      Example: 
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2configure terminal


      Example: 
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3interface wideband-cable {slot/port | slot/subslot/port }:wideband-channel


      Example: 
      Router(config)# interface wideband-cable 1/0/0:0
       

      Configures a wideband cable interface.

      • slot —Chassis slot number of the cable interface line card.

        Cisco uBR7246VXR router: The valid range is from 3 to 6.

        Cisco uBR7225VXR router: The valid range is from 1 to 2.

        Cisco uBR10012 router: The valid range is from 5 to 8.

      • subslot —(Cisco uBR10012 only) Secondary slot number of the cable interface line card. Valid subslots are 0 or 1.

      • port —Downstream port number.

        Cisco uBR7246VXR and Cisco uBR7225VXR routers: The valid port value is 0 or 1.

        Cisco uBR10012 router: The valid range is from 0 to 4 (depending on the cable interface).

      • wideband-channel—Wideband channel number.

        Cisco uBR7246VXR and Cisco uBR7225VXR routers: The valid values are from 0 to 5.

        Cisco uBR10012 router: The valid range is from 0 to 11.

       
      Step 4shutdown


      Example: 
      Router(config-if)# shutdown
       

      Shuts down the interface selected in Step 3 prior to configuring dynamic bandwidth sharing.

       
      Step 5 cable dynamic-bw-sharing


      Example: 
      Router(config-if)# cable dynamic-bw-sharing
       

      Enables dynamic bandwidth sharing (DBS) on the wideband cable interface.

      Use the no form of this command to enable static bandwidth sharing (SBS) on the interface.

      Note    Starting with Cisco IOS Release 12.2(33)SCE, the DBS mode is enabled by default, on the WB, MC, and IC interfaces. To disable the DBS mode, configure the no cable dynamic-bw-sharing command.
       
      Step 6 no shutdown


      Example: 
      Router(config-if)# no shutdown
       

      Enables the interface on which dynamic bandwidth sharing is configured.

       
      Step 7cable rf-channelrf-port [bandwidth-percent bw-percent ] [remaining ratioexcess-value ]


      Example: 
      Router(config-if)# cable rf-channel 10 bandwidth-percent 50 remaining-ratio 5
       

      Associates an RF channel on a Wideband SPA with a wideband channel and allocates bandwidth. The range for bandwidth-percent is 1–100. If bandwidth-percent is not used, the default bandwidth value is 100 percent.

      The remaining-ratio option is only available if DBS is enabled. The default excess-value is 1. The range for excess-value is 1–100.

       

      Configuring DBS for an Integrated Cable Interface

      To configure DBS for an integrated cable interface, use the cable dynamic-bw-sharing command in interface configuration mode.


      Note
      The interface must be administratively shutdown before DBS can be configured on the integrated cable interface.
         Command or ActionPurpose
        Step 1enable


        Example: 
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2configure terminal


        Example: 
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 interface integrated-cable {slot/port | slot/subslot/port }:rf-channel


        Example: 
        Router(config)# interface integrated-cable 1/0/0:0
         

        Enters the cable interface mode.

        • slot —Chassis slot number of the cable interface line card.

          Cisco uBR7246VXR router: The valid range is from 3 to 6.

          Cisco uBR7225VXR router: The valid range is from 1 to 2.

          Cisco uBR10012 router: The valid range is from 5 to 8.

        • subslot—(Cisco uBR10012 only) Secondary slot number of the cable interface line card. Valid subslots are 0 or 1.
        • port—Downstream port number.

          Cisco uBR7246VXR and Cisco uBR7225VXR routers: The valid port value is 0 or 1.

          Cisco uBR10012 router: The valid range is from 0 to 4 (depending on the cable interface).

        • rf-channel—RF channel number with a range of 0 to 3.
         
        Step 4shutdown


        Example: 
        Router(config-if)#  shutdown
         

        Shuts down the interface selected in Step 3 prior to configuring dynamic bandwidth sharing.

         
        Step 5cable dynamic-bw-sharing


        Example: 
        Router(config-if)# cable dynamic-bw-sharing
         

        Enables dynamic bandwidth sharing on the wideband cable interface.

        Use the no form of this command to enable static bandwidth sharing (SBS) on the interface.

        Note    Starting with Cisco IOS Release 12.2(33)SCE, the DBS mode is enabled by default, on the WB, MC, and IC interfaces. To disable the DBS mode, configure the no cable dynamic-bw-sharing command.
         
        Step 6no shutdown


        Example: 
        Router(config-if)# no shutdown
         

        Enables the interface where dynamic bandwidth sharing is configured.

         
        Step 7 cable rf-channel rf-port [bandwidth-percent bw-percent] [remaining ratio excess-value]


        Example: 
        Router(config-if)# cable rf-channel 10 bandwidth-percent 50 remaining-ratio 5
         

        Enables either static or dynamic bandwidth percentage sharing for an IC interface in interface configuration mode.

        • bw-percent—Static bandwidth allocation of a downstream RF channel. The range is 1 to 100%. The default is 0.
        • remaining ratio—(Optional) Indicates the ratio of the remaining or excess bandwidth that can be allocated to the modular cable channel.

          This option is available only when dynamic bandwidth sharing is enabled. Run the cable dynamic-bw-sharing command to enable DBS.

        • excess-value—Value of excess bandwidth that can be allocated to the cable channel. The range is from 1 to 100. The default value is 1.
         

        Verifying Configuration of DBS

        To verify the configuration of the CMTS DBS, use the show commands described below.

        Cisco uBR10012 Universal Broadband Router

        To view the parallel express forwarding (PXF) queueing and link queue statistics, use the show pxf cpu queue command for either modular cable or wideband cable interfaces.

        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 1/0/0:1
Link Queues : 
QID   CIR(act/conf)       EIR            MIR       RF Chan.   Status
  420   19661/19661        1/1        65535/65535      0       Inactive

        Wideband 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 1/0/0:0
Link Queues : 
QID   CIR(act/conf)       EIR            MIR       RF Chan.   Status
  419   32768/32768        1/1        65535/65535      0       Inactive
  566   19661/19661        1/1        65535/65535      1       Inactive

        Cisco uBR7200 Series Universal Broadband Router

        To view the DBS configuration on the Cisco uBR7200 series universal broadband router, use show interface wideband-cable slot/port:wideband-channel dbs and show interface integrated-cable slot/port:rf-channel dbs commands as shown below:

        Wideband cable interface 

        Router(config)# interface wideband-cable 5/1:0
...
Router(config-if)# cable dynamic-bw-sharing
...
Router# show 
interface wideband-cable 5/1:0 dbs
        Dynamic Bandwidth Sharing is enabled
        bg_rf_channel_bitmap_local 70, active 0
        RF 4: tokens 32500, active 0, policer 3250 KB/s, max_tokens 32500
                deficit counter 0, quantum 10000
                ticks_limit: 62500, max_ticks:687500, policer(ticks): 212
                dbs_pct: 100, remain_bytes: 0, if range: 7-7
        RF 5: tokens 32500, active 0, policer 3250 KB/s, max_tokens 32500
                deficit counter 0, quantum 10000
                ticks_limit: 62500, max_ticks:687500, policer(ticks): 212
                dbs_pct: 100, remain_bytes: 0, if range: 7-7
        RF 6: tokens 32500, active 0, policer 3250 KB/s, max_tokens 32500
                deficit counter 0, quantum 10000
                ticks_limit: 62500, max_ticks:687500, policer(ticks): 212
                dbs_pct: 100, remain_bytes: 0, if range: 7-7
                dbs state: start:4, end:6

        Integrated cable interface

        Router(config)# interface integrated-cable 5/1:0
...
Router(config-if)# cable dynamic-bw-sharing
...
Router# show 
interface integrated 5/1:0 dbs
        Dynamic Bandwidth Sharing is enabled
        active 0
        RF 4: tokens 32500, active 0, policer 3250 KB/s, max_tokens 32500
              deficit counter 0, quantum 0
              ticks_limit: 62500, max_ticks:687500, policer(ticks): 212
              dbs_pct: 100, remain_bytes: 0, if range: 7-7

        Enabling DBS Debug

        To enable specific DBS debug output, use the debug cr10k-rp dbs-queue command on the Cisco uBR10012 router and the debug cable dbs command on the Cisco uBR7200 series routers as shown in the following examples: 

        Router# debug cr10k-rp dbs-queue
CR10K RP debug dynamic BG link queue setup debugging is on
Router# debug cable dbs
DBS for cable 8x8 LC debugging is on

        Note
        Routine use of the debug cr10k-rp dbs-queue and debug cable dbs commands is not recommended.

        Configuration Examples for Dynamic Bandwidth Sharing

        This section provides the following configuration examples:

        Example: Configuring DBS on a Modular Cable Interface

        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.

        Cisco uBR10012 Universal Broadband Routers

        configure terminal
interface modular-cable 1/0/0:1
shutdown
cable dynamic-bw-sharing
no shutdown
cable rf-bandwidth-percent 45 remaining ratio 22

        Example: Configuring DBS on a Wideband Cable Interface

        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.

        Cisco uBR10012 Universal Broadband Routers

        configure terminal
interface wideband-cable 1/0/0:0
shutdown
cable dynamic-bw-sharing
no shutdown
cable rf-channel 10 bandwidth-percent 50 remaining ratio 5

        Cisco uBR7200 Series Universal Broadband Routers

        configure terminal
interface wideband-cable 1/0:0
shutdown
cable dynamic-bw-sharing
no shutdown
cable rf-channel 10 bandwidth-percent 50 remaining ratio 5

        Example: Configuring DBS on an Integrated Cable Interface

        In the following example, DBS is enabled on integrated channel 0. Because DBS is enabled, the percent value is converted to a CIR value of 50, which means the integrated 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 integrated channel.

        Cisco uBR10012 Universal Broadband Routers

        configure terminal
interface integrated-cable 1/0/0:0
shutdown
cable dynamic-bw-sharing
no shutdown
cable rf-channel 10 bandwidth-percent 50 remaining ratio 5

        Cisco uBR7200 Series Universal Broadband Routers

        configure terminal
interface integrated-cable 1/0:0
shutdown
cable dynamic-bw-sharing
no shutdown

        cable rf-channel 10 bandwidth-percent 50 remaining ratio 5

        Where to Go Next

        For further information on the commands required to configure, maintain, and troubleshoot Cisco uBR10012 universal broadband router or Cisco uBR7200 series 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/​cbl_​book.html .

        Additional References

        The following sections provide references related to the dynamic bandwidth sharing (DBS) on the Cisco CMTS.

        Related Documents

        Related Topic

        Document Title

        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/​cbl_​book.html

        Standards

        Standard

        Title

        No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

        —

        MIBs

        MIB

        MIBs Link

        No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

        To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

        http:/​/​www.cisco.com/​go/​mibs

        RFCs

        RFC

        Title

        No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

        —

        Technical Assistance

        Description

        Link

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        http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

        Feature Information for Dynamic Bandwidth Sharing

        Table below 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 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.


        Note

        The table below lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

        Table 2 Feature Information for Dynamic Bandwidth Sharing

        Feature Name

        Releases

        Feature Information

        CMTS Dynamic Bandwidth Sharing

        12.3(23)BC1

        The Cisco CMTS new feature enables dynamic bandwidth sharing on a modular cable or wideband cable interface.

        The following commands were introduced or modified by this feature:

        • cable dynamic-bw-sharing
        • cable rf-bandwidth-percent
        • cable rf-channel
        • debug cr10k-rp dbs-queue
        • show pxf cable controller
        • show pxf cpu queue

        CMTS Dynamic Bandwidth Sharing

        12.2(33)SCD

        Support on the Cisco uBR7225VXR and Cisco uBR7246VXR routers was added.

        The following commands were introduced or modified:

        • debug cable dbs
        • interface integrated-cable
        • interface wideband-cable
        • show interface integrated-cable
        • show interface wideband-cable