Upstream Scheduler Mode

This document describes how to configure optional upstream (US) scheduler modes.

With this feature, you can select Unsolicited Grant Services (UGS), Real Time Polling Service (rtPS) or Non-Real Time Polling Service (nrtPS) scheduling types, as well as packet-based or Time Division Multiplex (TDM) based scheduling. Low latency queuing (LLQ) emulates a packet-mode-like operation over the TDM infrastructure of DOCSIS. As such, the feature provides the typical trade-off between packets and TDM. With LLQ, you have more flexibility in defining service parameters for UGS, rtPS or nrtPS, but with no guarantee (other than statistical distribution) regarding parameters such as delay and jitter.


Note

LLQ is not supported on the Cisco cBR Series Converged Broadband Routers running Cisco IOS-XE Release 3.15.0S.

Finding Feature Information

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 find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​tools.cisco.com/​ITDIT/​CFN/​. An account on http:/​/​www.cisco.com/​ is not required.

Hardware Compatibility Matrix for Cisco cBR Series Routers


Note

The hardware components introduced in a given Cisco IOS-XE Release are supported in all subsequent releases unless otherwise specified.

Table 1 Hardware Compatibility Matrix for the Cisco cBR Series Routers

Cisco CMTS Platform

Processor Engine

Interface Cards

Cisco cBR-8 Converged Broadband Router

Cisco IOS-XE Release 3.15.0S and Later Releases

Cisco cBR-8 Supervisor:

  • PID—CBR-CCAP-SUP-160G

  • PID—CBR-CCAP-SUP-60G1

  • PID—CBR-SUP-8X10G-PIC

Cisco IOS-XE Release 3.15.0S and Later Releases

Cisco cBR-8 CCAP Line Cards:

  • PID—CBR-LC-8D30-16U30

  • PID—CBR-LC-8D31-16U30

  • PID—CBR-RF-PIC

  • PID—CBR-RF-PROT-PIC

Cisco cBR-8 Downstream PHY Modules:

  • PID—CBR-D30-DS-MOD

  • PID—CBR-D31-DS-MOD

Cisco cBR-8 Upstream PHY Modules:

  • PID—CBR-D30-US-MOD

1 Effective with Cisco IOS-XE Release 3.17.0S, CBR-CCAP-SUP-60G supports 8 cable line cards. The total traffic rate is limited to 60Gbps, the total number of downstream service flow is limited to 72268, and downstream unicast low-latency flow does not count against the limits.

Restrictions for Upstream Scheduler Mode

  • LLQ mode is not supported on the Cisco cBR Series routers running Cisco IOS-XE Release 3.15.0S.

  • To ensure proper operation, Interface-based Admission Control must be enabled. When the LLQ option is enabled, it is possible for the upstream path to be filled with so many calls that it becomes unusable, making voice quality unacceptable. Interface-based admission control must be used to limit the number of calls to ensure acceptable voice quality, as well as to ensure traffic other than voice traffic.

  • Even if Interface-based admission control is not enabled, the default (DOCSIS)scheduling mode blocks traffic after a certain number of calls.

  • UGS with Activity Detection (UGS-AD) is not supported by the LLQ scheduler mode but remains supported by the default DOCSIS scheduler mode.

Information About Upstream Scheduler Mode for the Cisco CMTS Routers

With UGS, a service flow is created that enables a cable modem to transmit fixed-size bursts of data at a guaranteed rate and with a guaranteed level of jitter by providing periodic transmission opportunities to the cable modem for fixed-sized frames. This kind of service flow is particularly suitable for VoIP applications.

With rtPS, a service flow is created that provides a periodic opportunity for a cable modem to request permission to transmit data by polling a single cable modem for a bandwidth request, rather than all the cable modems. This satisfies applications that have a requirement for real-time data transmission, and enables the cable modem to transmit data bursts of varying length. This kind of service flow is particularly suitable for MPEG VoIP.

The rtPS requests, by default, are internally treated as priority 7—the highest priority for all Best Effort traffic. This high priority reduces the latency of rtPS traffic under congestion.

With nrtPS, a service flow is created that provides a periodic opportunity for a cable modem to request permission to transmit data by polling a single cable modem for a bandwidth request, rather than all the cable modems. The data bursts may be of varying length. This kind of service flow is particularly suitable for non-interactive services such as file transfers.

How to Configure Upstream Scheduler Modes

Procedure
     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 Use one the following commands:

    • interface cable slot/subslot/port

    • interface cable slot/port


    Example: 
    Router(config)# interface cable 7/0/1
     

    Enters interface configuration mode for the specified cable interface.

     
    Step 4 cable upstream n scheduling type ugs mode [llq |docsis]


    Example: 
    Router(config-if)# cable upstream 4 scheduling type ugs mode llq
     

    Enables LLQ-type (packet-based) scheduling for UGS services.

    Note    Any combination of ugs, rtps, nrtps, llq, and docsis is allowed. The only default value is docsis .
     
    Step 5 cable upstream n scheduling type rtps mode [llq |docsis]


    Example: 
    Router(config-if)# cable upstream 4 scheduling type rtps mode docsis
     

    Enables standard DOCSIS (TDM-based) scheduling for rtPS services.

    Note    Any combination of ugs, rtps, nrtps, llq, and docsis is allowed. The only default value is docsis .
     
    Step 6end


    Example: 
    Router(config-if)# end
     

    Exits interface configuration mode and returns to privileged EXEC mode.

     
    What to Do Next

    To confirm whether the scheduler is operating in DOCSIS mode, use the show interface cable mac-scheduler command. 

    Router# show interface cable 7/0/1 mac-scheduler 0
     DOCSIS 1.1 MAC scheduler for Cable7/0/1/U0 : rate 30720000
     wfq:None 
     us_balance:OFF 
     fairness:OFF 
     Queue[Rng Polls] flows 0
     Queue[CIR Grants] flows 0
     Queue[BE(07) Grants] flows 0
     Queue[BE(06) Grants] flows 0
     Queue[BE(05) Grants] flows 0
     Queue[BE(04) Grants] flows 0
     Queue[BE(03) Grants] flows 0
     Queue[BE(02) Grants] flows 0
     Queue[BE(01) Grants] flows 0
     Queue[BE(00) Grants] flows 0
     Req Slots 2601578997, Req/Data Slots 4484512
     Init Mtn Slots 38265829, Stn Mtn Slots 78753
     Short Grant Slots 0, Long Grant Slots 0
     Adv Phy Short Grant Slots 412, Adv Phy Long Grant Slots 5519087
     Adv Phy UGS Grant Slots 0
     Avg upstream channel utilization : 1%
     Avg percent contention slots : 98%
     Avg percent initial ranging slots : 1%
     Avg percent minislots lost on late MAPs : 0%

     MAP TSS: lch_state 9, init_retries 0
              late_initial_maps 0, late_ucd_maps 0
              mac-phy tss errors 0, missed ccc 0

    Additional References

    The following sections provide references related to the Cisco CMTS routers.

    Related Documents

    Related Topic

    Document Title

    Cisco CMTS command reference

    Cisco CMTS Cable Command Reference

    http:/​/​www.cisco.com/​c/​en/​us/​td/​docs/​cable/​cmts/​cmd_ref/​b_​cmts_​cable_​cmd_​ref.html

    Standards

    Standard

    Title

    DOCSIS

    Data-Over-Cable Service Interface Specifications, DOCSIS 2.0, Radio Frequency Interface Specification, CM-SP-RFIv2.0-I08-050408

    Technical Assistance

    Description

    Link

    The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

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

    Feature Information for Upstream Scheduler Mode

    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:/​/​tools.cisco.com/​ITDIT/​CFN/​. An account on http:/​/​www.cisco.com/​ is not required.


    Note

    The below table 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 Upstream Scheduler Mode

    Feature Name

    Releases

    Feature Information

    Upstream Scheduler Mode

    Cisco IOS-XE Release 3.15.0S

    This feature was introduced on the Cisco cBR Series Converged Broadband Routers.