Voice Port Configuration Guide, Cisco IOS Release 15M&T
NextPort-Based Voice Tuning and Echo Cancellation
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NextPort-Based Voice Tuning and Echo Cancellation

Contents

NextPort-Based Voice Tuning and Echo Cancellation

This chapter describes how to dynamically configure voice services on the NextPort-based platforms: Cisco AS5350, Cisco AS5400, Cisco AS5400HPX, and Cisco AS5850. This chapter contains the following sections:

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 module.

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

Prerequisites for NextPort Services

To use the Nextport-Based Voice Tuning and Background Noise Statistics feature, you must be running NextPort service processing element (SPE) firmware version 8.8.1 or a later version and Cisco IOS Release 12.3(4)T or a later release.

To use the NextPort dual-filter G.168 echo canceller, you must be running SPE firmware version 10.2.2 or a later version and Cisco IOS Release 12.3(11)T or a later release.

Information About NextPort Voice Services

NextPort Dual-Filter G.168 Echo Canceller

The CSMV6 dial feature card (DFC) for NextPort platforms offers dual-filter G.168 echo canceller capability. The NextPort dual-filter G.168 echo canceller (EC) improves voice quality in VoIP connections by providing relatively less residual echo leakage, better nonlinear processing (NLP) timing, less clipping, and better comfort noise generation (CNG) in most environments.

The dual-filter G.168 echo canceller features two concurrently operating adaptive filters (which control echo tail coverage) and two double-talk detection functions. In addition, the comfort noise model uses "Hoth noise" spectrum shaping to better replicate the true noise spectrum.


Note


Detailed information for all Cisco IOS commands mentioned in this section can be found in the Cisco IOS Voice Command Reference.


The NextPort dual-filter G.168 echo canceller uses the same voice-tuning (VC tune) interface for configuring voicecap parameters as the Cisco-proprietary G.164 echo canceller. To adjust the dual-filter echo canceller, use a voicecap or the Cisco IOS command-line interface (CLI) during configuration. You can also adjust settings while the system is running by using the show port log and show port operational-statuscommands. However because of the differences in internal operation of these ECs, there are some changes in the set of available parameters for voice tuning.

See the echo-cancel coverage command for updated Cisco IOS command usage with this feature. The NextPort dual-filter G.168 echo canceller adds the following benefits on NextPort platforms:

  • Configurable parameters--Range checking that is performed on the voicecap parameters in the I960 NextPort layer has been updated. (Voicecap parameters in "raw mode" are never range-checked.)
  • Up to 128 ms of echo tail coverage--Beginning with Cisco IOS Release 12.4(20)T, the NextPort dual-filter G.168 echo canceller supports echo tails from 24-ms to 128-ms in 16-ms increments. The echo-cancel coverage command limits the echo canceller coverage to 128-ms on NextPort platforms. For backward compatibility, a voicecap used in "raw mode" will still configure older SPEware to settings greater than 64-ms when used with newer releases of Cisco IOS software. For situations when new SPEware is loaded onto an older Cisco IOS release, the NextPort dual-filter G.168 echo canceller automatically sets coverage time to 64 ms.
  • Updated set of reported statistics--Text in the show voice port command output has been changed to describe voicecap parameters and reported statistics. The show port operational-status command output has been updated to report TX/RX mean speech level statistics.
  • Power statistics (RX and TX)--These statistics average only the power that is received during signal periods that are classified as speech.
  • Unchanged configuration steps--Use voicecaps and the echo-cancel coverage command to configure this feature. See the Voicecap Strings.
  • SPE firmware and Cisco IOS software packaging support--The SPEware that contains the dual-filter G.168 echo canceller is field-upgradeable and can be used interchangeably with previous firmware versions with no effect on platform call density. The new SPEware interoperates with any Cisco IOS software release that supports voicecaps.

Note


When older Cisco IOS software releases are used, voicecaps must be used in raw mode for some parameters. Some statistics may not be displayed or recorded properly with older software releases.


NextPort SPE Firmware

NextPort SPE firmware is software that drives the digital signal processor (DSP) portion of the NextPort dial feature cards (DFCs). NextPort firmware is bundled with Cisco IOS software.

NextPort SPE firmware runs on the NextPort DFC60, DFC108, 1 CT3_UPC 216, and UPC324 DFCs on the Cisco AS5350, Cisco AS5400, Cisco AS5400HPX, and Cisco AS5850 platforms. The ports on these modules can support modem, voice, fax, and digital services and can be aggregated at any of the following levels:

  • Slot level of the NextPort module
  • SPE level within the NextPort module
  • Individual port level

Note


To use the NextPort Voice Tuning and Background Noise Statistics feature, you must use the default bundled NextPort SPE firmware code that runs with Cisco IOS software. The NextPort-Based Voice Tuning and Background Noise feature uses SPE firmware version 8.8.1 or a later version. The NextPort dual-filter G.168 echo canceller uses NextPort firmware version 10.2.2, which is bundled with Cisco IOS Release 12.3(11)T. NextPort firmware version 10.2.2 can be used with Cisco IOS Release 12.3(7)T, 12.3(10), and later releases.


For more information about NextPort SPE firmware, see the NextPort SPE Release Notes on Cisco.com.

Voicecap Strings

Additional configuration of voice services on NextPort DFCs is achieved by configuring the voice tuning configuration capability (called voicecaps) using voicecap strings. Voicecap strings are created with the the voicecap entry command and are applied with the voicecap configure command.

Voice Tuning

This feature allows the following parameters, among others, to be configured:

  • PSTN gains--PSTN gains adjust the power levels at the PSTN side of a VoIP connection to make up for loss plan imbalances and to ensure minimum echo return losses (ERLs) in a call. PSTN gain is configured with the CLI rather than with voicecaps.
  • IP gains--IP gains adjust IP-side levels and are applied to the signal before it is propagated through the echo canceller. This point is also known as the reference signal.
  • Dynamic attenuation--Dynamic attenuation mitigates low volume calls when attenuation has been added on the PSTN call leg to compensate for low ERL calls.
  • Comfort noise generation--CNG enables and disables EC comfort noise.
  • Minimum ERL--Minimum ERL switches off near-end talker clipping and poor echo canceller performance.

Note


You must have specific knowledge of the behavior of the telephone network in order to use these voicecap capabilities.


Background Noise

The NextPort Voice Tuning and Background Noise Statistics feature reports EC background noise level, voice activity detection (VAD) background noise level, ERL level, and Acombined (ACOM) statistics by averaging the combined values that are computed over the duration of the call. These statistics are appended to the end of each entry in the voice log, which you can see in the output from the show port log and show port operational-status commands.

How to Configure NextPort Services

To configure the Nextport-Based Voice Tuning and the NextPort Dual-Filter G.168 Echo Canceller feature, complete the following tasks:

Downloading NextPort SPE Firmware

To download NextPort SPE firmware, use the following commands:

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    spe {first slot | first slot / spe} {last slot | last slot / spe}

    4.    firmware location [IFS :[/]]filename

    5.    end

    6.    copy running-config startup-config


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 spe {first slot | first slot / spe} {last slot | last slot / spe}


    Example:
    Router(config)# spe 1 1/17
     

    Enters SPE configuration mode and sets the range of SPEs.

    • first slot and last slot--Identifies slots for the range. For the Cisco AS5350, slot values range from 1 to 3. For the Cisco AS5400, slot values range from 1 to 7. All ports on the specified slot are affected.
    • first slot / spe and last slot/spe--Identifies slots for the range. For the Cisco AS5350, slot values range from 1 to 3. For the Cisco AS5400, slot values range from 1 to 7. SPE values range from 1 to 17. You must include the slash mark. All ports on the specified slot and SPE are affected.
     
    Step 4 firmware location [IFS :[/]]filename


    Example:
    Router(config-spe)# firmware location flash:np.8.8.1.spe 
     

    Downloads SPE modem code to all modems in a particular slot (that is, all modems on a feature card that contains 18 6-port modem modules).

    • IFS --(Optional) Cisco IOS file specification (IFS), which can be any valid IFS on any local file system. Examples of legal specifications include:
      • bootflash:--Loads the firmware from a separate flash memory device.
      • flash:--Loads the firmware from the flash NVRAM located within the router.
      • null:--Specifies a firmware file from null: File System.
      • system:/--Loads the firmware from a built-in file within the Cisco IOS image. The optional forward slash (/) and system path must be entered with this specification.
    • filename --The firmware filename. When the filename is entered without an IFS specification, this name defaults to the file in flash memory.
    • Use the dir all-filesystems EXEC command to display legal IFSs.
    • The no form of the command reverts the router back to the system-embedded default. When the access server is booted, the firmware location command displays the location for the firmware that is embedded in the Cisco IOS image. If the firmware locationcommand is issued to download a firmware image from flash and then the no version of the exact command is subsequently issued, then the firmware location command downloads the embedded firmware in Cisco IOS software.
     
    Step 5 end


    Example:
    Router(config-spe)# end
     

    Completes the download and exits SPE configuration mode.

     
    Step 6 copy running-config startup-config


    Example:
    Router# copy running-config startup-config
     

    Copies the configuration from running RAM into NVRAM.

    • The download occurs when the modems become available and the display shows the SPE firmware upgrade option defined (default: busyout).
    • The spe command generates NVRAM modem download and configuration file entries.
    Note   

    If the configuration is not saved as described in this step, download of the firmware specified with the spe command will not occur after the next reboot.

    • For detailed information on the spe command, see the following Cisco document: "SPE and Firmware Download Enhancements".
     

    Creating and Applying Voicecaps

    Voicecaps can be used to configure any of the voice service parameters. Voicecaps are, however, primarily used to configure only those parameters that do not have associated Cisco IOS commands.

    Restrictions

    • Voicecaps are configured in global configuration mode. A maximum of five voicecap entries can be defined.
    • Applying a voicecap is possible only in voice-port configuration mode. Once applied to a voice port, the voicecap affects all calls associated with that voice port.
    • To achieve the specified functionality, an SPE image capable of voice tuning must be used in conjunction with the Cisco IOS software and module controller software.
    • For backward compatibility, a voicecap used in raw mode will configure older SPEware to allow echo canceller coverage settings greater than 64 ms when the older SPEware is used with newer releases of Cisco IOS software. For situations when new SPEware is loaded onto an older Cisco IOS software release, the NextPort dual-filter G.168 echo canceller automatically sets coverage time to 64 ms.

    Note


    Voicecap parameters in raw mode are never range-checked.


    For a list of available voicecap parameters and code words that are used with the NextPort dual-filter G.168 echo canceller feature, see the "NextPort-Based Voice Tuning and Echo Cancellation Guide".

    Setting Voice Tuning Parameters with V Registers

    The following sections contain information about voice tuning parameters with V registers:


    Note


    All data specified in dB is entered in the form (dB * 10). So, for example, to specify 6.0 dB, 60 must be entered.


    Set PSTN Gains

    To fix poor loss plans and to ensure minimum ERLs, use PSTN gains to adjust the power levels on the PSTN call leg. To adjust these levels, make sure that the sum of the output attenuation, the input attenuation, and the lowest expected functional ERL is greater than the MinERL parameter setting described below. You should balance the power levels of the far-end talker and near-end talker as seen at the echo canceller.


    Note


    Too much attenuation may cause some calls to have low volume speech. For more information, see the dynamic attenuation feature described in the "NextPort-Based Voice Tuning and Echo Cancellation Guide".



    Note


    Use the Cisco IOS CLI, not voicecap indexes, to set PSTN gains.


    Set IP Gains

    To adjust IP-side levels that are applied to the signal before it is propagated through the echo canceller, use IP gains. IP gains are controlled with the following V registers. The valid range for both input and output gain is -14 dB to 14 dB.

    • v261--IP output gain.
    • v263--IP input gain.

    Note


    There have been some instances where the IP-side power has been too high. Using index v263 can mitigate this problem.


    Set Dynamic Attenuation

    To mitigate low volume calls when attenuation has been added on the PSTN call leg to compensate for low ERL calls, use dynamic attenuation. Dynamic attenuation is controlled with the following V registers:

    • v289--Dynamic EC Attenuation Feature Enable. Set to 1 to enable. Set to 0 to disable.
    • v290--Dynamic EC Attenuation Minimum ERL Value. Valid range is from 0 dB to 60 dB.
    • v291--Dynamic EC Attenuation Final Rout Gain. Set to the lowest level desired for PSTN output attenuation. This value is usually set to 0. Valid range is from -14 dB to 6 dB.
    • v292--Dynamic EC Attenuation Final Sin Gain. Set to the lowest level desired for PSTN input attenuation. This value is usually set to 0. Valid range is from -14 dB to 6 dB.

    Set Comfort Noise Generation

    During periods of far-end single talk, the echo canceller engages the non-linear processor (NLP) to suppress residual echo. However, it will also suppress any noise signal that is coming from the near-end side. This can lead to dead silence, which the listener may confuse with a dropped call. To overcome this condition, comfort noise generation (CNG) is added.

    To choose between NLP silence or background noise reproduction, use comfort noise generation. CNG is controlled with the following V register:

    • v294--CNG Enable. Set to 1 to enable. Set to 0 to disable.

    Set Minimum ERL

    The echo canceller uses the minimum ERL (MinERL) value to decide whether the incoming signal on the PSTN call leg is an echo or a near-end talker. If this value is too high, the echo canceller will not properly identify echo and will not adapt. If this value is too low, clipping of the near-end talker may occur.

    To reduce near-end talker clipping and poor echo canceller performance, use minimum ERL. MinERL is controlled with the following V register:

    v270--Sets the level that the echo canceller expects the lowest ERL of the PSTN to be. The valid range is from 0 dB to 20 dB. The default is 6.

    Creating and Applying Voice Caps

    To create and apply voice caps and voice cap entries, complete the following tasks:

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    voicecap entry name string

      4.    voice-port slot / port :D

      5.    voicecap configure name

      6.    exit


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 voicecap entry name string


      Example:
      Router(config)# voicecap entry qualityERL v270=120
       

      Creates a voicecap.

      • The name argument is a word that uniquely identifies this voicecap.
      • The string argument is a string of characters composed of a series of voicecap register entries, similar to a modemcap. Each entry is of the form vINDEX=VALUE, where INDEX refers to a specific V register, and VALUE designates the value to set that V register to.
      • For more information about V_register entries, see the Setting Voice Tuning Parameters with V Registers.
      • The example creates a simple voicecap string named "qualityERL" with V register 270 set to 120.
       
      Step 4 voice-port slot / port :D


      Example:
      Router(config)# voice-port 3/0:D
       

      Enters voice-port configuration mode on the selected slot and port.

       
      Step 5 voicecap configure name


      Example:
      Router(config-voiceport)# voicecap configure qualityERL
       

      Applies a voicecap.

      • The name argument designates which of the newly created voicecaps to use on this voice port. This character value must be identical to the value entered when you created the voicecap entry. In this case, the value is "qualityERL."
      Note   

      To configure multiple voice ports, repeat Step 4 and Step 5 for each voice port.

       
      Step 6 exit


      Example:
      Router(config-voiceport)# exit
       

      Exits voice-port configuration mode and completes the configuration.

       

      Verifying Voicecap Configurations

      Use the following show commands in privileged EXEC mode to verify your configuration. Relevant fields are shown in bold.

      SUMMARY STEPS

        1.    show voice port

        2.    show port operational-status slot / port

        3.    show port voice log


      DETAILED STEPS
        Step 1   show voice port

        Use this command to display configured voicecaps, for example:



        Example:
        Router# show voice port
        ISDN 2/0:D - 2/0:D
         Type of VoicePort is ISDN
         Operation State is DORMANT
         Administrative State is UP
         No Interface Down Failure
         Description is not set
        .
        .
        .
         Station name None, Station number None
         Translation profile (Incoming):
         Translation profile (Outgoing):
         Voicecap:EXAMPLE
        
        Step 2   show port operational-status slot / port

        Use this command to display background noise level information on current calls. Significant fields are shown in bold in the following example:



        Example:
        Router# show port operational-status 1/0
        Slot/SPE/Port -- 1/0
        Service Type                            :Voice service
        Voice Codec                             :G.711 u-law
        Echo Canceler Length                    :8 ms
        Echo Cancellation Control               :Echo cancellation       - enabled
                                                  Echo update             - enabled
                                                  Non-linear processor    - enabled
                                                  Echo reset coefficients - disabled
                                                  High pass filter enable - disabled
        Digit detection enable                  :DTMF signaling          - enabled
        Voice activity detection                :Disabled
        Comfort noise generation                :Generate comfort noise
        Digit relay enable                      :OOB Digit relay         - disabled
                                                  IB Digit relay          - disabled
        Information field size                  :20 ms
        Playout de-jitter mode                  :adaptive
        Encapsulation protocol                  :RTP
        Input Gain                              :0.0 dB
        Output Gain                             :0.0 dB
        Tx/Rx SSRC                              :20/0
        Current playout delay                   :65 ms
        Min/Max playout delay                   :65/105 ms
        Clock offset                            :142003 ms
        Predictive concealment                  :0 ms
        Interpolative concealment               :0 ms
        Silence concealment                     :0 ms
        Buffer overflow discards                :1
        End-point detection errors              :0
        Tx/Rx Voice packets                     :1337/1341
        Tx/Rx signaling packets                 :0/0
        Tx/Rx comfort noise packets             :0/0
        Tx/Rx duration                          :26745/26745 ms
        Tx/Rx voice duration                    :0/0 ms
        Out of sequence packets                 :0
        Bad protocol headers                    :0
        Num. of late packets                    :0
        Num. of early packets                   :1
        Tx/Rx Power                           :-87.0/-57.3 dBm
        Tx/Rx Talker Level                      :-86.3/-57.0 dBm
        TX/RX Mean Speech level                 :-86.3/-57.0 dBm
        VAD Background noise level              :6.2 dBm
        ERL level                               :127.0 dB
        ACOM level                              :127.0 dB
        Tx/Rx current activity                  :silence/silence
        Tx/Rx byte count                        :213920/214240
        ECAN Background noise level             :-83.4 dBm
        Latest SSRC value                       :391643394
        Number of SSRC changes                  :1
        Number of payload violations            :0
        
        Step 3   show port voice log

        Use this command to display background noise level information on completed calls. Significant fields are shown in bold in the following example:



        Example:
        Router# show port voice log
        Port 1/00 Events Log
          *Aug 22 07:59:27.515:Voice Terminate event:
            Disconnect Reason                  :  normal call clearing (16)
            Call Timer                         :  57  secs
            Current playout delay              :  65  ms
            Min/Max playout delay              :  65/105  ms
            Clock offset                       :  142003  ms
            Predictive concealment             :  0  ms
            Interpolative concealment          :  0  ms
            Silence concealment                :  0  ms
            Buffer overflow discards           :  1
            End-point detection errors         :  0
            Tx/Rx Voice packets                :  2813/2816
            Tx/Rx signaling packets            :  0/0
            Tx/Rx comfort noise packets        :  0/0
            Tx/Rx duration                     :  56260/56260  ms
            Tx/Rx voice duration               :  0/0  ms
            Out of sequence packets            :  0
            Bad protocol headers               :  0
            Num. of late packets               :  0
            Num. of early packets              :  1
            Tx/Rx Power                        :  -87.0/-57.3  dBm
            Tx/Rx Mean Speech Level            :  -86.7/-57.0  dBm 
            Tx/Rx Talker Level                 :  -86.3/-57.0 dBm
            Average VAD Background noise level :  6.2  dBm
           
         Average ERL level                  :  127.0  dB
            Average ACOM level                 :  127.0  dB
            Tx/Rx current activity             :  silence/silence
            Tx/Rx byte count                   :  450080/450240
            Average ECAN Background noise level:  -83.4  dBm
           *Aug 22 07:59:27.515:Voice SSRC change events:
            Latest ssrc value                  :  391643394
            Total ssrc changes                 :  1
        

        Troubleshooting NextPort Voicecaps

        Use the following debug and showcommands in privileged EXEC mode to debug the application of a voicecap and to check debugging output:

        SUMMARY STEPS

          1.    debug nextport vsmgr detail

          2.    debug dspapi detail

          3.    show debug


        DETAILED STEPS
          Step 1   debug nextport vsmgr detail

          Use this command to turn on debugging for NextPort voice services, for example:



          Example:
          Router# debug nextport vsmgr detail
          NextPort Voice Service Manager:
            NP Voice Service Manager Detail debugging is on
          .
          .
          .
          
          Step 2   debug dspapi detail

          Use this command to turn on debugging for DSP API message event details, for example:



          Example:
          Router# debug dspapi detail
          DSP API:
            DSP API Command debugging is on
            DSP API Detail debugging is on
          .
          .
          .
          
          Step 3   show debug

          Use this command to check voicecap application debugging. The significant field in the output is highlighted in bold in the following example:



          Example:
          Router# show debug
          NextPort Voice Service Manager:
            NP Voice Service Manager Detail debugging is on
          DSP API:
            DSP API Command debugging is on
            DSP API Detail debugging is on
          *Aug 22 08:34:47.399:dspapi [2/1:1 (4)] dsp_init
          *Aug 22 08:34:47.399:dspapi [2/1:1 (4)] dsp_voice_config_params:10 params
          *Aug 22 08:34:47.399:  [0] ENCAP RTP:t_ssrc=20 r_ssrc=0 t_vpxcc=0 r_vpxcc=0
                                  ifp_payload_type=122 sid_support=19 tse_payload=101 seq_num_start=6303 redundancy=0 cc_payload_typ
          Router# e=125 fax_payload_type=122 alaw_pcm_switchover=8 mulaw_pcm_switchover=0 dtmf_payload_type=121, nte_rcv_payload_type=101dynamic_payload=0, codec=5
          *Aug 22 08:34:47.399:  [1] PO_JITTER:mode=2 initial=60 max=200 min=40 fax_nom=300
          *Aug 22 08:34:47.399:  [2] INBAND_SIG:mode=0x1 enable
          *Aug 22 08:34:47.399:  [3] ECHO_CANCEL:flags=0x17 echo_len=256
          *Aug 22 08:34:47.399:  [4] IDLE_CODE_DET:enable = 0 code=0x0 duration=6000
          *Aug 22 08:34:47.403:  [5] GAIN:input=0 output=0
          *Aug 22 08:34:47.403:  [6] CNG:
          Router# 1
          *Aug 22 08:34:47.403:  [7] INFO_FIELD_SIZE:160
          *Aug 22 08:34:47.403:  [8] DIGIT_RELAY:2
          *Aug 22 08:34:47.403:  [9] VOICECAP:EXAMPLE
          *Aug 22 08:34:47.403:dspapi [2/1:1 (4)] dsp_start_service:G711_U (5)
          *Aug 22 08:34:47.403:Matched voicecap:v0=0 v1=1
          *Aug 22 08:34:47.403:msg length = 0x001D
          *Aug 22 08:34:47.403:session ID = 0x006D
          *Aug 22 08:34:47.403:   msg tag = 0x0000
          *Aug 22 08:34:47.403:    msg ID = 0xF201

          Configuring the NextPort Dual-Filter G.168 Echo Canceller

          The NextPort dual-filter G.168 echo canceller is enabled by default on NextPort platforms in Cisco IOS Release 12.3(11)T and later releases. However, you can adjust the echo canceller tail coverage time at the voice-port interface by completing the following tasks:

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    voice-port slot / port :D

            4.    echo-cancel coverage {24 | 32 | 48 | 64 | 80 | 96 | 112 | 128}

            5.    exit


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Router> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 configure terminal


            Example:
            Router# configure terminal
             

            Enters global configuration mode.

             
            Step 3 voice-port slot / port :D


            Example:
            Router(config)# voice-port 3/0:D
             

            Enters voice-port configuration mode on the selected slot and port.

             
            Step 4 echo-cancel coverage {24 | 32 | 48 | 64 | 80 | 96 | 112 | 128}


            Example:
            Router(config-voiceport)# echo-cancel coverage 64
             

            Adjusts the size of the echo canceller (EC) and selects the extended EC when the Cisco default EC is present.

            • Starting with Cisco IOS Release 12.4(20)T, the default coverage time and maximum possible coverage is 128 ms for both 8.x and 10.2.2 SPEware versions.
             
            Step 5 exit


            Example:
            Router(config-voiceport)# exit
             

            Exits voice-port configuration mode and completes the configuration.

             

            Configuration Examples for NextPort Services

            The following sections contain examples that could be used to optimize a NextPort-based gateway for a given telephone network:

            High ERL in the Network Example

            Register v270 is used to set the limit for the minimum expected ERLs that the gateway will encounter. If the gateway encounters ERLs that are lower than the v270 setting, the echo canceller performance will be suboptimal.

            The default setting for v270 is 6 dB. This setting should work well for usual telephone networks. However, when the gateway is used on a well-managed telephone network with organized loss plans in place, the ERL is often greater than 6 dB. In these cases, v270 can be raised. Making this change reduces any clipping of the near-end signal; however, it will underperform if a low ERL is encountered.

            In this example, the network is designed to have an ERL of 12 dB or greater. In this case, the following voicecap may improve performance. Notice that the value for v270 is entered as decibels multiplied by 10.

            Router> enable
            Router# configure terminal 
            Router(config)# voicecap entry qualityERL v270=120
            Router(config)# end
            

            Low ERL in the Network Example

            Unlike the scenario described in the previous example, some telephone networks may not always produce sufficient ERLs to meet the default setting of 6 dB. The best way to solve this problem would be to institute better loss plans on the telephone network. However, because this is not always possible, a voicecap can be used to alleviate the problem.

            A low ERL means that the echo canceller must do a much deeper cancellation to remove sufficient echo. Also, lowering the minimum ERL can increase the incidence of clipping. The best way to improve this situation is to make up for the telephone network’s lack of loss plan by adding some loss in the gateway. If the lowest ERL seen is 4 dB, adding 1 dB of output attenuation and -1 dB of input gain will ensure that the echo canceller never sees more than a 6-dB effective ERL.

            Adding this attenuation can be done by entering a voicecap, but using the CLI is the recommended approach in this example. The following commands set the gains that are needed for this example:

            Router> enable
            Router# configure terminal
             
            Router(config)# voice-port
             3/0:D
            Router(config-voiceport)# output attenuation 1
            Router(config-voiceport)# input gain -1
             
            Router(config-voiceport)# end 
            

            Clipped or Squelched Speech and Low ERL in the Network Example

            In this example, a network in which signal level imbalance is already causing clipping to occur with a MinERL setting of 6 dB and in which ERLs of less than 6 dB are already occurring, a dual approach must be taken. To stop the clipping, the MinERL setting should be lowered to 12 dB. If 4-dB ERLs are occurring, 4 dB of attenuation must be added to the input and the output to ensure that there is 12 dB of effective ERL at the echo canceller (4 dB of real ERL, plus 4 dB of output attenuation, plus 4 dB of input attenuation equals 12 dB of effective ERL). To create these settings, the following commands are used:

            Router> enable
            Router# configure terminal 
            Router(config)# voicecap entry qualityERL v270=120
            Router(config)# voice-port 3/0:D
            Router(config-voiceport)# voicecap configure qualityERL
            Router(config-voiceport)# output attenuation 4
            Router(config-voiceport)# input gain -4
            Router(config-voiceport)# end
            

            Dynamic Attenuation Example

            It is possible that worst-case settings are only required when the primary telephone circuits are all used and an alternate carrier with a poor loss plan must be used instead. For these cases, the dynamic attenuation feature removes the attenuation when the ERL is sufficient. In the following example, 4 dB of input and output attenuation is to be removed when it is not necessary to ensure the minimum ERL setting. To do this, the dynamic attenuation feature (using v289) is enabled. The required ERL must be set before attenuation is removed (using v290), and minimum attenuation levels for the input and output (using v291 and v292) must also be set. In this example, attenuation is set to 15 dB and then removed.

            Router> enable
            Router# configure terminal 
            Router(config)# voicecap entry dynatten v270=120 v289=1 v290=15 v291=0 v292=0
            Router(config)# voice-port 3/0:D
            Router(config-voiceport)# voicecap configure dynatten
            Router(config-voiceport)# output attenuation 4
            Router(config-voiceport)# input gain -4
            Router(config-voiceport)# end
            

            Echo Canceller Tail Coverage Example

            The following example adjusts echo canceller tail coverage to 64 ms on the Cisco AS5400:

            Router(config) voice-port 1
            /0:0
            Router(config-voiceport)# echo-cancel coverage 64
            

            Enabling NextPort Echo Canceller Control for G.711 Encoded VoIP Packets

            This section describes how to enable NextPort echo canceller control on the Cisco AS5350, AS5400, AS5400HPX, and AS5850 universal gateways when these gateways detect 2100 Hz tones, received in G.711 encoded VoIP packets. You can enable NextPort voicecaps to control the echo canceller from either the PSTN or IP side of the network.


            Note


            NextPort control over the echo canceller is possible only in G.711 codec modes. Cisco recommends that you do not enable NextPort control over the echo canceller in conjunction with modem pass-through.


            IP tone detection and NextPort control over the echo canceller is enabled using the command-line interface. Use the following commands to enable NextPort control over the echo canceller by creating a voicecap entry and applying it to the voice port.

            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    voicecap entry name string

              4.    voice-port slot / port

              5.    voicecap configure name

              6.    exit


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3 voicecap entry name string


              Example:
              Router(config)# voicecap entry npecho_ctrl v2=512 v51=32769
               

              Creates a voicecap entry.

              • The name argument is a word that uniquely identifies this voicecap.
              • The string argument is a series of voicecap register entries, similar to a modemcap. Each entry is of the form vINDEX=VALUE, where INDEX refers to a specific V register, and VALUE designates the value to which the V register should be set.
              • Example settings:
                • The v2=512setting enables the 250-ms silence detection. This setting is optional. When this setting is used in conjunction with the v51 = 32769 setting, NextPort restores the echo canceller to its original state after it detects the 250-ms silence.
                • The v51=32769 setting enables IP side tone detection/notification and allows NextPort to disable the NLP or the echo canceller upon reception of 2100 Hz answer tones from the IP side. This setting is required in Cisco IOS Release 12.3T.
               
              Step 4 voice-port slot / port


              Example:
              Router(config)# voice-port 3/0
               

              Enters voice-port configuration mode on the selected slot and port.

               
              Step 5 voicecap configure name


              Example:
              Router(config-voiceport)# 
              voicecap configure npecho_ctrl
              
               

              Applies a voicecap entry to the voice port.

              • The name argument designates which of the newly created voicecaps to use on this voice port. This character value must be identical to the value entered when you created the voicecap entry.
              Note   

              To configure multiple voice ports, repeat Step 4 and Step 5 for each voice port.

               
              Step 6 exit


              Example:
              Router(config-voiceport)# exit
               

              Exits voice-port configuration mode.

               

              Troubleshooting NextPort Echo Canceller Control for G.711 Encoded VoIP Packets

              You can display the EST trace messages that show the tone detections and the resultant echo operations if you enter the debug trace module f080 0010 s / d / m command. NextPort enables and disables the NLP and the echo canceller based on reception of 2100 Hz answer tones from the IP side or PSTN side and generates EST trace messages for each tone detected and its echo operation. NextPort also detects the 250 ms of silence and generates EST trace messages to indicate such detection and to indicate that the echo state has been restored.

              Router# debug trace module f080 0010 s/d/m
              

              Use this command to display the EST trace messages. In the command, s/d/m is defined as follows:

              • s = slot
              • d = dfc
              • m = module number

              When the default configuration values for Index 51 and Index 52 are used, IP tone detection and notification are disabled, and all existing features continue to function normally.

              The following example shows EST trace messages collected from the console:

              Router#
              *Apr 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:      Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:51.735:      Data Len   : 56
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received Early ANS tone 0x01 from IP side
              *Apr 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:
              Router#  Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:51.735:      Data Len   : 63
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received Tone Off ntf for code 0x01 from IP side
              *Apr 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:      Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              Router#*Apr 26 21:40:51.735:      Data Len   : 45
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received ANS tone 0x03 from IP
              *Apr 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:      Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:51.735:      Data Len   : 47
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Non-linear Processor Is Disabled
              *Apr
              Router# 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:      Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:51.735:      Data Len   : 63
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received Tone Off ntf for code 0x03 from IP side
              *Apr 26 21:40:51.735:   00:00:14: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:
              Router#   Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:51.735:      Data Len   : 47
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received ANSam tone 0x07 from IP
              *Apr 26 21:40:51.735:   00:00:13: Port Trace Event:
              *Apr 26 21:40:51.735:      Port       : 3/00
              *Apr 26 21:40:51.735:      Address    : 0x3000000
              *Apr 26 21:40:51.735:      Trace Event: 0x2
              *Apr 26 21:40:51.735:      Data Format: ASCII
              *Apr 26 21:40:5
              Router#1.735:      Data Len   : 63
              *Apr 26 21:40:51.735:      Data       : Session 0x0144 Received Tone Off ntf for code 0x07 from IP side
              *Apr 26 21:40:51.739:   00:00:13: Port Trace Event:
              *Apr 26 21:40:51.739:      Port       : 3/00
              *Apr 26 21:40:51.739:      Address    : 0x3000000
              *Apr 26 21:40:51.739:      Trace Event: 0x2
              *Apr 26 21:40:51.739:      Data Format: ASCII
              *Apr 26 21:40:51.739:      Data Len   : 48
              *Apr 26 21:40:51.739:      Data       : Session 0x0144 Received /ANSam tone 0x0f from IP
              Router#*Apr 26 21:40:51.739:   00:00:13: Port Trace Event:
              *Apr 26 21:40:51.739:      Port       : 3/00
              *Apr 26 21:40:51.739:      Address    : 0x3000000
              *Apr 26 21:40:51.739:      Trace Event: 0x2
              *Apr 26 21:40:51.739:      Data Format: ASCII
              *Apr 26 21:40:51.739:      Data Len   : 31
              *Apr 26 21:40:51.739:      Data       : Session 0x0144 ECAN Is Disabled
              *Apr 26 21:40:51.739:   00:00:04: Port Trace Event:
              *Apr 26 21:40:51.739:      Port       : 3/00
              *Apr 26 21:40:51.739:      Address    : 0x3000000
              Router#*Apr 26 21:40:51.739:      Trace Event: 0x2
              *Apr 26 21:40:51.739:      Data Format: ASCII
              *Apr 26 21:40:51.739:      Data Len   : 63
              *Apr 26 21:40:51.739:      Data       : Session 0x0144 Received Tone Off ntf for code 0x0f from IP side
              *Apr 26 21:46:36.431:   00:00:08: Port Trace Event:
              *Apr 26 21:46:36.431:      Port       : 3/00
              *Apr 26 21:46:36.431:      Address    : 0x3000000 
              *Apr 26 21:46:36.431:      Trace Event: 0x2
              *Apr 26 21:46:36.431:      Data Format: ASCII
              *Apr 26 21:46:36.431:      Data Len   : 43
              *Apr 26 21:46:36.431:      Data       : Session 0x0144 detected 250 msec of silence
              *Apr 26 21:46:36.431:   00:00:08: Port Trace Event:
              *Apr 26 21:46:36.431:      Port       : 3/00
              *Apr 26 21:46:36.431:      Address    : 0x3000000 
              *Apr 26 21:46:36.435:      Trace Event: 0x2
              *Apr 26 21:46:36.435:      Data Format: ASCII
              *Apr 26 21:46:36.435:      Data Len   : 41
              *Apr 26 21:46:36.435:      Data       : Session 0x0144 Ecan State 0x0007 Restored