Cisco Unified IP Phone 8941 and 8945 Administration Guide for Cisco Unified Communications Manager 9.0 (SCCP and SIP)
Troubleshooting and maintenance
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Troubleshooting and maintenance

Contents

Troubleshooting and maintenance

This chapter provides information that can assist you in troubleshooting problems with your Cisco Unified IP Phone or with your IP telephony network. It also explains how to clean and maintain your phone.

If you need additional assistance to resolve an issue, see Documentation, support, and security guidelines.

This chapter includes these topics:

Troubleshooting

The following sections describe how to resolve problems that may be experienced with the phones.

Startup Problems

After installing a Cisco Unified IP Phone into your network and adding it to Cisco Unified Communications Manager, the phone should start up as described in the Phone Startup Process. If the phone does not start up properly, see the following sections for troubleshooting information:

Cisco Unified IP Phone Does Not Go Through Normal Startup Process

When you connect a Cisco Unified IP Phone into the network port, the phone should go through its normal startup process as described in Phone Startup Process and the LCD screen should display information. If the phone does not go through the startup process, the cause may be faulty cables, bad connections, network outages, lack of power, or the phone may not be functional.

To determine whether the phone is functional, follow these suggestions to systematically eliminate these other potential problems:

  • Verify that the network port is functional:
    • Exchange the Ethernet cables with cables that you know are functional.
    • Disconnect a functioning Cisco Unified IP Phone from another port and connect it to this network port to verify the port is active.
    • Connect the Cisco Unified IP Phone that will not start up to a different network port that is known to be good.
    • Connect the Cisco Unified IP Phone that will not start up directly to the port on the switch, eliminating the patch panel connection in the office.
  • Verify that the phone is receiving power:
    • If you are using external power, verify that the electrical outlet is functional.
    • If you are using in-line power, use the external power supply instead.
    • If you are using the external power supply, switch with a unit that you know to be functional.
  • If the phone still does not start up properly, power up the phone with the handset off-hook. When the phone is powered up in this way, it attempts to launch a backup software image.
  • If the phone still does not start up properly, perform a factory reset of the phone. For instructions, see the Perform Factory Reset.

If after attempting these solutions, the LCD screen on the Cisco Unified IP Phone does not display any characters after at least five minutes, contact a Cisco technical support representative for additional assistance.

Cisco Unified IP Phone does not register with Cisco Unified Communications Manager

If the phone proceeds past the first stage of the startup process (LED buttons flashing on and off) but continues to cycle through the messages displaying on the LCD screen, the phone is not starting up properly. The phone cannot successfully start up unless it is connected to the Ethernet network and it has registered with a Cisco Unified Communications Manager server.

In addition, problems with security may prevent the phone from starting up properly. See the Cisco Unified IP Phone Security Problems for more information.

The following sections can assist you in determining the reason the phone is unable to start up properly.

Phone Displays Error Messages
Problem

Phone status messages display errors during startup.

Solution

As the phone cycles through the startup process, you can access status messages that might provide you with information about the cause of a problem. See the Status Messages Screen for instructions about accessing status messages and for a list of potential errors, their explanations, and their solutions.

Phone Cannot Connect to TFTP Server or to Cisco Unified Communications Manager
Problem

If the network is down between the phone and either the TFTP server or Cisco Unified Communications Manager, the phone cannot start up properly.

Solution

Ensure that the network is currently running.

TFTP Server Settings
Problem

The TFTP server settings may not be correct.

Solution

Check the TFTP settings. See Check TFTP Settings.

IP Addressing and Routing
Problem

The IP addressing and routing fields may not be correctly configured.

Solution

You should verify the IP addressing and routing settings on the phone. If you are using DHCP, the DHCP server should provide these values. If you have assigned a static IP address to the phone, you must enter these values manually. See Check DHCP Settings.

DNS settings
Problem

The DNS settings may be incorrect.

Solution

If you use DNS to access the TFTP server or Cisco Unified Communications Manager, you must ensure that you specify a DNS server. Check your DNS settings.

Cisco CallManager and TFTP Services Are Not Running
Problem

If the Cisco CallManager or TFTP services are not running, phones may not be able to start up properly. In such a situation, it is likely that you are experiencing a systemwide failure, and other phones and devices are unable to start up properly.

Solution

If the Cisco CallManager service is not running, all devices on the network that rely on it to make phone calls are affected. If the TFTP service is not running, many devices cannot start up successfully. For more information, see Start service.

Configuration file corruption

Problem

If you continue to have problems with a particular phone that other suggestions in this chapter do not resolve, the configuration file may be corrupted.

Solution

Create a new phone configuration file. See Create New Phone Configuration File

Cisco Unified Communications Manager Phone Registration
Problem

The phone is not registered with the Cisco Unified Communications Manager

Solution

A Cisco Unified IP Phone can register with a Cisco Unified Communications Manager server only if the phone has been added to the server or if autoregistration is enabled and if there are sufficient number of unit licenses. Review the information and procedures to ensure that the phone has been added to the Cisco Unified Communications Manager database.

To verify that the phone is in the Cisco Unified Communications Manager database, choose Device > Phone > Find from Cisco Unified Communications Manager Administration to search for the phone based on its MAC Address.

If the phone is already in the Cisco Unified Communications Manager database, its configuration file may be damaged.

For more information on licensing go to the "Licenses for Phones" section in the Cisco Unified Communications Manager System Guide.

Cisco Unified IP Phone Cannot Obtain IP Address

Problem

If a phone cannot obtain an IP address when it starts up, the phone may not be on the same network or VLAN as the DHCP server, or the switch port to which the phone connects may be disabled.

Solution

Ensure that the network or VLAN to which the phone connects has access to the DHCP server, and ensure that the switch port is enabled.

Cisco Unified IP Phone Resets Unexpectedly

If users report that their phones are resetting during calls or while idle on their desk, you should investigate the cause. If the network connection and Cisco Unified Communications Manager connection are stable, a Cisco Unified IP Phone should not reset on its own.

Typically, a phone resets if it has problems connecting to the Ethernet network or to Cisco Unified Communications Manager. These sections can help you identify the cause of a phone resetting in your network:

Physical Connection Problems

Problem

The physical connection to the LAN may be broken.

Solution

Verify that the Ethernet connection to which the Cisco Unified IP Phone connects is up. For example, check whether the particular port or switch to which the phone connects is down and that the switch is not rebooting. Also ensure that no cable breaks exist.

Intermittent network outages

Problem

Your network may be experiencing intermittent outages.

Solution

Intermittent network outages affect data and voice traffic differently. Your network might be experiencing intermittent outages without detection. If so, data traffic can resend lost packets and verify that packets are received and transmitted. However, voice traffic cannot recapture lost packets. Rather than retransmitting a lost network connection, the phone resets and attempts to reconnect to the network. Contact the system administrator for information on known problems in the voice network.

DHCP Settings Errors

Problem

The DHCP settings may be incorrect.

Solution

Verify that you have properly configured the phone to use DHCP. See the Network Setup Menu for more information. Verify that the DHCP server has been set up properly. Verify the DHCP lease duration. Cisco recommends that you set it to 8 days.

Static IP Address Settings Errors

Problem

The static IP address assigned to the phone may be incorrect.

Solution

If the phone has been assigned a static IP address, verify that you have entered the correct settings. See the Network Setup Menu for more information.

Voice VLAN Configuration Errors

Problem

If the Cisco Unified IP Phone appears to reset during heavy network usage (for example, following extensive web surfing on a computer connected to the same switch as the phone), it is likely that you do not have a voice VLAN configured.

Solution

Isolating the phones on a separate auxiliary VLAN increases the quality of the voice traffic. See the Cisco Unified IP Phone and VLAN Interaction for details.

Phones have not been intentionally reset

Problem

If you are not the only administrator with access to Cisco Unified Communications Manager, you should verify that no one else has intentionally reset the phones.

Solution

You can check if a Cisco Unified IP Phone received a command from Cisco Unified Communications Manager to reset by pressing Applications on the phone and choosing Administrator Settings > Status > Network Statistics.

  • If the Restart Cause field displays Reset-Reset, the phone received a Reset/Reset from Cisco Unified Communications Manager Administration.
  • If the Restart Cause field displays Reset-Restart, the phone reset because it received a Reset/Restart from Cisco Unified Communications Manager Administration.

DNS or Other Connectivity Errors

Problem

The phone continues to reset and you suspect DNS of other connectivity issues.

Solution

If the phone continues to reset, eliminate DNS or other connectivity errors with Determine DNS or connectivity issues.

Power Connection Problems

Problem

The phone does not appear to be powered up.

Solution

In most cases, a phone restarts if it powers up by using external power but loses that connection and switches to PoE. Similarly, a phone may restart if it powers up by using PoE and then connects to an external power supply.

Cisco Unified IP Phone Security Problems

The following sections provides troubleshooting information for the security features on the Cisco Unified IP Phone. For information relating to the solutions for any of these issues, and for additional troubleshooting information about security and encryption, see the Cisco Unified Communications Manager Security Guide.

CTL File Problems

The following sections describe problems with the CTL file.

Authentication Error, Phone Cannot Authenticate CTL File
Problem

A device authentication error occurs.

Cause

CTL file does not have a Cisco Unified Communications Manager certificate or has an incorrect certificate.

Solution

Install a correct certificate.

Phone Cannot Authenticate CTL File
Problem

Phone cannot authenticate the CTL file.

Cause

The security token that signed the updated CTL file does not exist in the CTL file on the phone.

Solution

Change the security token in the CTL file and install the new file on the phone.

CTL File Authenticates but Other Configuration Files Do Not Authenticate
Problem

Phone cannot authenticate any configuration files other than the CTL file.

Cause

A bad TFTP record exists, or the configuration file may not be signed by the corresponding certificate in the phone Trust List.

Solution

Check the TFTP record and the certificate in the Trust List.

Phone Does Not Register
Problem

Phone does not register with Cisco Unified Communications Manager.

Cause

The CTL file does not contain the correct information for the Cisco Unified Communications Manager server.

Solution

Change the Cisco Unified Communications Manager server information in the CTL file.

Signed Configuration Files Are Not Requested
Problem

Phone does not request signed configuration files.

Cause

The CTL file does not contain any TFTP entries with certificates.

Solution

Configure TFTP entries with certificates in the CTL file.

802.1X Authentication Problems

801.1X authentication problems can be broken into the categories described in the following table.

Table 1 Identifying 802.1X Authentication Problems

If all the following conditions apply

See

802.1X is Enabled on Phone but Phone Does Not Authenticate

802.1X is Not Enabled

  • Phone cannot obtain a DHCP-assigned IP address
  • Phone does not register with Cisco Unified Communications Manager
  • Phone status display as Configuring IP or Registering
  • Cannot access phone menus to verify 802.1X status

Factory Reset of Phone Deleted 802.1X Shared Secret

802.1X is Enabled on Phone but Phone Does Not Authenticate
Problem

The phone cannot authenticate.

Cause

These errors typically indicate that 802.1X authentication is enabled on the phone, but the phone is

unable to authenticate.

Solution

To resolve this problem, you need to check the 802.1X and shared secret configuration. See Identify 802.1X Authentication Problems.

802.1X is Not Enabled
Problem

The phone does not have 802.1X configured.

Cause

These errors typically indicate that 802.1X is not enabled on the phone.

Solution

To enable it, see the Security Configuration menu for information on enabling 802.1X on the phone.

Factory Reset of Phone Deleted 802.1X Shared Secret
Problem

After a reset, the phone does not authenticate.

Cause

These errors typically indicate that the phone has completed a factory reset while 802.1X was enabled. A factory reset deletes the shared secret, which is required for 802.1X authentication and network access.

Solution

To resolve this, you have two options:

  • Temporarily disable 802.1X on the switch.
  • Temporarily move the phone to a network environment that is not using 802.1X authentication.

After the phone starts up normally in one of these conditions, you can access the 802.1X configuration menus and enter the shared secret again.

Audio and Video Problems

The following sections describe how to troubleshoot common audio and video problems.

Choppy Speech

Problem

A user complains of choppy speech on a call.

Cause

There may be a mismatch in the jitter configuration.

Solution

Check the AvgJtr and the MaxJtr statistics. A large variance between these statistics might indicate a problem with jitter on the network or periodic high rates of network activity. See the Call Statistics Screen for information about displaying these statistics.

Phone display is wavy

Problem

The display appears to have rolling lines or a wavy pattern.

Cause

The phone might be interacting with certain types of older fluorescent lights in the building.

Solution

Move the phone away from the lights or replace the lights to resolve the problem.

Poor Audio Quality with Calls That Route Outside Cisco Unified Communications Manager

Problem

Poor quality occurs with tandem audio encoding. Tandem encoding can occur when calls are made between an IP Phone and a digital cellular phone, when a conference bridge is used, or in situations where IP-to-IP calls are partially routed across the PSTN.

Cause

In these cases, use of voice codecs such as G.729 and iLBC may result in poor voice quality.

Solution

Use the G.729 and iLBC codecs only when absolutely necessary.

No speech path

Problem

One or more people on a call do not hear any audio.

Solution

When at least one person in a call does not receive audio, IP connectivity between phones is not established. Check the configuration of routers and switches to ensure that IP connectivity is properly configured.

Insufficient bandwidth for video calls

Problem

Users report that calls with video suddenly drop the video component of the call. The video part of a call cannot be established.

Cause

The network has run out of resources for the video call.

Solution

Changes need to be made on the Cisco Unified Communications Manager. For more information, see Cisco Unified Communications Manager Systems Guide.

General telephone call problems

The following sections help troubleshoot general telephone call problem.

Phone call cannot be established

Problem

A user complains about not being able to make a call.

Cause

The phone does not have a DHCP IP address, is unable to register to Cisco Unified Communications Manager. Phones with an LCD display show the message Configuring IP or Registering. Phones without an LCD display play the reorder tone (instead of dial tone) in the handset when the user attempts to make a call.

Solution
  1. Verify the following:
    1. The Ethernet cable is attached.
    2. The Cisco CallManager service is running on the Cisco Unified Communications Manager server.
    3. Both phones are registered to the same Cisco Unified Communications Manager.
  2. Audio server debug and capture logs are enabled for both phones. If needed, enable Java debug.

Phone does not recognize DTMF digits or digits are delayed

Problem

The user complains that numbers are missed or delayed when the keypad is used.

Cause

Pressing the keys too quickly can result in missed or delayed digits.

Solution

Keys should not be pressed rapidly.

Troubleshooting Procedures

These procedures can be used to identify and correct problems.

Check TFTP Settings

Procedure
    Step 1   Press Applications.
    Step 2   Select Administrator Settings > Network Setup > IPv4 > TFTP Server 1.
    Step 3   If you have assigned a static IP address to the phone, you must manually enter a setting for the TFTP Server 1 option.
    Step 4   If you are using DHCP, the phone obtains the address for the TFTP server from the DHCP server. Check the IP address configured in Option 150.
    Step 5   You can also enable the phone to use an alternate TFTP server. Such a setting is particularly useful if the phone was recently moved from one location to another.

    Check DHCP Settings

    Procedure
      Step 1   On the Cisco Unified IP Phone, press Applications.
      Step 2   Select Administrator Settings > Network Setup > IPv4, and look at the following options:
      Step 3   If you are using DHCP, check the IP addresses distributed by your DHCP server. Refer to the Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks document, available at this URL: http:/​/​www.cisco.com/​en/​US/​tech/​tk648/​tk361/​technologies_​tech_​note09186a00800f0804.shtml

      Determine DNS or connectivity issues

      Procedure
        Step 1   Use the Reset Settings menu to reset phone settings to their default values. See the Cisco Unified IP Phone Reset or Restore for details.
        Step 2   Modify DHCP and IP settings:
        1. Disable DHCP. See the Network Setup Menu for instructions.
        2. Assign static IP values to the phone. See the Network Setup Menu for instructions. Use the same default router setting used for other functioning Cisco Unified IP Phones.
        3. Assign a TFTP server. See the Network Setup Menu for instructions. Use the same TFTP server used for other functioning Cisco Unified IP Phones.
        Step 3   On the Cisco Unified Communications Manager server, verify that the local host files have the correct Cisco Unified Communications Manager server name mapped to the correct IP address.
        Step 4   From Cisco Unified Communications Manager, choose System > Server and verify that the server is referred to by its IP address and not by its DNS name.
        Step 5   From Cisco Unified Communications Manager, choose Device > Phone > Find and verify that you have assigned the correct MAC address to this Cisco Unified IP Phone. For information about determining a MAC address, see Cisco Unified IP Phone MAC Address Determination.
        Step 6   Power cycle the phone.

        Identify 802.1X Authentication Problems

        Procedure
          Step 1   Verify that you have properly configured the required components. For more information, see 802.1X Authentication.
          Step 2   Confirm that the shared secret is configured on the phone. For more information, see Security Configuration menu.
          • If the shared secret is configured, verify that you have the same shared secret entered on the authentication server.
          • If the shared secret is not configured, enter it, and ensure that it matches the one on the authentication server.

          Verify DNS settings

          To verify DNS settings, follow these steps:

          Procedure
            Step 1   Press Applications.
            Step 2   Select Administrator Settings > Network Setup > Ethernet Setup > IPv4 Setup > DNS Server 1.
            Step 3   You should also verify that a CNAME entry was made in the DNS server for the TFTP server and for the Cisco Unified Communications Manager system.

            You must also ensure that DNS is configured to do reverse lookups.


            Create New Phone Configuration File

            If you continue to have problems with a particular phone that other suggestions in this chapter do not resolve, the configuration file may be corrupted.


            Note


            • When you remove a phone from the Cisco Unified Communications Manager database, its configuration file is deleted from the Cisco Unified Communications Manager TFTP server. The phone directory number or numbers remain in the Cisco Unified Communications Manager database. They are called "unassigned DNs" and can be used for other devices. If unassigned DNs are not used by other devices, delete them from the Cisco Unified Communications Manager database. You can use the Route Plan Report to view and delete unassigned reference numbers. For more information, see the Cisco Unified Communications Manager Administration Guide.
            • Changing the buttons on a phone button template, or assigning a different phone button template to a phone, may result in directory numbers that are no longer accessible from the phone. The directory numbers are still assigned to the phone in the Cisco Unified Communications Manager database, but there is no button on the phone with which calls can be answered. These directory numbers should be removed from the phone and deleted if necessary.

            To create a new configuration file, perform these steps:

            Procedure
              Step 1   From Cisco Unified Communications Manager, choose Device > Phone > Find to locate the phone experiencing problems.
              Step 2   Choose Delete to remove the phone from the Cisco Unified Communications Manager database.
              Step 3   Add the phone back to the Cisco Unified Communications Manager database. See the Cisco Unified Communications Manager Phone Addition Methods for details.
              Step 4   Power cycle the phone.

              Start service


              Note


              A service must be activated before it can be started or stopped. To activate a service, choose Tools > Service Activation.


              To start a service, follow these steps:

              Procedure
                Step 1   From Cisco Unified Communications Manager Administration, choose Cisco Unified Serviceability from the Navigation drop-down list and click Go.
                Step 2   Choose Tools > Control Center - Feature Services.
                Step 3   Choose the primary Cisco Unified Communications Manager server from the Server drop-down list.

                The window displays the service names for the server that you chose, the status of the services, and a service control panel to start or stop a service.

                Step 4   If a service has stopped, click the corresponding radio button and then click Start.

                The Service Status symbol changes from a square to an arrow.


                General troubleshooting information

                The following table provides general troubleshooting information for the Cisco Unified IP Phone.

                Table 2 Cisco Unified IP Phone general troubleshooting

                Summary

                Explanation

                Connecting a Cisco Unified IP Phone to another Cisco Unified IP Phone.

                Cisco does not support connecting an IP phone to another IP phone through the PC port. Each IP phone should directly connect to a switch port. If phones are connected together in a line (by using the PC port), the phones will not work.

                Prolonged broadcast storms cause IP phones to reset, or be unable to make or answer a call.

                A prolonged Layer 2 broadcast storm (lasting several minutes) on the voice VLAN may cause IP phones to reset, lose an active call, or be unable to initiate or answer a call. Phones may not come up until a broadcast storm ends.

                Moving a network connection from the phone to a workstation.

                If you are powering your phone through the network connection, you must be careful if you decide to unplug the phone network connection and plug the cable into a desktop computer.

                Caution   

                The network card of the computer cannot receive power through the network connection; if power comes through the connection, the network card can be destroyed. To protect a network card, wait 10 seconds or longer after unplugging the cable from the phone before plugging it into a computer. This delay gives the switch enough time to recognize that there is no longer a phone on the line and to stop providing power to the cable.

                Changing the telephone configuration.

                By default, the network setup options are locked to prevent users from making changes that could impact their network connectivity. You must unlock the network setup options before you can configure them. See Password Protection for details.

                Phone resetting.

                The phone resets when it loses contact with the Cisco Unified Communications Manager software. This lost connection can be due to any network connectivity disruption, including cable breaks, switch outages, and switch reboots.

                Codec mismatch between the phone and another device.

                The RxType and the TxType statistics show the codec that is being used for a conversation between this Cisco Unified IP phone and the other device. The values of these statistics should match. If they do not, verify that the other device can handle the codec conversation, or that a transcoder is in place to handle the service.

                See the Call Statistics Screen for information about displaying these statistics.

                Sound sample mismatch between the phone and another device.

                The RxSize and the TxSize statistics show the size of the voice packets that are being used in a conversation between this Cisco Unified IP phone and the other device. The values of these statistics should match.

                See the Call Statistics Screen for information about displaying these statistics.

                Loopback condition.

                A loopback condition can occur when the following conditions are met:

                • The SW Port Configuration option in the Network Setup menu on the phone is set to 10 Half (10-BaseT / half duplex)
                • The phone receives power from an external power supply
                • The phone is powered down (the power supply is disconnected)

                In this case, the switch port on the phone can become disabled and the following message will appear in the switch console log:

                HALF_DUX_COLLISION_EXCEED_THRESHOLD

                To resolve this problem, enable the port from the switch.

                Additional Troubleshooting Information

                If you have additional questions about troubleshooting the Cisco Unified IP Phones, several Cisco.com web sites can provide you with more tips. Choose from the sites available for your access level.

                Maintenance

                Cisco Unified IP Phone Reset or Restore

                There are two general methods for resetting or restoring the Cisco Unified IP Phone:

                Perform Basic Reset

                Performing a basic reset of a Cisco Unified IP Phone provides a way to recover if the phone experiences an error and provides a way to reset or restore various configuration and security settings.

                The following table describes the ways to perform a basic reset. You can reset a phone with any of these operations after the phone has started up. Choose the operation that is appropriate for your situation.

                Table 3 Basic Reset Methods

                Operation

                Performing

                Explanation

                Restart phone

                Press Services, Applications, or Directories and then press **#**.

                Resets any user and network setup changes that you have made, but that the phone has not written to its flash memory, to previously saved settings, then restarts the phone.

                Reset Settings

                To reset settings, press Applications and choose Administrator Settings > Reset Settings > Network.

                Resets user and network setup settings to their default values, and restarts the phone.

                To reset the CTL file, press Applications and choose Administrator Settings > Reset Settings > Security.

                Resets the CTL file.

                Perform Factory Reset

                When you perform a factory reset of the Cisco Unified IP Phone, the following information is erased or reset to its default value:

                • User configuration settings: Reset to default values
                • Network setup settings: Reset to default values
                • Call histories: Erased
                • Locale information: Reset to default values

                Before you perform a factory reset, ensure that the following conditions are met:

                • The phone must be on a DHCP-enabled network.
                • A valid TFTP server must be set in DHCP option 150 or option 66 on the DHCP server.

                To perform a factory reset of a phone, you can press Applications and choose Administrator Settings > Reset Settings > All.

                Alternatively, you can also perform these steps:

                Procedure
                  Step 1   While powering up the phone, press and hold #.
                  Step 2   When the light on the mute button and handset light strip turns off and all other lights (line button, headset button, speakerphone button and Select button) stay green, press 123456789*0# in sequence.

                  When you press 1, the lights on the line buttons turn red. The light on the Select button flashes when a button is pressed.

                  If you press the buttons out of sequence, the lights on the line button, headset button, speakerphone button, and Select button turn green. You need to start over and press 123456789*0# in sequence again.

                  After you press these buttons, the phone goes through the factory reset process.

                  Caution   

                  Do not power down the phone until it completes the factory reset process, and the main screen appears.


                  Voice Quality Monitoring

                  To measure the voice quality of calls that are sent and received within the network, Cisco Unified IP Phones use these statistical metrics that are based on concealment events. The DSP plays concealment frames to mask frame loss in the voice packet stream.

                  • Concealment Ratio metrics: Show the ratio of concealment frames over total speech frames. An interval conceal ratio is calculated every 3 seconds.
                  • Concealed Second metrics: Show the number of seconds in which the DSP plays concealment frames due to lost frames. A severely "concealed second" is a second in which the DSP plays more than five percent concealment frames.
                  • Mean Opinion Score (MOS) for Listening Quality (LQK) Voice Metrics: Uses a numeric score to estimate the relative voice-listening quality. The Cisco Unified IP Phones calculate the MOS LQK based audible-concealment events due to a frame loss in the preceding 8 seconds and includes weighting factors such as codec type and frame size. MOS LQK scores are produced by a Cisco-proprietary algorithm, the Cisco Voice Transmission Quality (CVTQ) index. Depending on the MOS LQK version number, these scores may comply with the International Telecommunications Union (ITU) standard P.564. This standard defines evaluation methods and performance accuracy targets that predict listening quality scores based on observation of actual network impairment.

                  Note


                  Concealment ratio and concealment seconds are primary measurements based on frame loss. A Conceal Ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.


                  You can access voice quality metrics from the Cisco Unified IP Phone by using the Call Statistics screen or remotely by using Streaming Statistics.

                  Voice Quality Troubleshooting Tips

                  When you observe significant and persistent changes to metrics, use the following table for general troubleshooting information.

                  Table 4 Changes to Voice Quality Metrics

                  Metric change

                  Condition

                  Conceal Ratio and Conceal Seconds increase significantly

                  Network impairment from packet loss or high jitter.

                  Conceal Ratio is near or at zero, but the voice quality is poor.

                  • Noise or distortion in the audio channel such as echo or audio levels.
                  • Tandem calls that undergo multiple encode/decode such as calls to a cellular network or calling card network.
                  • Acoustic problems coming from a speakerphone, handsfree cellular phone or wireless headset.

                  Check packet transmit (TxCnt) and packet receive (RxCnt) counters to verify that voice packets are flowing.

                  MOS LQK scores decrease significantly

                  Network impairment from packet loss or high jitter levels:

                  • Average MOS LQK decreases may indicate widespread and uniform impairment.
                  • Individual MOS LQK decreases may indicate bursty impairment.

                  Cross-check the conceal ratio and conceal seconds for evidence of packet loss and jitter.

                  MOS LQK scores increase significantly

                  • Check to see if the phone is using a different codec than expected (RxType and TxType).
                  • Check to see if the MOS LQK version changed after a firmware upgrade.

                  Note


                  Voice quality metrics do not account for noise or distortion, only frame loss.


                  Voice Quality Metrics

                  When using the metrics for monitoring voice quality, note the typical scores under normal conditions of zero packet loss and use the metrics as a baseline for comparison.

                  It is also important to distinguish significant changes from random changes in metrics. Significant changes are scores that change about 0.2 MOS or more and persist in calls that last longer than 30 seconds. Conceal ratio changes indicate a frame loss greater than 3 percent.

                  The MOS LQK scores can vary based on the codec that the Cisco Unified IP Phone uses. The following codecs provide these corresponding maximum MOS LQK scores under normal conditions with zero frame loss for Cisco Unified Phone 8941 and 8945:

                  • G.711: 4.5 MOS LQK
                  • G.722: 4.5 MOS LQK
                  • G.728/iLBC: 3.9 MOS LQK
                  • G729A/AB: 3.7 MOS LQK

                  Note


                  • Cisco Voice Transmission Quality (CVTQ) does not support wideband (7 kHz) speech codecs, because ITU has not defined the extension of the technique to wideband. Therefore, MOS LQK scores that correspond to G.711 performance are reported for G.722 calls to allow basic quality monitoring, rather than not reporting an MOS score.
                  • Reporting G.711-scale MOS scores for wideband calls through the use of CVTQ allows basic-quality classifications to be indicated as good/normal or bad/abnormal. Calls with high scores (approximately 4.5) indicate high quality or a low packet loss, and lower scores (approximately 3.5) indicate low quality or a high packet loss.
                  • Unlike MOS, the conceal ratio and concealed seconds metrics remain valid and useful for both wideband and narrowband calls.

                  A conceal ratio of zero indicates that the IP network is delivering frames and packets on time with no loss.

                  Cisco Unified IP Phone Cleaning

                  To clean your Cisco Unified IP phone, use only a dry soft cloth to gently wipe the phone and the LCD screen. Do not apply liquids or powders directly on the phone. As with all non-weather-proof electronics, liquids and powders can damage the components and cause failures.