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  1. Information Required when Reporting a Problem to Mediatrix
  2. Wireshark
  3. Audacity
  4. SIP Scenario
  5. Syslog Daemons and Enabling Debug Traces
  6. Signaling Logs (SIP or MGCP)


This Technical Bulletin aims to inform the reader on the troubleshooting software tools available and how to use them, thus providing capabilities to diagnose a problem or properly report the problem to Mediatrix. Some examples are used to illustrate the functionality of each software tool. More specifically, the following is detailed in this Technical Bulletin 

Information Required when Reporting a Problem to Mediatrix

When reporting a problem and to make sure that all the relevant information is given to the Mediatrix support team at once, a Mediatrix partner should consider providing the following:

  • A detailed description of the network configuration, the call setup, and all the participants.
  • The configuration file of the Mediatrix unit(s) involved.
  • A Wireshark capture of the problem (the Wireshark capture should contain the signaling protocol – SIP, MGCP or H.323 – the RTP stream, and the syslog messages in debug mode).


Network Configuration / Call Setup 

  • Mediatrix product name, release and build number.
  • Serial number of the Mediatrix unit if a hardware problem is suspected.
  • Name / manufacturer / type of other VoIP devices along with their IP addresses.
  • Name / manufacturer / software version of the Proxy server (SIP), Call agent (MGCP), or Gatekeeper (H.323).
  • Whenever possible, a diagram of the network or wiring setup.
  • Call flow / call scenario to reproduce the problem.
  • Please mention if the call goes through a NAT, Firewall, Bridge, VPN, Router, Soft switch, etc.
  • Please detail any change to the configuration made recently.


Saving the Configuration of a Mediatrix Product using SIP v5.0, H.323 or MGCP 

The following is the recommended method to save the whole configuration of a Mediatrix analog product 

  1. Install the latest GA version of the Mediatrix Unit Manager Network (UMN).
  2. Auto detect your unit.
  3. Note the last 5 alphanumerical values of the unit's MAC address.
  4. Right-click the unit’s MAC address, then select Configuration File and Save to XML.
  5. Put checks in both options, and then click OK.

Saving config sip.png
Send the proper XML file to Mediatrix (based on the MAC address). It can normally be found in C:\Program Files\Unit Manager Network 3.2\UnitManager\CfgFile.

Saving the Configuration of a Mediatrix Product using Dgw v2.0 

  1. Using the Web configuration page, go to the Management web page.
  2. Under the section Export Script, set the content field to All config
  3. Click on download.
  4. Save the configuration script file to your computer.

Saving config dgw.png

Wireshark

Wireshark is a network protocol analyzer. It is an Open Source software released under the GNU General Public License. It can decode SIP, MGCP, H.323, RTP, and a lot more protocols.

Download Site 
The following link should take you directly to the latest Wireshark download site: http://www.wireshark.org/download.html.

  Note: Select the Windows version. Make sure you install winpcap and read the instructions. 


Using Wireshark 

In the Capture menu, select options(Ctrl+K).

  1. In the following screen:
    • Make sure the proper Ethernet network adapter is selected in the interface field.
    • In the Capture Filter: field, use the button to select a pre-saved filter or enter your own filter. Useful examples could be to capture send/receive packets from known devices:

      Knowing the MAC address of the device, the capture filter would be

ether host 00:90:f8:00:60:82 

  Note: Capturing at the MAC level allows to capture Ethernet protocols such as DHCP. 
  • Knowing the IP address of the device, the capture filter would be

host 192.168.0.250 

  1. For real-time display, enable Update list of packet in real time and Automatic scrolling in live capture in the Display options section.
  2. When troubleshooting a random problem happening weekly, we suggest using the above filters along with the multiple files functionality.
  • As an example you could set Next file every field to 1 day 

1day.png
Important Note: 

  1. It is not recommended to capture in a switching network unless the PC running Wireshark itself is also participating in the call (is either a proxy server or a soft phone), meaning that it is directly receiving/sending network messages.
  2. For better results, it is sometimes useful to temporarily connect a hub into the switch and then connect both the PC capturing and the VoIP equipment into the hub.
  3. Refer to your Wireshark Manual or Display Filters Manual for more information about Wireshark. 


Remote Capture 

When using a Mediatrix unit running firmware DGW v2.0r17.285 or higher, it is possible to remotely start a network capture on the Mediatrix unit and send the result to a PC running Wireshark. CLI access is required to execute this procedure.

  1. From the PC, download the plink utility from this download site : http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
  2. Save the plink utility somewhere accessible from a command line.

    Open a command line and enter the following command by replacing each field with the information in your setup 

plink.exe -pw "PASSWORD" USERNAME@IP_ADDRESS "pcapture -raw –i any" | wireshark -k -i – 

For example

plink.exe -pw "1234" public@192.168.0.100 "pcapture -raw –i any" | “wireshark -k -i – 
This command would connect to the CLI of unit with IP address 192.168.0.100 using the public username and the 1234 password. The pcapture command will be executed in the CLI and the result will be sent to a new Wireshark window.
You can look at the DGW v2.0 Software Configuration Guide for more information on the pcapture command.

How to Create Filters 

  1.  Once looking at a previously made or running capture, you can use the Filter field to show specific frames.
    • Use any protocol name to filter out all other protocols: 

sip || bootp || syslog || rtp || t38 || mgcp || h245 || q931 || h225 

    • When converting PCMU/PCMA RTP streams into audio files, use the following display filter to remove every “Comfort Noise” and “DTMF out-of-band” based on their RTP payload type: 

rtp && rtp.p_type != 13 && rtp.p_type != 96 

    • The following is a screenshot of a “display filter”

Display filter.png

2.  To create a new filter for a particular field value in any frame, select a frame (must be a known protocol, meaning decoded by Wireshark). Then right-click Apply as Filter and then choose your type of filter.

Apply as filter.png

Converting an RTP Stream to an Audio File 

  1.  The following are the steps to convert a PCMA/PCMU RTP stream into an audio file:
    • Make sure you remove all non-voice packets by using a display filter, typically:

rtp && rtp.p_type != 13 && rtp.p_type != 96 

    • Make sure all RTP streams in the capture are decoded as RTP by Wireshark.
    • Depending on the firmware used in the Mediatrix unit, the PCM capture could be generated by using both PCMA and PCMU. If the PCM capture contains both PCMA and PCMU RTP packets, you will need to convert each RTP stream separately, otherwise the audio file will contain noise. To get an audio file without the noise, use the following display filters before you analyse the RTP streams to create separate audio files. 

rtp.p_type == 0 && rtp.p_type != 13 && rtp.p_type != 96 
rtp.p_type == 8 && rtp.p_type != 13 && rtp.p_type != 96 

    • Go in the Statistics menu, then select RTP, then Show All Stream.
    • In the following screen, select any RTP stream you would like to convert, then click the Analyze button. 

Rtp.png

2.  In the following screen, click the Save payload button. 

Save playload.png

3.  In the following screen, select the .au format and the forward direction. Select also the proper folder, enter a filename, then click the OK button to save your audio file.

Audio file.png

4.  To view this file in Audacity, drag and drop from Windows explorer into the Audacity screen.

Audacity

Audacity is a free, easy-to-use audio editor and recorder. It is an Open Source software released under the GNU General Public License.

Download Site 
The following link should take you directly to the latest Audacity download site: http://audacity.sourceforge.net/ 

Using Audacity 

  1. To start viewing a file, drag and drop a supported audio file in Audacity’s window or use the File/Open option.
  2. In the View menu, use the Fit Vertically or Fit to Windows options to quickly fit the audio file in your screen.
  3. Use the mouse to select a portion of the audio file, then the Zoom to Selection option to zoom in a particular part of the audio file.
  4. When ready, hit the play button to listen for the selected portion. 

Proxy.png

Plot Spectrum Utility 

  1. A North American ring back is displayed in this audio file. To analyze the frequencies used in this ring back, carefully select the ring portion of the audio file then use the Plot Spectrum functionality from the View menu. 
  2. Select 8192 as the bit rate. 

8192.png

  • The two peaks indicate that this ring is made up of two frequencies: 440 Hz and 480 Hz.

Note:

  • Plot Spectrum can be used to analyze tones played by PBX or PSTN (SCN) lines to help configure the Far-End-Disconnect tone on a 1204 or to understand why Dial tone detection is not working.
  • We have seen many PBXs having offset frequencies when playing tones, making it hard for a 1204 to recognize them with default settings until set properly.

 

SIP Scenario

The SIP Scenario Generator creates SIP Call Flows or SIP scenario diagrams, in HTML format, of SIP messages from Ethernet capture files. SIP Scenario Generator shows the actual call processing trace in a format that is easily understood using browser technology. Clicking on a SIP message hyperlink displays the contents of the traced SIP. It definitely helps reporting a problem to a vendor or a customer.

Download Site 
SIP Scenario can be downloaded at http://www.iptel.org/~sipsc/

Creating a SIP Scenario File

  1. Copy your Wireshark file into your SIP Scenario directory.
  2. Open the Command Prompt window and use the CD command to work in your SIP Scenario directory.
  3. Type sip_scenario.exe followed by the name of your capture.

Sip scenario.png

  • SIP Scenario will then create several files based on the name of your capture.
  • The following screenshot is a portion of what we can see by opening SIP_call.html.

Sip call.png

Syslog Daemons and Enabling Debug Traces

The following syslog daemons have been used successfully by Mediatrix

  Note: Wireshark can also decode syslog messages; therefore, a syslog daemon is not mandatory. 

Kiwi Syslog Daemon has logging and filter functionalities and can run as a service on Windows NT-based machines. This daemon listens on port 514 for incoming syslog messages. The Kiwi Syslog Daemon can also receive signaling logs from our units (see Signaling Logs).

Enabling Syslogs in Debug Mode 

Using the Unit Manager Network (Mediatrix 1100/1200/4100, 2102, Liaison)

  • In the Syslog daemon section of the Administration page, enter the static IP address of the PC running the syslog daemon.
  • Set the Messages to debug.

Using the unit’s web page of the Mediatrix 1200/4100, 2102, Liaison

  • Login to the Administration web page
  • In the Monitoring sub-link of the Device Info section, enter the static IP address of the PC running the syslog daemon.
  • Set the Syslog Max. Severity to debug. 

Using the unit’s web page of the Mediatrix 3400/3500/3600/4400

  • In the Syslog sub-link of the System section, enter the static IP address of the PC running the syslog daemon.
  • Set the Diagnostic Traces to Enable.
  • Click the Edit button next to Filter.
  • Make sure all Traces are set to All.

Signaling Logs (SIP or MGCP)

Signaling logs, which are copies of the ongoing SIP or MGCP signaling, can be sent to a program listening for UDP packets on a specific port, much like syslog daemons. Mediatrix has created a little UDP Listener for its own need. It is provided “as is” with no guarantee that it will not harm or slow down your system. Logging over a long period of time would require file logging capability as you may overload your system memory. Note that the Kiwi syslog daemon has file logging capability and can receive UDP logs as well.
You can use Signaling logs when debugging a remote unit and/or when taking a Wireshark capture is impossible.

Download Site 

The Mediatrix UDP Listener can be freely downloaded on the Mediatrix Download Portal (http://www.mediatrix.com). 

Enabling Signaling Logs on a Mediatrix 1100/1200/4100, 2102 and Liaison 

  1. With the Unit Manager Network, right-click the unit’s MAC address and select Edit SNMP. This takes you to the MIB.

    The following path should take you to the signaling log configuration

private>enterprises-->mediatrix-->mediatrixExperimental-->mxDebugMib--> mxDebugMibObjects-->mxDebugSignalingLog

  • Enable the signaling log then set the host and port to those on which your UDP program is listening.


Enabling Signaling Logs on a Mediatrix 3400/3500/3600/4400 

  1. With the Unit Manager Network, right-click the unit’s MAC address and select Edit SNMP. This takes you to the MIB.

    The following path should take you to the signaling log configurationprivate>enterprises-->mediatrix-->mediatrixSystem-->gen5-->mediatrixCommon--> mediatrixServices-->sipEpMIB-->sipEpMIBObjects-->debugGroup

  • Enable the signaling log then set the host and port to those on which your UDP program is listening.