ISDN Troubleshooting

This document is destined to customers wanting to configure and troubleshoot Mediatrix ISDN gateways connected to a PSTN or a PBX ISDN Interface.

This document provides general tips on how to troubleshoot ISDN issues.

Different scenarios are analysed and suggestion of possible solutions are proposed.


Protocols and Connection

The Mediatrix gateways support the following protocols:
  • QSIG
    Note: The support of the QSIG protocol is restricted to basic calls.
  • DSS1
  • DMS100
  • NI2
  • R2
  • 5ESS
In the Europe, the DSS1 protocol is mainly used for interconnection with public carrier and QSIG is mainly used for connections with PBXs.

The R2 protocol is more specific to Central America / Latin America countries.

In North America, the most common protocols are DMS100 and NI2.

Note that the PTSN configuration can be different from carrier to carrier. Sometimes even the same carrier may have a different PSTN configuration. Connecting an ISDN gateway to a PBX can be done in point-to-point or point-to-multipoint mode. Please refer to the PBX to see if it is configured as point-to-point or point-to-multipoint.

The Mediatrix unit can be set in TE or NT mode:
  • User side (TE): implemented in ISDN terminals (phones, terminal adapters, etc.).
    • Generally, use TE when the Mediatrix unit is used to connect to the PSTN or is replacing ISDN phones.
  • Network side (NT): implemented in the exchange switches of the network operator.
    • Generally, use NT when phones are plugged into the Mediatrix unit or when the Mediatrix unit replaces the PSTN.
Again this configuration will depend on the configuration of the PBX. If the PBX is configured as NT, the Mediatrix unit must be configured as TE. If the PBX is configured as TE, the Mediatrix unit must be configured as NT.

PRI cards can be configured as E1 or T1 line. Generally, E1 are available in Europe and T1 in America


Troubleshooting Tools


The Mediatrix CPE provides several troubleshooting features such as notification messages, diagnostic traces and SIP signalling logs.

The Syslog daemon is a general purpose utility for monitoring applications and network devices with the TCP/ IP protocol. With this software, you can monitor useful messages coming from the Mediatrix CPE.
  • Diagnostic Traces are sent using the Syslog to the Technical Assistance Centre to further assist in resolving some issues such as Interoperability.
  • PCM traces are two different RTP streams made specifically to record all analog signals that are either sent or received on the analog or ISDN side of the Mediatrix device. PCM traces are an efficient tool to identify problems with:
    • Echo in your network
    • DTMF signals
    • Caller ID signals
    • Fax signals or false Fax detection
    • Message Waiting Indicator signals
    • Any other analog or digital signal
  • Statistics are collected on each port of the PRI card, on Ping/Pingv6 on the CLI or on Media. Statistics are collected on:
    • Packet loss
    • Jitter
    • Latency
    • Packet count
    • Octet count
  • Live Network Captures can be taken with the pcapture command and sent to Wireshark located on a separate terminal. The SBC can also capture the SIP/RTP traffic of a specific call, selected by rules. The Network Capture will gather information on:
    • Interoperability
    • Timing issues
  • Configuration scripts can be generated from the configuration running on the Mediatrix CPE. This provides the content of your configuration that can be used by technical support to troubleshoot your faulty configuration.


Capturing a Trace Using Wireshark

Before you begin
You must have downloaded Wireshark at the following link (Wireshark is a network protocol analyzer. It is an Open Source software released under the GNU General Public Licence. It can decode most VoIP protocols: SIP, MGCP, H.323, RTP, etc.). Select the Windows version. Make sure to install winpcap and read the instructions.

If you are taking a trace on a switch, the port of the switch connected to the PC must be configured to mirror the port connected to the Mediatrix unit. Alternatively, you could use a hub, which should be connected to both the PC running Wireshark and the Mediatrix unit.

Otherwise you will not capture the packets from the unit.

  1. In the Capture menu, select Capture Options.
  2. In the Capture selection list, select the Ethernet network adapters to use.
  3. In the (Display) Options section, select the Update list of packet in real time check box.
  4. Select the Automatic scrolling in live capture check box.
  5. If troubleshooting a random problem happening weekly, select the Use multiple files check box.
    Note: For the latest Wireshark release, this can be configured via Capture/Options/Ouput/Create a new file automatically after…

In Wireshark release 2.2.0

In older Wireshark releases


Enabling Syslog Menu

  1. Go to System/Syslog.
  2. In the Remote Host field, set the IP address of the PC running the syslog daemon or Wireshark.
  3. In the Syslog Configuration table, set Diagnostic Traces to Enable.


Enabling Syslog Filters

Before you begin
Must have completed the task Enabling Syslog Menu
  1. Go to System/Syslog.
  2. In the Syslog Configuration table, click Edit next to Filter
  3. In the Module table, set each module's type of syslog traces you want to receive.


Signalling Down Troubleshooting

Make sure you have correctly configured the following:
  • Endpoint Type
  • Signalling Protocol
  • Line Coding
  • Line Framing
On some BRI connections, the Signaling status can be Down even when the link is functional. When the variable Link Establishment is at its default setting “On Demand”, the signaling link will be seen as up only when calls occur.
If the link is correctly configured, we suggest trying a call in both directions even if the Signaling Status is Down.


Troubleshooting Failed Calls when Physical and Signalling Status is up

Troubleshooting SIP to ISDN Calls

  1. Go to Call Router/Route Config to verify if a route from a SIP gateway to an ISDN interface is configured.
  2. Go to ISDN/Primary Rate Interface, and set Calling Name Max Length to 0.
    Note: Some providers do not accept User-to-user information (UUI) to be sent in setup messages. Any setup containing a UUI Information Element (IE) will be rejected by the provider, most likely with an ISDN Status message. One reason for this is that this feature might not be provided for free.
  3. Verify the setup sent to the ISDN interface by looking at the syslog messages.
  4. Go to ISDN/Primary Rate Interface and set Preferred Encoding Scheme to G.711 u-law
    Note: By default, the Mediatrix units are configured to use the a-law codec as encoding scheme in ISDN SETUP messages. A-law is usually used in Europe. Some North-American providers and PBX reject the SETUP message unless it uses the u-law codec


Party Number Parameters Default Value

DGW sets the following default values:
SIP to ISDN Calls Default value
TON (called and calling) Unknown
NPI (calling and called) Unknown
SI (calling) User-side: not-screened Network-side: network
ITC (calling) 3.1 kHz audio
PI (calling)
  1. When the Calling Party Number E.164 is missing: interworking. In this case, this value overrides any value set by the call router.
  2. When CLIR is enabled (user-side only): restricted. In this case, this value overrides any value set by the call router.
All other cases: allowed. This is the default value if the two cases above do not apply and no value has been set by the call router.


Troubleshooting Generic Non-Working Calls

  1. Go to ISDN/Interop.
  2. In the Interop Configuration table, set Progress Indicator In Call Proceeding to Disable

  • Depending on the provider or the Pbx, the Mediatrix unit can receive an ISDN STATUS message such as the following:

IsdnStackL3Msg [1C9F] 0 < Call 22182-Inbound TEI 0 Unicast RECV Status (125)

IsdnStackL3Msg [1CA0] 0 < IE Cause [Coding: CCITT (0) Location: Public network serving local user (2) Cause: Information element non-existent or not implemented (99)]

IsdnStackL3Msg [1CA1] 0 < IE Call State [Coding standard: CCITT (0) State value: 9_INCOMING_CALL_PROCEEDING (9)]

The cause 99, Information element non-existent or not implemented, refers to the previous ISDN message sent. If the previous message contains an IE Progress Indicator like in this example:

IsdnStackL3Msg [1C48] 0 > Call 22182-Inbound TEI 0 SENDCall Proceeding (2)

IsdnStackL3Msg [1C49] 0 > IE Channel Id 1/2 [IntID: Implicit Primary (1) 0 Preferred DChan: Is not D channel Pref: Exclusive]

IsdnStackL3Msg [1C4A] 0 > IE Channel Id 2/2 [Chan Sel: 1]

IsdnStackL3Msg [1C4B] 0 > IE Progress Indicator [Coding standard: CCITT (0) Location: User (0) Description: Destination address is non-ISDN (2)]


Troubleshooting ISDN to SIP Calls

  1. Go to Call Router/Route Config to verify if a route from an ISDN interface to a SIP gateway is configured.
  2. Using syslog traces,verify if a SIP INVITE was generated by the gateway after it received the ISDN Setup from the ISDN interface.
    Note: SIP debug must be enabled.
  3. Verify if the provider is sending a ISDN Setup message without the Called Number, with an empty Called number or only part of the Called number (last 4 digits for example). If this is the case, it is possible, via the call router, to manipulate the Called number before it is sent via SIP.


Enabling Calling Line Information Presentation

  1. Go to ISDN/Services.
  2. From the Select Interface drop-down menu, select the interface you want to configure.
  3. In the Services Configuration table, set Facility Services to Enable.
  4. Set Calling Line Information Presentation to Enable.
  5. In the MSN field, enter the numbers that will be allowed when a call is incoming from the SIP side.
    Note: Please refer to Show Help to apply the appropriate syntax.
  6. From the Apply To The Following Interfaces section, select the interfaces for which the configuration will be applied to.
  7. Click Apply.

Support of ISDN FACILITY messages will be enabled.


Disabling Double DTMF

By default, Mediatrix units listen for out-of-band and inband DTMF. Some ISDN links provide, for the same DTMF, an out-of-band and inband signal, resulting in two DTMFs being sent to the SIP proxy.

  1. Go to ISDN/Primary Rate Interface.
  2. Using Select Interface drop down menu, select the interface you want to configure.
  3. In the Interface Configuration table, set Inband DTMF Dialing to Disable.
  4. Click Apply.


Country/Provider Specific Configuration - France

  • Connection to France Telecom

    In France, the prevalent protocol is VN6 (a variant of ISDN protocol)

    If you are having issues with the ISDN connection, verify with your ISDN provider if it is possible to set the ISDN link to Euro ISDN.


Online Help

If you are not familiar with the meaning of the fields and buttons, click Show Help, located at the upper right corner of the Web page. When activated, the fields and buttons that offer online help will change to green and if you hover over them, the description will bedisplayed.


DGW Documentation

Mediatrix devices are supplied with an exhaustive set of documentation.

Mediatrix user documentation is available on the Media5 Documentation Portal.

Several types of documents were created to clearly present the information you are looking for. Our documentation includes:
  • Release notes: Generated at each GA release, this document includes the known and solved issues of the software. It also outlines the changes and the new features the release includes.
  • Configuration notes: These documents are created to facilitate the configuration of a specific use case. They address a configuration aspect we consider that most users will need to perform. However, in some cases, a configuration note is created after receiving a question from a customer. They provide standard step-by-step procedures detailing the values of the parameters to use. They provide a means of validation and present some conceptual information. The configuration notes are specifically created to guide the user through an aspect of the configuration.
  • Technical bulletins: These documents are created to facilitate the configuration of a specific technical action, such as performing a firmware upgrade.
  • Hardware installation guide: They provide the detailed procedure on how to safely and adequately install the unit. It provides information on card installation, cable connections, and how to access for the first time the Management interface.
  • User guide: The user guide explains how to customise to your needs the configuration of the unit. Although this document is task oriented, it provides conceptual information to help the user understand the purpose and impact of each task. The User Guide will provide information such as where and how TR-069 can be configured in the Management Interface, how to set firewalls, or how to use the CLI to configure parameters that are not available in the Management Interface.
  • Reference guide: This exhaustive document has been created for advanced users. It includes a description of all the parameters used by all the services of the Mediatrix units. You will find, for example, scripts to configure a specific parameter, notification messages sent by a service, or an action description used to create Rulesets. This document includes reference information such as a dictionary, and it does not include any step-by-step procedures.


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