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ISDN Troubleshooting

October 11, 2012

Proprietary

2012 Media5 Corporation

Technical Bulletin 671

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Table of Contents

Introduction ........................................................................................................................................................................... 3

Protocols and Connection ..................................................................................................................................................... 3

Troubleshooting Tools .......................................................................................................................................................... 4

Status Page ................................................................................................................................................................ 4

Syslog Traces ............................................................................................................................................................. 4

Physical Link Down ............................................................................................................................................................... 6

ISDN Auto Configuration ............................................................................................................................................ 6

ISDN Preset................................................................................................................................................................ 6

BRI connection ........................................................................................................................................................... 6

PRI Connection .......................................................................................................................................................... 7

Troubleshooting Signalling Down ......................................................................................................................................... 7

Troubleshooting Failed Calls when Physical and Signalling Status is up .............................................................................. 7

SIP to ISDN Calls not Working ................................................................................................................................... 7

ISDN to SIP Calls not Working ................................................................................................................................. 10

Generic Non-Working Calls ...................................................................................................................................... 11

Calling Line Identification Presentation ............................................................................................................................... 12

Double DTMF ..................................................................................................................................................................... 13

Country/Provider Specific Configuration ............................................................................................................................. 13

France ...................................................................................................................................................................... 13

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Introduction

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

DSS1

DMS100

NI2

R2

5ESS

In Europe, the DSS1 protocol is mainly used for interconnection with public carrier and QSIG is mainly used for connections with PBXs.

Note: The support of the QSIG protocol is restricted to basic calls.

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.).

o 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.

o 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.

Two ISDN cards are supported on Mediatrix 3000 Series:

PRI (Primary Rate Interface)

BRI (Basic Rate Interface)

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

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Troubleshooting Tools

Status Page

The first thing to look at when installing a Mediatrix unit is the ISDN -> Status page. On this page you will find:

Physical link

o Up/down: Unit ready/not ready to transmit/receive signal

Signaling

o Up/down: Signaling defined/not defined for the interface

Channel 1-Channel X: Active bearer availability

o Idle / In Use : Channel available/Busy for new communication

Syslog Traces

In order to troubleshoot ISDN issue, the Mediatrix gateways can be configured to send via syslog ISDN messages level 1, 2 and 3. This information is delivered in ASCII format easy to read.

Since most syslog deamons/servers cannot keep up with the number of syslog message generated by Mediatrix units, the more convenient way to collect syslogs is to install the free application Wireshark.

Wireshark

Wireshark is a network protocol analyzer. It is Open Source software released under the GNU General Public License. It can decode most VoIP protocols: SIP, MGCP, H.323, RTP, etc.

The following link takes you directly to the latest Wireshark download site: http://www.wireshark.org/download.html.

Syslog menu

Enable the Diagnostic Traces in the System -> Syslog page to have the Mediatrix unit send the ISDN messages to the syslog address (Remote Host).

Set the Remote Host field with the IP address of the PC running the syslog daemon or Wireshark.

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Diagnostic traces are used for advanced troubleshooting.

You can control the level of verbosity for each module:

Call Router: Troubleshoot the configured routes

ISDN: Troubleshoot the different layers of the ISDN protocol/interface and IP synchronization

R2 CAS: Troubleshoot the different layers of the R2 protocol and R2 interface

You can filter the ISDN level desired:

ISDN Stack Layer 1: These messages are related to the Physical Link status of the ISDN Status page

ISDN Q.921: These messages are related to the Signaling status of the ISDN Status page

ISDN Q.931: These messages are related to the establishment of calls

In this example only ISDN level 3 are sent:

Example of syslog messages:

IsdnStackL3Msg:0 < Call 1-Inbound RECV Setup (5)

IsdnStackL3Msg:0 < IE Bearer Capability [Coding: CCITT (0) Info transfer cap: Speech (0) Trans

mode/rate: Circuit (0) 64 kbps (16) User info Layer 1/2/3: g.711 a-law (3) Unused (-1) Unused (-

1) In Band Neg Pos: 0]

IsdnStackL3Msg:0 < IE Channel Id 1/2 [IntID: Implicit Basic (0) 0 Preferred DChan: Is not D

channel Pref: Preferred]

IsdnStackL3Msg:0 < IE Channel Id 2/2 [Chan Sel: Any channel selected]

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IsdnStackL3Msg:0 < IE Calling Party Number [TON: Unknown (0) NPI: ISDN Telephony (1) PI:

Presentation allowed (0) SI: User provided, not screened (0) '201']

IsdnStackL3Msg:0 < IE Called Party Number [TON: Unknown (0) NPI: ISDN Telephony (1) '101']

Physical Link Down

ISDN Auto Configuration

Starting with the release DGW 2.0.23.338, an ISDN Auto-configuration feature has been added. This feature allows you to detect and to configure all ISDN interfaces so that the ISDN link goes up and becomes usable with minimal user interaction.

When launching an auto-configuration process, it stops automatically when all interfaces have been tested. For each interface, the auto configuration process is considered successful when the link becomes up or a failure when all combinations have been tried without having a link up.

This feature is available under the web interface, ISDN -> Status page.

Caution: Launching the Automatic Configuration may terminate abruptly all ongoing ISDN calls. The auto-configuration may take some time to complete and some of the current ISDN configuration settings might be replaced by new values.

ISDN Preset

The ISDN Preset Configuration section allows you to load a set of preset configuration for your ISDN connections. These preset files are located in the file system's persistent memory. Using preset files is especially useful for units that do not use the default values provided by Media5 (for instance, T1 instead of E1 for Mediatrix 3000 units).

You can also export your current ISDN configuration in a preset. Please note that these user-defined presets are not kept in the event of a partial or factory reset.

This feature is available under the web interface, ISDN -> Status page.

Note: Depending on your unit's profile, it may be possible that no preset files are available.

BRI connection

1. Check the cable on your BRI interface. On a 4400, you can use a straight Ethernet cable. However on a 3400 in NT mode, you will need to use a BRI cross-over cable.

2. Verify the cable length.

o The cable length between the Mediatrix gateway and the PBX must not exceed 600 metres. o For short Bus application (all terminals / wall-plugs are put in parallel at arbitrary positions of the bus): max

120 metres. o For extended bus installation (all terminals / wall-plugs are hooked in parallel on the bus on the last 30 to

50 metres of the bus): max 450 metres

Proper termination of the ISDN bus / ISDN line on both ends with 100 Ohms is mandatory.

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PRI Connection

1. Check the cable on your PRI interface.

2. Straight cable versus PRI Cross-over

The Mediatrix gateway will automatically try to select the correct pinout according to the Endpoint Type (NT/TE). If your PRI connection requires it, you can, without changing cable, modify the Mediatrix unit pinout by using the Port Pinout option of the ISDN -> Primary Rate Interface page. You can therefore always use an Ethernet straight cable and change the port pinout option if you have an issue.

Troubleshooting Signalling Down

Make sure you have correctly configured the following:

Endpoint Type

Signaling 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

SIP to ISDN Calls not Working

1. Verify the call router settings. There must be a route created from a SIP gateway to an ISDN interface.

2. 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. In order to avoid this behavior, it is possible to deactivate the calling name by setting Calling Name Max Length to 0.

The setup sent to the ISDN interface can be verified by looking at the syslog messages:

Example below:

IsdnStackL3Msg [0FE1] 1 > Call 2-Outbound TEI 0 SEND Setup (5)

IsdnStackL3Msg [0FE2] 1 > IE Bearer Capability [Coding: CCITT (0) Info transfer cap: 3.1 kHz

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audio (16) Trans mode/rate: Circuit (0) 64 kbps (16) User info Layer 1/2/3: g.711 a-law (3)

Unused (-1) Unused (-1) In Band Neg Pos: 1]

IsdnStackL3Msg [0FE3] 1 > IE Channel Id 1/2 [IntID: Implicit Primary (1) 0 Preferred DChan: Is

not D channel Pref: Preferred]

IsdnStackL3Msg [0FE4] 1 > IE Channel Id 2/2 [Chan Sel: 31]

IsdnStackL3Msg [0FE5] 1 > IE Calling Party Number [TON: Unknown (0) NPI: Unknown (0) PI:

Presentation allowed (0) SI: User provided, not screened (0) '12224222006']

IsdnStackL3Msg [0FE6] 1 > IE Called Party Number [TON: Unknown (0) NPI: Unknown (0) '100']

IsdnStackL3Msg [0FE7] 1 > IE User User [Discriminator: IA5 Characters (4) Info: 'Test'].

IsdnStackL3Msg [0FE8] 1 > IE Sending Complete

The provider might reject this Setup message with a Status message that looks like this:

IsdnStackL3Msg [1AFE] 1 < Call 2-Outbound TEI 0 Unicast RECV Status (125)

IsdnStackL3Msg [1AFF] 1 < IE Cause [Coding: CCITT (0) Location: Public network serving local user

(2) Cause: Requested facility not subscribed (50)]

IsdnStackL3Msg [1B00] 1 < IE Call State [Coding standard: CCITT (0) State value: 1_CALL_INITIATED

(1)]

3. Some providers will only accept SETUP that contains specific Party Number parameters.

The Dgw v2.0 Application sets the following default values.

Party Number parameters default value

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.

3. 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.

Note that when the Endpoint type is set to NT, the calling PI, SI, TON and NPI are present in the Calling Party Number in ISDN SETUP messages only when CLIP is enabled. See section “Calling Line Identification Presentation” for details.

Starting with the release DGW 2.0.23.338, these default parameters can be overwritten for every call using the variables in the web configuration ISDN -> Primary Rate Interface/BRI page.

If you need to change these parameters for a specific call, then the Party Number parameters can be modified with the use of the Call Router.

For example: If carrier requirements are as follow:

o Setup must be sent with TON=national and NPI= ISDN

Then the following should be configured in the Call Router:

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4. 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. To correct this issue, the Preferred Encoding Scheme should be set to G.711 u-Law.

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5. If a call is dropped by the provider before being connected and no ISDN CONNECT is received, the ISDN Disconnect message might provide a reason why the call is disconnected.

The Disconnect error “Unallocated” indicates that the called party number cannot be reached because, although the called party number is in a valid format, it is not allocated (assigned).

Example of ISDN Disconnect message:

IsdnStackL3Msg [2B07] 0 < Call 2-Outbound TEI 0 Unicast RECV Disconnect (69)

IsdnStackL3Msg [2B08] 0 < IE Cause [Coding: CCITT (0) Location: Public network serving local

user (2) Cause: Unallocated (1)]

With this error message, the called number party needs to be verified. If this number is modified by the Call Router, the Call Router mapping will need to be validated. This can be done by enabling the Call Router syslog messages.

ISDN to SIP Calls not Working

1. Verify the call router settings. There must be a route created from an ISDN interface to a SIP gateway.

2. Enabling the SIP debug, capture a syslog trace and verify if a SIP INVITE was generated by the gateway after it received the ISDN Setup from the ISDN interface.

Example of SIP INVITE below:

SipSignaling [02FF] > [192.168.0.1:5060] Sending SIP packet to: 192.168.0.2:5060

SipSignaling [0300] > INVITE sip:201@192.168.0.2 SIP/2.0

SipSignaling [0301] > Via: SIP/2.0/UDP 192.168.0.1:5060;branch=z9hG4bK74fff1fc4432ead8b

SipSignaling [0302] > Max-Forwards: 70

SipSignaling [0303] > From: <sip:101@192.168.0.2>;tag=d57dfdd4cd

SipSignaling [0304] > To: <sip:201@192.168.0.2>

SipSignaling [0305] > Call-ID: ec92e732ffbf7115

SipSignaling [0306] > CSeq: 2135957990 INVITE

SipSignaling [0307] > Allow: INVITE, ACK, BYE, CANCEL, REFER, NOTIFY, UPDATE

SipSignaling [0308] > Contact: <sip:101@192.168.0.1:5060>

SipSignaling [030D] > User-Agent: Mediatrix 3301-001/v2.0.8.118 3XXX-MX-D2000-44

3. The provider could send an 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. Please refer to the DGW v2.0 Software Configuration Guide for more information on how to manipulate numbers using the Call Router.

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Generic Non-Working Calls

1. 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 SEND Call 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)]

disabling the Progress Indicator for this ISDN message should help. For this example, the Progress Indicator In Call Proceeding, available in the ISDN Interop page, should be set to Disable.

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Calling Line Identification Presentation

By default, Mediatrix units will send the “Calling Party Number” or CLIP when the Endpoint type is set as “TE”. Set the Calling Line Information Presentation to Enable to send the CLIP information when the Endpoint type is set as “NT”.

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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. This can be verified in the SIP INVITE. To prevent the Mediatrix unit from sending duplicate DTMF, set the Inband DTMF Dialing to Disable.

Country/Provider Specific Configuration

France

Connection to France Telecom

In France, the most used 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.