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Dialogic® IMG Integrated Media Gateway

IMG 1010 outbound ISDN calls fail due to NAI value

Symptom:
An E1 line on a Dialogic® IMG 1010 Integrated Media Gateway ("IMG 1010") connected to British Telecom (BT)  is able to receive inbound calls but attempting to make an outbound call can fail with a cause code relating to the number being invalid or incorrect.


Analysis:
The following traces were obtained from a telnet session with the IMG 1010. By entering ‘Advanced Debug’ mode (d) from the main menu, then ‘ISDN Diags’ (I) and ‘2->06->ff’ we enabled a raw Q.931 trace on all E1s. The trace is disabled with ‘2->00’.

A successful inbound call:

08:43:25.927 ISDN(I) 7bf8 01 R 00 00 1 55 40 0 021 SETUP 0001
08:43:25.927 ISDN(I) 020180aa0802000105a104039090a31803a983811e028583700781353831323139


 02  000000--  Sapi = 0
     ------1-  C/R: Command
     -------0  Extension Bit = with extension
 01  0000000-  TEI = 0
     -------1  Extension Bit = no extension
 80  1000000-  N(S) = 64
     -------0  I-Frame
 AA  1010101-  N(R) = 85
     -------0  P/F = 0
 08  00001000  ProtocolDiscriminator DSS1
 02  00000010  Length of CallReference = 2
 00  0-------  CallRef-Flag: Origination Side
     -0000000  CallReference = 1
 01  00000001  (CallReference)
 05  00000101  MSG-Type: SETUP
 A1  10100001  I-Element: Sending Complete
 04  00000100  I-Element: Bearer
 03  00000011    Length = 3
 90  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---10000    Information Transfer Capability: 3.1 kHz Audio
 90  1-------    Extension Bit = no extension
     -00-----    Transfer Mode: circuit mode
     ---10000    Information Transfer Rate: 64 kbit/s
 A3  1-------    Extension Bit = no extension
     -01-----    Layer 1 Identifier
     ---00011    User Info Layer 1 Protocol: G.711 A-Law
 18  00011000  I-Element: Channel Identification
 03  00000011    Length = 3
 A9  1-------    Extension Bit = no extension
     -0------    Interface Identifier present: interface implicitly identified
     --1-----    Interface Type: other interface
     ---0----    Spare
     ----1---    Preferred/Exclusive: exclusiv, only indicated channel is acceptable
     -----0--    D-channel indicator: is not the D-channel
     ------01    Information Channel Selection = as indicated in following octets
 83  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---0----    Number/Map: Channel by Number
     ----0011    Channel Type/Map Element Typ: B-Channel Units
 81  1-------    Extension Bit = no extension
     -0000001    Channel number: 1
 1E  00011110  I-Element: Progress Indicator
 02  00000010    Length = 2
 85  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---0----    Spare
     ----0101    Location: private network serving remote user
 83  1-------    Extension Bit = no extension
     -0000011    Progress Description: origination address is non-ISDN
 70  01110000  I-Element: Called Party Number
 07  00000111    Length = 7
 81  1-------    Extension Bit = no extension
     -000----    Type of Number: unknown
     ----0001    Numbering Plan: ISDN/Telephony
 35  0-------    Spare
     -0110101    Number digit: 5
 38  0-------    Spare
     -0111000    Number digit: 8
 31  0-------    Spare
     -0110001    Number digit: 1
 32  0-------    Spare
     -0110010    Number digit: 2
 31  0-------    Spare
     -0110001    Number digit: 1
 39  0-------    Spare
     -0111001    Number digit: 9

08:43:25.927 ISDN(I) 7bf8 01 T 00 00 0 41 55 0 00e CALL PROCEEDING 8001
08:43:25.927 ISDN(I) 0001aa8208028001021803a98381
08:43:26.157 ISDN(I) 7c0f 01 T 00 00 0 41 56 0 009 ALERTING 8001
08:43:26.157 ISDN(I) 0001ac820802800101
08:43:28.857 ISDN(I) 7d1d 01 T 00 00 0 41 57 0 009 CONNECT 8001
08:43:28.857 ISDN(I) 0001ae820802800107
08:43:28.917 ISDN(I) 7d23 01 R 00 00 1 58 41 0 009 CONNECT ACK 0001
08:43:28.917 ISDN(I) 020182b0080200010f
08:43:31.697 ISDN(I) 7e39 01 R 00 00 1 58 42 0 011 DISCONNECT 0001
08:43:31.697 ISDN(I) 020184b00802000145080285901e028288
08:43:31.757 ISDN(I) 7e3f 01 T 00 00 0 43 58 0 009 RELEASE 8001
08:43:31.757 ISDN(I) 0001b086080280014d
08:43:31.817 ISDN(I) 7e45 01 R 00 00 1 59 43 0 009 REL COMP 0001
08:43:31.817 ISDN(I) 020186b2080200015a

A failing outbound call:

08:45:34.256 ISDN(I) ae19 01 T 00 00 0 44 59 0 02a SETUP 0023
08:45:34.256 ISDN(I) 0001b288080200230504038090a31803a983816c06218032303031700ca13037373131333130353538a1


 00  000000--  Sapi = 0
     ------0-  C/R: Response
     -------0  Extension Bit = with extension
 01  0000000-  TEI = 0
     -------1  Extension Bit = no extension
 B2  1011001-  N(S) = 89
     -------0  I-Frame
 88  1000100-  N(R) = 68
     -------0  P/F = 0
 08  00001000  ProtocolDiscriminator DSS1
 02  00000010  Length of CallReference = 2
 00  0-------  CallRef-Flag: Origination Side
     -0000000  CallReference = 35
 23  00100011  (CallReference)
 05  00000101  MSG-Type: SETUP
 04  00000100  I-Element: Bearer
 03  00000011    Length = 3
 80  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---00000    Information Transfer Capability: Speech
 90  1-------    Extension Bit = no extension
     -00-----    Transfer Mode: circuit mode
     ---10000    Information Transfer Rate: 64 kbit/s
 A3  1-------    Extension Bit = no extension
     -01-----    Layer 1 Identifier
     ---00011    User Info Layer 1 Protocol: G.711 A-Law
 18  00011000  I-Element: Channel Identification
 03  00000011    Length = 3
 A9  1-------    Extension Bit = no extension
     -0------    Interface Identifier present: interface implicitly identified
     --1-----    Interface Type: other interface
     ---0----    Spare
     ----1---    Preferred/Exclusive: exclusiv, only indicated channel is acceptable
     -----0--    D-channel indicator: is not the D-channel
     ------01    Information Channel Selection = as indicated in following octets
 83  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---0----    Number/Map: Channel by Number
     ----0011    Channel Type/Map Element Typ: B-Channel Units
 81  1-------    Extension Bit = no extension
     -0000001    Channel number: 1
 6C  01101100  I-Element: Calling Party Number
 06  00000110    Length = 6
 21  0-------    Extension Bit = with extension
     -010----    Type of Number: national
     ----0001    Numbering Plan: ISDN/Telephony
 80  1-------    Extension Bit = no extension
     -00-----    Presentation Indicator: presentation allowed
     ---000--    Spare
     ------00    Screening Indicator: user-provided, not screened
 32  0-------    Spare
     -0110010    Number digit: 2
 30  0-------    Spare
     -0110000    Number digit: 0
 30  0-------    Spare
     -0110000    Number digit: 0
 31  0-------    Spare
     -0110001    Number digit: 1
 70  01110000  I-Element: Called Party Number
 0C  00001100    Length = 12
 A1  1-------    Extension Bit = no extension
     -010----    Type of Number: national
     ----0001    Numbering Plan: ISDN/Telephony
 30  0-------    Spare
     -0110000    Number digit: 0
 37  0-------    Spare
     -0110111    Number digit: 7
 37  0-------    Spare
     -0110111    Number digit: 7
 31  0-------    Spare
     -0110001    Number digit: 1
 31  0-------    Spare
     -0110001    Number digit: 1
 33  0-------    Spare
     -0110011    Number digit: 3
 31  0-------    Spare
     -0110001    Number digit: 1
 30  0-------    Spare
     -0110000    Number digit: 0
 35  0-------    Spare
     -0110101    Number digit: 5
 35  0-------    Spare
     -0110101    Number digit: 5
 38  0-------    Spare
     -0111000    Number digit: 8
 A1  10100001  I-Element: Sending Complete

08:45:34.446 ISDN(I) ae2c 01 R 00 00 1 5a 44 0 00e CALL PROCEEDING 8023
08:45:34.446 ISDN(I) 020188b408028023021803a98381
08:45:36.156 ISDN(I) aed7 01 R 00 00 1 5a 45 0 011 DISCONNECT 8023
08:45:36.156 ISDN(I) 02018ab40802802345080282811e028288


 02  000000--  Sapi = 0
     ------1-  C/R: Command
     -------0  Extension Bit = with extension
 01  0000000-  TEI = 0
     -------1  Extension Bit = no extension
 8A  1000101-  N(S) = 69
     -------0  I-Frame
 B4  1011010-  N(R) = 90
     -------0  P/F = 0
 08  00001000  ProtocolDiscriminator DSS1
 02  00000010  Length of CallReference = 2
 80  1-------  CallRef-Flag: Destination Side
     -0000000  CallReference = 35
 23  00100011  (CallReference)
 45  01000101  MSG-Type: DISCONNECT
 08  00001000  I-Element: Cause
 02  00000010    Length = 2
 82  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---0----    Spare
     ----0010    Location: public network serving local user
 81  1-------    Extension Bit = no extension
     -000----    Cause Class: normal event
     ----0001    Cause Value: Unallocated number;unassigned
 1E  00011110  I-Element: Progress Indicator
 02  00000010    Length = 2
 82  1-------    Extension Bit = no extension
     -00-----    Coding Standard: CCITT
     ---0----    Spare
     ----0010    Location: public network serving local user
 88  1-------    Extension Bit = no extension
     -0001000    Progress Description: in-band information or appropriate pattern now available

08:45:36.256 ISDN(I) aee1 01 T 00 00 0 46 5a 0 009 RELEASE 0023
08:45:36.256 ISDN(I) 0001b48c080200234d
08:45:36.316 ISDN(I) aee7 01 R 00 00 1 5b 46 0 009 REL COMP 8023
08:45:36.316 ISDN(I) 02018cb6080280235a

From looking at the above, we can see that in the failure case the call is being rejected by the network because the number we dialled was unallocated or unassigned. Comparing the dialled number in the successful case against that of the failure case, we can see that the ‘type of number’ is set differently, i.e., ‘national’ in the failure call from the IMG1010 and ‘000 - unknown’ in the successful call from BT.

By default, the IMG 1010 will pass whatever Nature of Address Indicator (NAI) it sees on the inbound call leg out to the outbound call leg. In the above case, the NAI is set to ‘national’ for the inbound leg and this will therefore be propogated to the outbound leg.

A solution  is to change the behaviour on the IMG 1010 for this E1 by forcing the NAI for outbound calls over this E1 to ‘000 - unknown’.


Fix / Solution:
A new outgoing translation table to the routing configuration may need to be added if one does not already exist. Right-click on the ‘Routing Configuration’ node and select ‘New Outgoing Translation Tables’ to add the ‘Outgoing Translation Tables’ group. Then right-click on ‘Outgoing Translation Tables’ and select ‘New Translation Table’ to add a new table:



To this table, we need to add a single dummy entry to apply to all dial strings. Right-click the table and select ‘New Translation Entry’. Set the ‘String’ and ‘Dialed # Translation’ as follows:



This will allow any number dialled through unmodified. It will, however allow for applying an ‘Advanced Dialed Number Translation’ so that the NAI for this E1 can be modified. Right-click the entry just added and add the advanced translation and modify the ‘Nature of Address’ parameter:



Finally, find the outbound channel group for this E1 and apply the outbound translation table to the channel group:



Once the above changes have been committed, it should be possible to route calls successfully to a British Telecom ISDN line.
 




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