ISDN Diagnostic Codes

ISDN Diagnostic Codes

00 128 00 80 Normal Disconnect

01 129 01 81 Unassigned (Unallocated number)

02 130 02 82 No route to specified transit network

03 131 03 83 No route to destination

04 132 04 84 Send special information tone*

05 133 05 85 Misdialled trunk prefix*

06 134 06 86 Channel unacceptable

07 135 07 87 Call awarded and being delivered in an established channel

08 136 08 88 Preemption*

09 137 09 89 Preemption, circuit reserved for re-use* Category 1 - normal event

16 144 10 90 Normal call clearing

17 145 11 91 User busy

18 146 12 92 No user responding

19 147 13 93 User alerting, no answer

20 148 14 94 Subscriber absent*

21 149 15 95 Call rejected

22 150 16 96 Number changed

23 151 17 97 Redirection to new destination*

24 153 19 99 Exchange routing error*

26 154 1A 9A Non-selected user clearing

27 155 1B 9B Destination out of order

28 156 1C 9C Invalid number format

29 157 1D 9D Facility rejected

30 158 1E 9E Response to STATUS ENQUIRY

31 159 1F 9F Normal unspecified

Category 2 - resource unavailable

34 162 22 A2 No circuit/channel available

38 166 26 A6 Network out of order

39 167 27 A7 Permanent frame mode connection out of service* 40 168 28 A8 Permanent frame mode connection operational*

41 169 29 A9 Temporary failure

42 170 2A AA Switching equipment congestion

43 171 2B AB Access information discarded

44 172 2C AC Requested circuit/channel not available

46 174 2E AE Precedence call blocked*

47 175 2F AF Resource unavailable, unspecified

Category 3 - service or option not available

19 177 31 B1 Quality of service unavailable

50 178 32 B2 Requested facility not subscribed

53 181 35 B5 Outgoing calls barred within CUG* 55 183 37 B7 Incoming calls barred within CUG*

57 185 39 B9 Bearer capability not authorized

58 186 3A BA Bearer capability not presently available 63 191 3F BF Service or option not available, unspecified Category 4 - service or option not implemented

65 193 41 C1 Bearer capability not implemented

66 194 42 C2 Channel type not implemented

69 197 45 C5 Requested facility not implemented

70 198 46 C6 Only restricted information bearer capability available 79 207 4F CF Service or option not available, unspecified

Category 5 - invalid message (e.g. parameter out of range)

81 209 51 D1 Invalid call reference value

82 210 52 D2 Identified channel does not exist

83 211 53 D3 A suspended call exists, but this identity does not

84 212 54 D4 Call identity in use

85 213 55 D5 No call suspended

86 214 56 D6 Call having the requested call identity has been cleared

87 215 57 D7 User not a member of CUG*

88 216 58 D8 Incompatible destination

90 218 5A DA Non-existent CUG*

91 219 5B DB Invalid transit network selection

95 223 5F DF Invalid message, unspecified

Category 6 - protocol error (e.g. unknown message)

96 224 60 E0 Mandatory Information Element is missing

97 225 61 E1 Message type non-existent or not implemented

98 226 62 E2 Message not compatible with call state, or not implemented 99 227 63 E3 Information Element non-existent or not implemented

100 228 64 E4 Invalid Information Element contents 101 229 65 E5 Message not compatible with call state

102 230 66 E6 Recovery on time expiry

103 231 67 E7 Parameter not implemented*

111 232 6F EF Protocol Error, unspecified

Category 7 - interworking

127 255 7F FF Interworking, unspecified

Extracting ISDN Cause Codes from a trace

Introduction to DiTrace - please read this first ISDN cause codes

ISDN location codes

When using ISDN, it is useful to be able to interpret the information returned by RELEASE and DISCONNECT frames, since this gives the reason that a call has been disconnected or refused. You see the DISCONNECT or RELEASE frames in one of two situations:

1. When a call SETUP has been issued, the device at the other end (or the network itself) can refuse to connect the call by sending DISCONNECT or RELEASE.

2. When a call is already connected (i.e. the SETUP was met with a CONNECT message, and a point-to-point connection is now established), then either party can end the call by sending a DISCONNECT. Also, the network itself might end the connection (for example, if some network equipment fails or the network becomes congested).

The information that we are interested in is coded in an 'information element' present on RELEASE, DISCONNECT and STATUS messages called 'cause'. The whole information element consists of 4 bytes; for instance: 08 02 82 BF

The "08" means "Cause" and the "02" means that two further bytes of information follow. So, the 'cause' is '82 BF'. These further two bytes break down into bit fields as follows:

7 6 5 4 3 2 1 0 +----+----+----+----+----+----+----+----+ | 1 | Coding | 0 | Location | +----+----+----+----+----+----+----+----+ | 1 | Cause Value | +----+----+----+----+----+----+----+----+

The Coding field gives the Coding Standard, showing what standard you need to refer to in order to understand the Cause Value. Generally, coding standard will be "00" means CCITT standard, which is also used for the ETSI standard (EuroISDN). For completeness, Coding Standard field can be one of the following:

00 CCITT standardized

01 reserved for national standards 10 national standard

11 standard specific to identified location

The Location field shows who issued this diagnostic code. This is useful information where the two communicating devices are on different ISDN networks (perhaps with one or more transit networks between), or are using ISDN though private network such as a PABX. The possible location codes are:

Binary Hex _{in trace} Value Meaning

0000 0 80 user

0001 1 81 private network serving the local user 0010 2 82 public network serving the local user 0011 3 83 transit network

0100 4 84 public network serving the remote user 0101 5 85 private network serving the remote user 0111 7 87 international network

1010 A 8A network beyond interworking point More information on what these codes mean

In the example trace above, value for this byte is 0x82 (in binary this is 1000 0010), so we can break this down as follows:

1000 0010

1... .... This bit is always 1. .00. .... Coding Standard = CCITT ...0 .... This bit is always 0.

.... 0010 Location is "public network serving the local user"

The Cause Value field is where the diagnostic code itself appears. Note that the top bit is always set, so in fact we only need to look at the lower 7 bits when we look up this value. In the example above, we have the value 0xBF which decodes as follows:

1011 1111

1... .... This bit is always 1.

.011 1111 Code is 0x3F (63 in decimal) which means "Service or option not available, unspecified". When we interpret the value 0x3F, we know that we use the CCITT list because the Location field (in the previous byte) told us so.

In fact there is more information that we can get from the Cause code because the first three bits give a general category of error, and the last four bits give the error within the category. The categories are:

000 normal event 001 normal event 010 resource unavailable

011 service or option not available 100 service or option not implemented

101 invalid message (e.g. parameter out of range) 110 protocol error (e.g. unknown message) 111 interworking

So the breakdown of code 0xBF is actually as follows: 1011 1111

1... .... This bit is always 1.

.011 .... Category is "service or option not available"

...1111 Code is 0xF in category 3, "Service or option not available, unspecified".

Line Check Errors

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Success! Line Check test passed

Failure! No ISDN card found. DIVA software not correctly installed

Failure! ISDN card does not work correctly. Installation probably not correct

Failure! Unknown error. A resource conflict probably exists in your system or the DIVA card has been removed

Failure! Test aborted with an error - Layer 1 error. Check cable/NT! - TEI Error

- Layer 2 error

Failure! Unknown error. Please contact support

Success! Line Check test passed.

This is the successful (and desired) outcome of the Line Check test. It indicates that the DIVA card is installed correctly and is communicating with the network. This is not an exhaustive test and does not necessarily mean that all calls placed through the card will always work.

Failure! No ISDN card found. DIVA software not correctly installed.

This Line Check utility is unable to locate any DIVA card in your system. Follow these instructions for problem diagnosis on Windows 95/98 and these instructions for Windows NT.

Failure! ISDN card does not work correctly. Installation probably not correct.

The Line Check utility has located a DIVA card on your system, but is unable to communicate with it. Follow these instructions for problem diagnosis on Windows 95/98 and these instructions for Windows NT.

Failure! Unknown error. A resource conflict probably exists in your system or the DIVA card

has been removed.

The Line Check utility has located a DIVA card on your system, but is unable to communicate with it. This is probably due to a conflict with other devices in your computer. Follow these instructions for problem diagnosis on Windows 95/98 and these instructions for Windows NT.

Failure! Test aborted with an error.

The message will report some additional information:

Layer 1 error. Check cable/NT!

connected to the port that you are testing. Beware if you have LAN adapter in your PC that you have not connected the ISDN line to this card.

TEI Error.

Repeat the test. If the problem is persistent, you may need to change the card configuration to match your ISDN line.

Layer 2 error.

Repeat the test. Some ISDN switches are sensitive to equipment being unplugged and will cause this error. If the problem is persistent, this needs in-depth analysis using the DiTrace tool. Use this link for Windows 95/98

and this link for Windows NT.

Failure! Unknown error. Please contact support.

Internal Line Check error.

Location codes

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An ISDN Cause code consists of 2 bytes; the first byte contains the 'location' code (with some other information) and the second byte contains the diagnostic code.

The Location field shows who issued the diagnostic code. This is particularly useful information where the two communicating devices are on different ISDN networks (perhaps with one or more transit networks between), or are using ISDN though a 'private network' such as a PABX.

The possible location codes are: Location

code (Hex)

Value in trace

Meaning

(Click on a link below to highlight the component)

0 80 user

1 81 private network serving the local user 2 82 public network serving the local user 3 83 transit network

4 84 public network serving the remote user 5 85 private network serving the remote user 7 87 international network

MDL Errors

Extracting 'Cause' information from a trace Other errors

The following table shows errors reported by the MDL-ERROR-INDICATION primitive to do with layer-2 establishment on the "D" channel.

MDL is the standard prefix for messages to do with communication between layer management and the data link layer.

In a DIVA trace, these codes appear in messages 'MDL-ERROR(x)', where 'x' is one of the following error codes.

Error Code

Error Condition Action Error Type

A Supervisory (F=1) Error Log Receipt of unsolicited

response

B DM (F=1) Error Log Receipt of unsolicited

response

C UA (F=1) TEI removal procedure or

TEI check procedure, then if TEI:

free: remove TEI single: no action multiple: TEI removal procedure

Receipt of unsolicited response

D UA (F=0) TEI removal procedure or

TEI check procedure, then if TEI:

free: remove TEI single: no action multiple: TEI removal procedure

Receipt of unsolicited response

E DM (F=0) Error Log Receipt of unsolicited

response

F SABME Error Log Peer initiated re-establish.

G SABME TEI check procedure, then if

TEI:

free: remove TEI single: no action multiple: TEI removal

Unsuccessful retransmission (N200 times)

procedure

H DISC TEI check procedure, then if

TEI:

free: remove TEI single: no action multiple: TEI removal procedure

Unsuccessful retransmission (N200 times)

I Status Enquiry Error Log Unsuccessful retransmission

(N200 times)

J N(R) error Error Log Other

K Receipt of FRMR Error Log Other

L Receipt of frame with

undefined control field

Error Log Other

M Receipt of I field not permitted

Error Log Other

N Receipt of frame with wrong size

Error Log Other

O N201 error Error Log Other