DESCRIPTION

This document describes the cause messages, used with the ISDN D-channel protocols EDSS1 and 1TR6 and their format, visible to the user.

FORMAT

Cause messages are 2-byte information elements, describing the state transitions of an ISDN line. Each cause message describes its origination (location) in one byte, while the cause code is described in the other byte. Internally, when EDSS1 is used, the first byte contains the location while the second byte contains the cause code. When using 1TR6, the first byte contains the cause code while the location is coded in the second byte. In the Linux ISDN subsystem, the cause messages visible to the user are unified to avoid confusion. All user visible cause messages are displayed as hexadecimal strings. These strings always have the location coded in the first byte, regardless if using 1TR6 or EDSS1. When using EDSS1, these strings are preceded by the character 'E'.

CAUSE MESSAGES WITH EDSS1

LOCATION

The following location codes are defined when using EDSS1:

00

Message generated by user.

01

Message generated by private network serving the local user.

02

Message generated by public network serving the local user.

03

Message generated by transit network.

04

Message generated by public network serving the remote user.

05

Message generated by private network serving the remote user.

07

Message generated by international network.

0A

Message generated by network beyond inter-working point.

CAUSE

The following cause codes are defined when using EDSS1:

01

Unallocated (unassigned) number.

02

No route to specified transit network.

03

No route to destination.

06

Channel unacceptable.

07

Call awarded and being delivered in an established channel.

10

Normal call clearing.

11

User busy.

12

No user responding.

13

No answer from user (user alerted).

15

Call rejected.

16

Number changed.

1A

Non-selected user clearing.

1B

Destination out of order.

1C

Invalid number format.

1D

Facility rejected.

1E

Response to status enquiry.

1F

Normal, unspecified.

22

No circuit or channel available.

26

Network out of order.

29

Temporary failure.

2A

Switching equipment congestion.

2B

Access information discarded.

2C

Requested circuit or channel not available.

2F

Resources unavailable, unspecified.

31

Quality of service unavailable.

32

Requested facility not subscribed.

39

Bearer capability not authorised.

3A

Bearer capability not presently available.

3F

Service or option not available, unspecified.

41

Bearer capability not implemented.

42

Channel type not implemented.

45

Requested facility not implemented.

46

Only restricted digital information bearer.

4F

Service or option not implemented, unspecified.

51

Invalid call reference value.

52

Identified channel does not exist.

53

A suspended call exists, but this call identity does not.

54

Call identity in use.

55

No call suspended.

56

Call having the requested call identity.

58

Incompatible destination.

5B

Invalid transit network selection.

5F

Invalid message, unspecified.

60

Mandatory information element is missing.

61

Message type non-existent or not implemented.

62

Message not compatible with call state or message or message type non existent or not implemented.

63

Information element non-existent or not implemented.

64

Invalid information element content.

65

Message not compatible.

66

Recovery on timer expiry.

6F

Protocol error, unspecified.

7F

Inter working, unspecified.

CAUSE MESSAGES WITH 1TR6

LOCATION

The following location codes are defined when using 1TR6:

00

Octet not available. (Not always generated.)

44

Message generated by public network.

45

Message generated by private network.

4F

Unknown.

CAUSE

The following cause codes are defined when using 1TR6:

00

Normal call clearing.

01

Invalid Call reference value.

03

Bearer service not implemented.

07

Call identity does not exist.

08

No channel available.

10

Requested facility not implemented.

11

Requested facility not subscribed.

20

Outgoing calls barred.

21

User access busy.

22

Closed user group mismatch.

23

Non existent closed user group.

25

SPV connection not allowed.

35

Destination not obtainable.

38

Number changed.

3A

No user responding.

3B

User busy.

3D

Incoming calls barred.

3E

Call rejected.

59

Network congestion.

5A

Remote user initiated.

70

Local procedure error.

71

Remote procedure error.

72

Remote user suspended.

73

Remote user resumed.

7F

User info discarded locally.