Release Reason Mapping; Reason Header; Fixed Mapping Of Isdn Release Reason To Sip Response; Table 9-1: Mapping Of Isdn Release Reason To Sip Response - AudioCodes Mediant 2000 User Manual

9.2

Release Reason Mapping

This section describes the available mapping mechanisms of SIP responses to Q.850
Release Causes and vice versa. The existing mapping of ISDN Release Causes to SIP
Responses is described in ''Fixed Mapping of ISDN Release Reason to SIP Response'' on
page 394 and ''Fixed Mapping of SIP Response to ISDN Release Reason'' on page 396. To
override this hard-coded mapping and flexibly map SIP responses to ISDN Release
Causes, use the ini file (CauseMapISDN2SIP and CauseMapSIP2ISDN, as described in
''ISDN and CAS Interworking-Related Parameters'' on page 307) or the Web interface (refer
to ''Release Cause Mapping'' on page 189).
It is also possible to map the less commonly used SIP responses to a single default ISDN
Release Cause. Use the parameter DefaultCauseMapISDN2IP (described in ''ISDN and
CAS Interworking-Related Parameters'' on page 307) to define a default ISDN Cause that is
always used except when the following Release Causes are received: Normal Call Clearing
(16), User Busy (17), No User Responding (18) or No Answer from User (19). This
mechanism is only available for Tel-to-IP calls.
9.2.1

Reason Header

The device supports the Reason header according to RFC 3326. The Reason header
conveys information describing the disconnection cause of a call:
Sending Reason header: If a call is disconnected from the Tel side (ISDN), the
Reason header is set to the received Q.850 cause in the appropriate message (BYE /
CANCEL / final failure response) and sent to the SIP side. If the call is disconnected
because of a SIP reason, the Reason header is set to the appropriate SIP response.
Receiving Reason header: If a call is disconnected from the IP side and the SIP
message includes the Reason header, it is sent to the Tel side according to the
following logic:
•
If the Reason header includes a Q.850 cause, it is sent as is.
•
If the Reason header includes a SIP response:
♦
♦
•
When the Reason header is received twice (i.e., SIP Reason and Q.850), the
Q.850 takes precedence over the SIP reason and is sent to the Tel side.
9.2.2

Fixed Mapping of ISDN Release Reason to SIP Response

The following table describes the mapping of ISDN release reason to SIP response.

Table 9-1: Mapping of ISDN Release Reason to SIP Response

ISDN
Release
Reason
1 Unallocated number
2 No route to network
3 No route to destination
6 Channel unacceptable
SIP User's Manual
If the message is a final response, the response status code is translated to
Q.850 format and passed to ISDN.
If the message isn't a final response, it is translated to a Q.850 cause.
Description
SIP
Response
404
404
404
406
*
394
Mediant 2000
Description
Not found
Not found
Not found
Not acceptable
Document #: LTRT-68808