Reason Header; Fixed Mapping Of Isdn Release Reason To Sip Response; Table 9-1: Mapping Of Isdn Release Reason To Sip Response - AudioCodes Mediant 1000 User Manual

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 348) 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
Call awarded and being delivered in an
7
established channel
16 Normal call clearing
17 User busy
18 No user responding
19 No answer from the user
21 Call rejected
22 Number changed w/o diagnostic
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
*
500
-*
486
408
480
403
410
460
Mediant 1000 & Mediant 600
Description
Not found
Not found
Not found
Not acceptable
Server internal error
BYE
Busy here
Request timeout
Temporarily unavailable
Forbidden
Gone
Document #: LTRT-83303