User`s manual

SIP User's Manual 460 Document #: LTRT-83303
Mediant 1000 & Mediant 600
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:
♦ 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.
• 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
Description
SIP
Response
Description
1 Unallocated number 404 Not found
2 No route to network 404 Not found
3 No route to destination 404 Not found
6 Channel unacceptable 406
*
Not acceptable
7
Call awarded and being delivered in an
established channel
500 Server internal error
16 Normal call clearing -* BYE
17 User busy 486 Busy here
18 No user responding 408 Request timeout
19 No answer from the user 480 Temporarily unavailable
21 Call rejected 403 Forbidden
22 Number changed w/o diagnostic 410 Gone