4 Mapping ITU SS7 Cause Codes to SIP Responses
Establishing a Session in the IMS 123
SIP provides a bit more granularity about failed or terminated sessions. Because of
this there are more options for possible SIP responses than there are SS7 cause codes
to map. Table 5.6 shows how SIP responses are mapped to SS7 cause codes (from SIP
to SS7).
Figure 5.3 is a simplified call flow, but it does illustrate the difference between SIP
and SS7 signaling, as well as the relationship between the two protocols. There is a lot
more conversation between network entities within the SIP/IMS domain than there is
within the SS7 domain.
SS7 Cause Code SIP Response
34 No circuit/channel available 480 Temporarily Unavailable
38 Network out of order 480 Temporarily Unavailable
41 Temporary failure 480 Temporarily Unavailable
42 Switching equipment congestion 480 Temporarily Unavailable
43 Access information discarded 480 Temporarily Unavailable
44 Requested circuit/channel not available 480 Temporarily Unavailable
46 Precedence call blocked 480 Temporarily Unavailable
47 Resource unavailable??”unspecified 480 Temporarily Unavailable
50 Requested facility not subscribed 500 Server Internal Error
57 Bearer capability not authorized 500 Server Internal Error
58 Bearer capability not presently available 500 Server Internal Error
63 Service option not available, unspecified 500 Server Internal Error
65 Bearer capability not implemented 500 Server Internal Error
69 Requested facility not implemented 500 Server Internal Error
70 Only restricted digital information bearer capability
is available
500 Server Internal Error
79 Service or option not implemented??”unspecified 500 Server Internal Error
88 Incompatible destination 500 Server Internal Error
91 Invalid transit network selection 404 Not Found
95 Invalid message 500 Server Internal Error
97 Message type non-existent or not implemented 500 Server Internal Error
99 Info element/parameter non-existent or not implemented 500 Server Internal Error
102 Recovery on timer expiry 480 Temporarily Unavailable
103 Parameter non-existent or not implemented, passed on 500 Server Internal Error
110 Message with unrecognized parameter, discarded 500 Server Internal Error
111 Protocol error, unspecified 500 Server Internal Error
127 Interworking, unspecified 480 Temporarily Unavailable
TABLE 5.
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