SIP Statuses to Q.850 Reasons (2024)

This section explains the Oracle® Enterprise Session Border Controller’s ability to map Q.850 cause values with SIP responses, a feature used in SIP calls and calls that require IWF.

RFC 3326 defines a header that might be included in any in-dialogue request. This reason header includes cause values that are defined as either a SIP response code or ITU-T Q.850 cause values. You can configure the Oracle® Enterprise Session Border Controller to support sending and receiving RFC 3326 in SIP messages for:

Mapping H.323 Q.850 cause values to SIP responses with reason header and cause value
Mapping SIP response messages and RFC 3326 reason header and cause
Locally generated SIP response with RFC 3326 reason header and cause

As specified in RFC 3326, the Oracle® Enterprise Session Border Controller sends SIP responses to the softswitch that contain the received Q.850 cause code and the reason.

Though the Oracle® Enterprise Session Border Controller can generate RFC 3326 headers, the default behavior for this feature is disabled. Furthermore, the Oracle® Enterprise Session Border Controller can receive and pass SIP error messages (4xx, 5xx, and 6xx) that contain the SIP reason header with a Q.850 cause code and reason (as specified in RFC 3326). If the system receives an error message without the Reason header, then the Oracle® Enterprise Session Border Controller is not required to insert one.

In calls that require IWF, the Q.850 cause generated in the SIP response are the same as the cause received in the following H.225 messages: Disconnect, Progress, Release, Release Complete, Resume Reject, Status, and Suspend Reject. In addition, the Q.850 cause codes that the Oracle® Enterprise Session Border Controller receives in RFC 3326 headers are passed to the H.323 part of the call unmodified; the H.323 call leg uses this cause code for releasing the call.

SIP-SIP Calls

The SIP Reason header might appear in any request within a dialog, in a CANCEL request, and in any response where the status code explicitly allows the presence of this header field. The syntax of the header follows the standard SIP parameter:

Configure Reason and Cause Mapping for SIP-SIP Calls

To configure reason-cause mapping for SIP-SIP calls, you must set up the ACLI local-response-map configuration with appropriate entries to generate the SIP response and the Q.850 cause code value used for particular error scenarios. If you want to add a Reason header, you must enable that capability in the global SIP configuration.

In the following procedure use the method parameter and the register-response-expires parameter to enable a SIP registration response mapping feature that allows you to configure the system to remap a SIP failure response to a 200 OK. The failure response can come from another network device or the system can generate the response locally. You might want the system to perform such mapping when a non-malicious endpoint continually attempts registration, but stops when the system sends a 200 OK. The failure response mapping does not register the client with the system, which leaves neither a registration cache entry nor a CAM ACL for the entry.

For the 200 OK it generates, the system removes any Reason or Retry-After header in the 200 OK and sets the expires time. By default, the expires time is the Retry-After time (if there is one in the response) or the expires value in the Register request (if there is no Retry-After expires time). You can also set this value using the register-response-expires parameter, but the value you set should never exceed the Register request’s expires time.

Access the entries configuration element.

ORACLE# configure terminalORACLE(configure)# session-routerORACLE(session-router)# local-response-mapORACLE(local-response-map)# local-response-map-entriesORACLE(local-response-map-entries)#

(Optional) Type ? to see the entire menu for the local response map entries configuration.
local-error—Set the local error that triggers the use of this local response map. No default.
Note:
The Enterpriseand Service Provider systems both display the full list, but some items do notapply to both systems. Such items are noted.
Type local-error? to see the entire list of local errors that you can configure.
sip-status—Set the SIP response code to use. No default value. Range: 100-699.
sip-reason—Set the SIP reason string you want to use for this mapping. No default value. If the value contains spaces between the characters, you must surround the entry with quotation marks.
q850-cause—Set the Q.850 cause. No default value.
q850-reason—Set the Q.850 reason string that you want to use for this mapping. No default value. If your value has spaces between characters, then your entry must be surrounded by quotation marks.
method—Enter the name of the received SIP failure response message you want to map to a 200 OK.
No default. Leave the parameter empty to turn off the SIP registration response mapping feature.
register-response-expires—Enter the time you want to use for the expires time you identified in the method parameter.
The maximum is 999999999. By default, the expires time is the Retry-After time (if there is one in the response) or the expires value in the Register request (if there is no Retry-After expires time). Any value you configure in this parameter (when not using the defaults) should never exceed the Register request’s expires time.
(Optional) Repeat this process to create the number of local response map entries that you need.
Save and activate the configuration for changes to take effect.

Calls Requiring IWF

For interworking calls between SIP and H.323, you can configure:

Mappings for SIP status codes to Q.850 values
Mappings for particular Q.850 cause codes to SIP status codes

If it cannot find the appropriate mapping, then the Oracle® Enterprise Session Border Controller uses default mappings defined in the Default Mappings table below.

The following describes how the Oracle® Enterprise Session Border Controller handles different IWF call scenarios:

SIP request containing a Reason header—When it receives a request containing a Reason header, the Oracle® Enterprise Session Border Controller determines if the request is a SIP BYE or SIP CANCEL message. RFC 3326 states that the Reason header is mainly used for these types of requests. If there is a Reason header and it contains the Q.850 cause value, then the Oracle® Enterprise Session Border Controller releases the call on the H.323 side using the specified cause value.
SIP response—When it receives the error response to an initial SIP INVITE, the Oracle® Enterprise Session Border Controller uses its SIP-Q.850 map to determine the Q.850 that it will use to release the call. If there is not a map entry, then the Oracle® Enterprise Session Border Controller uses the default mappings shown in the Default Mappings table.
Active call released from the H.323 side—If an active call is released from the H.323 side, the Oracle® Enterprise Session Border Controller checks the outgoing realm (the SIP side) to see if the addition of the Reason header is enabled. If it is, then the Oracle® Enterprise Session Border Controller adds the Reason header in the SIP BYE request with the Q.850 value it received from the H.323 side.
Error during setup of the call on the H.323 side—In the event of an error during setup on the H.323 side of the call, the system needs to send:
- An error response, if this is a SIP to H.323 call
- A SIP CANCEL, if this is a H.323 to SIP call and the H.323 side hangs up before the call is answered on the SIP side
  In this case, the Oracle® Enterprise Session Border Controller checks to see if adding the Reason header is enabled in the IWF configuration. If it is, then the Oracle® Enterprise Session Border Controller adds the Reason header with the Q.850 cause value it received from the H.323 side.
Call released due to a Oracle® Enterprise Session Border Controller error—If the call is released due a Oracle® Enterprise Session Border Controller error and adding the Reason header is enabled in the IWF configuration, the error response to the initial INVITE contains the Reason header. The Oracle® Enterprise Session Border Controller checks the SIP to Q.850 map configurations to determine whether or not the SIP error response code it is generating is configured. If it is, then the Oracle® Enterprise Session Border Controller maps according to the configuration. If if it not, the Oracle® Enterprise Session Border Controller derives cause mapping from the default table.

Like the configuration for SIP-only calls that enable this feature, you can set a parameter in the IWF configuration that enables adding the Reason header in the SIP requests or responses.

Default Mappings

This table defines the default mappings the Oracle® Enterprise Session Border Controller uses when it cannot locate an appropriate entry thatyou have configured.

Q.850 Cause Value Number	Q.850 Cause Value Number	SIP Status Number	SIP Status Text	Comments
1	Unallocated number	404	Not found	N/A
2	No route to specified transit network	404	Not found	N/A
3	No route destination	404	Not found	N/A
16	Normal calling clearing	N/A	BYE message	A call clearing BYE message containing cause value 16 normally results in the sending of a SIP BYE or CANCEL request. However, if a SIP response is to be sent to the INVITE request, the default response code should be used.
17	User busy	486	Busy here	N/A
18	No user responding	408	Request timeout	N/A
19	No answer from the user	480	Temporarily unavailable	N/A
20	Subscriber absent	480	Temporarily unavailable	N/A
21	Call rejected	603	Decline (if location filed in Cause information element indicates user; otherwise 403 Forbidden is used)	N/A
22	Number changed	301	Moved permanently (if information in diagnostic field of Cause information element is suitable for generating SIP Contact header; otherwise 410 Gone is used)	N/A
23	Redirection to new destination	410	Gone	N/A
25	Exchange routing error	483	Too many hops	N/A
27	Destination out of order	502	Bad gateway	N/A
28	Address incomplete	484	Address incomplete	N/A
29	Facility rejected	501	Not implemented	N/A
31	Normal, unspecified	480	Temporarily unavailable	N/A
34	No circuit, channel unavailable	503	Service unavailable	N/A
38	Network out of order	503	Service unavailable	N/A
41	Temporary failure	503	Service unavailable	N/A
42	Switching equipment congestion	503	Service unavailable	N/A
47	Resource unavailable unspecified	503	Service unavailable	N/A
55	Incoming calls barred with CUG	403	Forbidden	N/A
57	Bearer capability not authorized	403	Forbidden	N/A
58	Bearer capability not presently available	503	Service unavailable	N/A
65	Bearer capability not implemented	488	Not acceptable here	N/A
69	Requested facility not implemented	501	Not implemented	N/A
70	Only restricted digital information available	488	Not acceptable here	N/A
79	Service or option not implemented, unspecified	501	Not implemented	N/A
87	User not member of CUG	403	Forbidden	N/A
88	Incompatible destination	503	Service unavailable	N/A
102	Recovery on timer expiry	504	Server time-out	N/A