This feature is triggered from the I-CSCF and retrieves reorigination information; optionally it can retrieve the subscriber’s assigned S-CSCF either from a HSS or from a profile from network configuration, then acts as a B2BUA between the I-CSCF and the subscriber’s assigned S-CSCF .

It is one of two features that enable circuit switched originating calls to be processed in the SCC-AS. The related feature is SCCCamelToIMSReOriginationIN. These features are part of service centralization in the IMS.

Note For this feature’s fit into the overall flow, please see the Reorigination basic flow diagram.

Relevant specifications

  • 3GPP TS 23.292 and 24.292

  • GSMA IR.64.

Feature cheat sheet

B2BUA Instance SAS Support Originating / Terminating Point in Session Plan Network Operator Data Subscriber Data Stateful or Stateless POJO Feature or SBB Feature

SCC signalling anchor B2BUA


From SIP triggering perspective, neither. Mobile Originating and Mobile Terminating determined from saved CAMEL InitialDP (IDP)





Triggered by the I-CSCF

Network operator data

Common network configuration data is stored in a profile table named SCCCommonReOriginationConfigProfileTable. Each network operator supported by the platform has one entry in this table.

For more information, see the shared configuration between the SCCCamelToIMSReOriginationSIP feature and the SCCCamelToIMSReOriginationIN feature.

Use of Correlation resource adaptor

For information about use of the Correlation RA, please see the shared Correlation RA..

Session output variables

Variable name Type Comment


Set to true if the feature finds reorigination data


SCCCamelToIMSReOriginationSIP statistics are tracked by the volte.sentinel.sip SBB and can be found under the following parameter set:
SLEE-Usage → volte.sentinel.sip service → volte.sentinel.sip SBB → feature → SCCCamelToIMSReOriginationSIP

Statistic Incremented when…​


The feature ran to completion


Multiple history-info headers found on the INVITE


no history-info header found on the INVITE


One history-info header found on the INVITE and removed


HSS lookup failed


HSS lookup succeeded


HSS lookup was skipped due to SkipHSSLookup feature configuration flag


Correlation RA was queried for the call information


The Correlation RA query succeeded


The Correlation RA query failed


The VLR number is present in the initial IDP


The VLR number is not present in the initial IDP


The feature could set the Visited Network Id based on the Location information or on the VLR address


The feature could set the Visited Network Id


The initial IDP has a called party number or called party BCD number


The initial IDP does not have a called party number or called party BCD number


The SCSCF could not be found in configuration, or retrieved from the HSS


AccessNetworkInfo was found in the original InitialDP


AccessNetworkInfo could not be found in the original InitialDP


The feature starts


The feature failed to start due to an error


The feature raised a warning


The feature failed due to a major error


The feature timed out during execution


The feature is triggered on receipt of a SIP INVITE from the I-CSCF.

It checks for network operator data. If not present, the feature informs Sentinel that it failed to execute due to invalid configuration.

It looks at the received INVITE Request URI, and checks that it represents a phone number.

If the network configuration indicates a prefix is in use, it checks that the request URI’s digits start with that prefix. If not, the feature finishes execution without modifying any state. In other words, this is treated as an INVITE that is not for this feature.

The feature then attempts to retrieve the correlation data that was stored by the IN feature. This data is looked up using the request URI’s digits as the key for the correlation data.

If correlation data is not found, the feature finishes execution without modifying any state.

If correlation data is found, the feature tries to extract the Mobile Country Code and the Mobile Network Code from the Cell Global Id or Location Area Id present in the Location Information section of the Initial IDP. If a MCC and MNC is found, a Visited Network Id is created in the format epc.ims.mnc<MNC>.mcc<MCC>, according to IR65 section 6.2.1.

In the case of originating Initial DP arguments, if a MCC and MNC is found, and the Initial DP includes a Cell Global ID with a Location Area Code, the P-Access-Network-Info header is set to the form 3GPP-GERAN;cgi=3gpp=<mcc><mnc><location area code><cellId>.

If MCC or MNC is not present, the feature uses the Visited Network ID Address List to find the Visited Network ID for the VLR address in the data. If a matching Visited Network ID is found, it is included in a header in the outgoing SIP request. If no matching ID is found then reorigination will be aborted. In practice this should never happen, as the IN reorigination feature performs this check as well and will terminate reorigination before any SIP signalling occurs if no Visited Network ID is found.

Next, the feature then retrieves the S-CSCF name for the calling party from either of two places based on the SkipHSSLookup flag:

Flag Value Effect


Use the value in DirectRoutingURI from network configuration.


Do a lookup from the HSS through the Sh Cache RA.

The feature then adjusts or sets various headers in the outgoing INVITE.

Finally, the SIP Sentinel instance hosting this feature acts as a B2BUA between the I-CSCF and the S-CSCF.

SIP headers in the outgoing INVITE

The feature sets or adjusts the following headers in the outgoing INVITE:

Header Name Change


Set to a tel URI with the digits being the original IDP’s called party number digit string (non-BCD encoded).


Set to the original IDP’s called party number digit string (non-BCD encoded).


If only one such header exists on the INVITE, it is removed.


If it is not present in the INVITE it is set to a tel URI using the calling party number from the original IDP.


Set to id if the original IDP CallingPartyNumber presentation parameter value is RESTRICTED or NETWORK_RESTRICTED.


A new route to the S-CSCF for the served user is added, if the feature was invoked on an originating trigger an orig parameter will be included.


In case of originating Initial DP argument containing suitable location information, the feature sets this header in the form of 3GPP-GERAN;cgi=3gpp=<mcc><mnc><location area code><cellId>


Set to a Visited Network ID if the feature was invoked on an originating trigger.


Set to a Visited Network ID if the feature was invoked on an terminating trigger.


Set to the VLR address from the correlation data as a VLR Number address in a string.


If such header exists in the INVITE, it is removed.

Note The OC-Term-P-Visited-Network and OC-VLR-Number are proprietary headers created by OpenCloud.

Formatting of the P-Access-Network-Info header

The encoding follows 3GPP TS 24.229, in particular section '7.2A.4.3 Additional coding rules for P-Access-Network-Info header', which states:

The Cell Global Identity is a concatenation of MCC, MNC, LAC and CI …​ The value of "cgi-3gpp" parameter is therefore coded as a text string as follows: Starting with the most significant bit, MCC (3 digits), MNC (2 or 3 digits depending on MCC value), LAC (fixed length code of 16 bits using full hexadecimal representation) and CI (fixed length code of 16 bits using a full hexadecimal representation).

Formatting of the OC-VLR-Number header

The OC-VLR-Number header value is built by:

  • retrieving the VLR address in the original InitialDP

  • converting the SCCP address into an ascii string, formatted according to SS7’s AddressStringParser

  • setting resulting the string into the SIP header value

The resulting complete header will be OC-VLR-Number: address=651232343,nature=INTERNATIONAL,numberingPlan=ISDN

Formatting of the OC-Term-P-Visited-Network header

This header has the same format as a P-Visited-Network header.

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