Support for MT Call Forwarding

When handling a mobile terminating (MT) call, CCF can forward the call to another number if the call is not answered, or the called number is busy.

You can enable call forwarding for any voice service that is for MT calls. When enabled, if the call is not answered, or the called number is busy, CCF forwards calls to the destination specified in the following field in the MtxTcapMsg MDC:

RatingMsg.ServiceInfo.VcsInfo.DestinationRoutingAddress

Engine Configuration

During engine configuration, you enable call forwarding for an MT voice service by answering y to the following create_config.info question:

Camel Gateway:VCS voice_mt_service:Do you wish to support service based call forwarding in the voice_mt_service service (y/n)?y

where voice_mt_service is the name of the MT voice service.

When enabled, CCF arms the tBusy and tNoAnswer event detection points (EDPs) as interrupted. If CCF sends a TCAP CONTINUE(RRBCSME,Continue) message to the MSC, and the MSC returns a TCAP CONTINUE(ERBCSM(tBusy)) message, then CCF sends the call forwarding number (cfn) to the MSC in a TCAP END(Cancel,Connect(cfn)) message.

Pricing Configuration

You configure the destination number specified in the VcsInfo.DestinationRoutingAddress field during pricing configuration. For example, you could configure pricing so that CCF forwards calls to:

A specified number in the subscriber's profile.
A single, system wide, voice mail number if the call is not answered.

Note: CCF denormalization rules can interpret references to MDC fields based on the MtxSubscriberObject MDC. This means that you can configure pricing to set VcsInfo.DestinationRoutingAddress to reference a field in a custom MDC, such as MyMtxSubscriberObject:MyRedirection. The custom MDC field would contain the call forwarding number.

For information, see the discussion about specifying MDC fields to supply digits sent in CCF messages.

During pricing and rating configuration, you must also:

Set the redirect reason in the following field in the MtxTcapMsg MDC:
```
RatingMsg.ServiceInfo.VcsInfo.ServiceRedirectReason
```
Define the CREDIT_CONTROL_NOT_APPLICABLE (4011) denial code so that the original call (before it is forwarded) is not charged. For information about defining denial codes, see the discussion about denial codes in Pricing and Rating.

Call Forwarding Process

If CCF cannot connect an MT call because the call is not answered or the called number is busy, then CCF passes an Accounting:interim message to pricing and rating. To ensure that the call is not charged, CREDIT_CONTROL_NOT_APPLICABLE is sent in the Accounting:interim result. After pricing and rating, CCF forwards the call only if both the following fields are set in MtxTcapMsg.RatingMsg.ServiceInfo.VcsInfo:

DestinationRoutingAddress
ServiceRedirectReason

To forward the call, CCF sends a TCAP END(Cancel, Connect) message to the MSC. The MSC then sends a new IDP for the forwarded call in a new TCAP dialog, for which charging is applied.

The parameters of the Connect operation are set as shown in Table 1.

Table 1. Call Forwarding Connect Parameters
Connect Parameter	Set to	Description
destinationRoutingAddress	VcsInfo.DestinationRoutingAddress	The denormalized destination number set using CCF denormalization rules. This is the number to use to forward the call.
legID	2	The called party leg (B-leg).
originalCalledPartyID	IDP.originalCalledPartyID If not present, the calledPartyNumber from the IDP is used.	The original number of the called party.
redirectingPartyID	The calledPartyNumber from the IDP.
redirectionInformation.Original redirecting reason	IDP.redirectionInformation.Original redirecting reason. If not present, the configured VcsInfo.ServiceRedirectionReason is used.
redirectionInformation.Redirecting indicator	diverted
redirectionInformation.Redirecting reason	VcsInfo.ServiceRedirectReason
redirectionInformation.Redirection counter	IDP.redirectionInformation.Redirection counter + 1
oCSIApplicable		Set by CCF only for call forwarding.