Using the IM-SSF

Before you can use the IM-SSF in a service composition you must create a service reference in your SIS SIP instance. Use the sis-console command createlocalserviceref to do this (see 1 Creating Local Service References):

The O-IM-CSI and VT-IM-CSI tables are keyed on the MSISDN field (this field is actually of type String, so we can use things other than digit sequences as a key if we wish). The IM-SSF will also recognise a proprietary header: IM-CSI-KEY that it will use in place of the subscriber’s MSISDN when selecting an appropriate CSI.

So, one can define O-IM-CSI and VT-IM-CSI with the MSISDN field = <some string that corresponds to a service> and use a SIS signaling interceptor to add a header to the initial INVITE with IM-CSI-KEY: <some string that corresponds to a service>. The IM-SSF removes this header so we do not propagate it forward.

In the following example, we can see a fragment of an INVITE message that uses the IM-CSI-KEY header with the value to use as the CSI key of VPN.

The IMSSF uses parameters in the route header to determine whether to use originating or terminating access. However, some use cases require an alternate method to classify the call as originating or terminating treatment. The IMSSF can recognise a proprietary header to decide how to treat the call.

The header is called IM-Access-Override, with valid values of orig and term. If this header exists, then the route is ignored and the value of the header is used instead.

If the values provided are not orig or term, the IM-SSF falls back onto the default behaviour.

The IM-SSF also removes this header so we do not propagate it forward.

One can use a SIS signaling interceptor to perform any ad-hoc determination of originating or terminating access, and add an IM-Access-Override header.

The IM-SSF supports a per-CSI tracing option that will generate detailed output of messages sent and received, and generate a flow-trace output. You may configure this feature with the sis-console command imssfenabletracing (see Configuring IM-SSF Subscription Information).

The IM-SSF supports ETC/ARI for announcements. It acts as an assisting SSP when it receives an ETC, by opening a second dialog to the SCP and issuing an ARI on it. The properties of the ARI can be configured using the sis-console, with commands such as imssfaddariipavailable and imssfaddariipsspcapabilities (see Configuring IM-SSF User Interaction).

These commands let you manage a lookup table of assistSSPIPRoutingAddres → AssistRequestInstructions properties.

If there is no entry in the IP-capabilities table, then the IM-SSF will use defaults of IPSSPCapabilities(supported=(IPRoutingAddress, VoiceBack)).

See the CGIN RA javadoc and the INAP and CAP specs for the layout of the byte[].

The IM-SSF defines a custom rate limiter endpoint, imssf-triggers. By default this limiter endpoint is not associated with a limiter. You can create a limiter in the SIS using the sis-console, and associate it with the IM-SSF limiter endpoint if you wish.