N2 LHO-SCP

Overview

The LHO-SCP Application is a general-purpose component which can be used to implement many other Value Added Service (VAS) functions using the SCP call control model. For example, the N-Squared Automated Call Distribution SCP (N2ACD-SCP) service is implemented using the LHO-SCP applications.

The LHO-SCP application is responsible for handling CAMEL/INAP call-session control under the direction of an separate logic application, typically a LogicApp application executing a Lua script.

Communication with the LogicApp is via the N2SVCD message-passing layer, using the SCP Messages which exist for this very purpose. The LHO-SCP application sends SCP-HANDLE-... messages to the LogicApp, which responses with SCP-DO-... messages to initiate SCP activity such as terminations or interaction.

The LogicApp may of course use any other Lua Agents to perform tasks using other protocols. For example it may use the RestClientApp or SoapClientApp to perform REST or SOAP client requests. Equally it may use SMPP or Diameter, or even initiate other secondary TCAP transactions via a SigtranApp.

N2SVCD Components

When deploying the N2LHO-SCP product, the LhoScpApp (Diameter/CAMEL Gateway) application is used in conjunction with other components as shown in the following component deployment diagram:

• Alarms and Statistics may be sent by the various applications.
• The EdrApp, ManageApp, WatchdogApp provide core service functions.
• The SigtranApp provides the SIGTRAN connectivity to the signalling network (including SRF).
• The LhoScpApp coordinates CAMEL/INAP operations into an SCP state machine.
• The LogicApp controls the SCP state machine via instruction messages.

The additional integrations for the LogicApp now depend entirely on the nature of the Value-Added Service being performed by the LogicApp.

For example, if the service is performing Automated Call Distribution (i.e. “Toll-Free”) then it will typically use the following additional applications:

• The DbApp is used to load the “Toll-Free Call Flow” from the database.
• The RestClientApp or SoapClientApp may be used to fetch additional service control information.

Other services may use DiameterApp, SMPPApp, etc.

Note that the LHO-SCP will typically use a an on-switch or external Specialized Resource Function (SRF) to perform audio announcements and/or to collect DTMF input.

All interaction between the N2SCP and the SRF components is performed via the SigtranApp over an SCTP/SIGTRAN link.

Traffic Type Determination

Received calls may be for Originating, Forwarding, or Terminating call legs.

The LHO-SCP applies the following rules, in order, to determine the traffic type of a received InitialDP:

1. If the InitialDP → EventTypeBCSM field value is 12 (termAttemptAuthorized), set the traffic type to Terminating.

2. If:

   1. The SSP model inap value is camel1, camel2, camel3, or camel4.
   2. The InitialDP → EventTypeBCSM field value is 2 (CollectedInfo) or 3 (AnalyzedInformation).
   3. The InitialDP → locationInformation field is present.

   …set the traffic type to Forwarding.

3. If:

   1. The SSP model inap value is cs1.
   2. The InitialDP → EventTypeBCSM field value is 2 (CollectedInfo) or 3 (AnalyzedInformation).
   3. The InitialDP → redirectingPartyID field is present.

   …set the traffic type to Forwarding.

4. If the InitialDP → EventTypeBCSM field value is 2 (CollectedInfo) or 3 (AnalyzedInformation), set the traffic type to Originating.

The traffic-type is passed to the service logic in the .call_trigger attribute of the SCP-HANDLE-ALEG-IDP message.

Refer to the LHO-SCP configuration for further details.