SCP Lua Service

LhoScpLuaService Module

Introduction

The LhoScpLuaService is a service for initiating LUA scripts running within the LogicApp (see core n2svcd documentation). It operates in conjunction with the Logic Hand-Off SCP Application, LhoScpApp and the SigtranApp.

The SigtrapApp receives the TCAP over SIGTRAN and passes it to the LhoScpApp which contains the INAP/CAMEL Codecs and performs the SCP state-machine management for each call.

The LhoScpApp sends SCP messages to the LhoScpLuaService which is a plugin configured within the LogicApp. The LhoScpLuaService receives the SCP-... messages and initiates a LUA script execution within the LogicApp. The LUA script contains the service logic which makes calls back via the LhoScpLuaService plugin to instruct the LhoScpApp to perform SCP functions.

For underlying details, see the documentation for the SCP-… messages.

Configuring LhoScpLuaService

The LhoScpLuaService is configured within a LogicApp as follows:

    <?xml version="1.0" encoding="utf-8"?>
    <n2svcd>
      ...
      <applications>
        ...
        <application name="Logic" module="LogicApp">
          <include>
            <lib>../apps/logic/lib</lib>
          </include>
          <parameters>
            ...
          </parameters>
          <config>
            <services>
              <service module="LhoScpApp::LhoScpLuaService" libs="../../n2scp/apps/lho_scp/lib">
                <triggers>
                  <trigger called_suffix="02" script_name="scenario_02_release_call"/>
                  <trigger called_suffix="03" script_name="scenario_03_continue"/>
                  <trigger called_suffix="04" script_name="scenario_04_abort"/>
                  <trigger called_suffix="05" script_name="scenario_05_connect"/>
                </triggers>
              </service>
            </services>
            <agents>
              ...
            </agents>
          </config>
        </application>
        ...
      </application>
      ...
    </n2svcd>

Under normal installation, following service attributes apply:

Script Trigger Rules

Each SCP trigger rule defines the name of a script which is ready to handle an call for some/all called and/or calling party addresses.

Note that called and calling party addresses may contain hex digits A-F, and the matching is case-insensitive.

Each trigger Object in the config.triggers Array is configured as follows.

Script Selection (SCP call Request)

The LUA Script selection to execute for a SCP InitialDP incall is a function of the called party and/or calling party digits derived from the InitialDP. These digits will have been normalised before handover.

The SCP LUA Service will iterate the configure trigger entries in the sequence in which they are configured and find the first trigger which matches the received called and/or calling parties (or a script which matches all called and/or calling parties).

Refer to the LogicApp configuration for more information on directories, library paths, and script caching parameters.

Script Entry Parameters (SCP Call Request)

The LUA script must be a LUA chunk which returns an n2svcd.handler, such as the following:

    local n2svcd = require "n2.n2svcd"
    local scp_api = require "n2.n2svcd.scp"

    local handler = function (scp_call)

        scp_api.release (32)

        return
    end

    return n2svcd.handler (handler)

The handler will be executed with a single scp_call entry parameter.

Script Return Parameters (SCP Call Response)

The return value from the LUA script should always be nil. Returning any other value will generate a warning to the syslog.

The LhoScpLuaService API

A script processing SCP incalls must use the SCP API.

    local scp_api = require "n2.n2svcd.scp"

The following telephony functions are available for a controlled call.

• TCAP Abort
• Release Call
• Termination (Final)
• Termination (Attempt)
• Interaction