This module provides a simple Online Charging Server Module for working with the ims_charging module. It communicates with the ims_charging module via the Diameter-Ro Interface.

This module is dependent on the CDP (C Diameter Peer) modules for communicating with a Charging-Server as specified in 3GPP specification TS xx.xxx.

Please also refer to RFC 4006 (Diameter Credit-Control Application).

The module works will create fake SIP messages and provide them to an event route for further operations. It up to the script writer to do the processing.

2. Dependencies

2.1. Kamailio Modules

The Following modules must be loaded before this module:

CDP - C Diameter Peer
CDP_AVP - CDP AVP Applications

2.2. External Libraries or Applications

No external libraries are required.

3. Faked Messages

3.1. Translating SIP to Diameter

The incoming Charging requests are translated into the following methods:

INVITE - For "Start" Charging Requests
UPDATE - For "Interim" Charging Requests
BYE - For "Stop" Charging Requests

3.2. SIP-Information in the faked messages

The faked messages contain the following information:

Method - See previous section
Request-URI - The dialed number of the call
From-Header - The originator of the session
To-Header - Same as request-URI
Call-ID - The Diameter-Charging-ID (not the SIP-Call-ID)
P-Requested-Units - The requested units for this call
P-Used-Units - The used units for this call (only useful for Interim and Stop Events)
P-Access-Network-Info - The used access network - if available
P-Service-Identifier - The service identifier, if you want to differentiate different services (e.g. Audio and Video)

4. Functions

4.1. `ccr_result(resultcode, grantedunits, finalunit)`

This method sets the response code of the Diameter Request.

Meaning of the parameters is as follows:

resultcode - the Diameter Response code for the request. Typical response codes are:
- “2001” - Ok
- “5030” - User unknown
- “5031” - Rating failed
- “4010” - End-User Service denied (e.g. Service blocked)
- “5006” - Resources exceeded (e.g. too many concurrent calls)
grantedunits - the number of granted units for this particular user
finalunit - indication, that all following requests will be denied (this is the final unit for the session)

This function can be used from the event route.

Example 1.1. ds_select_dst usage

...
ccr_result("2001", "600", "0");
...
$var(result) = 2001;
$var(granted) = $hdr(P-Requested-Units);
$var(final) = 0;
ccr_result("$var(result)", "$var(granted)", "$var(final)");
...
ccr_result("2001", "$hdr(P-Requested-Units)", "0");
...

5. Event routes

5.1. `ocs:ccr-orig`

This route is called for Charging Requests with the session-case "originating" - a call from a user to another destination.

...
event_route[ocs:ccr-orig] {
	xlog("Session-Case: Originating\n");
	xlog("----------------------------------------\n");
	if (is_method("INVITE")) {
		xlog("START - Request\n");
	} else if (is_method("UPDATE")) {
		xlog("INTERIM - Request\n");
	} else if (is_method("BYE")) {
		xlog("STOP - Request\n");
	}
	xlog("----------------------------------------\n");
	xlog("From:               $fu\n");
	xlog("To:                 $ru\n");
	xlog("Call-ID:            $ci\n");
	xlog("Requested Units:    $hdr(P-Requested-Units)\n");
	xlog("Used Units:         $hdr(P-Used-Units)\n");
	xlog("Access Network:     $hdr(P-Access-Network-Info)\n");
	xlog("Service Identifier: $hdr(P-Service-Identifier)\n");

	ccr_result("2001", "600", "0");
}
...

5.2. `ocs:ccr-term`

This route is called for Charging Requests with the session-case "terminating" - a call to a user from another destination.

You can have an "originating" and a "terminating" request for a single call, e.g. if a user calls another user. Since the Diameter-Session-ID is provided as "Call-ID", it will have a different Call-ID, since it is logical two separate sessions.

This route is optional.

...
event_route[ocs:ccr-term] {
	xlog("Session-Case: Terminating\n");
	xlog("----------------------------------------\n");
	if (is_method("INVITE")) {
		xlog("START - Request\n");
	} else if (is_method("UPDATE")) {
		xlog("INTERIM - Request\n");
	} else if (is_method("BYE")) {
		xlog("STOP - Request\n");
	}
	xlog("----------------------------------------\n");
	xlog("From:               $fu\n");
	xlog("To:                 $ru\n");
	xlog("Call-ID:            $ci\n");
	xlog("Requested Units:    $hdr(P-Requested-Units)\n");
	xlog("Used Units:         $hdr(P-Used-Units)\n");
	xlog("Access Network:     $hdr(P-Access-Network-Info)\n");
	xlog("Service Identifier: $hdr(P-Service-Identifier)\n");

	ccr_result("2001", "600", "0");
}
...

IMS Online Charging Server (OCS) Module

Carsten Bock

Chapter 1. Admin Guide

1. Overview