ims_charging_admin.xml

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<!-- Module Admin Guide -->
<chapter>
  <title>Admin Guide</title>

  <section>
    <title>Overview</title>

    <para>This module contains all methods related to the IMS charging control
    functions performed by a network element (e.g. a S-CSCF) over the 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.</para>

    <para>Please also refer to RFC 4006 (Diameter Credit-Control
    Application)</para>
  </section>

  <section>
    <title>Dependencies</title>

    <section>
      <title>Kamailio Modules</title>

      <para>The Following modules must be loaded before this module:</para>

      <itemizedlist>
        <listitem>
          <para>ims_dialog</para>
        </listitem>

        <listitem>
          <para>TM - Transaction Manager</para>
        </listitem>

        <listitem>
          <para>CDP - C Diameter Peer</para>
        </listitem>

        <listitem>
          <para>CDP_AVP - CDP AVP Applications</para>
        </listitem>
      </itemizedlist>
    </section>

    <section>
      <title>External Libraries or Applications</title>

      <para>This modules requires the internal IMS library.</para>
    </section>
  </section>

  <section>
    <title>Understanding Charging in the IP-Multimedia-Subsystem (IMS)</title>

    <para>Before each service usage, the charging system must be asked for
    permission (credit authorization). The charging server must make a
    decision: Either authorize or deny the session. For postpaid scenarios
    this is fairly easy: The charging-server only needs to collect the usage
    data for processing it at the end of the month. As no realtime account
    updating is needed, this is often called "offline-charging". For prepaid
    scenarios the charging server needs to know the user's account balance and
    it will need to update the account in real-time. This is often referred to
    as "online-charging".</para>

    <para>Question: What is the double of the Radius? Answer: It's the
    Diameter!</para>

    <para>As quite often, we use the Diameter-Protocol to do the Charging in
    the IMS. And as quite often, IMS uses a huge bunch of acronyms to describe
    the different interfaces: We call the diameter-interface for
    offline-charging the "Rf"-interface and the interface for online charging
    the "Ro"-interface.</para>

    <para>Each system, that needs this credit authorization, have to be
    equipped with a proper charging trigger, a so-called
    charging-trigger-function (CTF) in order to communicate with the
    charging-server (also called charging-function):</para>

    <mediaobject>
      <imageobject>
        <imagedata fileref="./images/charging1.png"/>
      </imageobject>
    </mediaobject>

    <section>
      <title>Offline Charging (Rf)</title>

      <para>For the offline charging (Rf), we have the following two
      diameter-messages:</para>

      <itemizedlist>
        <listitem>
          <para>ACR - Accounting Request</para>
        </listitem>

        <listitem>
          <para>ACA - Accounting Answer</para>
        </listitem>
      </itemizedlist>

      <para>Each request can have the following Accounting-Record-Type:</para>

      <itemizedlist>
        <listitem>
          <para>START_RECORD - used to start an accounting session, typically
          when the application receives a SIP 200 OK acknowledging an initial
          SIP INVITE.</para>
        </listitem>

        <listitem>
          <para>INTERIM_RECORD - used to update a session, for example, in the
          case of SIP RE-INVITE and/or UPDATE in the current SIP
          dialog.</para>
        </listitem>

        <listitem>
          <para>STOP_RECORD - used to stop an accounting session, for example,
          when the application receives a SIP BYE message.</para>
        </listitem>

        <listitem>
          <para>EVENT_RECORD - used for event-based accounting, e.g. a short
          message or similar</para>
        </listitem>
      </itemizedlist>
    </section>

    <section>
      <title>Online Charging (Ro)</title>

      <para>For online charging (Ro), this get's a little bit more
      complicated. The charging function needs to perform credit control
      before allowing resource usage. The prepaid subscriber needs to exist in
      the charging-server and all activities must be monitored by the
      charging-server. We must distinguish between the following two
      cases:</para>

      <itemizedlist>
        <listitem>
          <para>Direct debiting - the amount is immediately deducted from the
          user's account in one single transaction. This could be for example
          a SMS or the ordering of a movie in case of Video-on-Demand.</para>
        </listitem>

        <listitem>
          <para>Unit reservation - an amount is reserved by the
          charging-server. This is done, because the charging-server does not
          know yet, how many units are needed to provide the service. During
          the session, the used amount may be deducted and more units can be
          requested; at the end of the session the used sessions are reported
          in the final request. These sessions could be typically a voice- or
          video-call or a Pay-TV session, if you pay per usage.</para>
        </listitem>
      </itemizedlist>

      <para>As a result, we have the following three scenarios:</para>

      <itemizedlist>
        <listitem>
          <para>Immediate Event Charging (IEC) - used for simple Event-based
          charging</para>
        </listitem>

        <listitem>
          <para>Event Charging with Unit Reservation (ECUR) (of type
          Event-based charging)</para>
        </listitem>

        <listitem>
          <para>Session Charging with Unit Reservation (SCUR) (of type
          Session-based charging)</para>
        </listitem>
      </itemizedlist>
    </section>

    <section>
      <title>Online Charging (Ro): A practical example</title>

      <para>But how does it look in reality? Let us make a more practical
      example:</para>

      <para>Let us assume we have a subscriber, who has sufficient credit for
      75 seconds of talking. The subscriber initiates a call; as we do not
      know, how long the call will take, we start with requesting credit for
      30 seconds (CCR-Request, we could request any duration, e.g. 2 hours,
      but it would probably block other calls if we reserve all the required
      credit).</para>

      <para>The call proceeds, so after 30 seconds we send another CCR-Request
      with the indication that we used the reserved 30 seconds and that we
      request another 30 seconds. We reduce the account of the subscriber by
      30 seconds, so he has a credit of 45 seconds. Since 45 seconds is more
      than the requested 30 seconds, this second request can also easily be
      accepted and another 30 seconds can be granted. After this request, the
      account is at 45 seconds and we still (or again) have 30 seconds
      reserved.</para>

      <para>Meanwhile the subscriber initiates a second call. We try to
      request again 30 seconds from the charging-server, but as our account is
      at 45 seconds of speaking time and since we reserved another 30 seconds
      for the first call, we can only grant 15 seconds for the second call.
      The last 15 seconds are now reserved for this subscriber; we have 45
      seconds on the account of which 45 seconds are reserved.</para>

      <para>Now the first call gets terminated: We only used 20 seconds from
      the granted 30 seconds. So we decrease the account of the subscriber by
      20 seconds and we reduce the amount of reserved units by 30. We have 25
      seconds in the account and we have still reserved 15 seconds for the
      second call.</para>

      <para>As the second call is still proceeding, we will try to request
      another 30 seconds and we indicate, that we used the granted 15 seconds.
      The account is deducted by 15 seconds (the used units) and we can grant
      another 10 seconds for the second call, as this is the remains on the
      account.</para>

      <para>After 10 seconds, no more units can be granted, so the call is
      teared down.</para>

      <para>The following diagram is a graphical representation of the above
      example:</para>

      <mediaobject>
        <imageobject>
          <imagedata fileref="./images/charging2.png"/>
        </imageobject>
      </mediaobject>
    </section>
  </section>

  <section>
    <title>Parameters</title>

    <section>
      <title><varname>hash_size</varname>(int)</title>

      <para>The size of the hash table internally used to keep the
      Diameter-Ro-Session. A larger table is much faster but consumes more
      memory. The hash size must be a power of two number.</para>

      <para>IMPORTANT: If Ro-Session's information should be stored in a
      database, a constant hash_size should be used, otherwise the restoring
      process will not take place. If you really want to modify the hash_size
      you must delete all table's rows before restarting the server.</para>

      <para><emphasis>Default value is 4096.</emphasis></para>

      <example>
        <title><varname>hash_size</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "hash_size", 1024)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>db_mode</varname> (int)</title>

      <para>Should a database be used to store dialog information.</para>

      <para>Available database modes: 0 for no database, 1 for real-time mode and
      2 for shutdown mode. Mode 2 seems to be not fully implemented.</para>

      <para><emphasis>Default value is 0 - no database is used.</emphasis></para>

      <example>
        <title><varname>db_mode</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "db_mode", 0)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>db_url</varname> (string)</title>

      <para></para>

      <para><emphasis>Default value is <quote>&defaultdb;</quote></emphasis></para>

      <example>
        <title><varname>db_url</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "db_url", "&exampledb;")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>interim_update_credits</varname>(int)</title>

      <para>How much credit should be requested interim request? At the start
      of the call, we request the amount of seconds as per Command. For each
      interim request, we would request credit for
      "interim_update_credits".</para>

      <para><emphasis>Default value is 30.</emphasis></para>

      <example>
        <title><varname>interim_update_credits</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "interim_update_credits", 600)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>timer_buffer</varname>(int)</title>

      <para>How many seconds before expiry of our credit should we request
      more credit?</para>

      <para><emphasis>Default value is 8.</emphasis></para>

      <example>
        <title><varname>timer_buffer</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "timer_buffer", 10)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>ro_forced_peer</varname>(string)</title>

      <para>FQDN of Diameter Peer (OCS) to use for communication (CCR). If you
      use this, the routing defined in your diameter xml configuration file
      (CDP) will be ignored and as a result you will lose the benefits of load
      balancing and failover. </para>

      <para><emphasis>Default value is ''.</emphasis></para>

      <example>
        <title><varname>ro_forced_peer</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "ro_forced_peer", "ocs.ims.smilecoms.com")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>ro_auth_expiry</varname>(integer)</title>

      <para>This is the expiry length in seconds of the initiated Diameter
      sessions.</para>

      <para><emphasis>Default value is 7200.</emphasis></para>

      <example>
        <title><varname>ro_auth_expiry</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "ro_auth_expiry", 14400)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>ro_auth_expiry</varname>(integer)</title>

      <para>This is the expiry length in seconds of the initiated Diameter
      sessions.</para>

      <para><emphasis>Default value is 7200.</emphasis></para>

      <example>
        <title><varname>ro_auth_expiry</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "ro_auth_expiry", 14400)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>cdp_event_latency</varname>(integer)</title>

      <para>This is a flag to determine whether or slow CDP responses should
      be reported in the log file. 1 is enabled and 0 is disabled.</para>

      <para><emphasis>Default value is 1.</emphasis></para>

      <example>
        <title><varname>cdp_event_latency</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "cdp_event_latency", 1)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>cdp_event_threshold</varname>(integer)</title>

      <para>This time in milliseconds is the limit we should report a CDP
      response as slow. i.e. if a CDP response exceeds this limit it will be
      reported in the log file. This is only relevant is cdp_event_latency is
      enabled (set to 0).</para>

      <para><emphasis>Default value is 500.</emphasis></para>

      <example>
        <title><varname>cdp_event_threshold</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "cdp_event_threshold", 500)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>cdp_event_latency_log</varname>(integer)</title>

      <para>This time log level at which we should report slow CDP responses.
      0 is ERROR, 1 is WARN, 2 is INFO and 3 is DEBUG. This is only relevant
      is cdp_event_latency is enabled (set to 0)</para>

      <para><emphasis>Default value is 0.</emphasis></para>

      <example>
        <title><varname>cdp_event_latency_log</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "cdp_event_latency_log", 1)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>single_ro_session_per_dialog</varname>(integer)</title>

      <para>This tells the module whether it should do a single ro session per
      dialog no matter how many times Ro_send_CCR is called from the config
      file or initiate an ro session each time Ro_send_CCR is called. It is
      useful for IMS charging where you might want to charge for on-net
      originating and off-net originating calls but always have only a single
      ro session.</para>

      <para><emphasis>Default value is 0.</emphasis></para>

      <example>
        <title><varname>single_ro_session_per_dialog</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "single_ro_session_per_dialog", 1)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>origin_host</varname>(string)</title>

      <para>Origin host to be used in Diameter messages to
      charging-server.</para>

      <para><emphasis>Default value is "".</emphasis></para>

      <example>
        <title><varname>origin_host</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "origin_host", "scscf.kamailio-ims.org")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>origin_realm</varname>(string)</title>

      <para>Origin Realm to be used in Diameter messages to
      charging-server.</para>

      <para><emphasis>Default value is "".</emphasis></para>

      <example>
        <title><varname>origin_realm</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "origin_realm", "kamailio-ims.org")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>destination_host</varname>(string)</title>

      <para>Destination host to be used in Diameter messages to
      charging-server.</para>

      <para><emphasis>Default value is "".</emphasis></para>

      <example>
        <title><varname>destination_host</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "destination_host", "ocs.kamailio-ims.org")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>destination_realm</varname>(string)</title>

      <para>Destination realm to be used in Diameter messages to
      charging-server.</para>

      <para><emphasis>Default value is "".</emphasis></para>

      <example>
        <title><varname>destination_realm</varname>parameter usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "destination_realm", "kamailio-ims.org")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>service_context_id_root</varname>(string)</title>

      <para>This defines a root-element of the Service-Context-Id AVP used in
      the diameter-message</para>

      <para>The Service-Context-Id AVP is of type UTF8String (AVP Code 461)
      and contains a unique identifier of the Diameter credit-control service
      specific document that applies to the request (as defined in section RFC
      4006 4.1.2). This is an identifier allocated by the service provider, by
      the service element manufacturer, or by a standardization body, and MUST
      uniquely identify a given Diameter credit-control service specific
      document. The format of the Service-Context-Id is:</para>

      <programlisting format="linespecific">
"service-context" "@" "domain" service-context = Token
      </programlisting>

      <para>The Token is an arbitrary string of characters and digits.</para>

      <para>'domain' represents the entity that allocated the
      Service-Context-Id. It can be ietf.org, 3gpp.org, etc., if the
      identifier is allocated by a standardization body, or it can be the FQDN
      of the service provider (e.g., provider.example.com) or of the vendor
      (e.g., vendor.example.com) if the identifier is allocated by a private
      entity.</para>

      <para>Service-specific documents that are for private use only (i.e., to
      one provider's own use, where no interoperability is deemed useful) may
      define private identifiers without need of coordination. However, when
      interoperability is wanted, coordination of the identifiers via, for
      example, publication of an informational RFC is RECOMMENDED in order to
      make Service-Context-Id globally available.</para>

      <para><emphasis>Default value is "32260@3gpp.org".</emphasis></para>

      <example>
        <title><varname>service_context_id_root</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "service_context_id_root", "calls@kamailio-ims.org")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>service_context_id_ext</varname>(string)</title>

      <para>This defines the extension of the Service-Context-Id AVP used in
      the diameter-message.</para>

      <para><emphasis>Default value is "ext".</emphasis></para>

      <example>
        <title><varname>service_context_id_ext</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "service_context_id_ext", "ext2")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>service_context_id_mnc</varname>(string)</title>

      <para>This defines Mobile-Network-Code (MNC) of the Service-Context-Id
      AVP used in the diameter-message.</para>

      <para><emphasis>Default value is "01".</emphasis></para>

      <example>
        <title><varname>service_context_id_mnc</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "service_context_id_mnc", "42")
...
        </programlisting>
      </example>
    </section>
    
    <section>
      <title><varname>voice_service_identifier</varname>(string)</title>

      <para>This defines the service identifier to be used for charging voice.</para>

      <para><emphasis>Default value is "1000".</emphasis></para>

      <example>
        <title><varname>voice_service_identifier</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "voice_service_identifier", "1000")
...
        </programlisting>
      </example>
    </section>
    
    <section>
      <title><varname>voice_rating_group</varname>(string)</title>

      <para>This defines the rating group to be used for charging voice.</para>

      <para><emphasis>Default value is "100".</emphasis></para>

      <example>
        <title><varname>voice_rating_group</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "voice_rating_group", "100")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>video_service_identifier</varname>(string)</title>

      <para>This defines the service identifier to be used for charging video.</para>

      <para><emphasis>Default value is "1001".</emphasis></para>

      <example>
        <title><varname>video_service_identifier</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "video_service_identifier", "1000")
...
        </programlisting>
      </example>
    </section>
    
    <section>
      <title><varname>video_rating_group</varname>(string)</title>

      <para>This defines the rating group to be used for charging video.</para>

      <para><emphasis>Default value is "200".</emphasis></para>

      <example>
        <title><varname>video_rating_group</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "video_rating_group", "100")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>service_context_id_mcc</varname>(string)</title>

      <para>This defines Mobile-Country-Code (MCC) of the Service-Context-Id
      AVP used in the diameter-message.</para>

      <para>see https://en.wikipedia.org/wiki/Mobile_country_code_(MCC) for
      details.</para>

      <para><emphasis>Default value is "001".</emphasis></para>

      <example>
        <title><varname>service_context_id_mcc</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "service_context_id_mcc", "262")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>service_context_id_release</varname>(string)</title>

      <para>This defines Release of the Service-Context-Id AVP used in the
      diameter-message.</para>

      <para><emphasis>Default value is "8" (Release 8).</emphasis></para>

      <example>
        <title><varname>service_context_id_release</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "service_context_id_release", "262")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>custom_user_avp</varname> (avp string)</title>

      <para>When this parameter is set and the contents of the AVP is not
      empty, the User-AVP in the Ro-Charging-Request will be based on the 
      this parameter rather than on the P-Asserted or From-Header.</para>
      <para>
      This parameter allows you to setup an AVP with which you can customise
      the user to be used in the Diameter-Request.</para>

      <para><emphasis> Default value: if not set, P-Asserted-Identity with a
      fallback to the From-Header is used. </emphasis></para>

      <example>
        <title><varname>custom_user_avp</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "custom_user_avp", "$avp(from_user)")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>app_provided_party_avp</varname> (avp string)</title>

      <para>When this parameter is set and the contents of the AVP is not
      empty, an Application-Provided-Called Party-Address AVP will be
      addedd to charging related requests. This is required for special
      cases e.g. related to roaming for some diameter server.</para>

      <para><emphasis> Default value: if not set, the
      Application-Provided-Called-Party-Address AVP will be not set.</emphasis></para>

      <example>
        <title><varname>app_provided_party_avp</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "app_provided_party_avp", "$avp(app_user)")
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>vendor_specific_chargeinfo</varname> (int)</title>

      <para>This parameter can be used to activate or deactivate the addition
      of Vendor-Specific-Termination-Clause and Vendor-Specific-Termination-Reason
      AVPs to the requests. To activate set this parameter to 1.</para>

      <para><emphasis>Default value is "0" (deactivated).</emphasis></para>

      <example>
        <title><varname>vendor_specific_chargeinfo</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "vendor_specific_chargeinfo", 1)
...
        </programlisting>
      </example>
    </section>

    <section>
      <title><varname>vendor_specific_id</varname> (int)</title>

      <para>To set the ID of the Vendor-Specific information, not implemented right
      now.</para>

      <para><emphasis>Default value is "10".</emphasis></para>

      <example>
        <title><varname>vendor_specific_id</varname>parameter
        usage</title>

        <programlisting format="linespecific">
...
modparam("ims_charging", "vendor_specific_id", 10)
...
        </programlisting>
      </example>
    </section>

  </section>

  <section>
    <title>Functions</title>

    <section>
      <title><function moreinfo="none">Ro_CCR(route_name, direction,
      reservation_units, incoming_trunk_id, outgoing_trunk_id)</function>
      </title>

      <para>Perform a CCR on Diameter Ro interface for Charging</para>

      <para>Meaning of the parameters is as follows:</para>

      <itemizedlist>
        <listitem>
          <para><emphasis>route_name</emphasis> route to be executed upon
          reception of charging requests</para>
        </listitem>

        <listitem>
          <para><emphasis>direction</emphasis> "orig"inating or
          "term"inating</para>
        </listitem>

        <listitem>
          <para><emphasis>reservation_units</emphasis> how many units (at the
          moment seconds) should be reserved at the moment.</para>
        </listitem>
	
	<listitem>
          <para><emphasis>incoming_trunk_id</emphasis> Identifies the trunk group 
	  from which this originates.</para>
        </listitem>
	
	<listitem>
          <para><emphasis>outgoing_trunk_id</emphasis> Identifies the trunk 
	  group where this will be terminated.</para>
        </listitem>
      </itemizedlist>

      <para>This function can be used from REQUEST_ROUTE.</para>

      <para>This method is executed asynchronously. See example on how to
      retrieve return value.</para>

      <example>
        <title>Ro_CCR</title>

        <programlisting format="linespecific">
...
  xlog("L_DBG","Sending initial CCR Request for call\n");
    Ro_CCR("RO_ASYNC_TERM_REPLY", "term", 30, "1", "1");
}

route[CHARGING_CCR_REPLY] 
  xlog("L_DBG","cca_return code is $avp(s:cca_return_code)\n");
  switch ($avp(s:cca_return_code)) {
    case 1: #success
        xlog("L_DBG", "CCR success - will route message\n");
        route(Finalize_Orig);
        break;
    case -1: #failure
        xlog("L_ERR", "CCR failure - error response sent from module\n");
        sl_send_reply("402","Payment required");
        break;
    case -2: #error
        xlog("L_ERR", "CCR error - error response sent from module\n");
        sl_send_reply("500", "Charging Error");
        break;
    default:
        xlog("L_ERR", "Unknown return code from CCR: [$avp(s:cca_return_code)] \n");
        break;
  }
  exit;
  }
...
        </programlisting>
      </example>
    </section>
    
    <section>
      <title><function moreinfo="none">Ro_set_session_id_avp()</function>
      </title>

      <para>Sets the Ro session ID to an AVP for use in the config file</para>

      <para>This function can be used from REQUEST_ROUTE or ONREPLY_ROUTE.</para>

      <example>
        <title>Ro_set_session_id_avp</title>

        <programlisting format="linespecific">
...
            Ro_set_session_id_avp();
            xlog("L_DBG","Ro session AVP has been set: $avp(ro_session_id)\n");
...
        </programlisting>
      </example>
    </section>
    
  </section>

  <section>
    <title>Statistics</title>

    <section>
      <title>Initial CCRs (initial_ccrs)</title>

      <para>The number of initial CCRs, i.e., the CCRs that were sent for the
      initial INVITEs.</para>
    </section>

    <section>
      <title>Interim CCRs (interim_ccrs)</title>

      <para>The number of CCRs sent within established sessions.</para>
    </section>

    <section>
      <title>Final CCRs (final_ccrs)</title>

      <para>The number of CCRs sent to terminate a session.</para>
    </section>

    <section>
      <title>Successful initial CCRs (successful_initial_ccrs)</title>

      <para>Initial CCRs that ended with DIAMETER_SUCCESS response
      code.</para>
    </section>

    <section>
      <title>Successful interim CCRs (successful_interim_ccrs)</title>

      <para>Interim CCRs that ended with DIAMETER_SUCCESS response
      code.</para>
    </section>

    <section>
      <title>Successful final CCRs (successful_final_ccrs)</title>

      <para>Final CCRs that ended with DIAMETER_SUCCESS response code.</para>
    </section>

    <section>
      <title>Failed initial CCRs (failed_initial_ccrs)</title>

      <para>Initial CCRs that ended with no DIAMETER_SUCCESS response or with
      some other error during processing.</para>
    </section>

    <section>
      <title>Failed interim CCRs (failed_interim_ccrs)</title>

      <para>Interim CCRs that ended with no DIAMETER_SUCCESS response or with
      some other error during processing.</para>
    </section>

    <section>
      <title>Failed final CCRs (failed_final_ccrs)</title>

      <para>Final CCRs that ended with no DIAMETER_SUCCESS response or with
      some other error during processing.</para>
    </section>

    <section>
      <title>CCRs average response time (ccr_avg_response_time)</title>

      <para>Average CCA arrival time in milliseconds.</para>
    </section>

    <section>
      <title>CCRs responses time (ccr_responses_time)</title>

      <para>Total CCA arrival time in milliseconds.</para>
    </section>

    <section>
      <title>CCRs requests, which ended with a timeout (ccr_timeouts)</title>

      <para>Number of CCR-Requests, which ran into a timeout.</para>
    </section>

    <section>
      <title>Billed seconds (billed_secs)</title>

      <para>Number of seconds billed in total.</para>
    </section>

    <section>
      <title>Killed calls (killed_calls)</title>

      <para>Number of calls that were killed due to lack of credit.</para>
    </section>
  </section>
</chapter>