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<!-- Module User's Guide -->
<chapter>
  <title>&adminguide;</title>

  <section>
    <title>Overview</title>

    <para>CDP (C Diameter Peer) allows Diameter communication to and from
    Kamailio. Most of the code is inherited from DISC
    http://developer.berlios.de/projects/disc/ and OpenIMS and modified for
    use within Kamailio. A few improvements and new functionality has been
    added along the way, for example, threshold reporting on Diameter calls
    that are serviced above a certain threshold.</para>
  </section>

  <section>
    <title>How it works</title>

    <para>CDP forks the following processes:</para>

    <itemizedlist>
      <listitem>
        <para>1 x Timer</para>
      </listitem>

      <listitem>
        <para>1 x Acceptor</para>
      </listitem>

      <listitem>
        <para>k x Workers (k configurable through configuration)</para>
      </listitem>

      <listitem>
        <para>i x Receivers (one for each peer plus one for unknown
        peers)</para>
      </listitem>
    </itemizedlist>

    <para>CDP is really only an API and offers all of its methods to other
    modules. No commands are made available to the main Kamailio configuration
    file. The exported API can be seen in mod.c. The Full Diameter API is in
    diameter.h and diameter_api.h. IMS-specific constants can be found in
    diameter_ims.h. The protocol coding is implemented in diameter_avp.c and
    diameter_msg.c. The diameter state machine is implemented in
    peerstatemachine.c - there is one of these for each peer which maintains
    all protocol/application state for each peer. peermanager.c is responsible
    for peer administration. Diameter transactions are implemented in
    transaction.c.</para>

    <para>There are 2 configuration areas for CDP. Firstly it must be loaded
    and configured in the Kamailio.cfg file (this is the normal task
    associated with Kamailio modules). Then, an XML file is required to
    configure various Diameter parameters and all related peers and the
    associated routes.</para>
  </section>

  <section>
    <title>Dependencies</title>

    <section>
      <title>&kamailio; Modules</title>

      <para>The following modules must be loaded before this module:
      <itemizedlist>
          <listitem>
            <para><emphasis>None</emphasis>.</para>
          </listitem>
        </itemizedlist></para>
    </section>

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

      <para>The following libraries or applications must be installed before
      running &kamailio; with this module loaded: <itemizedlist>
          <listitem>
            <para><emphasis>None</emphasis>.</para>
          </listitem>
        </itemizedlist></para>
    </section>
  </section>

  <section>
    <title>Parameters</title>

    <section>
      <title>config_file (string)</title>

      <para>This is the location of the XML configuration file.</para>

      <para><emphasis> Default value is <quote>DiameterPeer.xml</quote>.
      </emphasis></para>

      <example>
        <title>Set <varname>config_file</varname> parameter</title>

        <programlisting format="linespecific">...
modparam("cdp", "config_file", "/etc/kamailio/diametercfg.xml")
...
</programlisting>
      </example>
    </section>

    <section>
      <title>latency_threshold (int)</title>

      <para>The time in ms above which a log error is wrtten to log file for
      long CDP transactions.</para>

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

      <example>
        <title>Set <varname>latency_threshold</varname> parameter</title>

        <programlisting format="linespecific">...
modparam("cdp", "latency_threshold", 1000)
...
</programlisting>
      </example>
    </section>
    <section>
      <title>workerq_length_threshold_percentage (int)</title>

      <para>The threshold of the length of the worker queue as a percentage of 
	  the maximum queue size - when exceeded a warning is written to the log
	  file. 0  means disabled</para>

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

      <example>
        <title>Set <varname>workerq_length_threshold_percentage</varname> parameter</title>

        <programlisting format="linespecific">...
modparam("cdp", "workerq_length_threshold_percentage", 25)
...
	</programlisting>
      </example>
    </section>
  </section>

  <section>
    <title>RPC Commands</title>

    <para>exported RPC commands.</para>

    <section>
      <title>cdp.disable_peer</title>

      <para>instantly disable a particular diameter peer.</para>
    </section>

    <section>
      <title>cdp.enable_peer</title>

      <para>enabe/re-enable a diameter peer</para>
    </section>
  </section>

  <section>
    <title>Configuration Examples</title>

    <section>
      <title>DiameterPeer.xml example</title>

      <para>This is an example CDP configuration file. The location of this
      file is configured as a CDP parameter (config_file) - See section 4.1
      Above</para>

      <example>
        <title>DiameterPeer.xml example</title>

        <programlisting format="linespecific">&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!-- 

 DiameterPeer Parameters 
  - FQDN - FQDN of this peer, as it should apper in the Origin-Host AVP
  - Realm - Realm of this peer, as it should apper in the Origin-Realm AVP
  - Vendor_Id - Default Vendor-Id to appear in the Capabilities Exchange
  - Product_Name - Product Name to appear in the Capabilities Exchange 
  - AcceptUnknownPeers - Whether to accept (1) or deny (0) connections from peers with FQDN 
    not configured below
  - DropUnknownOnDisconnect - Whether to drop (1) or keep (0) and retry connections (until restart)
    unknown peers in the list of peers after a disconnection.
  - Tc - Value for the RFC3588 Tc timer - default 30 seconds
  - Workers - Number of incoming messages processing workers forked processes.
  - Queue - Length of queue of tasks for the workers:
     - too small and the incoming messages will be blocked too often;
     - too large and the senders of incoming messages will have a longer feedback loop to notice that
     this Diameter peer is overloaded in processing incoming requests;
     - a good choice is to have it about 2 times the number of workers. This will mean that each worker
     will have about 2 tasks in the queue to process before new incoming messages will start to block.
  - ConnectTimeout - time in seconds to wait for an outbound TCP connection to be established.
  - TransactionTimeout - time in seconds after which the transaction timeout callback will be fired,
    when using transactional processing.
  - SessionsHashSize - size of the hash-table to use for the Diameter sessions. When searching for a 
    session, the time required for this operation will be that of sequential searching in a list of 
    NumberOfActiveSessions/SessionsHashSize. So higher the better, yet each hashslot will consume an
    extra 2xsizeof(void*) bytes (typically 8 or 16 bytes extra).
  - DefaultAuthSessionTimeout - default value to use when there is no Authorization Session Timeout 
  AVP present.
  - MaxAuthSessionTimeout - maximum Authorization Session Timeout as a cut-out measure meant to
  enforce session refreshes.
      
 --&gt;
&lt;DiameterPeer 
        FQDN="pcscf.ims.smilecoms.com"
        Realm="ims.smilecoms.com"
        Vendor_Id="10415"
        Product_Name="CDiameterPeer"
        AcceptUnknownPeers="0"
        DropUnknownOnDisconnect="1"
        Tc="30"
        Workers="4"
        QueueLength="32"
        ConnectTimeout="5"
        TransactionTimeout="5"
        SessionsHashSize="128"
        DefaultAuthSessionTimeout="60"
        MaxAuthSessionTimeout="300"
&gt;

        &lt;!--
                Definition of peers to connect to and accept connections from. For each peer found in here
                a dedicated receiver process will be forked. All other unkwnown peers will share a single
                receiver. NB: You must have a peer definition for each peer listed in the realm routing section
        --&gt;
        &lt;Peer FQDN="pcrf1.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;
        &lt;Peer FQDN="pcrf2.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;
        &lt;Peer FQDN="pcrf3.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;
        &lt;Peer FQDN="pcrf4.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;
        &lt;Peer FQDN="pcrf5.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;
        &lt;Peer FQDN="pcrf6.ims.smilecoms.com" Realm="ims.smilecoms.com" port="3868"/&gt;

        &lt;!--
                Definition of incoming connection acceptors. If no bind is specified, the acceptor will bind
                on all available interfaces.
        --&gt;
        &lt;Acceptor port="3868"  /&gt;
        &lt;Acceptor port="3869" bind="127.0.0.1" /&gt;
        &lt;Acceptor port="3870" bind="192.168.1.1" /&gt;

        &lt;!--
                Definition of Auth (authorization) and Acct (accounting) supported applications. This
                information is sent as part of the Capabilities Exchange procedures on connecting to
                peers. If no common application is found, the peers will disconnect. Messages will only
                be sent to a peer if that peer actually has declared support for the application id of 
                the message.
        --&gt;
        &lt;Acct id="16777216" vendor="10415" /&gt;
        &lt;Acct id="16777216" vendor="0" /&gt;
        &lt;Auth id="16777216" vendor="10415"/&gt;
        &lt;Auth id="16777216" vendor="0" /&gt;

        &lt;!-- 
                Supported Vendor IDs - list of values which will be sent in the CER/CEA in the
                Supported-Vendor-ID AVPs
        --&gt;
        &lt;SupportedVendor vendor="10415" /&gt;

        &lt;!--
                Realm routing definition.
                Each Realm can have a different table of peers to route towards. In case the Destination
                Realm AVP contains a Realm not defined here, the DefaultRoute entries will be used.

                Note: In case a message already contains a Destination-Host AVP, Realm Routeing will not be
                applied.
                Note: Routing will only happen towards connected and application id supporting peers.
                
                The metric is used to order the list of prefered peers, while looking for a connected and
                application id supporting peer. In the end, of course, just one peer will be selected.
        --&gt;
        &lt;Realm name="ims.smilecoms.com"&gt;
                &lt;Route FQDN="pcrf1.ims.smilecoms.com" metric="3"/&gt;
                &lt;Route FQDN="pcrf2.ims.smilecoms.com" metric="5"/&gt;
        &lt;/Realm&gt;

        &lt;Realm name="temp.ims.smilecoms.com"&gt;
                &lt;Route FQDN="pcrf3.ims.smilecoms.com" metric="7"/&gt;
                &lt;Route FQDN="pcrf4.ims.smilecoms.com" metric="11"/&gt;
        &lt;/Realm&gt;
        &lt;DefaultRoute FQDN="pcrf5.ims.smilecoms.com" metric="15"/&gt;
        &lt;DefaultRoute FQDN="pcrf6.ims.smilecoms.com" metric="13"/&gt;


&lt;/DiameterPeer&gt;

</programlisting>
      </example>
    </section>

    <section/>
  </section>
</chapter>
