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<chapter>
  <header>
    <copyright>
      <year>2004</year><year>2009</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
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      Erlang Public License along with this software. If not, it can be
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      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
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      under the License.
    
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    <title>Manager Functional Description</title>
    <prepared></prepared>
    <responsible></responsible>
    <docno></docno>
    <approved></approved>
    <checked></checked>
    <date></date>
    <rev></rev>
    <file>snmp_manager_funct_descr.xml</file>
  </header>

  <section>
    <title>Features</title>
    <marker id="features"></marker>
    <p>The manager provided with the tool is a lightweight manager
      that basically provides a means to communicate with agents.</p>
    <p>It does not really implement any management capabilities by 
      itself. That is up to the <em>user</em>. 
      </p>
    <p>A <em>user</em> in this context is basically a module implementing
      the <seealso marker="snmpm_user">snmpm_user</seealso> behaviour. 
      A <em>user</em> can issue snmp requests and receive 
      notification/traps.</p>
    <p>Agents to be accessed by the manager needs to be registered by 
      a user. Once registered, they can be accessed by all registered 
      users.</p>
    <p>Notifications/traps from an agent is delivered to the user that 
      did the registration.</p>
    <p>Any message from an agent that is not registered is delivered to 
      the <em>default user</em>.</p>
    <p>By default, the <em>default user</em> is set to the 
      <c>snmpm_user_default</c> module, which simply sends an info message
      to the error_logger. It is however highly recommended that this
      module be replaced by another that does something useful
      (see <seealso marker="snmp_config#configuration_params">configuration params</seealso> for more info).</p>
    <p>When using version 3, then (at least one) <em>usm user</em> has to 
      be registered.</p>
    <p>Requests can be issued in two different ways. Synchronous (see
      <seealso marker="snmpm#sync_set">sync_set</seealso>,
      <seealso marker="snmpm#sync_get">sync_get</seealso>, 
      <seealso marker="snmpm#sync_get_next">sync_get_next</seealso> and 
      <seealso marker="snmpm#sync_get_bulk">sync_get_bulk</seealso>)
      and asynchronous (see 
      <seealso marker="snmpm#async_set">async_set</seealso>,
      <seealso marker="snmpm#async_get">async_get</seealso>, 
      <seealso marker="snmpm#async_get_next">async_get_next</seealso> and  
      <seealso marker="snmpm#async_get_bulk">async_get_bulk</seealso>). 
      With synchronous 
      the snmp reply is returned by the function. With asynchronous,
      the reply will instead be delivered through a call to one of the
      <c>handle_pdu</c> callback function defined by the 
      <seealso marker="snmpm_user#handle_pdu">handle_pdu</seealso> 
      behaviour.</p>
  </section>

  <section>
    <title>Operation</title>
    <marker id="operation"></marker>
    <p>The following steps are needed to get the manager running:</p>
    <list type="ordered">
      <item>
        <p>[optional] Implement the default user.</p>
      </item>
      <item>
        <p>Implement the user(s).</p>
      </item>
      <item>
        <p>Configure the application (manager).</p>
      </item>
      <item>
        <p>Start the application (manager).</p>
      </item>
      <item>
        <p>Register the user(s).</p>
      </item>
      <item>
        <p>The user(s) register their agents.</p>
      </item>
    </list>
  </section>

  <section>
    <title>MIB loading</title>
    <marker id="mib_loading"></marker>
    <p>It is possible to load mibs into the manager, but this is not 
      necessary for normal operation, and not recommended.</p>
  </section>
</chapter>

