kea/tests/tools/dhcp-ubench/dhcp-perf-guide.xml

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<?xml-stylesheet href="bind10-guide.css" type="text/css"?>

<book>
  <bookinfo>
    <title>DHCP Performance Guide</title>
    <!-- <subtitle>Various aspects of DHCP Performance in BIND 10</subtitle> -->

    <copyright>
      <year>2012</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
    <author>
      <firstname>Tomasz</firstname>
      <surname>Mrugalski</surname>
    </author>
    <author>
      <firstname>Marcin</firstname>
      <surname>Siodelski</surname>
    </author>
    <abstract>
      <para>BIND 10 is a framework that features Domain Name System
      (DNS) suite and Dynamic Host Configuration Protocol (DHCP)
      servers with development managed by Internet Systems Consortium (ISC).
      This document describes various aspects of DHCP performance,
      measurements and tuning. It covers BIND 10 DHCP (codename Kea),
      existing ISC DHCP4 software, perfdhcp (a DHCP performance
      measurement tool) and other related topics.</para>
    </abstract>

    <releaseinfo>This is a companion document for BIND 10 version
    &__VERSION__;.</releaseinfo>

  </bookinfo>

  <preface>
    <title>Preface</title>

    <section id="acknowledgements">
      <title>Acknowledgements</title>

      <para>ISC would like to acknowledge generous support for
      BIND 10 development of DHCPv4 and DHCPv6 components provided
      by <ulink url="http://www.comcast.com/">Comcast</ulink>.</para>

    </section>

  </preface>

  <chapter id="intro">
    <title>Introduction</title>
    <para>
      This document is in its early stages of development. It is
      expected to grow significantly in a near future. It will
      cover topics like database backend perfomance measurements,
      pros an cons of various optimization techniques and
      tools.
    </para>

  </chapter>

  <chapter id="dhcp4">
    <title>ISC DHCP 4.x</title>
    <para>
      TODO: Write something about ISC DHCP4 here.
    </para>
  </chapter>

  <chapter id="kea">
    <title>Kea</title>
    <para>

    </para>

    <section>
      <title>Backend performance evaluation</title>
      <para>
        Kea will support several different database backends, using
        both popular databases (like MySQL or SQLite) and
        custom-developed solutions (like in-memory database).  BIND 10
        source code features set of performance microbenchmarks.
        These are small tools written in C/C++ that simulate expected
        DHCP server behaviour and evaluate the performance of
        considered databases. As implemented benchmarks are not really
        simulating DHCP operation, but rather use set of primitives
        that can be used by a real server, they are called
        micro-benchmarks.
      </para>

      <para>Although there are many operations and data types that
      server could store in a database, the most frequently used data
      type is lease information. Although lease information for IPv4
      and IPv6 differs slightly, it is expected that the performance
      differences will be minimal between IPv4 and IPv6 lease operations.
      Therefore each test uses lease4 table for performance measurements.
      </para>

      <para>All benchmarks are implemented as single threaded applications
      that take advantage of a single database connection.</para>

      <para>
        Those benchmarks are stored in tests/tools/dhcp-ubench
        directory. This directory contains simplified prototypes for
        various DB back-ends that are planned or considered as a
        backend engine for BIND10 DHCP.  Athough trivial now, they are
        expected to evolve into useful tools that will allow users to
        measure performance in their specific environment.
      </para>

    <para>
      Currently the following benchmarks are implemented:
      <itemizedlist>
        <listitem><para>in memory+flat file</para></listitem>
        <listitem><para>SQLite</para></listitem>
        <listitem><para>MySQL</para></listitem>
      </itemizedlist>
    </para>

    <para>
      As they require additional (sometimes heavy) dependencies, they are not
      built by default. Actually, their build system is completely separated.
      It will be eventually merged with the main BIND10 makefile system, but
      that is a low priority for now.
    </para>

    <para>
      All benchmarks will follow the same pattern:
      <orderedlist>
        <listitem><para>prepare operation (connect to a database, create a file etc.)</para></listitem>
        <listitem><para>Measure timestamp 0</para></listitem>
        <listitem><para>Commit new lease4 (repeated X times)</para></listitem>
        <listitem><para>Measure timestamp 1</para></listitem>
        <listitem><para>Search for random lease4 (repeated X times)</para></listitem>
        <listitem><para>Measure timestamp 2</para></listitem>
        <listitem><para>Update existing lease4 (repeated X times)</para></listitem>
        <listitem><para>Measure timestamp 3</para></listitem>
        <listitem><para>Delete existing lease4 (repeated X times)</para></listitem>
        <listitem><para>Measure timestamp 4</para></listitem>
        <listitem><para>Print out statistics, based on X and measured timestamps.</para></listitem>
      </orderedlist>

      Although this approach does not attempt to simulate actual DHCP server
      operation that has mix of all steps intervening, it answers the
      questions about basic database strenghts and weak points. In particular
      it can show what is the impact of specific DB optimizations, like
      changing engine, optimizing for writes/reads etc.
    </para>

    <para>
      The framework attempts to do the same amount of operations for every
      backend thus allowing fair complarison between them.
    </para>
    </section>

    <section id="mysql-backend">
      <title>MySQL backend</title>
      <para>MySQL backend requires MySQL client development libraries. It uses
      mysql_config tool (that works similar to pkg-config) to discover required
      compilation and linking options. To install required packages on Ubuntu,
      use the following command:

      <screen>$ <userinput>sudo apt-get install mysql-client mysql-server libmysqlclient-dev</userinput></screen>

      Make sure that MySQL server is running. Make sure that you have your setup
      configured so there is a user that is able to modify used database.</para>

      <para>Before running tests, you need to initialize your database. You can
      use mysql.schema script for that purpose. WARNING: It will drop existing
      Kea database. Do not run this on your production server. Assuming your
      MySQL user is kea, you can initialize your test database by:

      <screen>$ <userinput>mysql -u kea -p &lt; mysql.schema</userinput></screen>
      </para>

      <para>After database is initialized, you are ready to run the test:
      <screen>$ <userinput>./mysql_ubench</userinput></screen>

      or

      <screen>$ <userinput>./mysql_ubench &gt; results->mysql.txt</userinput></screen>

      Redirecting output to a file is important, because for each operation
      there is a single character printed to show progress. If you have a slow
      terminal, this may considerably affect test perfromance. On the other hand,
      printing something after each operation is required, as poor DB setting
      may slow down operations to around 20 per second. Observant user is expected
      to note that initial dots are printed too slowly and abort the test.</para>

      <para>Currently all default parameters are hardcoded. Default values can be
      overwritten using command line switches. Although all benchmarks take
      the same list of parameters, some of them are specific to a given backend
      type. To get a list of supported parameters, run your benchmark with -h option:

      <screen>$ <userinput>./mysql_ubench -h</userinput>
This is a benchmark designed to measure expected performance
of several backends. This particular version identifies itself
as following:
MySQL client version is 5.5.24

Possible command-line parameters:
 -h - help (you are reading this)
 -m hostname - specifies MySQL server to connect (MySQL backend only)
 -u username - specifies MySQL user name (MySQL backend only)
 -p password - specifies MySQL passwod (MySQL backend only)
 -f name - database or filename (MySQL, SQLite and memfile)
 -n integer - number of test repetitions (MySQL, SQLite and memfile)
 -s yes|no - synchronous/asynchronous operation (MySQL, SQLite and memfile)
 -v yes|no - verbose mode (MySQL, SQLite and memfile)
 -c yes|no - should compiled statements be used (MySQL only)
</screen>

      </para>

      <section>
        <title>MySQL tweaks</title>

        <para>One parameter that has huge impact on performance is a a backend engine.
        You can get a list of engines of your MySQL implementation by using

        <screen>&gt; <userinput>show engines;</userinput></screen>

        in your mysql client. Two notable engines are MyISAM and InnoDB. mysql_ubench will
        use MyISAM for synchronous mode and InnoDB for asynchronous.</para>
    </section>
    </section>


    <section id="sqlite-ubench">
      <title>SQLite-ubench</title>
      <para>SQLite backend requires both sqlite3 development and run-time package. Their
      names may vary from system to system, but on Ubuntu 12.04 they are called
      sqlite3 libsqlite3-dev. To install them, use the following command:

      <screen>&gt; <userinput>sudo apt-get install sqlite3 libsqlite3-dev</userinput></screen>

      Before running the test the database has to be created. Use the following command for that:
      <screen>&gt; <userinput>cat sqlite.schema | sqlite3 sqlite.db</userinput></screen>

      A new database called sqlite.db will be created. That is the default name used
      by sqlite_ubench test. If you prefer other name, make sure you update
      sqlite_ubench.cc accordingly.</para>

      <para>Once the database is created, you can run tests:
      <screen>&gt; <userinput>./sqlite_ubench</userinput></screen>
      or
      <screen>&gt; <userinput>./sqlite_ubench > results-sqlite.txt</userinput></screen>
      </para>

      <section id="sqlite-tweaks">
        <title>SQLite tweaks</title>
        <para>To modify default sqlite_ubench parameters, command line
        switches can be used. Currently supported parameters are
        (default values specified in brackets):
        <orderedlist>
          <listitem><para>-f filename - name of the database file ("sqlite.db")</para></listitem>
          <listitem><para>-n num - number of iterations (100)</para></listitem>
          <listitem><para>-s yes|no - should the operations be performend in synchronous (yes)
          or asynchronous (no) manner (yes)</para></listitem>
          <listitem><para>-v yes|no - verbose mode. Should the test print out progress? (yes)</para></listitem>
          <listitem><para>-c yes|no - compiled statements. Should the SQL statements be precompiled?</para></listitem>
        </orderedlist>
        </para>

        <para>SQLite can run in asynchronous or synchronous mode. This
        mode can be controlled by using sync parameter. It is set
        using (PRAGMA synchronous = ON or OFF).</para>

        <para>Another tweakable feature is journal mode. It can be
        turned to several modes of operation. Its value can be
        modified in SQLite_uBenchmark::connect().  See
        http://www.sqlite.org/pragma.html#pragma_journal_mode for
        detailed explanantion.</para>
      </section>
    </section>

    <section id="memfile-ubench">
      <title>memfile-ubench</title>
      <para>Memfile backend is custom developed prototype backend that
      somewhat mimics operation of ISC DHCP4. It uses in-memory
      storage using standard C++ and boost mechanisms (std::map and
      boost::shared_ptr&lt;&gt;). All database changes are also
      written to a lease file. That file is strictly write-only. This
      approach takes advantage of the fact that simple append is faster
      than edition with potential whole file relocation.</para>

      <section id="memfile-tweaks">
        <title>memfile tweaks</title>
        <para>To modify default memfile_ubench parameters, command line
        switches can be used. Currently supported parameters are
        (default values specified in brackets):
        <orderedlist>
          <listitem><para>-f filename - name of the database file ("dhcpd.leases")</para></listitem>
          <listitem><para>-n num - number of iterations (100)</para></listitem>
          <listitem><para>-s yes|no - should the operations be performend in synchronous (yes)
          or asynchronous (no) manner (yes)</para></listitem>
          <listitem><para>-v yes|no - verbose mode. Should the test print out progress? (yes)</para></listitem>
        </orderedlist>
        </para>

        <para>memfile can run in asynchronous or synchronous mode. This
        mode can be controlled by using sync parameter. It uses
        fflush() and fsync() in synchronous mode to make sure that
        data is not buffered and physically stored on disk.</para>
      </section>
    </section>

    <section>
      <title>Performance measurements</title>
      <para>This section contains sample results for backend performance measurements,
      taken using microbenchmarks. Tests were conducted on reasonably powerful machine:
      <screen>
CPU: Quad-core Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz (8 logical cores)
HDD: 1,5TB Seagate Barracuda ST31500341AS 7200rpm (used only one of them), ext4 partition
OS: Ubuntu 12.04, running kernel 3.2.0-26-generic SMP x86_64
compiler: g++ (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
MySQL version: 5.5.24
SQLite version: 3.7.9sourceid version is 2011-11-01 00:52:41 c7c6050ef060877ebe77b41d959e9df13f8c9b5e</screen>
      </para>

      <para>Benchmarks were run in two series: synchronous and
      asynchronous. As those modes offer radically different
      performances, synchronous mode was conducted for 1000 (one
      thousand) repetitions and asynchronous mode was conducted for
      100000 (hundred thousand) repetitions.</para>

      <!-- raw results sync -->
      <table><title>Synchronous results</title>
      <tgroup cols='6' align='center' colsep='1' rowsep='1'>
        <colspec colname='Backend'/>
        <colspec colname='Num' />
        <colspec colname='Create'/>
        <colspec colname='Search'/>
        <colspec colname='Update'/>
        <colspec colname='Delete'/>
        <colspec colname='Average'/>
        <thead>
          <row>
            <entry>Backend</entry>
            <entry>Operations</entry>
            <entry>Create</entry>
            <entry>Search</entry>
            <entry>Update</entry>
            <entry>Delete</entry>
            <entry>Average</entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry>MySQL</entry>
            <entry>1000</entry>
            <entry>31.603978s</entry>
            <entry> 0.116612s</entry>
            <entry>27.964191s</entry>
            <entry>27.695209s</entry>
            <entry>21.844998s</entry>
          </row>

          <row>
            <entry>SQLite</entry>
            <entry>1000</entry>
            <entry>61.421356s</entry>
            <entry> 0.033283s</entry>
            <entry>59.476638s</entry>
            <entry>56.034150s</entry>
            <entry>44.241357s</entry>
          </row>

          <row>
            <entry>memfile</entry>
            <entry>1000</entry>
            <entry>41.711886s</entry>
            <entry> 0.000724s</entry>
            <entry>42.267578s</entry>
            <entry>42.169679s</entry>
            <entry>31.537467s</entry>
          </row>

        </tbody>
      </tgroup>
      </table>

      <para>Following parameters were measured for asynchronous mode.
      MySQL and SQLite were run with 100 thousand repetitions. Memfile
      was run for 1 million repetitions due to much larger performance.</para>

      <!-- raw results async -->
      <table><title>Asynchronous results</title>
      <tgroup cols='6' align='center' colsep='1' rowsep='1'>
        <colspec colname='Backend'/>
        <colspec colname='Num' />
        <colspec colname='Create'/>
        <colspec colname='Search'/>
        <colspec colname='Update'/>
        <colspec colname='Delete'/>
        <colspec colname='Average'/>
        <thead>
          <row>
            <entry>Backend</entry>
            <entry>Operations</entry>
            <entry>Create [s]</entry>
            <entry>Search [s]</entry>
            <entry>Update [s]</entry>
            <entry>Delete [s]</entry>
            <entry>Average [s]</entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry>MySQL</entry>
            <entry>100000</entry>
            <entry>10.584842s</entry>
            <entry>10.386402s</entry>
            <entry>10.062384s</entry>
            <entry> 8.890197s</entry>
            <entry> 9.980956s</entry>
          </row>

          <row>
            <entry>SQLite</entry>
            <entry>100000</entry>
            <entry> 3.710356s</entry>
            <entry> 3.159129s</entry>
            <entry> 2.865354s</entry>
            <entry> 2.439406s</entry>
            <entry> 3.043561s</entry>
          </row>

          <row>
            <entry>memfile</entry>
            <entry>1000000 (sic!)</entry>
            <entry> 6.084131s</entry>
            <entry> 0.862667s</entry>
            <entry> 6.018585s</entry>
            <entry> 5.146704s</entry>
            <entry> 4.528022s</entry>
          </row>

        </tbody>
      </tgroup>
      </table>

      <para>Presented performance results can be computed into operations per second metrics.
      It should be noted that due to large differences between various operations (sometime
      over 3 orders of magnitude), it is difficult to create a simple, readable chart with
      that data.</para>

      <table id="tbl-perf-results"><title>Estimated performance</title>
      <tgroup cols='6' align='center' colsep='1' rowsep='1'>
        <colspec colname='Backend'/>
        <colspec colname='Create'/>
        <colspec colname='Search'/>
        <colspec colname='Update'/>
        <colspec colname='Delete'/>
        <colspec colname='Average'/>
        <thead>
          <row>
            <entry>Backend</entry>
            <entry>Create [oper/s]</entry>
            <entry>Search [oper/s]</entry>
            <entry>Update [oper/s]</entry>
            <entry>Delete [oper/s]</entry>
            <entry>Average [oper/s]</entry>
          </row>
        </thead>
        <tbody>
          <row>
            <entry>MySQL (async)</entry>
            <entry>9447.47</entry>
            <entry>9627.97</entry>
            <entry>9938.00</entry>
            <entry>11248.34</entry>
            <entry>10065.45</entry>
          </row>

          <row>
            <entry>SQLite (async)</entry>
            <entry>26951.59</entry>
            <entry>31654.29</entry>
            <entry>34899.70</entry>
            <entry>40993.59</entry>
            <entry>33624.79</entry>
          </row>

          <row>
            <entry>memfile (async)</entry>
            <entry>164362.01</entry>
            <entry>1159195.84</entry>
            <entry>166152.01</entry>
            <entry>194299.11</entry>
            <entry>421002.24</entry>
          </row>


          <row>
            <entry>MySQL (sync)</entry>
            <entry>31.64</entry>
            <entry>8575.45</entry>
            <entry>35.76</entry>
            <entry>36.11</entry>
            <entry>2169.74</entry>
          </row>

          <row>
            <entry>SQLite (sync)</entry>
            <entry>16.28</entry>
            <entry>20045.37</entry>
            <entry>16.81</entry>
            <entry>17.85</entry>
            <entry>7524.08</entry>
          </row>

          <row>
            <entry>memfile (sync)</entry>
            <entry>23.97</entry>
            <entry>1381215.47</entry>
            <entry>23.66</entry>
            <entry>23.71</entry>
            <entry>345321.70</entry>
          </row>

        </tbody>
      </tgroup>
      </table>

      <mediaobject>
        <imageobject>
          <imagedata fileref="performance-results-graph1.png" format="PNG"/>
        </imageobject>
        <textobject>
          <phrase>Performance measurements</phrase>
        </textobject>
        <caption>
          <para>Graphical representation of the performance results
          presented in table <xref linkend="tbl-perf-results" />.</para>
        </caption>
      </mediaobject>

    </section>

    <section>
      <title>Possible further optimizations</title>
      <para>
        For debugging purposes the code was compiled with -g -O0
        flags. While majority of the time was spent in backend
        functions (that was probably compiled with -O2 flags), the
        benchmark code could perform faster, when compiled with -O2,
        rather than -O0. That is expected to affect memfile benchmark.
      </para>
      <para>
        Currently all operations were conducted on one by one
        basis. Each operation was treated as a separate
        transaction. Grouping X operations together will potentially
        bring almost X fold increase in synchronous operations.
        Extension for this benchmark in this regard should be considered.
        That affects only write operations (insert, update and delete). Read
        operations (search) are expected to be barely affected.
      </para>
      <para>
        Multi-threaded or multi-process benchmark may be considered in
        the future. It may be somewhat difficult as only some backends
        support concurrent access.
      </para>
    </section>

  </chapter>

  <chapter id="perfdhcp">
    <title>perfdhcp</title>
    <section>
      <title>Purpose</title>
      <para>
        There is a growing need to evaluate performance of DHCP servers in
        different traffic conditions to understand their bottle necks.
        This helps to elimante bugs in existing DHCP software as well
        as make informed decisions regarding new DHCP software designs
        to significantly improve its performance. The perfdhcp tool has
        been created to fill the gap in performance measurement capabilities
        mostly. However, the number of implemented features and parameters
        exposed to the user make this tool useful for functional testing as
        well.
      </para>
    </section>
    <section id="perfdhcp-key-features">
      <title>Key features</title>
      <para>
        The perfdhcp exposes the number of command line parameters to
        control DHCP message exchanges. Currently they fall back to
        the following categories:
        <orderedlist>
          <listitem>
            <para>
              Rate control - control how many DHCP exchanges
              are initiated within a period of time. Tool can also simulate
              best effort conditions attempting to initiate as many DHCP
              packet exchanges within a unit of time as possible.
            </para>
          </listitem>
          <listitem>
            <para>
              Test exit specifiers - control the conditions when test
              completes including number of initiated exchanges, test period or
              maximum number of dropped packets.
            </para>
          </listitem>
          <listitem>
            <para>
              Packet templates - specify files containing packet templates that
              are used by perfdhcp to create custom DHCP messages instead of
              default. Tool also allows to specify number of values indicating
              offsets of variable values within a packet that are modified in
              flight by the tool.
            </para>
          </listitem>
          <listitem>
            <para>
              Reporting - for each test produce the set of performance data
              including achieved packet exchange rate (server performance).
              There is also a number of diagnostic selectors available that
              enable periodic (intermediate) reporting, packet timestamps
              printing and detailed information about perfdhcp internal
              states (for debugging).
            </para>
          </listitem>
          <listitem>
            <para>
              Different mode of operations - specify DHCP version used
              (v4 or v6), 2-way or 4-way exchanges, use Rapid Commit option
              for DHCPv6.
            </para>
          </listitem>
          <listitem>
            <para>
              IP layer options - specify local/remote address, local interface
              and local port to be used for communication with DHCP server.
            </para>
          </listitem>
        </orderedlist>
      </para>
    </section>
    <section id="perfdhcp-command-line">
      <title>Command line options</title>
      <para>
        The following command line options may be used with perfdhcp tool.
        This summary also presents its possible exit codes as well as
        error counters printed along when test is complete:
        <screen>$ <userinput>./perfdhcp -h</userinput>
<![CDATA[perfdhcp [-hv] [-4|-6] [-r<rate>] [-t<report>] [-R<range>] [-b<base>]
    [-n<num-request>] [-p<test-period>] [-d<drop-time>] [-D<max-drop>]
    [-l<local-addr|interface>] [-P<preload>] [-a<aggressivity>]
    [-L<local-port>] [-s<seed>] [-i] [-B] [-c] [-1]
    [-T<template-file>] [-X<xid-offset>] [-O<random-offset]
    [-E<time-offset>] [-S<srvid-offset>] [-I<ip-offset>]
    [-x<diagnostic-selector>] [-w<wrapped>] [server]

The [server] argument is the name/address of the DHCP server to
contact.  For DHCPv4 operation, exchanges are initiated by
transmitting a DHCP DISCOVER to this address.

For DHCPv6 operation, exchanges are initiated by transmitting a DHCP
SOLICIT to this address.  In the DHCPv6 case, the special name 'all'
can be used to refer to All_DHCP_Relay_Agents_and_Servers (the
multicast address FF02::1:2), or the special name 'servers' to refer
to All_DHCP_Servers (the multicast address FF05::1:3).  The [server]
argument is optional only in the case that -l is used to specify an
interface, in which case [server] defaults to 'all'.

The default is to perform a single 4-way exchange, effectively pinging
the server.
The -r option is used to set up a performance test, without
it exchanges are initiated as fast as possible.

Options:
-1: Take the server-ID option from the first received message.
-4: DHCPv4 operation (default). This is incompatible with the -6 option.
-6: DHCPv6 operation. This is incompatible with the -4 option.
-a<aggressivity>: When the target sending rate is not yet reached,
    control how many exchanges are initiated before the next pause.
-b<base>: The base mac, duid, IP, etc, used to simulate different
    clients.  This can be specified multiple times, each instance is
    in the <type>=<value> form, for instance:
    (and default) mac=00:0c:01:02:03:04.
-d<drop-time>: Specify the time after which a request is treated as
    having been lost.  The value is given in seconds and may contain a
    fractional component.  The default is 1 second.
-E<time-offset>: Offset of the (DHCPv4) secs field / (DHCPv6)
    elapsed-time option in the (second/request) template.
    The value 0 disables it.
-h: Print this help.
-i: Do only the initial part of an exchange: DO or SA, depending on
    whether -6 is given.
-I<ip-offset>: Offset of the (DHCPv4) IP address in the requested-IP
    option / (DHCPv6) IA_NA option in the (second/request) template.
-l<local-addr|interface>: For DHCPv4 operation, specify the local
    hostname/address to use when communicating with the server.  By
    default, the interface address through which traffic would
    normally be routed to the server is used.
    For DHCPv6 operation, specify the name of the network interface
    via which exchanges are initiated.
-L<local-port>: Specify the local port to use
    (the value 0 means to use the default).
-O<random-offset>: Offset of the last octet to randomize in the template.
-P<preload>: Initiate first <preload> exchanges back to back at startup.
-r<rate>: Initiate <rate> DORA/SARR (or if -i is given, DO/SA)
    exchanges per second.  A periodic report is generated showing the
    number of exchanges which were not completed, as well as the
    average response latency.  The program continues until
    interrupted, at which point a final report is generated.
-R<range>: Specify how many different clients are used. With 1
    (the default), all requests seem to come from the same client.
-s<seed>: Specify the seed for randomization, making it repeatable.
-S<srvid-offset>: Offset of the server-ID option in the
    (second/request) template.
-T<template-file>: The name of a file containing the template to use
    as a stream of hexadecimal digits.
-v: Report the version number of this program.
-w<wrapped>: Command to call with start/stop at the beginning/end of
    the program.
-x<diagnostic-selector>: Include extended diagnostics in the output.
    <diagnostic-selector> is a string of single-keywords specifying
    the operations for which verbose output is desired.  The selector
    keyletters are:
   * 'a': print the decoded command line arguments
   * 'e': print the exit reason
   * 'i': print rate processing details
   * 'r': print randomization details
   * 's': print first server-id
   * 't': when finished, print timers of all successful exchanges
   * 'T': when finished, print templates
-X<xid-offset>: Transaction ID (aka. xid) offset in the template.

DHCPv4 only options:
-B: Force broadcast handling.

DHCPv6 only options:
-c: Add a rapid commit option (exchanges will be SA).

The remaining options are used only in conjunction with -r:

-D<max-drop>: Abort the test if more than <max-drop> requests have
    been dropped.  Use -D0 to abort if even a single request has been
    dropped.  If <max-drop> includes the suffix '%', it specifies a
    maximum percentage of requests that may be dropped before abort.
    In this case, testing of the threshold begins after 10 requests
    have been expected to be received.
-n<num-request>: Initiate <num-request> transactions.  No report is
    generated until all transactions have been initiated/waited-for,
    after which a report is generated and the program terminates.
-p<test-period>: Send requests for the given test period, which is
    specified in the same manner as -d.  This can be used as an
    alternative to -n, or both options can be given, in which case the
    testing is completed when either limit is reached.
-t<report>: Delay in seconds between two periodic reports.

Errors:
- tooshort: received a too short message
- orphans: received a message which doesn't match an exchange
   (duplicate, late or not related)
- locallimit: reached to local system limits when sending a message.

Exit status:
The exit status is:
0 on complete success.
1 for a general error.
2 if an error is found in the command line arguments.
3 if there are no general failures in operation, but one or more
  exchanges are not successfully completed.
]]>
        </screen>
      </para>
    </section>
    <section id="starting-perfdhcp">
      <title>Starting perfdhcp</title>
      <para>
        In order to run performance test at least two separate systems
        have to be installed: client and server. The first one has to have
        perfdhcp tool installed, the latter has to have DHCP server
        running (v4 or v6). If only single system is available the client
        and server can be run on virtual machines (running on the same
        phisical system) but in this case performance data may be heavily
        impacted by the performance of VMs.
      </para>
      <para>
        The DHCP operates on low port numbers (67 for DHCPv4 relays and
        547 for DHCPv6). Running perfdhcp with non-root priviliges will
        usually result in the error message similar to this:
        <screen><userinput>$./perfdhcp -4 -l eth3 -r 100 all</userinput>
Error running perfdhcp: Failed to bind socket 3 to 172.16.1.2/port=67
        </screen>
        perfdhcp has the '-L' command line option that
        imposes use of custom local port. Thus the following command
        line will work:
        <screen><userinput>$./perfdhcp -4 -l eth3 -r 100 -L 10067 all</userinput></screen>
        but in the standard configuration no responses will be received
        from the ISC DHCP server because server responds to default relay
        port 67.
        Alternative way to overcome this issue  is to run perfdhcp as root.
      </para>
      <para>
        Currently, perfdhcp is seen from the server perspective as relay agent.
        This simplifies its implementation (specifically there is no need to
        receive traffic sent to braodcast addresses). This imposes that IPv4
        address has to be set manually on the interface that will be used to
        communicate with the server. For example, if DHCPv4 server is listening
        on the interface connected to 172.16.1.0 subnet, interface on client
        machine has to have network address assigned from the same subnet
        on one of its interfaces connected to this subnet:
        <screen><userinput>#ifconfig eth3 172.16.1.2. netmask 255.255.255.0 up</userinput></screen>
      </para>
    </section>
    <section id="perfdhcp-commandline-examples">
      <title>perfdhcp command line examples</title>
      <para>
        In this section the perfdhcp command line examples
        are presented as a quick start guide for new users. For the
        detailed list of command line options refer to
        <xref linkend="perfdhcp-command-line"/>.
      </para>
      <section id="perfdhcp-basic-usage">
        <title>Example: basic usage</title>
        <para>
          If server is listening on interface with IPv4 address 172.16.1.1
          the simpliest perfdhcp command line will look like this:
          <screen><userinput>#./perfdhcp 172.16.1.1</userinput>
***Rate statistics***
Rate: 206.345

***Statistics for: DISCOVER-OFFER***
sent packets: 21641
received packets: 350
drops: 21291
orphans: 0

min delay: 9.022 ms
avg delay: 143.100 ms
max delay: 259.303 ms
std deviation: 56.074 ms
collected packets: 30

***Statistics for: REQUEST-ACK***
sent packets: 350
received packets: 268
drops: 82
orphans: 0

min delay: 3.010 ms
avg delay: 152.470 ms
max delay: 258.634 ms
std deviation: 56.936 ms
collected packets: 0
          </screen>
          In this case perfdhcp will use remote address 172.16.1.1 as a
          destination address and will use suitable local interface for
          communication. Since, no rate control parameters have been specified
          it will be initiating DHCP exchanges with the maximum possible
          rate (it will try to initiate maximum number of exchanges per
          second and count number of completed exchanged). Due to server's
          performance constraints, many DHCP packets sent to server are likely
          to be dropped. The performance test will be running until it is
          not interrupted by the user (with ^C).
        </para>
        <para>
          The default performance statistics reported by perfdhcp have the
          following meaning:
          <itemizedlist>
            <listitem><para>Rate - number of packet exchanges (packet sent
            to the server and matching response received from the server)
            completed within a second.</para></listitem>
            <listitem><para>sent packets - total number of DHCP packets of
            a specific type sent to the server.</para></listitem>
            <listitem><para>received packets - total number of DHCP packets
            of specific type received from the server.</para></listitem>
            <listitem><para>drops - number of dropped packets for the
            particular exchange. Number of dropped packets is calculated as
            a difference between number of sent packets and number of
            response packets received from the server. It is likely that
            server sent the reponse but perfdhcp execution had ended before
            reponse arrived. In such case this packet will be assumed
            dropped.</para></listitem>
            <listitem><para>orphans - number of packets that have been
            received from the server and did not match any packet sent by
            perfdhcp. This may occur if received packet has been sent
            to some other host or if exchange time out has occured and
            has been been garbage collected.</para></listitem>
            <listitem><para>min delay - minimum delay that occured between
            sending the packet to the server and receiving reponse from
            it.</para></listitem>
            <listitem><para>avg delay - average delay between sending the
            packet of the specific type the server and receiving response
            from it.</para></listitem>
            <listitem><para>max delay - maximum delat that occured between
            sedning the packet to the server and receiveing response from
            it.</para></listitem>
            <listitem><para>std deviation - standard deviation of delay
            between sending the packet of a specific type to the server and
            receiving response from it.</para></listitem>
            <listitem><para>collected packets - number of garbage collected
            sent packets. Packets may get garbage collected when waiting time
            for server response exceeds value set with
            <![CDATA[-d<drop-time>]]>.</para></listitem>
          </itemizedlist>
        </para>
        <para>
          perfdhcp allows to run the test using specified interface:
          <screen><userinput>#./perfdhcp -l eth3</userinput></screen>
          or local address assigned to it:
          <screen><userinput>#./perfdhcp -l 172.16.1.2</userinput></screen>
        </para>
      </section>
      <section id="perfdhcp-rate-control">
        <title>Example: rate control</title>
        <para>
          In the examples above perfdhcp initiates new exchanges with best
          effort rate. In this case many packets is expected to be dropped by the
          server due to performance limitations. Many times it is desired to set
          the expected (reasonable) rate and verify if generated traffic is
          handled without packet dropes by DHCP server. The following command will
          make perfdhcp to initiate 300 4-way exchanges per second and test will
          last for 60 seconds:
          <screen><userinput>#./perfdhcp -l eth3 -p 60 -r 300</userinput>
***Rate statistics***
Rate: 256.683 exchanges/second, expected rate: 300 exchanges/second

***Statistics for: DISCOVER-OFFER***
sent packets: 17783
received packets: 15401
drops: 2382
orphans: 0

min delay: 0.109 ms
avg delay: 75.756 ms
max delay: 575.614 ms
std deviation: 60.513 ms
collected packets: 11

***Statistics for: REQUEST-ACK***
sent packets: 15401
received packets: 15317
drops: 84
orphans: 0

min delay: 0.536 ms
avg delay: 72.072 ms
max delay: 576.749 ms
std deviation: 58.189 ms
collected packets: 0
          </screen>
          Note that in this example the packet drops have been significantly
          reduced thanks to setting reasonable rate. The non-zero number of
          packet drops and achived rate (256/s) below expected rate (300/s)
          indicate that server's measured performance is lower than 300 leases
          per second. Further rate decrease should eliminate most of the packet
          drops and bring achived rate close to expected rate:
          <screen><userinput>#./perfdhcp -l eth3 -p 60 -r 100 -R 30</userinput>
***Rate statistics***
Rate: 99.8164 exchanges/second, expected rate: 100 exchanges/second

***Statistics for: DISCOVER-OFFER***
sent packets: 5989
received packets: 5989
drops: 0
orphans: 0

min delay: 0.023 ms
avg delay: 2.198 ms
max delay: 181.760 ms
std deviation: 9.429 ms
collected packets: 0

***Statistics for: REQUEST-ACK***
sent packets: 5989
received packets: 5989
drops: 0
orphans: 0

min delay: 0.473 ms
avg delay: 2.355 ms
max delay: 189.658 ms
std deviation: 5.876 ms
collected packets: 0
          </screen>
          Note that the last parameter (-R 30) configures perfdhcp to simulate
          traffic from distinct 30 clients.
        </para>
      </section>
      <section id="perfdhcp-templates">
        <title>Example: templates</title>
        <para>
          By default the DHCP messages are formed in-flight with default options.
          If desired, there is a way to define custom packet format with template
          files. Content in template files is encoded in hexadecimal format. The
          perfdhcp forms the packet by replacing parts of the binary stream read
          from the file with variable data such as elapsed time, HW address, DUID
          etc. The offsets where such variable data is placed is specific to the
          template file and have to be specified from the command line. Refer to
          <xref linkend="perfdhcp-command-line"/> to find out how to
          specify offsets for particular options and fields. With the following
          command line the DHCPv6 SOLICIT and REQUEST packets will be formed from
          solicit-example.hex and request6-example.hex packets:
          <screen><userinput>#./perfdhcp -6 -l eth3 -r 100 -R 20 -T templates/solicit-example.hex -T templates/request6-example.hex -O 21 -E 84 -S 22 -I 40 servers</userinput>
***Rate statistics***
Rate: 99.5398 exchanges/second, expected rate: 100 exchanges/second

***Statistics for: SOLICIT-ADVERTISE***
sent packets: 570
received packets: 569
drops: 1
orphans: 0

min delay: 0.259 ms
avg delay: 0.912 ms
max delay: 6.979 ms
std deviation: 0.709 ms
collected packets: 0

***Statistics for: REQUEST-REPLY***
sent packets: 569
received packets: 569
drops: 0
orphans: 0

min delay: 0.084 ms
avg delay: 0.607 ms
max delay: 6.490 ms
std deviation: 0.518 ms
collected packets: 0
          </screen>
          where:
          <itemizedlist>
            <listitem><para>two occurences of -O 21 - DUID's last octet
            positions in SOLICIT and REQUEST respectively.</para></listitem>
            <listitem><para>-E 84 - elapsed time option position in
            REQUEST template</para></listitem>
            <listitem><para>-S 22 - server id position in REQUEST
            template</para></listitem>
            <listitem><para>-I 40 - IA_NA option position in REQUEST
            template</para></listitem>
          </itemizedlist>
        </para>
      </section>
    </section>
  </chapter>
</book>