shorewall_code/Shorewall/manpages/shorewall-tcclasses.xml

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<refentry>
  <refmeta>
    <refentrytitle>shorewall-tcclasses</refentrytitle>

    <manvolnum>5</manvolnum>

    <refmiscinfo>Configuration Files</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname>tcclasses</refname>

    <refpurpose>Shorewall file to define HTB and HFSC classes</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <cmdsynopsis>
      <command>/etc/shorewall[6]/tcclasses</command>
    </cmdsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>A note on the <emphasis>rate</emphasis>/bandwidth definitions used
    in this file:</para>

    <itemizedlist>
      <listitem>
        <para>don't use a space between the integer value and the unit: 30kbit
        is valid while 30 kbit is NOT.</para>
      </listitem>

      <listitem>
        <para>you can use one of the following units:</para>

        <variablelist>
          <varlistentry>
            <term><emphasis role="bold">kpbs</emphasis></term>

            <listitem>
              <para>Kilobytes per second.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term><emphasis role="bold">mbps</emphasis></term>

            <listitem>
              <para>Megabytes per second.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term><emphasis role="bold">kbit</emphasis></term>

            <listitem>
              <para>Kilobits per second.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term><emphasis role="bold">mbit</emphasis></term>

            <listitem>
              <para>Megabits per second.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term><emphasis role="bold">bps</emphasis> or <emphasis
            role="bold">number</emphasis></term>

            <listitem>
              <para>Bytes per second.</para>
            </listitem>
          </varlistentry>
        </variablelist>
      </listitem>

      <listitem>
        <para>if you want the values to be calculated for you depending on the
        output bandwidth setting defined for an interface in tcdevices, you
        can use expressions like the following:</para>

        <variablelist>
          <varlistentry>
            <term>full/3</term>

            <listitem>
              <para>causes the bandwidth to be calculated as 1/3 of the full
              outgoing speed that is defined.</para>
            </listitem>
          </varlistentry>

          <varlistentry>
            <term>full*9/10</term>

            <listitem>
              <para>will set this bandwidth to 9/10 of the full
              bandwidth</para>
            </listitem>
          </varlistentry>
        </variablelist>

        <para>Note that in a sub-class (a class that has a specified parent
        class), full refers to the RATE or CEIL of the parent class rather
        than to the OUT-BANDWIDTH of the device.</para>

        <para>DO NOT add a unit to the rate if it is calculated !</para>
      </listitem>
    </itemizedlist>

    <para>The columns in the file are as follows.</para>

    <variablelist>
      <varlistentry>
        <term><emphasis role="bold">INTERFACE</emphasis> -
        <emphasis>interface</emphasis>[[:<emphasis>parent</emphasis>]:<emphasis>class</emphasis>]</term>

        <listitem>
          <para>Name of <emphasis>interface</emphasis>.</para>

          <para>You may specify the interface number rather than the interface
          name. If the <emphasis role="bold">classify</emphasis> option is
          given for the interface in <ulink
          url="/manpages/shorewall-tcdevices.html">shorewall-tcdevices</ulink>(5),
          then you must also specify an interface class (an integer that must
          be unique within classes associated with this interface). If the
          classify option is not given, you may still specify a
          <emphasis>class</emphasis> or you may have Shorewall generate a
          class number from the MARK value. Interface numbers and class
          numbers are always assumed to be specified in hex and class number 1
          is reserved as the root class of the queuing discipline.</para>

          <para>You may NOT specify wildcards here, e.g. if you have multiple
          ppp interfaces, you need to put them all in here!</para>

          <para>Please note that you can only use interface names in here that
          have a bandwidth defined in the <ulink
          url="/manpages/shorewall-tcdevices.html">shorewall-tcdevices</ulink>(5)
          file.</para>

          <para>Normally, all classes defined here are sub-classes of a root
          class that is implicitly defined from the entry in <ulink
          url="/manpages/shorewall-tcdevices.html">shorewall-tcdevices</ulink>(5).
          You can establish a class hierarchy by specifying a
          <emphasis>parent</emphasis> class -- the number of a class that you
          have previously defined. The sub-class may borrow unused bandwidth
          from its parent.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">MARK</emphasis> -
        {-|<replaceable>value</replaceable>[:<replaceable>priority</replaceable>]}</term>

        <listitem>
          <para>The mark <emphasis>value</emphasis> which is an integer in the
          range 1-255. You set mark values in the <ulink
          url="/manpages/shorewall-mangle.html">shorewall-mangle</ulink>(5)
          file, marking the traffic you want to fit in the classes defined in
          here. You can use the same marks for different interfaces.</para>

          <para>The <replaceable>priority</replaceable>, if specified, is an
          integer in the range 1-65535 and determines the relative order in
          which the tc mark classification filter for this class is to be
          applied to packets being sent on the
          <replaceable>interface</replaceable>. Filters are applied in
          ascending numerical order. If not supplied, the value is derived
          from the class priority (PRIORITY column value below):
          (<replaceable>class priority</replaceable> &lt;&lt; 8) | 20.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">RATE</emphasis> -
        {-|<emphasis>rate</emphasis>[:<emphasis>dmax</emphasis>[:<emphasis>umax</emphasis>]]}</term>

        <listitem>
          <para>The minimum bandwidth this class should get, when the traffic
          load rises. If the sum of the rates in this column exceeds the
          INTERFACE's OUT-BANDWIDTH, then the OUT-BANDWIDTH limit may not be
          honored. Similarly, if the sum of the rates of sub-classes of a
          class exceed the CEIL of the parent class, things don't work
          well.</para>

          <para>When using the HFSC queuing discipline, this column specify
          the real-time (RT) service curve. leaf classes may specify
          <replaceable>dmax</replaceable>, the maximum delay in milliseconds
          that the first queued packet for this class should experience. May
          be expressed as an integer, optionally followed by 'ms' with no
          intervening white-space (e.g., 10ms).</para>

          <para>HFSC leaf classes may also specify
          <replaceable>umax</replaceable>, the largest packet expected in this
          class. May be expressed as an integer. The unit of measure is
          <emphasis>bytes</emphasis> and the integer may be optionally
          followed by 'b' with no intervening white-space (e.g., 800b).
          <replaceable>umax</replaceable> may only be given if
          <replaceable>dmax</replaceable> is also given.</para>

          <para>Beginning with Shorewall 4.5.6, HFSC classes may omit this
          column (e.g, '-' in the column), provided that an
          <replaceable>lsrate</replaceable> is specified (see CEIL below).
          These rates are used to arbitrate between classes of the same
          priority.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">CEIL</emphasis> -
        [<emphasis>lsrate</emphasis>:]<emphasis>rate</emphasis></term>

        <listitem>
          <para>The maximum bandwidth this class is allowed to use when the
          link is idle. Useful if you have traffic which can get full speed
          when more needed services (e.g. ssh) are not used.</para>

          <para>You can use the value <emphasis role="bold">full</emphasis> in
          here for setting the maximum bandwidth to the RATE of the parent
          class, or the OUT-BANDWIDTH of the device if there is no parent
          class.</para>

          <para>Beginning with Shorewall 4.5.6, you can also specify an
          <replaceable>lsrate</replaceable> (link sharing rate).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">PRIORITY</emphasis> -
        <emphasis>priority</emphasis></term>

        <listitem>
          <para>For HTB:</para>

          <blockquote>
            <para>The <emphasis>priority</emphasis> in which classes will be
            serviced by the packet shaping scheduler and also the priority in
            which bandwidth in excess of the rate will be given to each
            class.</para>

            <para>Higher priority classes will experience less delay since
            they are serviced first. Priority values are serviced in ascending
            order (e.g. 0 is higher priority than 1).</para>

            <para>Classes may be set to the same priority, in which case they
            will be serviced as equals.</para>
          </blockquote>

          <para>For both HTB and HFSC, the <emphasis>priority</emphasis> is
          used to calculate the priority of following Shorewall-generated
          classification filters that refer to the class:</para>

          <itemizedlist>
            <listitem>
              <para>Packet MARK</para>
            </listitem>

            <listitem>
              <para><emphasis role="bold">tcp-ack</emphasis> and the <emphasis
              role="bold">tos</emphasis> options (see below)</para>
            </listitem>
          </itemizedlist>

          <para>The rules for classes with lower numeric priorities will
          appear before those with higher numeric priorities.</para>

          <para>Beginning with Shorewall 4.5.8, the PRIORITY may be omitted
          from an HFSC class if you do not use the MARK column or the
          <emphasis role="bold">tcp-ack</emphasis> or <emphasis
          role="bold">tos</emphasis> options. If you use any of those features
          and omit the PRIORITY, then you must specify a
          <replaceable>priority</replaceable> along with the MARK or
          option.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><emphasis role="bold">OPTIONS</emphasis> (Optional) -
        [<emphasis>option</emphasis>[<emphasis
        role="bold">,</emphasis><emphasis>option</emphasis>]...]</term>

        <listitem>
          <para>A comma-separated list of options including the
          following:</para>

          <variablelist>
            <varlistentry>
              <term><emphasis role="bold">default</emphasis></term>

              <listitem>
                <para>This is the default class for that interface where all
                traffic should go, that is not classified otherwise.</para>

                <para/>

                <note>
                  <para>You must define <emphasis
                  role="bold">default</emphasis> for exactly one class per
                  interface.</para>
                </note>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">tos=0x</emphasis><emphasis>value</emphasis>[/0x<emphasis>mask</emphasis>][:<replaceable>priority</replaceable>]
              (mask defaults to 0xff)</term>

              <listitem>
                <para>This lets you define a classifier for the given
                <emphasis>value</emphasis>/<emphasis>mask</emphasis>
                combination of the IP packet's TOS/Precedence/DiffSrv octet
                (aka the TOS byte).</para>

                <para>Beginning with Shorewall 4.5.8, the
                <replaceable>value/mask</replaceable> may be followed by a
                colon (":") and a <replaceable>priority</replaceable>. This
                priority determines the order in which filter rules are
                processed during packet classification. If not specified, the
                value (<replaceable>class priority</replaceable> &lt;&lt; 8) |
                15) is used.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">tos-</emphasis><emphasis>tosname</emphasis>[:<replaceable>priority</replaceable>]</term>

              <listitem>
                <para>Aliases for the following TOS octet value and mask
                encodings. TOS encodings of the "TOS byte" have been
                deprecated in favor of diffserve classes, but programs like
                ssh, rlogin, and ftp still use them.</para>

                <para>Beginning with Shorewall 4.5.8, the
                <replaceable>tos-name</replaceable> may be followed by a colon
                (":") and a <replaceable>priority</replaceable>. This priority
                determines the order in which filter rules are processed
                during packet classification. If not specified, the value
                (<replaceable>class priority</replaceable> &lt;&lt; 8) | 15)
                is used.</para>

                <programlisting>        <emphasis role="bold">tos-minimize-delay</emphasis>       0x10/0x10
        <emphasis role="bold">tos-maximize-throughput</emphasis>  0x08/0x08
        <emphasis role="bold">tos-maximize-reliability</emphasis> 0x04/0x04
        <emphasis role="bold">tos-minimize-cost</emphasis>        0x02/0x02
        <emphasis role="bold">tos-normal-service</emphasis>       0x00/0x1e</programlisting>

                <note>
                  <para>Each of these options is only valid for ONE class per
                  interface.</para>
                </note>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">tcp-ack[:<replaceable>priority</replaceable>]</emphasis></term>

              <listitem>
                <para>If defined, causes a tc filter to be created that puts
                all tcp ack packets on that interface that have a size of
                &lt;=64 Bytes to go in this class. This is useful for speeding
                up downloads. Please note that the size of the ack packets is
                limited to 64 bytes because we want only packets WITHOUT
                payload to match.</para>

                <para>Beginning with Shorewall 4.5.8, the <emphasis
                role="bold">tcp-ack</emphasis> may be followed by a colon
                (":") and a <replaceable>priority</replaceable>. This priority
                determines the order in which filter rules are processed
                during packet classification. If not specified, the value
                (<replaceable>class priority</replaceable> &lt;&lt; 8) | 10)
                is used.</para>

                <note>
                  <para>This option is only valid for ONE class per
                  interface.</para>
                </note>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term><emphasis
              role="bold">occurs</emphasis>=<emphasis>number</emphasis></term>

              <listitem>
                <para>Typically used with an IPMARK entry in tcrules. Causes
                the rule to be replicated for a total of
                <emphasis>number</emphasis> rules. Each rule has a
                successively class number and mark value.</para>

                <para>When 'occurs' is used:</para>

                <itemizedlist>
                  <listitem>
                    <para>The associated device may not have the 'classify'
                    option.</para>
                  </listitem>

                  <listitem>
                    <para>The class may not be the default class.</para>
                  </listitem>

                  <listitem>
                    <para>The class may not have any 'tos=' options (including
                    'tcp-ack').</para>
                  </listitem>

                  <listitem>
                    <para>The class should not specify a MARK value. If one is
                    specified, it will be ignored with a warning
                    message.</para>
                  </listitem>
                </itemizedlist>

                <para>The 'RATE' and 'CEIL' parameters apply to each instance
                of the class. So the total RATE represented by an entry with
                'occurs' will be the listed RATE multiplied by
                <emphasis>number</emphasis>. For additional information, see
                <ulink
                url="/manpages/shorewall-tcrules.html">shorewall-tcrules</ulink>
                (5).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>flow=<emphasis>keys</emphasis></term>

              <listitem>
                <para>Shorewall attaches an SFQ queuing discipline to each
                leaf HTB class. SFQ ensures that each
                <firstterm>flow</firstterm> gets equal access to the
                interface. The default definition of a flow corresponds
                roughly to a Netfilter connection. So if one internal system
                is running BitTorrent, for example, it can have lots of
                'flows' and can thus take up a larger share of the bandwidth
                than a system having only a single active connection. The
                <option>flow</option> classifier (module cls_flow) works
                around this by letting you define what a 'flow' is. The
                classifier must be used carefully or it can block off all
                traffic on an interface! The flow option can be specified for
                an HTB leaf class (one that has no sub-classes). We recommend
                that you use the following:</para>

                <simplelist>
                  <member>Shaping internet-bound traffic:
                  flow=nfct-src</member>

                  <member>Shaping traffic bound for your local net:
                  flow=dst</member>
                </simplelist>

                <para>These will cause a 'flow' to consists of the traffic
                to/from each internal system.</para>

                <para>When more than one key is give, they must be enclosed in
                parenthesis and separated by commas.</para>

                <para>To see a list of the possible flow keys, run this
                command:</para>

                <blockquote>
                  <para><command>tc filter add flow help</command></para>
                </blockquote>

                <para>Those that begin with "nfct-" are Netfilter connection
                tracking fields. As shown above, we recommend flow=nfct-src;
                that means that we want to use the source IP address
                <emphasis>before NAT</emphasis> as the key.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>pfifo</term>

              <listitem>
                <para>When specified for a leaf class, the pfifo queuing
                discipline is applied to the class rather than the sfq queuing
                discipline.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>limit=<emphasis>number</emphasis></term>

              <listitem>
                <para>Added in Shorewall 4.4.3. When specified for a leaf
                class, determines the maximum number of packets that may be
                queued within the class. The <emphasis>number</emphasis> must
                be &gt; 2 and &lt;=128. If not specified, the value 127 is
                assumed.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>red=(<replaceable>redoption</replaceable>=<replaceable>value</replaceable>,
              ...)</term>

              <listitem>
                <para>Added in Shorewall 4.5.6. When specified on a leaf
                class, causes the class to use the RED (Random Early
                Detection) queuing discipline rather than SFQ. See tc-red (8)
                for additional information.</para>

                <para>Allowable <replaceable>redoptions</replaceable>
                are:</para>

                <variablelist>
                  <varlistentry>
                    <term>min <replaceable>min</replaceable></term>

                    <listitem>
                      <para>Average queue size at which marking becomes a
                      possibility.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>max <replaceable>max</replaceable></term>

                    <listitem>
                      <para>At this average queue size, the marking
                      probability is maximal. Must be at least twice
                      <replaceable>min</replaceable> to prevent synchronous
                      retransmits, higher for low
                      <replaceable>min</replaceable>.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>probability
                    <replaceable>probability</replaceable></term>

                    <listitem>
                      <para>Maximum probability for marking, specified as a
                      floating point number from 0.0 to 1.0. Suggested values
                      are 0.01 or 0.02 (1 or 2%, respectively).</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>limit <replaceable>limit</replaceable></term>

                    <listitem>
                      <para>Hard limit on the real (not average) queue size in
                      bytes. Further packets are dropped. Should be set higher
                      than
                      <replaceable>max</replaceable>+<replaceable>burst</replaceable>.
                      It is advised to set this a few times higher than
                      <replaceable>max</replaceable>. Shorewall requires that
                      <replaceable>limit</replaceable> be at least twice
                      <replaceable>min</replaceable>.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>burst <replaceable>burst</replaceable></term>

                    <listitem>
                      <para>Used for determining how fast the average queue
                      size is influenced by the real queue size. Larger values
                      make the calculation more sluggish, allowing longer
                      bursts of traffic before marking starts. Real life
                      experiments support the following guide‐line:
                      (<replaceable>min</replaceable>+<replaceable>min</replaceable>+<replaceable>max</replaceable>)/(3*<replaceable>avpkt</replaceable>).</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>avpkt <replaceable>avpkt</replaceable></term>

                    <listitem>
                      <para>Optional. Specified in bytes. Used with burst to
                      determine the time constant for average queue size
                      calculations. 1000 is a good value and is the Shorewall
                      default.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>bandwidth
                    <replaceable>bandwidth</replaceable></term>

                    <listitem>
                      <para>Optional. This rate is used for calculating the
                      average queue size after some idle time. Should be set
                      to the bandwidth of your interface. Does not mean that
                      RED will shape for you!</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>ecn</term>

                    <listitem>
                      <para>RED can either 'mark' or 'drop'. Explicit
                      Congestion Notification allows RED to notify remote
                      hosts that their rate exceeds the amount of bandwidth
                      available. Non-ECN capable hosts can only be notified by
                      dropping a packet. If this parameter is specified,
                      packets which indicate that their hosts honor ECN will
                      only be marked and not dropped, unless the queue size
                      hits <replaceable>limit</replaceable> bytes.
                      Recommended.</para>
                    </listitem>
                  </varlistentry>
                </variablelist>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>fq_codel[=(<replaceable>codeloption</replaceable>=<replaceable>value</replaceable>,
              ...)]</term>

              <listitem>
                <para>Added in Shorewall 4.5.12. When specified for a leaf
                class, causes the class to use the FQ_CODEL (Fair-queuing
                Controlled Delay) queuing discipline rather than SFQ. See
                tc-fq_codel (8) for additional information.</para>

                <para>Allowable <replaceable>codeloptions</replaceable>
                are:</para>

                <variablelist>
                  <varlistentry>
                    <term>limit</term>

                    <listitem>
                      <para>hard limit on the real queue size. When this limit
                      is reached, incoming packets are dropped. If the value
                      is lowered, packets are dropped so that the new limit is
                      met. Default is 1000 packets.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>flows</term>

                    <listitem>
                      <para>is the number of flows into which the incoming
                      packets are classified. Due to the stochastic nature of
                      hashing, multiple flows may end up being hashed into the
                      same slot. Newer flows have priority over older ones.
                      This parameter can be set only at load time since memory
                      has to be allocated for the hash table. Default value is
                      1024.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>target</term>

                    <listitem>
                      <para>is the acceptable minimum standing/persistent
                      queue delay. This minimum delay is identified by
                      tracking the local minimum queue delay that packets
                      experience. Default and recommended value is 5ms.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>interval</term>

                    <listitem>
                      <para>is used to ensure that the measured minimum delay
                      does not become too stale. The minimum delay must be
                      experienced in the last epoch of length interval. It
                      should be set on the order of the worst-case RTT through
                      the bottleneck to give endpoints sufficient time to
                      react. Default value is 100ms.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>quantum</term>

                    <listitem>
                      <para>is the number of bytes used as 'deficit' in the
                      fair queuing algorithm. Default is set to 1514 bytes
                      which corresponds to the Ethernet MTU plus the hardware
                      header length of 14 bytes.</para>
                    </listitem>
                  </varlistentry>

                  <varlistentry>
                    <term>ecn | noecn</term>

                    <listitem>
                      <para>can be used to mark packets instead of dropping
                      them. If ecn has been enabled, noecn can be used to turn
                      it off and vice-versa. By default, ecn is
                      enabled.</para>
                    </listitem>
                  </varlistentry>
                </variablelist>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Examples</title>

    <variablelist>
      <varlistentry>
        <term>Example 1:</term>

        <listitem>
          <para>Suppose you are using PPP over Ethernet (DSL) and ppp0 is the
          interface for this. You have 4 classes here, the first you can use
          for voice over IP traffic, the second interactive traffic (e.g.
          ssh/telnet but not scp), the third will be for all unclassified
          traffic, and the forth is for low priority traffic (e.g.
          peer-to-peer).</para>

          <para>The voice traffic in the first class will be guaranteed a
          minimum of 100kbps and always be serviced first (because of the low
          priority number, giving less delay) and will be granted excess
          bandwidth (up to 180kbps, the class ceiling) first, before any other
          traffic. A single VoIP stream, depending upon codecs, after
          encapsulation, can take up to 80kbps on a PPPoE/DSL link, so we pad
          a little bit just in case. (TOS byte values 0xb8 and 0x68 are
          DiffServ classes EF and AFF3-1 respectively and are often used by
          VOIP devices).</para>

          <para>Interactive traffic (tos-minimum-delay) and TCP acks (and ICMP
          echo traffic if you use the example in tcrules) and any packet with
          a mark of 2 will be guaranteed 1/4 of the link bandwidth, and may
          extend up to full speed of the link.</para>

          <para>Unclassified traffic and packets marked as 3 will be
          guaranteed 1/4th of the link bandwidth, and may extend to the full
          speed of the link.</para>

          <para>Packets marked with 4 will be treated as low priority packets.
          (The tcrules example marks p2p traffic as such.) If the link is
          congested, they're only guaranteed 1/8th of the speed, and even if
          the link is empty, can only expand to 80% of link bandwidth just as
          a precaution in case there are upstream queues we didn't account
          for. This is the last class to get additional bandwidth and the last
          to get serviced by the scheduler because of the low priority.</para>

          <programlisting>        #INTERFACE  MARK  RATE    CEIL      PRIORITY    OPTIONS
        ppp0        1     100kbit 180kbit   1           tos=0x68/0xfc,tos=0xb8/0xfc
        ppp0        2     full/4  full      2           tcp-ack,tos-minimize-delay
        ppp0        3     full/4  full      3           default
        ppp0        4     full/8  full*8/10 4</programlisting>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>FILES</title>

    <para>/etc/shorewall/tcclasses</para>

    <para>/etc/shorewall6/tcclasses</para>
  </refsect1>

  <refsect1>
    <title>See ALSO</title>

    <para><ulink
    url="/traffic_shaping.htm">http://www.shorewall.net/traffic_shaping.htm</ulink></para>

    <para><ulink
    url="/configuration_file_basics.htm#Pairs">http://www.shorewall.net/configuration_file_basics.htm#Pairs</ulink></para>

    <para>tc-hfsc(7)</para>

    <para>tc-red(8)</para>

    <para>shorewall(8)</para>
  </refsect1>
</refentry>