One document matched: draft-droms-dhc-dhcpv6-solmaxrt-update-02.xml


<?xml version="1.0" encoding="US-ASCII"?>
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<rfc category="std" docName="draft-droms-dhc-dhcpv6-solmaxrt-update-02" ipr='trust200902'>
  <!-- category values: std, bcp, info, exp, and historic
     ipr values: full3667, noModification3667, noDerivatives3667
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  <!-- ***** FRONT MATTER ***** -->

  <front>
    <!-- The abbreviated title is used in the page header - it is only necessary if the 
         full title is longer than 39 characters -->

    <title abbrev="DHCPv6 SOL_MAX_RT Option">Modification to Default Value of
    SOL_MAX_RT</title> 

    <!-- add 'role="editor"' below for the editors if appropriate -->

    <!-- Another author who claims to be an editor -->

    <author fullname="Ralph Droms" initials="R." surname="Droms">
      <organization>Cisco Systems</organization>

      <address>
        <postal>
          <street>1414 Massachusetts Avenue</street>

          <!-- Reorder these if your country does things differently -->

          <city>Boxborough</city>

          <region>MA</region>

          <code>01719</code>

          <country>USA</country>
        </postal>

        <phone>+1 978 936 1674</phone>

        <email>rdroms@cisco.com</email>

        <!-- uri and facsimile elements may also be added -->
      </address>
    </author>

    <date year="2012" />

    <!-- If the month and year are both specified and are the current ones, xml2rfc will fill 
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    <!-- Meta-data Declarations -->

    <area>Internet</area>

<!--    <workgroup>dhc</workgroup> -->

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    <abstract>
      <t>This document updates RFC 3315 by redefining the default
      value for SOL_MAX_RT and defining an option through which a
      DHCPv6 server can override the client's default value for
      SOL_MAX_RT with a new value.</t>
    </abstract>
  </front>

  <middle>
    <section title="Introduction">
      <t>Section 5.5 of the <xref target="RFC3315">DHCPv6
      specification</xref> defines the default value of SOL_MAX_RT to
      be 120 seconds.  In some circumstances, this default will lead
      to an unacceptably high volume of aggregated traffic at a DHCPv6
      server.</t>

      <t>The change to SOL_MAX_RT is in response to DHCPv6 message
      rates observed at a DHCPv6 server in a deployment in which many
      DHCPv6 clients are sending Solicit messages but the DHCPv6
      server has been configured not to respond to those Solicit
      messages.</t>

      <section title="Requirements Language">
        <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
        "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
        document are to be interpreted as described in <xref
        target="RFC2119">RFC 2119</xref>.</t>
      </section>

    </section>

    <section title="Update to RFC 3315">
      <t>This document changes section 5.5 of <xref
      target="RFC3315">RFC 3315</xref> as follows: 

      <figure>
        <artwork><![CDATA[
OLD:
   SOL_MAX_RT      120 secs  Max Solicit timeout value

NEW:
   SOL_MAX_RT     3600 secs  Max Solicit timeout value
         ]]></artwork>
        </figure>
      </t>

      <t>With this change, a DHCPv6 client that does not receive a
      satisfactory response will send Solicit messages with the same
      initial frequency and exponential backoff as specified in
      section 17.1.2 of <xref target='RFC3315'>RFC 3315</xref>.
      However, the long term behavior of these DHCPv6 clients will be
      to send a Solicit message every 3600 seconds rather than every
      120 seconds, significantly reducing the aggregated traffic at
      the DHCPv6 server.</t>

    </section>

    <section title="SOL_MAX_RT option">
      <t>A DHCPv6 server sends the SOL_MAX_RT option to a client to
      override the default value of SOL_MAX_RT.  The value of
      SOL_MAX_RT in the option replaces the default value defined in
      <xref target='RFC3315'>RFC 3315</xref>.  One use for the
      SOL_MAX_RT option is to set a longer value for SOL_MAX_RT, which
      reduces the Solicit traffic from a client that has not received
      a response to its Solicit messages.</t>

      <t>The format of the SOL_MAX_RT option is:

	<figure anchor="option_format">
	<artwork>
<![CDATA[
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          option-code          |         option-len            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                       SOL_MAX_RT value                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      option-code          OPTION_SOL_MAX_RT (TBD).

      option-len           4.

      SOL_MAX_RT value     Overriding value for SOL_MAX_RT in seconds.

]]>
	</artwork>
	</figure>
      </t>

      <t>A DHCPv6 client MUST include the SOL_MAX_RT option code in an
      <xref target='RFC3315'>Option Request option</xref> in any
      message it sends.</t>

      <t>The DHCPv6 server MAY include the SOL_MAX_RT option in any
      response it sends to a client that has included the SOL_MAX_RT
      option code in an Option Request option.  The SOL_MAX_RT option
      is sent in the main body of the message to client, not as a
      sub-option in, e.g., an <xref target="RFC3315">IA_NA, IA_TA</xref>
      or <xref target="RFC3633">IA_PD</xref> option.</t>

      <t>If a DHCPv6 client receives a message containing a SOL_MAX_RT
      option, the client MUST set its internal SOL_MAX_RT parameter to
      the value contained in the SOL_MAX_RT option.  As a result of
      receiving this option, the DHCPv6 client MUST NOT send any
      Solicit messages more frequently than allowed by the
      retransmission mechanism defined in sections 17.1.2 and 14 of
      <xref target='RFC3315'>RFC 3315</xref>.</t>
    </section>
  
    <section title="Updates to RFC 3315">
      <t><xref target="RFC3315">RFC 3315</xref>, section 17.1.3:

	<figure anchor="sec17-1-3">
	<artwork>
<![CDATA[

   OLD:

   The client MUST ignore any Advertise message that includes a Status
   Code option containing the value NoAddrsAvail, with the exception
   that the client MAY display the associated status message to the
   user.

   NEW:

   The client MUST ignore any Advertise message that includes a Status
   Code option containing the value NoAddrsAvail, with the exception
   that the client MUST process an included SOL_MAX_RT option and MAY
   display the associated status message to the user.

]]>
	</artwork>
	</figure>
      </t>

      <t><xref target="RFC3315">RFC 3315</xref>, section 17.2.2:

	<figure anchor="sec17-2-2">
	<artwork>
<![CDATA[

   OLD:

   If the server will not assign any addresses to any IAs in a
   subsequent Request from the client, the server MUST send an
   Advertise message to the client that includes only a Status Code
   option with code NoAddrsAvail and a status message for the user, a
   Server Identifier option with the server's DUID, and a Client
   Identifier option with the client's DUID.

   NEW:

   If the server will not assign any addresses to any IAs in a
   subsequent Request from the client, the server MUST send an
   Advertise message to the client that includes only a Status Code
   option with code NoAddrsAvail and a status message for the user, a
   Server Identifier option with the server's DUID, a Client
   Identifier option with the client's DUID and (optionally) a
   SOL_MAX_RT option.

]]>
	</artwork>
	</figure>
      </t>
    </section>

    <section title="Security Considerations">
      <t>This document introduces one security consideration beyond
      those described in <xref target='RFC3315'>RFC 3315</xref>.  A
      malicious DHCPv6 server might cause a client to set its
      SOL_MAX_RT parameter to an arbitrarily high value with the
      SOL_MAX_RT option.  Assuming the client also receives a response
      from a valid DHCPv6 server, the large value for SOL_MAX_RT will
      not have any effect.</t>
    </section>

    <section title="IANA Considerations">
      <t>IANA is requested to assign an option code from the "DHCP
      Option Codes" Registry for OPTION_SOL_MAX_RT.</t>
    </section>

  </middle>

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