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<rfc category="info" ipr="trust200902"
     docName="draft-venaas-mboned-mcaddrdoc-04.txt">

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<front>
  <title>Multicast Addresses for Documentation</title>
  <author fullname="Tim Chown" initials="T.J." surname="Chown">
    <organization> University of Southampton </organization>
    <address>
      <postal>
        <street> Highfield </street>
	<city> Southampton </city>
	<code> SO17 1BJ </code>
	<region> Hampshire </region>
	<country> United Kingdom </country>
      </postal>
      <email> tjc@ecs.soton.ac.uk </email>
    </address>
  </author>
  <author fullname="Marshall Eubanks" initials="M."
          surname="Eubanks">
    <organization>Iformata Communications</organization>
    <address>
      <postal>
        <street>130 W. Second Street</street>
        <city>Dayton</city>
        <region>Ohio</region>
        <code>45402</code>
        <country>US</country>
      </postal>
      <phone>+1 703 501 4376</phone>
      <email>marshall.eubanks@iformata.com</email>
      <uri>http://www.iformata.com/</uri>
    </address>
  </author>
  <author initials='R.' surname='Parekh' fullname='Rishabh Parekh'>
    <organization>cisco Systems</organization>
    <address><postal>
        <street>Tasman Drive</street>
	<city>San Jose</city> <region>CA</region>
	<code>95134</code>
	<country>USA</country>
      </postal>
      <email>riparekh@cisco.com</email></address>
  </author>
  <author initials="G." surname="Van de Velde" fullname="Gunter Van de Velde">
    <organization>cisco Systems</organization>
    <address>
      <postal>
        <street>De Kleetlaan 6a</street>
        <city>Diegem</city>
        <country>Belgium</country>
        <code>1831</code>
      </postal>
      <phone>+32 476 476 022</phone>
      <email>gvandeve@cisco.com</email>
    </address>
  </author>
  <author initials='S.' surname='Venaas' fullname='Stig Venaas'>
    <organization>cisco Systems</organization>
    <address><postal>
        <street>Tasman Drive</street>
	<city>San Jose</city> <region>CA</region>
	<code>95134</code>
	<country>USA</country>
      </postal>
      <email>stig@cisco.com</email></address>
  </author>
  <date/>
  <abstract>
    <t>This document discusses which multicast addresses should be used for
      documentation purposes and reserves multicast addresses for such
      use. Some multicast addresses are derived from
      AS numbers or unicast addresses. This document also explains how
      these can be used for documentation purposes.</t> 
  </abstract>
</front>

<middle>
  <section title="Introduction">
    <t>It is often useful in documentation, IETF documents, etc.,
    to provide examples containing IP multicast addresses.
    For documentation where examples of general purpose multicast addresses
    are needed, one should use multicast addresses that never will be
    assigned or in actual use. There is a risk that addresses used in
    examples may accidentally be used. It is then important that the
    same addresses are not used by other multicast applications or
    services. It may also be beneficial to filter out such addresses
    from multicast signalling and multicast data sent to such addresses.
    </t><t>
    For unicast there are both IPv4 and IPv6 addresses
    reserved for this purpose,
    see <xref target="RFC5737"/> and <xref target="RFC3849"/>
    respectively. This document reserves multicast addresses for this
    purpose.
    </t>
    <t>There are also some multicast addresses that are derived from AS
    numbers or unicast addresses. For examples where such addresses are
    desired, one should derive them from the AS numbers and unicast
    addresses reserved for documentation purposes. This document also
    discusses the use of these.
</t>
  </section>
  <section title="IPv4 multicast documentation addresses">
    <t>
    The type of multicast addresses most commonly used today, are
    addresses used for so-called ASM (Any-Source Multicast). For
    ASM, the IPv4 multicast addresses allocated for documentation purposes
    are 233.252.0.0 - 233.252.0.255 (233.252.0.0/24).
    </t>
    <t>
    Another type of multicast is SSM (Source-Specific Multicast). For
    SSM it is less important which multicast addresses are used, since
    a host/application joins a channel identified by both source and
    group. Any source addresses used in SSM examples should be unicast
    addresses reserved for documentation purposes,
    see <xref target="RFC5737"/>.
    </t>
    <t>Sometimes one wants to give examples where a specific
    type of address is desired. E.g. for text about multicast scoping,
    one might want the examples to use addresses that are to be used for
    administrative scoping. See below for guidance on how to construct
    specific types of example addresses.</t>

    <section title="Administratively scoped IPv4 multicast addresses">
      <t>Administratively scoped IPv4 multicast addresses
      <xref target="RFC2365"/> are reserved for scoped multicast. They can
      be used within a site or an organization. Apart from a small set of
      scope relative addresses, these addresses are not assigned. There are
      no specific scoped addresses available for documentation purposes.
      Except for examples detailing the use of scoped multicast, one should
      avoid using them.</t>
    </section>

    <section title="GLOP multicast addresses">
      <t>GLOP <xref target="RFC3180"/> is a method for deriving IPv4 multicast
      group addresses from 16 bit AS numbers.  For examples where GLOP
      addresses are desired, the addresses should be
      derived from the AS numbers reserved for documentation use. See
      <xref target="RFC5398"/>.</t>
    </section>

    <section title="Unicast prefix based IPv4 multicast addresses">
    <t>IPv4 multicast addresses can be derived from IPv4 unicast prefixes,
    see <xref target="RFC6034"/>. For examples where this type of addresses
    are desired, the addresses should be derived from the unicast addresses
    reserved for documentation purposes, see <xref target="RFC5737"/>.
    </t>
    </section>
  </section>

  <section title="IPv6 multicast documentation addresses">
    <t>
    The type of multicast addresses most commonly used today, are
    addresses used for so-called ASM (Any-Source Multicast). For
    ASM, the IPv6 multicast addresses allocated for documentation purposes
    are TBD.
    </t>
    <t>
    Another type of multicast is SSM (Source-Specific Multicast). For
    SSM it is less important which multicast addresses are used, since
    a host/application joins a channel identified by both source and
    group. Any source addresses used in SSM examples should be unicast
    addresses reserved for documentation purposes,
    see <xref target="RFC3849"/>.
    </t>
    <t>Sometimes one wants to give examples where a specific
    type of address is desired. E.g. for text about multicast scoping,
    one might want the examples to use addresses that are to be used for
    administrative scoping. See below for guidance on how to construct
    specific types of example addresses.</t>

    <section title="Unicast prefix based IPv6 multicast addresses">
      <t>IPv6 multicast addresses can be derived from IPv6 unicast prefixes,
      see <xref target="RFC3306"/>. For examples where this type of addresses
      is desired, the addresses should be derived from the unicast addresses
      reserved for documentation purposes, see <xref target="RFC3849"/>.
      </t> 
    </section>
    <section title="Embedded-RP IPv6 multicast addresses">
      <t>There is a type of IPv6 multicast addresses called Embedded-RP
      addresses where the IPv6 address of a Rendezvous-Point is embedded
      inside the multicast address, see <xref target="RFC3956"/>.
      For examples where this type of addresses is desired, the addresses should
      be derived from the unicast addresses reserved for documentation purposes,
      see see <xref target="RFC3849"/>.
      </t> 
    </section>
  </section>

  <section title="Security Considerations">
    <t>
The use of specific multicast addresses for documentation purposes has no
impact on security.
</t>
  </section>
  <section title="IANA Considerations">
    <t>IANA is requested to assign "variable scope" IPv6 multicast addresses
    for documentation purposes. This should be a /96 prefix of the form
    FF0X:...
    </t>
  </section>
  <section title="Acknowledgments">
	    <t>The authors thank Roberta Maglione for providing
	    comments on this document.</t>
  </section>
</middle>
<back>
  <references title='Informative References'>
    <?rfc include='reference.RFC.5737' ?>
    <?rfc include='reference.RFC.3849' ?>
    <?rfc include='reference.RFC.3180' ?>
    <?rfc include='reference.RFC.5398' ?>
    <?rfc include='reference.RFC.3306' ?>
    <?rfc include='reference.RFC.3956' ?>
    <?rfc include='reference.RFC.3307' ?>
    <?rfc include='reference.RFC.2365' ?>
    <?rfc include='reference.RFC.6034' ?>
  </references>
</back>
</rfc>
