One document matched: draft-ietf-mboned-rfc3171bis-03.xml
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<rfc category="bcp" ipr="full3978" docName="draft-ietf-mboned-rfc3171bis-03">
<front>
<title abbrev="IPv4 Multicast Guidelines">
IANA Guidelines for IPv4 Multicast Address Assignments
</title>
<author initials="M." surname="Cotton" fullname="Michelle Cotton">
<organization abbrev="ICANN">
Internet Corporation for Assigned Names and Numbers
</organization>
<address>
<postal>
<street>4676 Admiralty Way, Suite 330</street>
<code>90292</code> <city>Marina del Rey</city>
<country>United States</country>
</postal>
<phone>+310-823-9358</phone>
<email>michelle.cotton@icann.org</email>
<uri>
http://www.iana.org/
</uri>
</address>
</author>
<author initials="D." surname="Meyer" fullname="David Meyer">
<organization></organization>
<address>
<email>dmm@1-4-5.net</email>
</address>
</author>
<date month="June" year="2008"/>
<keyword>multicast</keyword>
<keyword>guidelines</keyword>
<abstract>
<t>
This document obsoletes RFC 3171. It provides guidance for the Internet Assigned Numbers
Authority (IANA) in assigning IPv4 multicast addresses.
</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>
The Internet Assigned Numbers Authority (IANA) (www.iana.org) is
charged with allocating parameter values for fields in protocols
which have been designed, created or are maintained by the Internet
Engineering Task Force (IETF). RFC 2780 [RFC2780] provides the IANA
guidance in the assignment of parameters for fields in newly
developed protocols. This memo expands on section 4.4.2 of RFC 2780
and attempts to codify existing IANA practice used in the assignment
IPv4 multicast addresses.
</t>
<t>
This document is a revision of RFC 3171 <xref target="RFC3171"/>, which it
obsoletes. It should retain RFC 3171's status as BCP 51. It also obsoletes
RFC 3138 <xref target="RFC3138"/>."
</t>
<t>
The terms "Specification Required", "Expert Review", "IESG Approval",
"IETF Consensus", and "Standards Action", are used in this memo to
refer to the processes described in <xref target="RFC2434"/>. The keywords MUST,
MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT,
SHOULD, SHOULD NOT are to be interpreted as defined in <xref target="RFC2119"/>.
</t>
<t>
In general, due to the relatively small size of the IPv4 multicast
address space, further assignment of IPv4 multicast address space
is recommended only in limited circumstances. Specifically, the IANA
should only assign addresses in those cases where the dynamic
selection (SDP/SAP), GLOP, SSM or Administratively Scoped address
spaces cannot be used. The guidelines described below are reflected
in <eref target="http://www.iana.org/numbers.html"/>.
</t>
</section>
<section title="Terminology">
<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 BCP 14, RFC 2119 <xref target="RFC2119"/>.
</t>
<t>
The word "allocation" is defined as a block of addresses managed by
a registry for the purpose of making assignments and allocations.
The word "assignment" is defined a block of addresses, or a single
address, registered to an end-user for use on a specific network,
or set of networks.
</t>
</section>
<section title="Definition of Current Assignment Practice">
<t>
Unlike IPv4 unicast address assignment, where blocks of addresses are
delegated to Regional Internet Registries (RIRs), IPv4 multicast addresses
are assigned directly by the IANA. Current registration groups appear as
follows <xref target="IANA"/>:
</t>
<figure><artwork>
224.0.0.0 - 224.0.0.255 224.0.0/24 Local Network Control Block
224.0.1.0 - 224.0.1.255 224.0.1/24 Internetwork Control Block
224.0.2.0 - 224.0.255.0 64769 AD-HOC Block (1)
224.1.0.0 - 224.1.255.255 224.1/16 RESERVED
224.2.0.0 - 224.2.255.255 224.2/16 SDP/SAP Block
224.252.0.0 - 224.255.255.255 224.252/14 RESERVED
225.0.0.0 - 231.255.255.255 7 /8s RESERVED
232.0.0.0 - 232.255.255.255 232/8 Source Specific Multicast Block
233.0.0.0 - 233.251.255.255 16515072 GLOP Block
233.252.0.0 - 233.255.255.255 233.252/14 AD-HOC Block (2)
234.0.0.0 - 238.255.255.255 5 /8s RESERVED
239.0.0.0 - 239.255.255.255 239/8 Administratively Scoped Block
</artwork></figure>
<t>
The IANA generally assigns addresses from the Local Network Control,
Internetwork Control and AD-HOC blocks. Assignment guidelines for
each of these blocks, as well as for the Source Specific Multicast,
GLOP and Administratively Scoped Blocks, are described below.
</t>
</section>
<section title="Local Network Control Block (224.0.0/24)">
<t>
Addresses in the Local Network Control block are used for protocol
control traffic that is not forwarded off link. Examples of this
type of use include OSPFIGP All Routers (224.0.0.5) <xref target="RFC2328"/>.
</t>
<section title="Assignment Guidelines">
<t>
Pursuant to section 4.4.2 of <xref target="RFC2780"/>, assignments from the
Local Network Control block follow an Expert Review, IESG Approval or
Standards Action process. See <xref target="IANA">IANA</xref> for the current set of
assignments.
</t>
</section>
</section>
<section title="Internetwork Control Block (224.0.1/24)">
<t>
Addresses in the Internetwork Control block are used for protocol
control that MAY be forwarded through the Internet. Examples
include 224.0.1.1 (NTP <xref target="RFC2030"/>) and 224.0.1.68 (mdhcpdiscover
<xref target="RFC2730"/>).
</t>
<section title="Assignment Guidelines">
<t>
Pursuant to section 4.4.2 of <xref target="RFC2780"/>, assignments from the
Internetwork Control block follow an Expert Review, IESG Approval or
Standards Action process. See <xref target="IANA">IANA</xref> for the current set of
assignments.
</t>
</section>
</section>
<section title="AD-HOC Blocks (including 224.0.2.0/24 - 224.0.255.0/24)">
<t>
Addresses in the AD-HOC blocks were traditionally used for assignments for
those applications that don't fit in either the Local or Internetwork
Control blocks. These addresses are globally routed and are
typically used by applications that require small blocks of
addressing (e.g., less than a /24 ). Future assignments of blocks of addresses that do not fit in the Local or Internetwork block will be made in the Extended block.
</t>
<section title="Assignment Guidelines">
<t>
In general, the IANA SHOULD NOT assign addressing in the AD-HOC
Block. However, the IANA MAY under special circumstances,
assign addresses from this block. Pursuant to section 4.4.2 of
<xref target="RFC2780"/>, assignments from the AD-HOC block follow an Expert
Review, IESG Approval or Standards Action process. See <xref target="IANA">IANA</xref> for
the current set of assignments.
</t>
</section>
</section>
<section title="SDP/SAP Block (224.2/16)">
<t>
Addresses in the SDP/SAP block are used by applications that receive
addresses through the Session Announcement Protocol <xref target="RFC2974"/> for use
via applications like the session directory tool (such as SDR [SDR]).
</t>
<section title="Assignment Guidelines">
<t>
Since addresses in the SDP/SAP block are chosen randomly from the
range of addresses not already in use <xref target="RFC2974"/>, no IANA assignment
policy is required. Note that while no additional IANA assignment is
required, addresses in the SDP/SAP block are explicitly for use by
SDP/SAP and MUST NOT be used for other purposes.
</t>
</section>
</section>
<section title="Source Specific Multicast Block (232/8)">
<t>
The Source Specific Multicast (SSM) is an extension of IP Multicast
in which traffic is forwarded to receivers from only those multicast
sources for which the receivers have explicitly expressed interest,
and is primarily targeted at one-to-many (broadcast) applications.
Note that this block as initially assigned to the VMTP transient
groups <xref target="IANA">IANA</xref>.
</t>
<section title="Assignment Guidelines">
<t>
Because the SSM model essentially makes the entire multicast address
space local to the host, no IANA assignment policy is required.
Note, however, that while no additional IANA assignment is required,
addresses in the SSM block are explicitly for use by SSM and MUST NOT
be used for other purposes.
</t>
</section>
</section>
<section title="GLOP Block (233/8)">
<t>
Addresses in the GLOP block are globally scoped statically assigned
addresses. The assignment is made, for a domain with 16 bit Autonomous
System Number (ASN), by mapping a domain's autonomous the number,
expressed in octets as X.Y, system number into the middle two octets
of of the GLOP block, yielding an assignment of 233.X.Y.0/24. The
mapping and assignment is defined in <xref target="RFC3180"/>. Domains
with 32 bit ASN should apply for space in the Extended AD-HOC block.
</t>
<section title="Assignment Guidelines">
<t>
Because addresses in the GLOP block are algorithmically pre-assigned,
no IANA assignment policy is required.
</t>
</section>
<section title="Extended AD-HOC">
<t>
<xref target="RFC3138"/> delegated assignment of the GLOP sub-block mapped by the
<xref target="RFC1930"/> private AS space (233.252.0.0 - 233.255.255.255)
to the RIRs. This space was known as eGLOP. The RIRs did not develop
policies or the mechanisms for the assignment of the eGLOP space and it is
important to make this space available for use by network operators. It is
therefore appropriate to obsolete RFC 3138 and classify this address range as
available for AD-HOC assignment as per the guidelines in section 6.
</t>
</section>
</section>
<section title="Administratively Scoped Address Block (239/8)">
<t>
Addresses in the Administratively Scoped Address block are for local
use within a domain and are described in <xref target="RFC2365"/>.
</t>
<section title="Assignment Guidelines">
<t>
Since addresses in this block are local to a domain, no IANA
assignment policy is required.
</t>
<section title="Relative Offsets">
<t>
The relative offsets <xref target="RFC2365"/> are used to ensure that a service can
be located independent of the extent of the enclosing scope (see <xref target="RFC3180"/>
for details). Since there are only 256 such offsets, the IANA
should only assign a relative offset to a protocol that provides an
infrastructure supporting service. Examples of such services include
the Session Announcement Protocol <xref target="RFC2974"/>. Pursuant to section
4.4.2 of <xref target="RFC2780"/>, assignments of Relative Offsets follow
an Expert Review, IESG Approval or Standards Action process. See
<xref target="IANA">IANA</xref> for the current set of assignments.
</t>
</section>
</section>
</section>
<section title="Application Form">
<t>
Requests for multicast address assignments can be submitted through the
application form on the IANA web site at:
</t>
<t>
<eref target="http://www.iana.org/cgi-bin/multicast.pl"/>
</t>
<t>
It is important to submit sufficient detail to allow the IESG designated
expert to review the application. If the details given in the request are not
clear, or further information is needed, the IESG designated expert may
request additional information before assigning an address.
</t>
<section title="Size of assignments of IPv4 Multicast Addresses">
<t>
Occasionally, more than one multicast address is required. In these cases
multiple addresses are available in the Extended AD-HOC block. Where a very
large number of addresses is required, the assignment will be staged, with
additional stages only being made after the complete use of the initial
assignment(s).
</t>
<t>
A separate document describing the policy governing assignment of addresses
in the AD-HOC and Extended AD-HOC blocks will be developed and published.
The format, location and content has not yet been decided and so these will
be documented in a future version of this document.
</t>
</section>
</section>
<section title="Annual Review">
<t>
Given the dynamic nature of IPv4 multicast and its associated infra-
structure, and the previously undocumented IPv4 multicast address
assignment guidelines, the IANA should conduct an annual review of
currently assigned addresses.
</t>
<section title="Address Reclamation">
<t>
During the review described above, addresses that were mis-assigned
should, where possible, be reclaimed or reassigned.
</t>
<t>
The IANA should also review assignments in the AD-HOC, DIS Transient
Groups, and ST Multicast Groups <xref target="RFC1190"/> blocks and reclaim those addresses
that are not in use on the global Internet (i.e, those applications
which can use SSM, GLOP, or Administratively Scoped addressing, or
are not globally routed).
</t>
</section>
<section title="Positive renewal">
<t>
It is occasionally appropriate to make temporary assignments that can be
renewed as necessary. In cases where this happens the registrant needs to
positively request an extension to the temporary assignment or the addresses
assigned. When the IANA has not received a request to renew the registration
of a temporary assignment within 30 days of the expiry of the assignment it
MUST be removed from the multicast registry.
</t>
<t>
Addresses returned to the IANA when a temporary assignment ends MUST NOT be
assigned for at least one calendar year.
</t>
</section>
</section>
<section title="Use of IANA Reserved Addresses">
<t>
Applications MUST NOT use addressing in the IANA reserved blocks.
</t>
</section>
<section title="IANA Considerations">
<t>
This document is all about IANA Considerations.
</t>
</section>
<section title="Security Considerations">
<t>
The assignment guidelines described in this document do not alter the
security properties of either the Any Source or Source Specific
multicast service models.
</t>
</section>
<section title="Acknowledgments">
<t>
The authors would like to thank Joe St. Sauver, John Meylor, Randy
Bush, Thomas Narten, Marshall Eubanks, Zaid Albanna (co-author of RFC3171),
Kevin Almeroth (co-author of RFC3171) and Leo Vegoda for their constructive
feedback and comments.
</t>
</section>
</middle>
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<reference anchor="IANA" target="http://www.iana.org/numbers.html">
<front>
<title>IANA Matrix for Protocol Parameter Assignment/Registration Procedures</title>
<author fullname="IANA"><organization>IANA</organization></author>
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