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Versions: (RFC 3171) 00 01 02 03 04 05 06 07
08 RFC 5771
INTERNET-DRAFT Z. Albanna
draft-ietf-mboned-rfc3171bis-02.txt K. Almeroth
M. Cotton
D. Meyer
Category Best Current Practice
Expires: September 2004 March 2004
IANA Guidelines for IPv4 Multicast Address Assignments
<draft-ietf-mboned-rfc3171bis-02.txt>
Status of this Document
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
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This document is a product of the ABC working group. Comments should
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
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Abstract
The Internet Assigned Numbers Authority is charged with allocating
parameter values for fields in protocols which have been designed,
created or are maintained by the Internet Engineering Task Force.
This document provides guidelines for the assignment of the IPv4 IP
multicast address space.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definition of Current Assignment Practice. . . . . . . . . . . 4
3. Local Network Control Block (224.0.0/24) . . . . . . . . . . . 5
3.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 5
4. Internetwork Control Block (224.0.1/24). . . . . . . . . . . . 5
4.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 5
5. AD-HOC Block (224.0.2/24 - 224.0.255/24) . . . . . . . . . . . 5
5.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 6
6. SDP/SAP Block (224.2/16) . . . . . . . . . . . . . . . . . . . 6
6.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 6
7. Source Specific Multicast Block (232/8). . . . . . . . . . . . 6
7.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 6
8. GLOP Block (233/8) . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 7
9. Administratively Scoped Address Block (239/8). . . . . . . . . 7
9.1. Assignment Guidelines . . . . . . . . . . . . . . . . . . . 7
9.1.1. Relative Offsets . . . . . . . . . . . . . . . . . . . . 8
10. Annual Review . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Address Reclamation. . . . . . . . . . . . . . . . . . . . 8
11. Usable IPv4 Multicast Addresses . . . . . . . . . . . . . . . 8
11.1. IGMP-snooping switches . . . . . . . . . . . . . . . . . . 9
11.2. Unusable Inter-domain Groups . . . . . . . . . . . . . . . 9
11.2.1. Administratively Scoped Addresses . . . . . . . . . . . 9
11.2.2. Special Use IPv4 Source Addresses . . . . . . . . . . . 10
12. Use of IANA Reserved Addresses. . . . . . . . . . . . . . . . 10
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
15. Security Considerations . . . . . . . . . . . . . . . . . . . 11
16. Normative References. . . . . . . . . . . . . . . . . . . . . 12
17. Informative References. . . . . . . . . . . . . . . . . . . . 12
18. Author's Addresses. . . . . . . . . . . . . . . . . . . . . . 13
19. Full Copyright Statement. . . . . . . . . . . . . . . . . . . 13
20. Intellectual Property . . . . . . . . . . . . . . . . . . . . 14
21. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
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.
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 RFC 2119 [RFC 2119].
2. Definition of Current Assignment Practice
Unlike IPv4 unicast address assignment, where blocks of addresses are
delegated to regional registries, IPv4 multicast addresses are
assigned directly by the IANA. Current assignments appear as follows
[IANA]:
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 AD-HOC Block
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
224.3.0.0 - 231.255.255.255 RESERVED
232.0.0.0 - 232.255.255.255 (232/8) Source Specific Multicast Block
233.0.0.0 - 233.255.255.255 (233/8) GLOP Block
234.0.0.0 - 238.255.255.255 RESERVED
239.0.0.0 - 239.255.255.255 (239/8) Administratively Scoped Block
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.
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3. Local Network Control Block (224.0.0/24)
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) [RFC2328].
3.1. Assignment Guidelines
Pursuant to section 4.4.2 of RFC 2780 [RFC2780], assignments from the
Local Network Control block follow an Expert Review, IESG Approval or
Standards Action process. See [IANA] for the current set of
assignments.
4. Internetwork Control Block (224.0.1/24)
Addresses in the Internetwork Control block are used for protocol
control that must be forwarded through the Internet. Examples include
224.0.1.1 (NTP [RFC2030]) and 224.0.1.68 (mdhcpdiscover [RFC2730]).
4.1. Assignment Guidelines
Pursuant to section 4.4.2 of RFC 2780 [RFC2780], assignments from the
Internetwork Control block follow an Expert Review, IESG Approval or
Standards Action process. See [IANA] for the current set of
assignments.
5. AD-HOC Block (224.0.2/24 - 224.0.255/24)
Addresses in the AD-HOC block have traditionally been assigned 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).
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5.1. Assignment Guidelines
In general, the IANA SHOULD NOT assign addressing in the AD-HOC
Block. However, the IANA may under special special circumstances,
assign addressing from this block. Pursuant to section 4.4.2 of RFC
2780 [RFC2780], assignments from the AD-HOC block follow an Expert
Review, IESG Approval or Standards Action process. See [IANA] for the
current set of assignments.
6. SDP/SAP Block (224.2/16)
Addresses in the SDP/SAP block are used by applications that receive
addresses through the Session Announcement Protocol [RFC2974] for use
via applications like the session directory tool (such as SDR [SDR]).
6.1. Assignment Guidelines
Since addresses in the SDP/SAP block are chosen randomly from the
range of addresses not already in use [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.
7. Source Specific Multicast Block (232/8)
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 [IANA].
7.1. Assignment Guidelines
Because the SSM model essentially makes the entire multicast address
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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.
8. GLOP Block (233/8)
Addresses in the GLOP block are globally scoped statically assigned
addresses. The assignment is made by mapping a domain's autonomous
system number into the middle two octets of 233.X.Y.0/24. The mapping
and assignment is defined in [RFC2770].
8.1. Assignment Guidelines
Because addresses in the GLOP block are algorithmically pre-assigned,
no IANA assignment policy is required. In addition, RFC 3138
[RFC3138] delegates assignment of the GLOP sub-block mapped by the
RFC 1930 [RFC1930] private AS space (233.252.0.0 - 233.255.255.255)
to the Internet Routing Registries. Note that while no additional
IANA assignment is required, addresses in the GLOP block are
assigned for use as defined in RFC 2770 and MUST NOT be used for
other purposes.
9. Administratively Scoped Address Block (239/8)
Addresses in the Administratively Scoped Address block are for local
use within a domain and are described in [RFC2365].
9.1. Assignment Guidelines
Since addresses in this block are local to a domain, no IANA
assignment policy is required.
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9.1.1. Relative Offsets
The relative offsets [RFC2365] are used to ensure that a service can
be located independent of the extent of the enclosing scope (see RFC
2770 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 [RFC2974]. Pursuant to section
4.4.2 of RFC 2780 [RFC2780], assignments of Relative Offsets follow
an Expert Review, IESG Approval or Standards Action process. See
[IANA] for the current set of assignments.
10. Annual Review
Given the dynamic nature of IPv4 multicast and its associated
infrastructure, and the previously undocumented IPv4 multicast
address assignment guidelines, the IANA should conduct an annual
review of currently assigned addresses.
10.1. Address Reclamation
During the review described above, addresses that were mis-assigned
should, where possible, be reclaimed or reassigned.
The IANA should also review assignments 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).
11. Usable IPv4 Multicast Addresses
Multicast datagrams that match the criteria in this section SHOULD
NOT be used, even on local, unrouted subnetworks.
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11.1. IGMP-snooping switches
RFC 1112 [RFC1112] describes the mapping of IPv4 Multicast Group
addresses to Ethernet MAC addresses, as follows:
An IP host group address is mapped to an Ethernet multicast
address by placing the low-order 23-bits of the IP address into
the low-order 23 bits of the Ethernet multicast address
01-00-5E-00-00-00 (hex). Because there are 28 significant bits
in an IP host group address, more than one host group address
may map to the same Ethernet multicast address.
Now, note that multicast group addresses in the 224.0.0.0/24 range
are used for local subnetwork control (see section 3 above). Under
the RFC 1112 mapping, this maps to the Ethernet multicast address
range 01-00-5E-00-00-XX, where XX is 00 through FF. Ethernet frames
within this range are always processed in the control plane of many
popular network devices, such as IGMP-snooping switches.
Because of the many-to-one mapping of IPv4 Multicast Group Addresses
to Ethernet MAC addresses, it is possible to overwhelm the control
plane of network devices by sending to group addresses that map into
the 01-00-5E-00-00-XX (hex) range.
IGMP-snooping network devices must also flood these frames to all
outgoing ports, so the damage may extend to end systems and routers.
11.2. Unusable Inter-domain Groups
Multicast datagrams that match the criteria in this section SHOULD
NOT be routed between administrative domains.
11.2.1. Administratively Scoped Addresses
RFC 2365 [RFC2365] defines 239.0.0.0/8 for use within an
administrative domain. As such, datagrams with group addresses that
match 239.0.0.0/8 SHOULD NOT be passed between administrative
domains.
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11.2.2. Special Use IPv4 Source Addresses
RFC 1918 [RFC1918] defines certain ranges of IPv4 unicast addresses
that can be used within an administrative domain. Multicast
datagrams are no exception to the rule that datagrams addressed
within these ranges SHOULD NOT be passed between administrative
domains. Examples include 127.0.0.0/8, which is widely used for
internal host addressing, and is generally not valid on datagrams
passed between hosts. 0.0.0.0/8 and 169.254.0.0/16 are also valid
only in the context of local links. Such source addresses are not
valid for datagrams passed between networks[RFC330]. Finally
192.0.2.0/24 is reserved for documentation and example code.
[RFC3330].
12. Use of IANA Reserved Addresses
Applications MUST NOT use addressing in the IANA reserved blocks.
13. IANA Considerations
This document provides guidelines for the IANA to use in assigning
IPv4 multicast addresses. It does not create any new namespaces for
the IANA to manage [RFC2434].
14. Acknowledgments
The authors would like to thank Scott Bradner, Randy Bush, John
Meylor, Thomas Narten, Joe St. Sauver, and Beau Williamson for their
constructive feedback and comments. Bill Nickless contributed the
text in section 11 describing IPv4 multicast unusable group and
source addresses.
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15. Security Considerations
The assignment guidelines described in this document do not alter the
security properties of either the Any Source or Source Specific
multicast service models.
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16. Normative References
[RFC1112] Deering, S., "Host extensions for IP
multicasting", RFC 1112, August, 1989.
[RFC1918] Rekhter, Y. et. al., "Address Allocation for
Private Internets", RFC 1918, February, 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", RFC 2119, March,
1997.
[RFC2365] Meyer, D., "Administratively Scoped IP
Multicast", RFC 2365, July 1998.
[RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330,
September, 2002.
17. Informative References
[IANA] http://www.iana.org/assignments/multicast-addresses
[RFC2026] Bradner, S., "The Internet Standards Process --
Revision 3", RFC 2026/BCP 9, October, 1996.
[RFC2028] Hovey, R. and S. Bradner, "The Organizations
Involved in the IETF Standards Process", RFC
2028/BCP 11, October, 1996.
[RFC2434] Narten, T., and H. Alvestrand, "Guidelines for
Writing an IANA Considerations Section in RFCs",
RFC 2434/BCP 26, October 1998.
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18. Author's Addresses
Zaid Albanna
Email: zaid@juniper.net
Kevin Almeroth
Email: almeroth@cs.ucsb.edu
David Meyer
Email: dmm@1-4-5.net
Michelle S. Cotton
Email: iana@iana.org
19. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78 and
except as set forth therein, the authors retain all their rights.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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20. Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
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Copies of IPR disclosures made to the IETF Secretariat and any
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The IETF invites any interested party to bring to its attention any
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21. Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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