RFC3171 - IANA Guidelines for IPv4 Multicast Address Assignments

Network Working Group Z. Albanna

Request for Comments: 3171 Juniper Networks

BCP: 51 K. Almeroth

Category: Best Current Practice UCSB

D. Meyer

Sprint

M. Schipper

IANA

August 2001

IANA Guidelines for IPv4 Multicast Address Assignments

Status of this Memo

This document specifies an Internet Best Current Practices for the

Internet Community, and requests discussion and suggestions for

improvements. Distribution of this memo is unlimited.

Abstract

This memo provides guidance for the Internet Assigned Numbers

Authority (IANA) in assigning IPv4 multicast addresses.

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). RFC2780 [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 RFC2780

and attempts to codify existing IANA practice used in the assignment

IPv4 multicast addresses.

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 [RFC2434]. The keyWords MUST,

MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT,

SHOULD, SHOULD NOT are to be interpreted as defined in RFC2119

[RFC2119].

In general, due to the relatively small size of the IPv4 multicast

addresses 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 http://www.iana.org/numbers.Html.

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) ST Multicast Groups

224.2.0.0 - 224.2.255.255 (224.2/16) SDP/SAP Block

224.252.0.0 - 224.255.255.255 DIS Transient Block

225.0.0.0 - 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.

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 RFC2780 [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 RFC2780 [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 (224.0.2.0/24 - 224.0.255.0/24)

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).

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

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, RFC3138

[RFC3138] delegates assignment of the GLOP sub-block mapped by the

RFC1930 [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 RFC2770 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.

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 RFC2780 [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 infra-

structure, 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 in the AD-HOC, DIS Transient

Groups, and ST Multicast Groups 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).

11. Use of IANA Reserved Addresses

Applications MUST NOT use addressing in the IANA reserved blocks.

12. 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.

13. Acknowledgments

The authors would like to thank Joe St. Sauver, John Meylor, Randy

Bush, and Thomas Narten for their constructive feedback and comments.

14. Authors' Addresses

Zaid Albanna

1149 N. Mathilda Ave

Sunnyvale, CA. 94089

EMail: zaid@juniper.net

Kevin Almeroth

UC Santa Barbara

Santa Barbara, CA.

EMail: almeroth@cs.ucsb.edu

David Meyer

Sprint ESolutions

EMail: dmm@sprint.net

Michelle Schipper

IANA Administrator

Internet Assigned Numbers Authority

4676 Admiralty Way, Suite 330

Marina del Rey, CA 90292

EMail: iana@iana.org

15. References

[IANA] http://www.iana.org/numbers.html

[RFC1190] Topolcic, C., "Experimental Internet Stream Protocol,

Version 2 (ST-II)", RFC1190, October 1990.

[RFC1930] Hawkinson, J. and T. Bates, "Guidelines for creation,

selection, and registration of an Autonomous System (AS)",

RFC1930, March 1996.

[RFC2026] Bradner, S., "The Internet Standards Process -- Revision

3", BCP 9, RFC2026, October 1996.

[RFC2030] Mills, D., "Simple Network Time Protocol (SNTP) Version 4

for IPv4, IPv6 and OSI", RFC2030, October 1996.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate

Requirement Levels", BCP 14, RFC2119, March 1997.

[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC2328, April 1998.

[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,

RFC2365, July 1998.

[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an

IANA Considerations Section in RFCs", BCP 26, RFC2434,

October 1998.

[RFC2730] Hanna, S., Patel, B. and M. Shah, "Multicast Address

Dynamic Client Allocation Protocol (MADCAP), RFC2730,

December 1999.

[RFC2770] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", RFC

2770, February 2000.

[RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For

Values In the Internet Protocol and Related Headers", BCP

37, RFC2780, March 2000.

[RFC2908] Thaler, D., Handley, M. and D.Estrin, "The Internet

Multicast Address Allocation Architecture", RFC2908,

September 2000.

[RFC2909] Thaler, D., Handley, M. and D. Estrin, "The Multicast

Address-Set Claim (MASC) Protocol", RFC2909, September

2000.

[RFC2974] Handley, M., Perkins, C. and E. Whelan, "Session

Announcement Protocol", RFC2974, October 2000.

[RFC3138] Meyer, D., "Extended Assignments in 233/8", RFC3138, June

2001.

[SDR] http://www-mice.cs.ucl.ac.uk/multimedia/software/

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