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rfc:rfc6676

Internet Engineering Task Force (IETF) S. Venaas Request for Comments: 6676 R. Parekh Category: Informational G. Van de Velde ISSN: 2070-1721 Cisco Systems

                                                              T. Chown
                                             University of Southampton
                                                            M. Eubanks
                                               Iformata Communications
                                                           August 2012
               Multicast Addresses for Documentation

Abstract

 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.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6676.

Venaas, et al. Informational [Page 1] RFC 6676 Multicast Addresses for Documentation August 2012

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................2
 2. IPv4 Multicast Documentation Addresses ..........................3
    2.1. Administratively Scoped IPv4 Multicast Addresses ...........3
    2.2. GLOP Multicast Addresses ...................................3
    2.3. Unicast Prefix-Based IPv4 Multicast Addresses ..............4
 3. IPv6 Multicast Documentation Addresses ..........................4
    3.1. Unicast Prefix-Based IPv6 Multicast Addresses ..............5
    3.2. Embedded-RP IPv6 Multicast Addresses .......................5
 4. Security Considerations .........................................5
 5. IANA Considerations .............................................5
 6. Acknowledgments .................................................6
 7. Informative References ..........................................6

1. Introduction

 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 will never 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
 not be used by other multicast applications or services.  It may also
 be beneficial to filter out such addresses from multicast signalling
 and to filter out multicast data sent to such addresses.
 For unicast, there are both IPv4 and IPv6 addresses reserved for this
 purpose; see [RFC5737] and [RFC3849], respectively.  This document
 reserves multicast addresses for this same purpose.

Venaas, et al. Informational [Page 2] RFC 6676 Multicast Addresses for Documentation August 2012

 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.

2. IPv4 Multicast Documentation Addresses

 For Any-Source Multicast (ASM), the IPv4 multicast addresses
 allocated for documentation purposes are 233.252.0.0 - 233.252.0.255
 (233.252.0.0/24).
 For Source-Specific Multicast (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.  There are three unicast address ranges
 provided for documentation use in [RFC5737].  The ranges are
 192.0.2.0/24, 198.51.100.0/24 and 203.0.113.0/24.
 Sometimes one wants to give examples where a specific type of address
 is desired.  For example, 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.

2.1. Administratively Scoped IPv4 Multicast Addresses

 Administratively scoped IPv4 multicast addresses [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.  The high order /24 in every scope
 is reserved for relative assignments.  A relative assignment is an
 integer offset from the highest address in the scope and represents
 an IPv4 address.  For documentation purposes, the integer offset is
 10.  This provides one multicast address per scope.
 For example in the Local Scope 239.255.0.0/16, the multicast address
 for documentation purposes is 239.255.255.245.

2.2. GLOP Multicast Addresses

 GLOP [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.

Venaas, et al. Informational [Page 3] RFC 6676 Multicast Addresses for Documentation August 2012

 The 16-bit AS numbers reserved for documentation use in [RFC5398] are
 64496 - 64511.  By use of [RFC3180], we then get 16 /24 multicast
 prefixes for documentation use.  The first one is 233.251.240.0/24,
 and the last one is 233.251.255.0/24.

2.3. Unicast Prefix-Based IPv4 Multicast Addresses

 IPv4 multicast addresses can be derived from IPv4 unicast prefixes,
 see [RFC6034].  For examples where this type of address is desired,
 the addresses should be derived from the unicast addresses reserved
 for documentation purposes, see [RFC5737].
 There are three unicast address ranges provided for documentation use
 in [RFC5737].  The ranges are 192.0.2.0/24, 198.51.100.0/24, and
 203.0.113.0/24.  Using [RFC6034], this leaves the unicast prefix-
 based IPv4 multicast addresses 234.192.0.2, 234.198.51.100, and
 234.203.0.113.

3. IPv6 Multicast Documentation Addresses

 For Any-Source Multicast (ASM), the IPv6 multicast addresses
 allocated for documentation purposes are FF0X::DB8:0:0/96.  This is a
 /96 prefix so that it can be used with group IDs, according to the
 allocation guidelines in [RFC3307].  Also note that for these
 addresses, the transient flag, or "T-flag" as defined in [RFC4291],
 is zero.  This is because they are permanently assigned.  There can
 be no permanently assigned addresses for documentation purposes with
 the transient flag set to one, since the flag set to one means that
 they are not permanently assigned.
 For Source-Specific Multicast (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.  The IPv6 unicast prefix reserved for
 documentation purposes is 2001:DB8::/32, see [RFC3849].
 Sometimes one wants to give examples where a specific type of address
 is desired.  For example, 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.

Venaas, et al. Informational [Page 4] RFC 6676 Multicast Addresses for Documentation August 2012

3.1. Unicast Prefix-Based IPv6 Multicast Addresses

 IPv6 multicast addresses can be derived from IPv6 unicast prefixes,
 see [RFC3306].  For examples where this type of address is desired,
 the addresses should be derived from the unicast addresses reserved
 for documentation purposes.
 The IPv6 unicast prefix reserved for documentation purposes is 2001:
 DB8::/32, see [RFC3849].  This allows a wide range of different IPv6
 multicast addresses.  Using just the base /32 prefix, one gets the
 IPv6 multicast prefixes FF3X:20:2001:DB8::/64 -- one for each
 available scope X.  One can also produce longer prefixes from this.
 Just as an example, one can pick a /64 prefix 2001:DB8:DEAD:
 BEEF::/64, which gives the multicast prefixes FF3X:40:2001:DB8:DEAD:
 BEEF::/96 -- one for each available scope X.

3.2. Embedded-RP IPv6 Multicast Addresses

 There is a type of IPv6 multicast address called an "Embedded-RP"
 address, where the IPv6 address of a Rendezvous-Point (RP) is
 embedded inside the multicast address, see [RFC3956].  For examples
 where this type of address is desired, the addresses should be
 derived from the unicast addresses reserved for documentation
 purposes, see [RFC3849].
 For documentation purposes, the RP address can be any address from
 the range 2001:DB8::/32 that follows the constraints specified in
 [RFC3956].  One example address could be 2001:DB8::1.  The
 Embedded-RP multicast prefixes might then be FF7X:120:2001:DB8::/96.
 Another example could be the RP address 2001:DB8:BEEF:FEED::7, which
 gives the prefixes FF7X:740:2001:DB8:BEEF:FEED::/96.  See also the
 examples in [RFC3956].

4. Security Considerations

 The use of specific multicast addresses for documentation purposes
 has no negative impact on security.

5. IANA Considerations

 IANA has added a reference to this document for the IPv4 MCAST-TEST-
 NET allocation so that all the different documentation multicast
 assignments reference this document.
 IANA has assigned a scope-relative IPv4 address for documentation
 purposes.

Venaas, et al. Informational [Page 5] RFC 6676 Multicast Addresses for Documentation August 2012

 IANA has assigned "variable-scope" IPv6 multicast addresses for
 documentation purposes.  This is a /96 prefix.

6. Acknowledgments

 The authors thank Roberta Maglione, Leonard Giuliano and Dave Thaler
 for providing comments on this document.

7. Informative References

 [RFC2365]  Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
            RFC 2365, July 1998.
 [RFC3180]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
            BCP 53, RFC 3180, September 2001.
 [RFC3306]  Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
            Multicast Addresses", RFC 3306, August 2002.
 [RFC3307]  Haberman, B., "Allocation Guidelines for IPv6 Multicast
            Addresses", RFC 3307, August 2002.
 [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
            Reserved for Documentation", RFC 3849, July 2004.
 [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous
            Point (RP) Address in an IPv6 Multicast Address",
            RFC 3956, November 2004.
 [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
            Architecture", RFC 4291, February 2006.
 [RFC5398]  Huston, G., "Autonomous System (AS) Number Reservation for
            Documentation Use", RFC 5398, December 2008.
 [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
            Reserved for Documentation", RFC 5737, January 2010.
 [RFC6034]  Thaler, D., "Unicast-Prefix-Based IPv4 Multicast
            Addresses", RFC 6034, October 2010.

Venaas, et al. Informational [Page 6] RFC 6676 Multicast Addresses for Documentation August 2012

Authors' Addresses

 Stig Venaas
 Cisco Systems
 Tasman Drive
 San Jose, CA  95134
 USA
 EMail: stig@cisco.com
 Rishabh Parekh
 Cisco Systems
 Tasman Drive
 San Jose, CA  95134
 USA
 EMail: riparekh@cisco.com
 Gunter Van de Velde
 Cisco Systems
 De Kleetlaan 6a
 Diegem  1831
 Belgium
 Phone: +32 476 476 022
 EMail: gvandeve@cisco.com
 Tim Chown
 University of Southampton
 Highfield
 Southampton, Hampshire  SO17 1BJ
 United Kingdom
 EMail: tjc@ecs.soton.ac.uk
 Marshall Eubanks
 Iformata Communications
 130 W. Second Street
 Dayton, Ohio  45402
 US
 Phone: +1 703 501 4376
 EMail: marshall.eubanks@iformata.com
 URI:   http://www.iformata.com/

Venaas, et al. Informational [Page 7]

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