IPv6 Working Group J-S. Park INTERNET DRAFT ETRI Expires:
June 2005January 18, 2006 M-K. Shin ETRI/NISTUpdates: 3306 ETRI H-J. Kim ETRI December 2004July 17, 2005 A Method for Generating Link Scoped IPv6 Multicast Addresses <draft-ietf-ipv6-link-scoped-mcast-08.txt><draft-ietf-ipv6-link-scoped-mcast-09.txt> Status of this Memo By submitting this Internet-Draft, I certifyeach author represents that any applicable patent or other IPR claims of which I amhe or she is aware have been or will be disclosed, and any of which I becomehe or she becomes aware will be disclosed, in accordance with RFC 3668.Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other docu- ments at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in pro- gress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 2005.January 18, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document specifies an extension to the multicast addressing architecture of the IPv6 protocol. The extension allows for the use of Interface Identifiers (IIDs) to allocate multicast addresses. When a link-local unicast address is configured at each interface of a node, an IID is uniquely determined. After that, each node can generate their unique multicast addresses automatically without conflicts. Basically, this document proposes an alternative method for creating link-local multicast addresses over a known method like unicast-prefix-based IPv6 multicast addresses. It is preferred to use this method for link-local scope rather than unicast- prefix-based IPv6 multicast addresses. This memo update RFC3306. Table of Contents: 1. Introduction................................................2 2. Applicability...............................................2 3. Link Scoped Multicast Address Format........................3 4. Example ....................................................3....................................................4 5. Consideration of Lifetime ..................................3..................................4 6. Security Considerations.....................................4 7. Acknowledgments.............................................4 8. References..................................................4References..................................................5 Author's Addresses.............................................5 1. Introduction This document defines an extension to the multicast portion of the IPv6 addressing architecture [RFC 3513]. The current architecture does not contain any built-in support for dynamic address allocation. The extension allows for use of IIDs to allocate multicast addresses. When a link-local unicast address is configured at each interface of a node, an IID is uniquely determined. After that, each node can generate their unique multicast addresses automatically without conflicts. That is, these addresses could safely be configured at any time after DAD (Duplicate Address Detection) has completed. Basically, it is preferred to use this method for the link-local scope rather than unicast-prefix-based IPv6 multicast addresses [RFC 3306].3306], since by delegating multicast addresses using the IID, each node can generate its multicast addresses automatically without allocation servers. This method goes well with applications in serverless environment such as ad-hoc and network mobility rather thant unicast-prefix-based method. This document restricts the usage of defined fields such as scop, plen and network prefix fields of [RFC 3306]. Therefore, this document specifies encoded information for link- locallink-local scope in 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]. 2. Applicability The allocation technique in this document is designed to be used in any environment in which link-local scope IPv6 multicast addresses are assigned or selected. Especially, this method goes well with nodes supplying multicast services in a zeroconf/serverless environment. For example, multicast addresses less than or equal to link-local scope are themselves generated by nodes supplying multicast services without conflicts. Also, hosts which are supplied multicast services from multicast servers then make multicast addresses of multicast servers using ND (address resolution) and well-known group IDs. Consequently, this technique MUST only be used for link scoped multicast addresses. If you want to use multicast addresses greater than link-local scope, you need to use other methods as described in [RFC 3306]. 3. Link Scoped Multicast Address Format This document specifies a new format that incorporates IID in the link-local scope multicast addresses. Figure 1 illustrates the new format for link scoped multicast addresses. | 8 | 4 | 4 | 8 | 8 | 64 | 32 | +--------+----+----+--------+--------+----------------+----------+ |11111111|flgs|scop|reserved| plen | IID | group ID | +--------+----+----+--------+--------+----------------+----------+ Figure 1: Link scoped multicast IPv6 address format Flgs, scop, and plen fields are used to identify whether an address is a multicast address as specified in this document as follows: 1. flgs MUST be "0011". 2. scop MUST be <= 2. 3. The reserved field MUST be zero. 4. "plen" field is a special value "1111 1111" (decimal 255). The IID field (replacing the 64-bit prefix field from [RFC 3306]) is used to distinguish each node from others. This value is obtained from the IEEE EUI-64 based interface identifier of the link-local unicast IPv6 address.Given the use of this method for link-local scope, the IID embedded in the multicast address MUST only come from the IID of the link-local unicast address on the interface after DAD has completed. That is, the creation of the multicast address MUST only occur after DAD has completed as part of the auto-configuration process. Group ID is generated to indicate a multicast application and is used to guarantee its uniqueness only in the host. It may also be set on the basis of the guidelines outlined in [RFC 3307]. 4. Example This is an example of link scoped IPv6 multicast addresses. For example in an ethernet environment, if the link-local unicast address is FE80::A12:34FF:FE56:7890, the link scoped multicast prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96. 5. Consideration of Lifetime Generally, Link scoped multicast addresses have no lifetime because link-local unicast addresses also have no lifetime. But, it is not true in environment of mobile. Even though multicast addresses are created from the unique IID of unicast address, their useful lifetime is linked to the period during which the IID is known to be unique. Thus, it is possible to conflict between IIDs, due to a new node in merged network that uses the same IID as a powered node. This is a scenario where DAD also fails to guarantee the uniqueness of the unicast address, so this document does not try to address this issue. 6. Security Considerations The uniqueness of multicast addresses using this method is guaranteed by the DAD process. So, it is needed to get a secure DAD process for stability of this method. This document proposes the mechanism in [RFC 3041] for this purpose. [RFC 3041] describes the privacy extension to IPv6 stateless address autoconfiguration to how to configure the IID of non-link- local scope unicast addresses. [RFC 3041] can not be used for making a link-local unicast address, and hence it cannot be used to create an IID for link-scoped multicast address. However, as [RFC 3041] does not protect the privacy of link-local unicast addresses, it does not protect the privacy of link-local unicast addresses, it does not seem to be required to protect the privacy of IID-based link-local multicast addresses. 7. Acknowledgements We would like to thank Dave Thaler and Brian Haberman for his comments related to the consistency between the unicast prefix- based multicast draft and this one. Special thanks are due to Erik Nordmark and Pekka Savola for valuable comments. 8. References Normative [RFC 2119] S. Bradner, "Key words for use in RFCs to indicate Requirement Levels", RFC 2119, March 1997. [RFC 2461] T. Narten, E. Nordmark and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [RFC 3041] T. Narten and R. Draves, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6," RFC 3041, April 2001. [RFC 3306] B. Haberman and D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses," RFC 3306, August 2002. [RFC 3307] B. Haberman, "Allocation Guidelines for IPv6 Multicast Addresses," RFC 3307, August 2002. [RFC 3513] R. Hinden and S. Deering, "IP Version 6 Addressing Architecture", RFC 3513, April 2003. Informative [RFC 3956] P. Savola and B. Haberman, "Embedding the Rendezvous Point (RP) Address in an IPv6 Multicast Address [SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast for IP", Work In Progress, September 2004. Authors' Addresses Jung-Soo Park ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Phone: +82 42 860 6514 Email: email@example.com Myung-Ki Shin ETRI/NIST 820 West Diamond Avenue Gaithersburg, MD 20899, USA Tel : +1 301 975-3613 Fax : +1 301 590-0932 E-mail : firstname.lastname@example.org Hyoung-Jun Kim ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejeon 305-350, Korea Phone: +82 42 860 6576 Email: email@example.com Intellectual Property Statement 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 found in BCP 78 and BCP 79. 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