IPv6 Working Group J-S. Park INTERNET DRAFT ETRI Expires:
JanuaryFebruary 2005 M-K. Shin ETRI/NIST H-J. Kim ETRI JulyAugust 2004 Link Scoped IPv6 Multicast Addresses <draft-ietf-ipv6-link-scoped-mcast-04.txt><draft-ietf-ipv6-link-scoped-mcast-05.txt> Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 progress." 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 JanuaryFebruary 2005. Abstract This document specifies an extension to the multicast addressing architecture of the IPv6 protocol. The extension allows for the use of interface-IDs to allocate multicast addresses. When thea link- local unicast address is configured at each interface of a host,node, an interface ID is uniquely determined. By delegating multicast addresses at the same time as the interface ID, each hostnode can identifygenerate their unique multicast addresses automatically at Layer 1without running an intra- or inter-domain allocation protocol in serverless environments.conflicts. Basically, it is preferred to use this method for the link-local scope rather than Unicast-Prefix-basedunicast-prefix-based IPv6 Multicast Addressesmulticast addresses [RFC 3306]. Table of Contents: 1. Introduction................................................2 2. Applicability...............................................3Applicability...............................................2 3. Link scoped multicast address format........................3format........................2 4. Examples....................................................4Example ....................................................4 5. Considerations..............................................4 6. Security Considerations.....................................5Considerations.....................................4 7. Acknowledgments.............................................5References..................................................4 8. References..................................................5Acknowledgments.............................................4 Authors' Addresses.............................................6Addresses.............................................5 1. Introduction This specification 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 interface-IDs to allocate multicast addresses. When thea link-local unicast address is configured at each interface of a host,node, an interface ID is uniquely determined. By delegating multicast addresses at the same time as the interface ID, each hostnode can identify itsgenerate their unique multicast addresses automatically without running an intra- or inter-domain allocation protocol in serverless environments. The current multicast address allocation architecture [RFC 2908] is based on a multi-layered, multi-protocol system. The goal of this proposal is to reduce the number of protocols and servers to get dynamic multicast address allocation. The use of interface ID-based multicast address allocation will, at a minimum, remove the need to run the Multicast Address-Set Claim (MASC) Protocol [RFC 2909] and the Multicast Address Allocation servers [RFC 2908].conflicts. Basically, it is preferred to use this method for the link-local scope rather than Unicast-Prefix-basedunicast-prefix-based IPv6 Multicast Addressesmulticast addresses [RFC 3306]. This document restricts the usage of defined fields such as scope, plen and network prefix field infields of [RFC 3306]. Therefore, this document specifies encoded information for link- local scope in the 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 zeroconfzeroconf/serverless environment. For example, multicast addresses less than or equal to link-local scope are themselves generated by nodes supplying multicast services.services without conflicts. Consequently, this technique MUST be used for link scoped multicast addresses. If you want to use multicast addresses greater than link- local,link-local scope, you need other methods such as [RFC 3306]. 3. Link scoped multicast address format Section 2.7 of [EFC 3513][RFC 3306] defines the following operationalformat of unicast-prefix-based IPv6 multicast addresses: | 8 | 4 | 4 | 1128 | 8 | 64 | 32 | +--------+----+----+--------+--------+----------------+----------+ |11111111|flgs|scop|reserved| plen | network prefix | +--------+----+----+---------------------------------------------+ |11111111|flgs|scop|group ID | +--------+----+----+---------------------------------------------++--------+----+----+--------+--------+----------------+----------+ Figure 1: GenericUnicast-Prefix-based IPv6 multicast address format This document introducesspecifies a new formatsformat that incorporateincorporates interface ID information in the multicast address.addresses. The idea of delegating multicast addresses at the same time as the interface ID can be applicable to link-local.link-local scope. Figure 2 illustrates the new format for link scoped multicast addresses. That is, if the scope of the multicast address is link- local scope, it is this format.| 8 | 4 | 4 | 168 | 8 | 64 | 32 | +--------+----+----+------------+----------------+---------------+ |11111111|flgs|scop| reserved+--------+----+----+--------+--------+----------------+----------+ |11111111|flgs|scop|reserved| LSM | Interface ID | group ID | +--------+----+----+------------+----------------+---------------++--------+----+----+--------+--------+----------------+----------+ Figure 2: linkLink scoped multicast IPv6 address format +-+-+-+-+flgs is a set of 4 flags: |0|0|P|T| +-+-+-+-+ o P = 0 indicates a multicast address that is not assigned on the basis of the interface ID. o P = 1 indicates a multicast address that is assigned on the basis of the interface ID. o If P = 1, TMUST be set to 1, otherwise the setting of the T bit is defined in Section 2.7 of [RFC 2373]."0011". (The first two bits have been yet undefined, sent as zero and ignored on receipt.) flgs shouldMUST use the same flag defined in section 4 of [RFC 3306]. That is, this document proposes the third bit of 'flgs' field to indicate an Interface ID-based multicast addresses.scop MUST be <= 2. It is preferred to use this method for the link- local scope rather than Unicast-Prefix-basedunicast-prefix-based IPv6 Multicast Addressesmulticast addresses [RFC 3306]. The reserved field MUST be zerozero. LSM (Link Scoped Multicast) field MUST be "1111 1111" which maps to aplen field in [RFC 3306], whereas the plen of zero[RFC 3306] MUST NOT be greater than 64. That is, flgs, scop, and LSM fields are used to identify whether an address is a multicast address as specified in RFC 3306.this document and to be processed any further. Interface ID field is used to distinguish each hostnode from others. And 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 interface ID embedded in the multicast address SHOULD come from the interface ID of the link-local unicast address on the interface after DAD has completed. That is, the creation of the multicast address MUST occur after DAD has completed as part of the auto-config process. Group ID is generated to indicate 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]. The lifetime of an Interface ID-basedlink scoped multicast addressaddresses has no dependency on the Valid Lifetime field in the Prefix Information option, corresponding to the unicast address being used, contained in the Router Advertisement message [RFC 2461]. 4. ExamplesExample This is an example of an interface ID-basedlink scoped IPv6 multicast address with link-local scope.addresses. For example in an Ethernetethernet environment, if the link-local unicast address is FE80::a12:34ff:fe56:7890,FE80::A12:34FF:FE56:7890, the link scoped multicast prefix of the hostnode is FF32:0:a12:34ff:fe56:7890::/96.FF32:00FF:A12:34FF:FE56:7890::/96. 5. Considerations It is preferred to use this method for scop <= 2 rather than Unicast-Prefix-based IPv6 Multicast Addresses [RFC 3306]. This document considers only link scoped multicast addresses. For this purpose, scop field is used shown in figure 2.The link scoped multicast address format supports source-specific multicast addresses by the same method, as defined by [RFC 3306]. Note that if an SSM implementation checks for FF3x::/32, not FF3x::/96, the other nodes not implementing this specification will interpret the link-local multicast addresses generated using this specification as SSM addresses, since the document uses the reserved field in such a fashion that plen=0 [RFC 3306]. In order to avoid this conflict, we recommend SSM implementations must check for FF3x::/96, as described in Allocation Guidelines for IPv6 Multicast Addresses [RFC 3307] section 3.6. Security Considerations [RFC 3041] describes the privacy extension to IPv6 stateless address autoconfiguration for an interface ID. The interface ID, generated by [RFC 3041], is also used in this method since the uniqueness is verified by DAD procedure as part of the secure auto- config process. Using source-specific multicast addresses can sometimes aid in the prevention of denial-of-service attacks by arbitrary sources, although no guarantee is provided. A more in-depth discussion of the security considerations for SSM can be found in [SSM ARCH].7. Acknowledgements We would like to thank Dave Thaler and Brian Haberman for histheir comments related to the consistency between the unicast prefix- based multicast draftaddresses [RFC 3306] 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 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",Architecture," RFC 3513, April 2003. Informative [RFC 2461] T. Narten, E. Nordmark and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)",(IPv6)," RFC 2461, December 1998. [RFC 2908] D. Thaler, M. Handley and D. Estrin, "The Internet Multicast Address Allocation Architecture," RFC 2908, September 2000. [RFC 2909] P. Radoslavov, D. Estrin, R. Govindan, M. Handley, S. Kumar, and D. Thaler, "The Multicast Address-Set Claim (MASC) Protocol", RFC 2909, September 2000.[SSM ARCH] H. Holbrook and B. Cain, "Source-Specific Multicast for IP",IP," Work In Progress, October 2003.July 2004. Authors' Addresses Jung-Soo Park ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejon 305-600,Daejeon 305-350, Korea Phone: +82 42 860 6514 Email: firstname.lastname@example.org 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 : email@example.com Hyoung-Jun Kim ETRI PEC 161 Gajeong-Dong, Yuseong-Gu, Daejon 305-600,Daejeon 305-350, Korea Phone: +82 42 860 6576 Email: firstname.lastname@example.org 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. 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