MALLOC Working Group B. Haberman Internet Draft Nortel Networks draft-ietf-malloc-ipv6-guide-00.txt May 2000 Expires November 2000 Dynamic Allocation Guidelines for IPv6 Multicast Addresses Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [RFC 2026]. 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 documents 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. Abstract With the current multicast address architecture and the proposed multicast address architecture, a set of guidelines is needed for multicast address allocation servers to use in assigning IPv6 multicast addresses. The purpose of these rules is to reduce the possibility of address collision not only at layer 3, but also on devices at layer 2. 1. Terminology 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. Introduction Haberman 1 Internet Draft IPv6 Multicast Address Architecture May 2000 With the current multicast address architecture [RFC 2373] and the multicast address architecture proposed in [NEW ARCH], a set of guidelines is needed for multicast address allocation servers [MALLOC] to use in assigning IPv6 multicast addresses. The purpose of these rules is to reduce the possibility of address collision not only at layer 3, but also on devices at layer 2. These guidelines specify how the lowest 32 bits of the IPv6 multicast address are chosen and assigned. The guidelines specify several mechanisms that can be used to determine the lowest 32 bits of the multicast address. By having several mechanisms of varying complexity, implementers and operators have the flexibility to choose a mechanism that is appropriate for their application. 3. Assignment of New IPv6 Multicast Addresses The current approach [RFC 2464] to map IPv6 multicast addresses into IEEE 802 MAC addresses takes the low order 32 bits of the IPv6 multicast address and uses it to create a MAC address. Group ID's less than or equal to 32 bits long will generate unique MAC addresses. The goal of this document is to present several mechanisms implementers and operators can use to select the group ID portion of the address so that the possibility of collisions at the IP layer and at the IEEE 802 layer is reduced. The following section presents several different mechanism of varying complexity that can be used to select an appropriate group ID. 4. Group ID Selection Guidelines The following guidelines assume that the upper 96 bits of the IPv6 multicast address have been set up. For unicast network prefix- based multicast addresses, the set up of those bits is done in the following manner: o An IPv6 multicast address prefix is initialized with the appropriate flags and scope fields o The IPv6 Network Prefix is inserted into the address and the plen field is set. The Network Prefix is obtained from the periodic Router Advertisements. o The reserved field in the IPv6 multicast address is set to zero With the multicast address architecture in [RFC 2373], the set up of those bits is done in the following manner: o An IPv6 multicast address prefix is initialized with the appropriate flags and scope fields Haberman 2 Internet Draft IPv6 Multicast Address Architecture May 2000 o The reserved field in the IPv6 multicast address is set to zero The group ID portion of the address is set using either a pseudo- random 32-bit number or a 32-bit number created using the guidelines in [RFC 1750]. Possible approaches to creating a pseudo-random number are to use an MD5 message-digest [RFC 1321] or portions of an NTP [RFC 1305] timestamp. The assignment of the group ID portion of the address SHOULD take care to ensure that the generated multicast address does not share a group ID with a permanently assigned IPv6 multicast address. The permanently assigned multicast addresses are defined in [RFC 2375]. Requests for more than one multicast address SHOULD be handled atomically. One possible approach is to use the initial group ID, created using the guidelines above, as the base address in a contiguous block of multicast addresses. Another approach is to create multiple group IDs and generate the appropriate multicast addresses. 5. Multicast Address Lifetime The lifetime of the assignment of unicast prefix-based multicast addresses MUST be less than or equal to the Valid Lifetime field in the Prefix Information option contained in the Neighbor Discovery Router Advertisement message [RFC 2461]. 6. Security Considerations This document does not have any direct impact on Internet infrastructure security. 7. References [RFC 2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [NEW ARCH] Haberman, B., Thaler, D., "IP Version 6 Multicast Addressing Architecture", draft-ietf-ipngwg-mcast-arch-00.txt, April 2000. [RFC 2373] Hinden, R., Deering, S., "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [MALLOC] Thaler, D., Handley, M., and Estrin, D., "The Internet Multicast Address Allocation Architecture", draft-ietf-malloc-arch-04.txt, January 2000. Haberman 3 Internet Draft IPv6 Multicast Address Architecture May 2000 [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP14, March 1999. [RFC 2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC 2464, December 1998. [RFC 1305] Mills, D., "Network Time Protocol (Version 3) Specification, Implementation", RFC 1305, March 1992. [RFC 1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [RFC 1750] Eastlake, D., Crocker, S., Schiller, J., "Randomness Recommendations for Security", RFC 1750, December 1994. [RFC 2375] Hinden, R., Deering, S., "IPv6 Multicast Address Assignments", RFC 2375, July 1998. [RFC 2461] Narten, T., Nordmark, E., Simpson, W., "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. Haberman 4 Author's Address Brian Haberman Nortel Networks 4309 Emperor Blvd. Suite 200 Durham, NC 27703 1-919-992-4439 Email : haberman@nortelnetworks.com Haberman 5