MALLOC Working Group B. Haberman
Internet Draft Nortel Networks
draft-haberman-malloc-ipv6-prefix-01.txt
March 2000
Expires September 2000
Dynamic Allocation Guidelines for
Network Prefix-based 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
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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
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
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Internet Draft IPv6 Multicast Address Architecture March 2000
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
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.
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. Security Considerations
This document does not have any direct impact on Internet
infrastructure security.
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Internet Draft IPv6 Multicast Address Architecture March 2000
6. References
[RFC 2026] S. Bradner, "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.
[NEW ARCH] B. Haberman, "IP Version 6 Multicast Addressing
Architecture", draft haberman
- -ipngwg-mcast-arch-00.txt,
December 1999.
[RFC 2373] R. Hinden, S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[MALLOC] D. Thaler, M. Handley, and D. Estrin, "The Internet
Multicast Address Allocation Architecture",
draft-ietf-malloc-arch-04.txt, January 2000.
[RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP14, March 1999.
[RFC 2464] M. Crawford, "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[RFC 1305] D. Mills, "Network Time Protocol (Version 3) Specification,
Implementation", RFC 1305, March 1992.
[RFC 1321] R. Rivest, "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992.
[RFC 1750] D. Eastlake, S. Crocker, J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
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Author's Address
Brian Haberman
Nortel Networks
4309 Emperor Blvd.
Suite 200
Durham, NC 27703
1-919-992-4439
Email : haberman@nortelnetworks.com
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