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draft-ietf-malloc-ipv6-guide-00.txt --> draft-ietf-malloc-ipv6-guide-01.txt

MALLOC Working Group B. Haberman
Internet Draft Nortel Networks
draft-ietf-malloc-ipv6-guide-00.txt
May
draft-ietf-malloc-ipv6-guide-01.txt
July 2000
Expires November 2000 January 2001

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

This document specifies guidelines is needed for
multicast address allocation servers to use in assigning be used when allocating IPv6
multicast addresses. The purpose of these rules guidelines is to reduce
the
possibility probability of IPv6 multicast address collision collision, not only at layer 3, the
IPv6 layer, but also on
devices at the MAC layer 2. of media that utilizes IEEE
802 addressing.

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

This document specifies guidelines to be used when allocating IPv6
multicast addresses. The purpose of these guidelines is to reduce

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the probability of IPv6 multicast address collision, not only at the
IPv6 layer, but also at the MAC layer of media that utilizes IEEE
802 addressing.

With the current IPv6 multicast address architecture [RFC 2373] and
the
multicast address architecture proposed extension to that architecture specified 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 supporting several mechanisms of varying
complexity, implementers and operators have mechanisms, these
guidelines can accommodate the flexibility to
choose a mechanism that is appropriate for their application. varying capabilities of multicast
address allocation servers.

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 IDs
less than or equal to 32 bits long will generate unique MAC
addresses.
addresses within a given multicast scope.

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 mechanisms 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 according to [RFC 2373] and
the plen field is set. The Network Prefix is obtained
from the periodic Router Advertisements.
o
[NEW ARCH].

The reserved field in the IPv6 T flag of each dynamically allocated multicast address is MUST be
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

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Internet Draft IPv6 Multicast Address Architecture May 2000

o The reserved field in '1'. Permanent addresses MUST NOT be allocated using the IPv6
multicast address is set
to zero allocation architecture.

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 include using an MD5 message-digest [RFC 1321] or portions of
an NTP [RFC 1305] timestamp.

The assignment high-order bit of the group Group ID portion of the address SHOULD take
care MUST be set to ensure that '1'. This will
distinguish the dynamically allocated addresses from the generated multicast address does not share a
group ID with a permanently assigned

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Internet Draft IPv6 multicast address. The
permanently Multicast Address Guidelines July 2000

assigned multicast addresses are defined in [RFC 2375].

Requests 2375] at the MAC layer
on any media that utilizes IEEE 802 addressing.

A request for more than one multiple multicast address addresses 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 known impact on Internet
infrastructure security.

7. Acknowledgements

The author would like to thank Dave Thaler and Steve Deering for
their thorough review of this document.

8. 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 "Unicast Prefix-based IPv6
Multicast
Addressing Architecture",
draft-ietf-ipngwg-mcast-arch-00.txt, April Addresses", Work in Progress, July 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.

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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.

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Internet Draft IPv6 Multicast Address Guidelines July 2000

[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.

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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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