One document matched: draft-haberman-malloc-ipv6-prefix-00.txt
MALLOC Working Group B. Haberman
Internet Draft Nortel Networks
draft-haberman-malloc-ipv6-prefix-00.txt
February 2000
Expires August 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
http://www.ietf.org/shadow.html.
Abstract
With the multicast address architecture proposed in [NEW ARCH], 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 collisions on layer 2 devices.
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 multicast address architecture proposed in [NEW ARCH], 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 collisions on layer 2 devices.
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.
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Internet Draft IPv6 Multicast Address Architecture December 1999
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 will generate unique MAC addresses.
Due to this, new IPv6 multicast addresses that are network prefix-based
have the following format:
| 8 | 4 | 4 | 8 | plen bits | 72 _ plen | 32 bits |
+--------+----+ +
---- --------+----------------+-----------+------------+
|11111111|flgs|scop| plen | Network prefix | reserved | group ID |
+--------+----+----+--------+----------------+-----------+------------+
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 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. 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
The group ID portion of the address is set using one of the following
mechanisms.
4.1 Network Time Protocol (NTP) Rule
The Network Time Protocol [RFC 1305] defines a 64-bit network
timestamp. The entity creating the IPv6 multicast address sets the
group ID portion of the IPv6 multicast address to the upper 32 bits of
the NTP timestamp. In order for a collision to occur at the IEEE 802
layer, two IPv6 multicast address allocations would have to occur at
the same second.
4.2 Network Time Protocol and IPv6 Unicast Address
This mechanism adds some complexity to the NTP approach defined above.
The entity creating the IPv6 multicast address once again obtains an
NTP timestamp. It then logically OR's the upper 32 bits of the NTP
timestamp with the lowest 32 bits of its IPv6 link-local address and
places that value in the group ID portion of the IPv6 multicast
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Internet Draft IPv6 Multicast Address Architecture December 1999
address. This approach addresses the scenario where two allocating
entities allocate addresses in the same second.
4.3 MD5 Digest
In this approach, the group ID is created using the MD5 Message-Digest
[RFC 1321]. The 64-bit IPv6 Network Prefix is appended with either the
64-bit NTP timestamp or a 64-bit value created using the guidelines in
[RFC 1750]. The corresponding 128-bit value is then fed into MD5. The
group ID portion of the IPv6 multicast address is set to the lowest 32
bits of the resulting MD5 digest value.
5.
Security Considerations
This document does not have any direct impact on Internet
infrastructure security.
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 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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