draft-ietf-mboned-ipv4-uni-based-mcast-01.txt   draft-ietf-mboned-ipv4-uni-based-mcast-02.txt 
Network Working Group Dave Thaler Network Working Group Dave Thaler
Internet-Draft Microsoft Internet-Draft Microsoft
Expires: July 2004 19 January 2004 Expires: April 2005 October 18, 2004
Unicast-Prefix-based IPv4 Multicast Addresses Unicast-Prefix-based IPv4 Multicast Addresses
<draft-ietf-mboned-ipv4-uni-based-mcast-01.txt> <draft-ietf-mboned-ipv4-uni-based-mcast-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with By submitting this Internet-Draft, I certify that any applicable
all provisions of Section 10 of RFC2026. patent or other IPR claims of which I am aware have been
disclosed, or will be 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 Internet-Drafts are working documents of the Internet Engineering
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skipping to change at page 1, line 36 skipping to change at page 2, line 5
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Draft Uni-Prefix-based IPv4 Multicast October 2004
Draft Uni-Prefix-based IPv4 Multicast January 2004 Abstract
This specification defines an extension to the multicast This specification defines an extension to the multicast
addressing architecture of the IP Version 4 protocol. The addressing architecture of the IP Version 4 protocol. The
extension presented in this document allows for unicast-prefix- extension presented in this document allows for unicast-prefix-
based allocation of multicast addresses. By delegating multicast based allocation of multicast addresses. By delegating multicast
addresses at the same time as unicast prefixes, network operators addresses at the same time as unicast prefixes, network operators
will be able to identify their multicast addresses without needing will be able to identify their multicast addresses without needing
to run an inter-domain allocation protocol. to run an inter-domain allocation protocol.
1. Introduction 1. Introduction
RFC 2770 [GLOP] defined an experimental allocation mechanism in RFC 3180 [GLOP] defined an experimental allocation mechanism in
233/8 whereby an Autonomous System (AS) number is embedded in the 233/8 whereby an Autonomous System (AS) number is embedded in the
middle 16 bits of an IPv4 multicast address, resulting in 256 middle 16 bits of an IPv4 multicast address, resulting in 256
multicast addresses per AS. Advantages of this mechanism include multicast addresses per AS. Advantages of this mechanism include
the ability to get multicast address space without an inter-domain the ability to get multicast address space without an inter-domain
multicast address allocation protocol, and the ease of determining multicast address allocation protocol, and the ease of determining
the AS of the owner of an address for debugging and auditing the AS of the owner of an address for debugging and auditing
purposes. purposes.
Some disadvantages of GLOP include: Some disadvantages of GLOP include:
o only 256 addresses are automatically available per AS, and
obtaining any more requires administrative effort.
o there is work in progress [AS4B] on expanding the size of an o there is work in progress [AS4B] on expanding the size of an
AS number to 4 bytes, and GLOP cannot work with such AS's. AS number to 4 bytes, and GLOP cannot work with such AS's.
o when an AS covers multiple sites or organizations, o when an AS covers multiple sites or organizations,
administration of the multicast address space within an AS administration of the multicast address space within an AS
must be handled by other mechanisms, such as manual must be handled by other mechanisms, such as manual
administrative effort or MADCAP [MADCAP]. administrative effort or MADCAP [MADCAP].
o during debugging, identifying the AS does not immediately o during debugging, identifying the AS does not immediately
identify the owning organization, when an AS covers multiple identify the owning organization, when an AS covers multiple
organizations. organizations.
o only 256 addresses are automatically available per AS, and
obtaining any more requires administrative effort.
More recently, a mechanism [V6UPBM] has been developed for IPv6 More recently, a mechanism [V6UPBM] has been developed for IPv6
which provides a multicast range to every IPv6 subnet, which is at which provides a multicast range to every IPv6 subnet, which is at
a much finer granularity than an AS. As a result, the latter a much finer granularity than an AS. As a result, the first three
three disadvantages above are avoided (and the first disadvantage disadvantages above are avoided (and the last disadvantage does
does not apply to IPv6 due to the extended size of the address not apply to IPv6 due to the extended size of the address space).
space).
Two significant advantages of providing multicast space to every
Draft Uni-Prefix-based IPv4 Multicast January 2004
subnet (rather than just to an entire AS) are that:
o multicast address allocation within the range need only be Draft Uni-Prefix-based IPv4 Multicast October 2004
coordinated within the subnet, and hence can be done with
zero configuration.
o bidirectional shared tree routing protocols may easily locate Another advantage of providing multicast space to every subnet
the direction to the root by doing a route lookup on a (rather than just to an entire AS) is that multicast address
unicast address derived from the multicast group address. allocation within the range need only be coordinated within the
subnet.
This draft specifies a mechanism similar to [V6UPBM], whereby a This draft specifies a mechanism similar to [V6UPBM], whereby a
range of IPv4 multicast address space is provided to most IPv4 range of IPv4 multicast address space is provided to most IPv4
subnets. A resulting advantage over GLOP is that the mechanisms subnets. A resulting advantage over GLOP is that the mechanisms
in IPv4 and IPv6 become more similar. in IPv4 and IPv6 become more similar.
This document proposes an experimental method of statically
allocating multicast addresses with global scope. As described in
section 4, this experiment will last for a period of one year, but
may be extended.
2. Address Space 2. Address Space
(RFC-editor: replace TBD below with IANA-assigned value, and (RFC-editor: replace TBD below with IANA-assigned value, and
delete this note.) delete this note.)
A multicast address with the prefix TBD/8 indicates that the A multicast address with the prefix TBD/8 indicates that the
address is a Unicast-Based Multicast (UBM) address. The address is a Unicast-Based Multicast (UBM) address. The
remaining 24 bits can be used as follows: remaining 24 bits can be used as follows:
Bits: | 8 | Unicast Prefix Length | 24 - Unicast Prefix Length | Bits: | 8 | Unicast Prefix Length | 24 - Unicast Prefix Length |
skipping to change at page 4, line 5 skipping to change at page 4, line 5
Compared to GLOP, an AS will receive more address space via this Compared to GLOP, an AS will receive more address space via this
mechanism if it has more than a /16 for unicast space. An AS will mechanism if it has more than a /16 for unicast space. An AS will
receive less address space than it does from GLOP if it has less receive less address space than it does from GLOP if it has less
than a /16. than a /16.
The owner of a UBM address can be determined by taking the The owner of a UBM address can be determined by taking the
multicast address, shifting it left by 8 bits, and identifying the multicast address, shifting it left by 8 bits, and identifying the
owner of the address space covering the resulting unicast address. owner of the address space covering the resulting unicast address.
Draft Uni-Prefix-based IPv4 Multicast January 2004 Draft Uni-Prefix-based IPv4 Multicast October 2004
3. IANA Considerations 3. Security Considerations
The same well known intra-domain security techniques can be
applied as with GLOP. Furthermore, when dynamic allocation is
used within a prefix, the approach described here may have the
effect of reduced exposure to denial of space attacks, since the
topological area within which nodes compete for addresses within
the same prefix is reduced from an entire AS to only within an
individual subnet.
4. IANA Considerations
IANA should assign a /8 in the IPv4 multicast address space for IANA should assign a /8 in the IPv4 multicast address space for
this purpose. this purpose.
4. Security Considerations This assignment should timeout one year after the assignment is
made. The assignment may be renewed at that time.
Since dynamic assignment does not cross domain boundaries, the
same well known intra-domain security techniques can be applied as
with GLOP. Furthermore, the approach described here may have the
effect of reduced exposure to denial of space attacks based on
dynamic allocation, since the area of dynamic allocation is
reduced from an entire AS to only within individual subnets.
5. Author's Address 5. Author's Address
Dave Thaler Dave Thaler
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052-6399 Redmond, WA 98052-6399
Phone: +1 425 703 8835 Phone: +1 425 703 8835
EMail: dthaler@microsoft.com EMail: dthaler@microsoft.com
6. Informative References 6. Informative References
[AS4B] [AS4B]
Vohra, Q. and E. Chen, "BGP support for four-octet AS number Vohra, Q. and E. Chen, "BGP support for four-octet AS number
space", draft-ietf-idr-as4bytes-07.txt, Work in progress, space", draft-ietf-idr-as4bytes-08.txt, Work in progress,
August 2003. March 2004.
[GLOP] [GLOP]
Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", RFC Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", RFC
2770, February 2000. 3180, September 2001.
[MADCAP] [MADCAP]
Hanna, S, Patel, B. and M. Shah, "Multicast Address Dynamic Hanna, S, Patel, B. and M. Shah, "Multicast Address Dynamic
Client Allocation Protocol (MADCAP)", RFC 2730, December Client Allocation Protocol (MADCAP)", RFC 2730, December
1999. 1999.
Draft Uni-Prefix-based IPv4 Multicast October 2004
[V6UPBM] [V6UPBM]
Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002. Multicast Addresses", RFC 3306, August 2002.
Draft Uni-Prefix-based IPv4 Multicast January 2004
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