draft-ietf-mboned-ipv4-uni-based-mcast-03.txt		draft-ietf-mboned-ipv4-uni-based-mcast-04.txt
	Network Working Group D. Thaler		Network Working Group D. Thaler
	Internet-Draft Microsoft		Internet-Draft Microsoft
	Expires: September 5, 2007 March 4, 2007		Expires: January 27, 2008 July 26, 2007
	Unicast-Prefix-based IPv4 Multicast Addresses		Unicast-Prefix-based IPv4 Multicast Addresses
	draft-ietf-mboned-ipv4-uni-based-mcast-03.txt		draft-ietf-mboned-ipv4-uni-based-mcast-04.txt
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, each author represents that any		By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware		applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes		have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.		aware will be disclosed, in accordance with Section 6 of BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 33		skipping to change at page 1, line 33
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on September 5, 2007.		This Internet-Draft will expire on January 27, 2008.
	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	Abstract		Abstract
	This specification defines an extension to the multicast addressing		This specification defines an extension to the multicast addressing
	architecture of the IP Version 4 protocol. The extension presented		architecture of the IP Version 4 protocol. The extension presented
	in this document allows for unicast-prefix-based allocation of		in this document allows for unicast-prefix-based allocation of
	skipping to change at page 3, line 17		skipping to change at page 3, line 17
	RFC 3180 [RFC3180] defined an experimental allocation mechanism		RFC 3180 [RFC3180] defined an experimental allocation mechanism
	(called "GLOP") in 233/8 whereby an Autonomous System (AS) number is		(called "GLOP") in 233/8 whereby an Autonomous System (AS) number is
	embedded in the middle 16 bits of an IPv4 multicast address,		embedded in the middle 16 bits of an IPv4 multicast address,
	resulting in 256 multicast addresses per AS. Advantages of this		resulting in 256 multicast addresses per AS. Advantages of this
	mechanism include the ability to get multicast address space without		mechanism include the ability to get multicast address space without
	an inter-domain multicast address allocation protocol, and the ease		an inter-domain multicast address allocation protocol, and the ease
	of determining the AS of the owner of an address for debugging and		of determining the AS of the owner of an address for debugging and
	auditing purposes.		auditing purposes.
	Some disadvantages of GLOP include:		Some disadvantages of GLOP include:
	o there is work in progress [AS4B] on expanding the size of an AS		o RFC 4893 [RFC4893] expands the size of an AS number to 4 bytes,
	number to 4 bytes, and GLOP cannot work with such AS's.		and GLOP cannot work with 4-byte AS numbers.
	o when an AS covers multiple sites or organizations, administration		o When an AS covers multiple sites or organizations, administration
	of the multicast address space within an AS must be handled by		of the multicast address space within an AS must be handled by
	other mechanisms, such as manual administrative effort or MADCAP		other mechanisms, such as manual administrative effort or MADCAP
	[RFC2730].		[RFC2730].
	o during debugging, identifying the AS does not immediately identify		o During debugging, identifying the AS does not immediately identify
	the owning organization, when an AS covers multiple organizations.		the owning organization when an AS covers multiple organizations.
	o only 256 addresses are automatically available per AS, and		o Only 256 addresses are automatically available per AS, and
	obtaining any more requires administrative effort.		obtaining any more requires administrative effort.
	More recently, a mechanism [RFC3306] has been developed for IPv6		More recently, a mechanism [RFC3306] has been developed for IPv6 that
	which provides a multicast range to every IPv6 subnet, which is at a		provides a multicast range to every IPv6 subnet, which is at a much
	much finer granularity than an AS. As a result, the first three		finer granularity than an AS. As a result, the first three
	disadvantages above are avoided (and the last disadvantage does not		disadvantages above are avoided (and the last disadvantage does not
	apply to IPv6 due to the extended size of the address space).		apply to IPv6 due to the extended size of the address space).
	Another advantage of providing multicast space to every subnet		Another advantage of providing multicast space to a subnet, rather
	(rather than just to an entire AS) is that multicast address		than just to an entire AS, is that multicast address allocation
	allocation within the range need only be coordinated within the		within the range need only be coordinated within the subnet.
	subnet.
	This draft specifies a mechanism similar to [RFC3306], whereby a		This draft specifies a mechanism similar to [RFC3306], whereby a
	range of IPv4 multicast address space is provided to most IPv4		range of IPv4 multicast address space is provided to each
	subnets. A resulting advantage over GLOP is that the mechanisms in		organization that has unicast address space. A resulting advantage
	IPv4 and IPv6 become more similar.		over GLOP is that the mechanisms in IPv4 and IPv6 become more
			similar.
	This document proposes an experimental method of statically		This document proposes an experimental method of statically
	allocating multicast addresses with global scope. As described in		allocating multicast address ranges with global scope. As described
	section Section 4, this experiment will last for a period of one		in section Section 4, this experiment will last for a period of one
	year, but may be extended.		year, but may be extended.
	2. Address Space		2. Address Space
	(RFC-editor: replace TBD below with IANA-assigned value, and delete		(RFC-editor: replace TBD below with IANA-assigned value, and delete
	this note.)		this note.)
	A multicast address with the prefix TBD/8 indicates that the address		A multicast address with the prefix TBD/8 indicates that the address
	is a Unicast-Based Multicast (UBM) address. The remaining 24 bits		is a Unicast-Based Multicast (UBM) address. The remaining 24 bits
	can be used as follows:		are used as follows:
	Bits: | 8 | Unicast Prefix Length | 24 - Unicast Prefix Length |		Bits: | 8 | Unicast Prefix Length | 24 - Unicast Prefix Length |
	+-----+-----------------------+----------------------------+		+-----+-----------------------+----------------------------+
	Value: | TBD | Unicast Prefix | Group ID |		Value: | TBD | Unicast Prefix | Group ID |
	+-----+-----------------------+----------------------------+		+-----+-----------------------+----------------------------+
	For subnets with a /24 or shorter prefix, the unicast prefix of the		For organizations with a /24 or shorter prefix, the unicast prefix of
	subnet is appended to the common /8. Any remaining bits may be		the organization is appended to the common /8. Any remaining bits
	locally assigned by hosts within the link (e.g., using manual		may be assigned by any mechanism the organization wishes. For
	configuration). Individual subnets with a prefix length longer than		example, an organization that has a subnet with a /24 or shorter
	24 do not receive any multicast address space from this mechanism; in		prefix assigned to a link may wish to embed the entire subnet prefix
	such cases, another mechanism must be used.		within the multicast address, with the remaining bits assigned by
			hosts within the link (e.g., using manual configuration).
			Organizations with a prefix length longer than 24 do not receive any
			multicast address space from this mechanism; in such cases, another
			mechanism must be used.
	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 than		receive less address space than it does from GLOP if it has less than
	a /16.		a /16.
	The owner of a UBM address can be determined by taking the multicast		The owner of a UBM address can be determined by taking the multicast
	address, shifting it left by 8 bits, and identifying the owner of the		address, shifting it left by 8 bits, and identifying the owner of the
	address space covering the resulting unicast address.		address space covering the resulting unicast address.
	3. Security Considerations		3. Security Considerations
	The same well known intra-domain security techniques can be applied		The same well known intra-domain security techniques can be applied
	as with GLOP. Furthermore, when dynamic allocation is used within a		as with GLOP. Furthermore, when dynamic allocation is used within a
	prefix, the approach described here may have the effect of reduced		prefix, the approach described here may have the effect of reduced
	exposure to denial of space attacks, since the topological area		exposure to denial of space attacks, since the topological area
	within which nodes compete for addresses within the same prefix is		within which nodes compete for addresses within the same prefix is
	reduced from an entire AS to only within an individual subnet.		reduced from an entire AS to only within an individual organization
			or an even smaller area.
	4. IANA Considerations		4. IANA Considerations
	IANA should assign a /8 in the IPv4 multicast address space for this		IANA should assign a /8 in the IPv4 multicast address space for this
	purpose.		purpose.
	This assignment should timeout one year after the assignment is made.		This assignment should time out one year after the assignment is
	The assignment may be renewed at that time.		made. The assignment may be renewed at that time.
	5. Informative References		5. Informative References
	[AS4B] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
	Number Space", February 2007, <http://www.ietf.org/
	internet-drafts/draft-ietf-idr-as4bytes-13.txt>.
	[RFC2730] Hanna, S., Patel, B., and M. Shah, "Multicast Address		[RFC2730] Hanna, S., Patel, B., and M. Shah, "Multicast Address
	Dynamic Client Allocation Protocol (MADCAP)", RFC 2730,		Dynamic Client Allocation Protocol (MADCAP)", RFC 2730,
	December 1999.		December 1999.
	[RFC3180] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",		[RFC3180] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
	BCP 53, RFC 3180, September 2001.		BCP 53, RFC 3180, September 2001.
	[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6		[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
	Multicast Addresses", RFC 3306, August 2002.		Multicast Addresses", RFC 3306, August 2002.
			[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
			Number Space", RFC 4893, May 2007.
	Author's Address		Author's Address
	Dave Thaler		Dave Thaler
	Microsoft Corporation		Microsoft Corporation
	One Microsoft Way		One Microsoft Way
	Redmond, WA 98052		Redmond, WA 98052
	USA		USA
	Phone: +1 425 703 8835		Phone: +1 425 703 8835
	Email: dthaler@microsoft.com		Email: dthaler@microsoft.com
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