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
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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
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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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