draft-ietf-mboned-addrarch-02.txt   draft-ietf-mboned-addrarch-03.txt 
Internet Engineering Task Force P. Savola Internet Engineering Task Force P. Savola
Internet-Draft CSC/FUNET Internet-Draft CSC/FUNET
Obsoletes: 2776,2908,2909 (if August 8, 2005 Obsoletes: 2776,2908,2909 (if October 18, 2005
approved) approved)
Expires: February 9, 2006 Expires: April 21, 2006
Overview of the Internet Multicast Addressing Architecture Overview of the Internet Multicast Addressing Architecture
draft-ietf-mboned-addrarch-02.txt draft-ietf-mboned-addrarch-03.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 35 skipping to change at page 1, line 35
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
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This Internet-Draft will expire on February 9, 2006. This Internet-Draft will expire on April 21, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
The lack of up-to-date documentation on IP multicast address The lack of up-to-date documentation on IP multicast address
allocation and assignment procedures has caused a great deal of allocation and assignment procedures has caused a great deal of
confusion. To clarify the situation, this memo describes the confusion. To clarify the situation, this memo describes the
allocation and assignment techniques and mechanisms currently (as of allocation and assignment techniques and mechanisms currently (as of
this writing) in use. this writing) in use.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology: Allocation or Assignment . . . . . . . . . . 3 1.1. Terminology: Allocation or Assignment . . . . . . . . . . 3
2. Multicast Address Allocation . . . . . . . . . . . . . . . . . 3 2. Multicast Address Allocation . . . . . . . . . . . . . . . . . 4
2.1 Derived Allocation . . . . . . . . . . . . . . . . . . . . 4 2.1. Derived Allocation . . . . . . . . . . . . . . . . . . . . 4
2.1.1 GLOP Allocation . . . . . . . . . . . . . . . . . . . 4 2.1.1. GLOP Allocation . . . . . . . . . . . . . . . . . . . 4
2.1.2 Unicast-prefix -based Allocation . . . . . . . . . . . 4 2.1.2. Unicast-prefix -based Allocation . . . . . . . . . . . 4
2.2 Scope-relative Allocation . . . . . . . . . . . . . . . . 5 2.2. Scope-relative Allocation . . . . . . . . . . . . . . . . 5
2.3 Static IANA Allocation . . . . . . . . . . . . . . . . . . 6 2.3. Static IANA Allocation . . . . . . . . . . . . . . . . . . 6
2.4 Dynamic Allocation . . . . . . . . . . . . . . . . . . . . 6 2.4. Dynamic Allocation . . . . . . . . . . . . . . . . . . . . 6
3. Multicast Address Assignment . . . . . . . . . . . . . . . . . 6 3. Multicast Address Assignment . . . . . . . . . . . . . . . . . 6
3.1 Derived Assignment . . . . . . . . . . . . . . . . . . . . 6 3.1. Derived Assignment . . . . . . . . . . . . . . . . . . . . 7
3.2 SSM Assignment inside the Node . . . . . . . . . . . . . . 7 3.2. SSM Assignment inside the Node . . . . . . . . . . . . . . 7
3.3 Manually Configured Assignment . . . . . . . . . . . . . . 7 3.3. Manually Configured Assignment . . . . . . . . . . . . . . 7
3.4 Static IANA Assignment . . . . . . . . . . . . . . . . . . 7 3.4. Static IANA Assignment . . . . . . . . . . . . . . . . . . 7
3.5 Dynamic Assignments . . . . . . . . . . . . . . . . . . . 8 3.5. Dynamic Assignments . . . . . . . . . . . . . . . . . . . 8
4. Summary and Future Directions . . . . . . . . . . . . . . . . 9 4. Summary and Future Directions . . . . . . . . . . . . . . . . 9
4.1 Prefix Allocation . . . . . . . . . . . . . . . . . . . . 9 4.1. Prefix Allocation . . . . . . . . . . . . . . . . . . . . 9
4.2 Address Assignment . . . . . . . . . . . . . . . . . . . . 10 4.2. Address Assignment . . . . . . . . . . . . . . . . . . . . 10
4.3 Future Actions . . . . . . . . . . . . . . . . . . . . . . 10 4.3. Future Actions . . . . . . . . . . . . . . . . . . . . . . 11
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1 Normative References . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2 Informative References . . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14 Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . . 14
A. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 A.1. Changes since -01 . . . . . . . . . . . . . . . . . . . . 14
A.1 Changes since -01 . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 15
1. Introduction 1. Introduction
Good, up-to-date documentation of IP multicast is close to non- Good, up-to-date documentation of IP multicast is close to non-
existent. Particularly, this is an issue with multicast address existent. Particularly, this is an issue with multicast address
allocations (to networks and sites) and assignments (to hosts and allocations (to networks and sites) and assignments (to hosts and
applications). This problem is stressed by the fact that there applications). This problem is stressed by the fact that there
exists confusing or misleading documentation on the subject exists confusing or misleading documentation on the subject
[RFC2908]. The consequence is that those who wish to learn of IP [RFC2908]. The consequence is that those who wish to learn of IP
multicast and how the addressing works do not get a clear view of the multicast and how the addressing works do not get a clear view of the
current situation. current situation.
The aim of this document is to provide a brief overview of multicast The aim of this document is to provide a brief overview of multicast
addressing and allocation techniques. The term 'addressing addressing and allocation techniques. The term 'addressing
architecture' refers to the set of addressing mechanisms and methods architecture' refers to the set of addressing mechanisms and methods
in an informal manner. in an informal manner.
It is important to note that Source-specific Multicast (SSM) It is important to note that Source-specific Multicast (SSM)
[I-D.ietf-ssm-arch] does not have these addressing problems; hence, [I-D.ietf-ssm-arch] does not have these addressing problems; hence,
this document focuses on Any Source Multicast (ASM) model. this document focuses on the Any Source Multicast (ASM) model.
This memo obsoletes RFCs 2776, 2908, and 2909 and re-classifies them This memo obsoletes RFCs 2776, 2908, and 2909 and re-classifies them
Historic. Historic.
1.1 Terminology: Allocation or Assignment 1.1. Terminology: Allocation or Assignment
Almost all multicast documents and many other RFCs (such as DHCPv4 Almost all multicast documents and many other RFCs (such as DHCPv4
[RFC2131] and DHCPv6 [RFC3315]) have used the terms address [RFC2131] and DHCPv6 [RFC3315]) have used the terms address
"allocation" and "assignment" interchangeably. However, the operator "allocation" and "assignment" interchangeably. However, the operator
and address management communities use these for two conceptually and address management communities use these for two conceptually
different processes. different processes.
In unicast operations, address allocations refer to leasing a large In unicast operations, address allocations refer to leasing a large
block of addresses from Internet Assigned Numbers Authority (IANA) to block of addresses from Internet Assigned Numbers Authority (IANA) to
a Regional Internet Registry (RIR) or from RIR to a Local Internet a Regional Internet Registry (RIR) or from RIR to a Local Internet
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Multicast address allocation, i.e., how a network operator might be Multicast address allocation, i.e., how a network operator might be
able to obtain a larger block of addresses, can be handled in a able to obtain a larger block of addresses, can be handled in a
number of ways as described below. number of ways as described below.
Note that these are all only pertinent to ASM -- SSM requires no Note that these are all only pertinent to ASM -- SSM requires no
address block allocation because the group address has only local address block allocation because the group address has only local
significance (however, we discuss the address assignment inside the significance (however, we discuss the address assignment inside the
node in Section 3.2). node in Section 3.2).
2.1 Derived Allocation 2.1. Derived Allocation
Derived allocations take the unicast prefix or some other properties Derived allocations take the unicast prefix or some other properties
of the network to determine unique multicast address allocations. of the network to determine unique multicast address allocations.
2.1.1 GLOP Allocation 2.1.1. GLOP Allocation
GLOP address allocation [RFC3180] inserts the 16-bit public GLOP address allocation [RFC3180] inserts the 16-bit public
Autonomous System (AS) number in the middle of the IPv4 multicast Autonomous System (AS) number in the middle of the IPv4 multicast
prefix 233.0.0.0/8, so that each AS number can get a /24 worth of prefix 233.0.0.0/8, so that each AS number can get a /24 worth of
multicast addresses. While this is sufficient for multicast testing multicast addresses. While this is sufficient for multicast testing
or small scale use, it might not be sufficient in all cases for or small scale use, it might not be sufficient in all cases for
extensive multicast use. extensive multicast use.
A minor operational debugging issue with GLOP addresses is that the A minor operational debugging issue with GLOP addresses is that the
connection between the AS and the prefix is not apparent from the connection between the AS and the prefix is not apparent from the
prefix, but has to be calculated (e.g., from [RFC3180], AS 5662 maps prefix when the AS number is greater than 255, but has to be
to 233.22.30.0/24). A usage issue is that GLOP addresses are not calculated (e.g., from [RFC3180], AS 5662 maps to 233.22.30.0/24). A
tied to any prefix but to routing domains, so they cannot be used or usage issue is that GLOP addresses are not tied to any prefix but to
calculated automatically. routing domains, so they cannot be used or calculated automatically.
2.1.2 Unicast-prefix -based Allocation 2.1.2. Unicast-prefix -based Allocation
RFC 3306 [RFC3306] describes a mechanism which embeds up to 64 first RFC 3306 [RFC3306] describes a mechanism which embeds up to 64 first
bits of an IPv6 unicast address in the prefix part of the IPv6 bits of an IPv6 unicast address in the prefix part of the IPv6
multicast address, leaving at least 32 bits of group-id space multicast address, leaving at least 32 bits of group-id space
available after the prefix mapping. available after the prefix mapping.
A similar mapping has been proposed for IPv4 [I-D.ietf-mboned-ipv4- A similar mapping has been proposed for IPv4 [I-D.ietf-mboned-ipv4-
uni-based-mcast], but it provides a rather low amount of addresses uni-based-mcast], but it provides a rather low amount of addresses
(e.g., 1 per an IPv4 /24 block). While there exist large networks (e.g., 1 per an IPv4 /24 block). While there exist large networks
without an AS number of their own, this has not been seen to add without an AS number of their own, this has not been seen to add
sufficient value compared to GLOP addressing. sufficient value compared to GLOP addressing.
The IPv6 unicast-prefix -based allocations are an extremely useful The IPv6 unicast-prefix-based allocations are an extremely useful way
way to allow each network operator, even each subnet, obtain to allow each network operator, even each subnet, obtain multicast
multicast addresses easily, through an easy computation. Further, as addresses easily, through an easy computation. Further, as the IPv6
the IPv6 multicast header also includes the scope value [RFC3513], multicast header also includes the scope value [RFC3513], multicast
multicast groups of smaller scope can also be used with the same groups of smaller scope can also be used with the same mapping.
mapping.
The IPv6 Embedded RP technique [RFC3956], used with Protocol The IPv6 Embedded RP technique [RFC3956], used with Protocol
Independent Multicast - Sparse Mode (PIM-SM), further leverages the Independent Multicast - Sparse Mode (PIM-SM), further leverages the
unicast prefix based allocations, by embedding the unicast prefix and unicast prefix based allocations, by embedding the unicast prefix and
interface identifier of the PIM-SM Rendezvous Point (RP) in the interface identifier of the PIM-SM Rendezvous Point (RP) in the
prefix. This provides all the necessary information needed to the prefix. This provides all the necessary information needed to the
routing systems to run the group in either inter- or intra-domain routing systems to run the group in either inter- or intra-domain
operation. A difference to RFC 3306 is, however, that the hosts operation. A difference to RFC 3306 is, however, that the hosts
cannot calculate their "multicast prefix" automatically, as the cannot calculate their "multicast prefix" automatically, as the
prefix depends on the decisions of the operator setting up the RP but prefix depends on the decisions of the operator setting up the RP but
rather requires an assignment method. rather requires an assignment method.
All the IPv6 unicast-prefix -based allocation techniques provide All the IPv6 unicast-prefix -based allocation techniques provide
sufficient amount of multicast address space for the network sufficient amount of multicast address space for the network
operators. operators.
2.2 Scope-relative Allocation 2.2. Scope-relative Allocation
Administratively scoped multicast [RFC2365] is provided by two Administratively scoped multicast [RFC2365] is provided by two
different means: under 239.0.0.0/8 in IPv4 or by 4-bit encoding in different means: under 239.0.0.0/8 in IPv4 or by 4-bit encoding in
the IPv6 multicast address prefix [RFC3513]. the IPv6 multicast address prefix [RFC3513].
As IPv6 scope-relative allocations can be handled with unicast-prefix As IPv6 scope-relative allocations can be handled with unicast-
-based multicast addressing as described in Section 2.1.2, and there prefix-based multicast addressing as described in Section 2.1.2, and
is no need for separate scope-relative allocations, we'll just there is no need for separate scope-relative allocations, we'll just
discuss IPv4 in this section. discuss IPv4 in this section.
The IPv4 scope-relative prefix 239.0.0.0/8 is further divided to The IPv4 scope-relative prefix 239.0.0.0/8 is further divided to
Local Scope (239.255.0.0/16) and Organization Local Scope Local Scope (239.255.0.0/16) and Organization Local Scope
(239.192.0.0/14); other parts of the administrative scopes are either (239.192.0.0/14); other parts of the administrative scopes are either
reserved for expansion or undefined [RFC2365]. However, RFC 2365 is reserved for expansion or undefined [RFC2365]. However, RFC 2365 is
ambiguous as to whether it's the enterprises or the IETF who are ambiguous as to whether it's the enterprises or the IETF who are
allowed to expand the space. allowed to expand the space.
Topologies which act under a single administration can easily use the Topologies which act under a single administration can easily use the
scoped multicast addresses for their internal groups. Groups which scoped multicast addresses for their internal groups. Groups which
need to be shared between multiple routing domains (but not need to be shared between multiple routing domains (but not
propagated through Internet) are more problematic and typically need propagated through the Internet) are more problematic and typically
an assignment of a global multicast address because their scope is need an assignment of a global multicast address because their scope
undefined. is undefined.
There is a large number of multicast applications (such as "Norton There is a large number of multicast applications (such as "Norton
Ghost") which are restricted either to a link or a site, but it is Ghost") which are restricted either to a link or a site, and it is
extremely undesirable to propagate them further (either to the rest extremely undesirable to propagate them further (either to the rest
of the site, or beyond the site). Typically many such applications of the site, or beyond the site). Typically many such applications
have been given a static IANA address assignment; this makes it have been given or have hijacked a static IANA address assignment;
challenging to implement proper propagation limiting -- which could this makes it challenging to implement proper propagation limiting --
be easier if such applications could have been assigned specific which could be easier if such applications could have been assigned
scope-relative addresses instead. This is an area of further future specific scope-relative addresses instead. This is an area of
work. further future work.
There has also been work on protocol to automatically discover There has also been work on a protocol to automatically discover
multicast scope zones [RFC2776], but it has never been seriously multicast scope zones [RFC2776], but it has never been widely
implemented or deployed. implemented or deployed.
2.3 Static IANA Allocation 2.3. Static IANA Allocation
In some rare cases, some organizations may have been able to obtain In some rare cases, some organizations may have been able to obtain
static multicast address allocations (of up to 256 addresses) static multicast address allocations (of up to 256 addresses)
directly from IANA. Typically these have been meant as a block of directly from IANA. Typically these have been meant as a block of
static assignments to multicast applications, as described in static assignments to multicast applications, as described in
Section 3.4. In principle, IANA does not allocate multicast address Section 3.4. In principle, IANA does not allocate multicast address
blocks to the operators but GLOP or Unicast-prefix -based allocations blocks to the operators but GLOP or Unicast-prefix -based allocations
should be used instead. should be used instead.
2.4 Dynamic Allocation 2.4. Dynamic Allocation
RFC 2908 [RFC2908] proposed three different layers of multicast RFC 2908 [RFC2908] proposed three different layers of multicast
address allocation and assignment, where layers 3 (inter-domain address allocation and assignment, where layers 3 (inter-domain
allocation) and layer 2 (intra-domain allocation) could be applicable allocation) and layer 2 (intra-domain allocation) could be applicable
here. Multicast Address-Set Claim Protocol (MASC) [RFC2909] is an here. Multicast Address-Set Claim Protocol (MASC) [RFC2909] is an
example of the former, and Multicast Address Allocation Protocol example of the former, and Multicast Address Allocation Protocol
(AAP) [I-D.ietf-malloc-aap] (abandoned in 2000 due lack of interest (AAP) [I-D.ietf-malloc-aap] (abandoned in 2000 due lack of interest
and technical problems) is an example of the latter. and technical problems) is an example of the latter.
Both of the proposed allocation protocols were quite complex, and Both of the proposed allocation protocols were quite complex, and
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For multicast address assignment, i.e., how an application learns the For multicast address assignment, i.e., how an application learns the
address it can use, or a node (or a set of nodes) learns an address address it can use, or a node (or a set of nodes) learns an address
it could use for an application, has a number of options as described it could use for an application, has a number of options as described
below. below.
Any IPv6 address assignment method should be aware of the guidelines Any IPv6 address assignment method should be aware of the guidelines
for the assignment of the group-IDs for IPv6 multicast addresses for the assignment of the group-IDs for IPv6 multicast addresses
[RFC3307]. [RFC3307].
3.1 Derived Assignment 3.1. Derived Assignment
There are significantly fewer options for derived address assignment There are significantly fewer options for derived address assignment
compared to derived allocation. Derived multicast assignment has compared to derived allocation. Derived multicast assignment has
only been specified for IPv6 link-scoped multicast [I-D.ietf-ipv6- only been specified for IPv6 link-scoped multicast [I-D.ietf-ipv6-
link-scoped-mcast], where the EUI64 is embedded in the multicast link-scoped-mcast], where the EUI64 is embedded in the multicast
address, providing a node with unique multicast addresses for link- address, providing a node with unique multicast addresses for link-
local ASM communications. local ASM communications.
3.2 SSM Assignment inside the Node 3.2. SSM Assignment inside the Node
While the SSM multicast addresses have only local (to the node) While the SSM multicast addresses have only local (to the node)
significance, there is still a minor issue on how to assign the significance, there is still a minor issue on how to assign the
addresses between the applications running on the same node (or more addresses between the applications running on the same node (or more
precisely, an IP address). precisely, an IP address).
This assignment is not considered to be a problem because typically This assignment is not considered to be a problem because typically
the addresses for the applications are selected manually or the addresses for the applications are selected manually or
statically, but if done using an Application Programming Interface statically, but if done using an Application Programming Interface
(API), the API could check that the addresses do not conflict prior (API), the API could check that the addresses do not conflict prior
to assigning one. to assigning one.
3.3 Manually Configured Assignment 3.3. Manually Configured Assignment
With manually configured assignment, the network operator who has a With manually configured assignment, the network operator who has a
multicast address prefix assigns the multicast group addresses to the multicast address prefix assigns the multicast group addresses to the
requesting nodes using a manual process. requesting nodes using a manual process.
Typically the user or administrator which wants to use a multicast Typically the user or administrator which wants to use a multicast
address for particular application requests an address from the address for particular application requests an address from the
network operator using phone, email, or similar means, and the network operator using phone, email, or similar means, and the
network operator provides the user with a multicast address. Then network operator provides the user with a multicast address. Then
the user/administrator of the node or application manually configures the user/administrator of the node or application manually configures
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This is a relatively simple process; it has been sufficient for This is a relatively simple process; it has been sufficient for
certain applications which require manual configuration in any case, certain applications which require manual configuration in any case,
or which cannot or do not want to justify a static IANA assignment. or which cannot or do not want to justify a static IANA assignment.
The manual assignment works when the number of participants in a The manual assignment works when the number of participants in a
group is small, as each participant has to be manually configured. group is small, as each participant has to be manually configured.
This is the most commonly used technique when the multicast This is the most commonly used technique when the multicast
application does not have a static IANA assignment. application does not have a static IANA assignment.
3.4 Static IANA Assignment 3.4. Static IANA Assignment
In contrast to manually configured assignment, as described above, In contrast to manually configured assignment, as described above,
static IANA assignment refers to getting a globally unique assignment static IANA assignment refers to getting a globally unique assignment
for the particular application directly from IANA. Guidelines for for the particular application directly from IANA. Guidelines for
IANA are described in [RFC3171][I-D.ietf-mboned-rfc3171bis]. IANA are described in [RFC3171][I-D.ietf-mboned-rfc3171bis].
This is seen as lucrative because it's the simplest approach for This is seen as lucrative because it's the simplest approach for
application developers because they can then hard-code the multicast application developers because they can then hard-code the multicast
address. Hard-coding requires no lease of the usable multicast address. Hard-coding requires no lease of the usable multicast
address, and likewise the client applications do not need to perform address, and likewise the client applications do not need to perform
any kind of service discovery (but depending on hard-coded any kind of service discovery (but depending on hard-coded
addresses). However, this is a bad approach architecturally, as we addresses). However, there is an architectural scaling problem with
should focus on enhancing and deploying service discovery and address this approach, as it encourages a "land-grab" of the limited
assignment (as needed) instead of encouraging a "land-grab" of multicast address space.
multicast addresses.
[RFC3138] describes how to handle those GLOP assignments (called [RFC3138] describes how to handle those GLOP assignments (called
"eGLOP") which use the private-use AS number space (233.252.0.0/14). "eGLOP") which use the private-use AS number space (233.252.0.0/14).
It was envisioned that IANA would delegate the responsibility of It was envisioned that IANA would delegate the responsibility of
these to RIRs, which would assign or allocate addresses as best these to RIRs, which would assign or allocate addresses as best
seemed fit. However, this was never carried out as IANA did not make seemed fit. However, this was never carried out as IANA did not make
these allocations to RIRs due to procedural reasons. these allocations to RIRs due to procedural reasons.
In summary, there are applications which have obtained a static IANA In summary, there are applications which have obtained a static IANA
assignment, some of which are really needed, and some of which assignment and while some of which are really needed, some of which
probably should not have been granted. probably should not have been granted. Conversely, there are some
applications that have not obtained a static IANA assignment, yet
should have requested an assignment and been granted one.
3.5 Dynamic Assignments 3.5. Dynamic Assignments
The layer 1 of RFC 2908 [RFC2908] described dynamic assignment from The layer 1 of RFC 2908 [RFC2908] described dynamic assignment from
Multicast Address Allocation Servers (MAAS) to applications and Multicast Address Allocation Servers (MAAS) to applications and
nodes, with Multicast Address Dynamic Client Allocation Protocol nodes, with Multicast Address Dynamic Client Allocation Protocol
(MADCAP) [RFC2730] as an example. Since then, there has been a (MADCAP) [RFC2730] as an example. Since then, there has been a
proposal for DHCPv6 assignment [I-D.jdurand-assign-addr-ipv6- proposal for DHCPv6 assignment [I-D.jdurand-assign-addr-ipv6-
multicast-dhcpv6]. multicast-dhcpv6].
It would be rather straightforward to deploy a dynamic assignment It would be rather straightforward to deploy a dynamic assignment
protocol which would lease group addresses based on a multicast protocol which would lease group addresses based on a multicast
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discovery/rendezvous). discovery/rendezvous).
In consequence, more work on rendezvous/service discovery would be In consequence, more work on rendezvous/service discovery would be
needed to make dynamic assignments more useful. needed to make dynamic assignments more useful.
4. Summary and Future Directions 4. Summary and Future Directions
This section summarizes the mechanisms and analysis discussed in this This section summarizes the mechanisms and analysis discussed in this
memo, and presents some potential future directions. memo, and presents some potential future directions.
4.1 Prefix Allocation 4.1. Prefix Allocation
Summary of prefix allocation methods for ASM is in Figure 1. Summary of prefix allocation methods for ASM is in Figure 1.
+-------+--------------------------------+--------+--------+ +-------+--------------------------------+--------+--------+
| Sect. | Prefix allocation method | IPv4 | IPv6 | | Sect. | Prefix allocation method | IPv4 | IPv6 |
+-------+--------------------------------+--------+--------+ +-------+--------------------------------+--------+--------+
| 2.1.1 | Derived: GLOP | Yes | NoNeed*| | 2.1.1 | Derived: GLOP | Yes | NoNeed*|
| 2.1.2 | Derived: Unicast-prefix -based |No -yet | Yes | | 2.1.2 | Derived: Unicast-prefix -based |No -yet | Yes |
| 2.2 | Separate Scope-relative | Yes | NoNeed*| | 2.2 | Separate Scope-relative | Yes | NoNeed*|
| 2.3 | Static IANA allocation | No | No | | 2.3 | Static IANA allocation | No | No |
skipping to change at page 10, line 8 skipping to change at page 10, line 16
allocation mechanism for now, but could be extended in future. allocation mechanism for now, but could be extended in future.
Scope-relative allocations provide the opportunity for internal Scope-relative allocations provide the opportunity for internal
IPv4 allocations. IPv4 allocations.
o Unicast-prefix -based addresses and the derivatives provide good o Unicast-prefix -based addresses and the derivatives provide good
allocation strategy with IPv6, also for scoped multicast allocation strategy with IPv6, also for scoped multicast
addresses. addresses.
o Dynamic allocations are a too complex and unnecessary mechanism. o Dynamic allocations are a too complex and unnecessary mechanism.
o Static IANA allocations are an architecturally unacceptable o Static IANA allocations are generally an architecturally
approach. unacceptable approach.
4.2 Address Assignment 4.2. Address Assignment
Summary of address assignment methods is in Figure 2. Summary of address assignment methods is in Figure 2.
+-------+--------------------------------+----------+----------+ +-------+--------------------------------+----------+----------+
| Sect. | Address assignment method | IPv4 | IPv6 | | Sect. | Address assignment method | IPv4 | IPv6 |
+-------+--------------------------------+----------+----------+ +-------+--------------------------------+----------+----------+
| 3.1 | Derived: link-scope addresses | No | Yes | | 3.1 | Derived: link-scope addresses | No | Yes |
| 3.2 | SSM (inside the node) | Yes | Yes | | 3.2 | SSM (inside the node) | Yes | Yes |
| 3.3 | Manual assignment | Yes | Yes | | 3.3 | Manual assignment | Yes | Yes |
| 3.4 | Static IANA/RIR assignment |LastResort|LastResort| | 3.4 | Static IANA/RIR assignment |LastResort|LastResort|
skipping to change at page 10, line 34 skipping to change at page 10, line 42
Figure 2 Figure 2
o Manually configured assignment is what's typically done today, and o Manually configured assignment is what's typically done today, and
works to a sufficient degree in smaller scale. works to a sufficient degree in smaller scale.
o Static IANA assignment has been done extensively in the past, but o Static IANA assignment has been done extensively in the past, but
it needs to be tightened down to prevent problems caused by "land- it needs to be tightened down to prevent problems caused by "land-
grabbing". grabbing".
o Dynamic assignment, e.g., using MADCAP have been implemented, but o Dynamic assignment, e.g., MADCAP has been implemented, but there
there is no wide deployment, so a solution is there. However, is no wide deployment, so a solution is there. However, either
either there are other gaps in the multicast architecture or there there are other gaps in the multicast architecture or there is no
is no sufficient demand for it in the first place when manual and sufficient demand for it in the first place when manual and static
static IANA assignments are available. Assignments using SAP also IANA assignments are available. Assignments using SAP also exist
exist but are not common; global SAP assignment is unfeasible with but are not common; global SAP assignment is unfeasible with IPv6.
IPv6.
o Derived assignments are only applicable in a fringe case of link- o Derived assignments are only applicable in a fringe case of link-
scoped multicast. scoped multicast.
4.3 Future Actions 4.3. Future Actions
o Multicast address discovery/"rendezvous" needs to be analyzed at o Multicast address discovery/"rendezvous" needs to be analyzed at
more length, and an adequate solution provided; the result also more length, and an adequate solution provided; the result also
needs to be written down to be shown to the IANA static assignment needs to be written down to be shown to the IANA static assignment
requestors. See [I-D.ietf-mboned-addrdisc-problems] for more. requestors. See [I-D.ietf-mboned-addrdisc-problems] for more.
o IPv6 multicast DAD and/or multicast prefix communication o IPv6 multicast DAD and/or multicast prefix communication
mechanisms should be analyzed (e.g., mechanisms should be analyzed (e.g.,
[I-D.jdurand-ipv6-multicast-ra]): whether there is demand or not, [I-D.jdurand-ipv6-multicast-ra]): whether there is demand or not,
and specify if yes. and specify if yes.
skipping to change at page 11, line 32 skipping to change at page 11, line 38
5. Acknowledgements 5. Acknowledgements
Tutoring a couple multicast-related papers, the latest by Kaarle Tutoring a couple multicast-related papers, the latest by Kaarle
Ritvanen [RITVANEN] convinced the author that the up-to-date Ritvanen [RITVANEN] convinced the author that the up-to-date
multicast address assignment/allocation documentation is necessary. multicast address assignment/allocation documentation is necessary.
Multicast address allocations/assignments were discussed at the Multicast address allocations/assignments were discussed at the
MBONED WG session at IETF59 [MBONED-IETF59]. MBONED WG session at IETF59 [MBONED-IETF59].
Dave Thaler, James Lingard, and Beau Williamson provided useful Dave Thaler, James Lingard, and Beau Williamson provided useful
feedback for the preliminary version of this memo. Myung-Ki Shin and feedback for the preliminary version of this memo. Myung-Ki Shin,
Jerome Durand also suggested improvements. Jerome Durand, and John Kristoff also suggested improvements.
6. IANA Considerations 6. IANA Considerations
This memo includes no request to IANA, but as the allocation and This memo includes no request to IANA, but as the allocation and
assignment of multicast addresses are related to IANA functions, it assignment of multicast addresses are related to IANA functions, it
wouldn't hurt if the IANA reviewed this entire memo. wouldn't hurt if the IANA reviewed this entire memo.
IANA considerations in sections 4.1.1 and 4.1.2 of [RFC2908] still IANA considerations in sections 4.1.1 and 4.1.2 of [RFC2908] still
apply to the administratively scoped prefixes. apply to the administratively scoped prefixes.
skipping to change at page 12, line 18 skipping to change at page 12, line 21
assigning multicast addresses, and this has no security assigning multicast addresses, and this has no security
considerations; the security analysis of the mentioned protocols is considerations; the security analysis of the mentioned protocols is
out of scope of this memo. out of scope of this memo.
Obviously, especially the dynamic assignment protocols are inherently Obviously, especially the dynamic assignment protocols are inherently
vulnerable to resource exhaustion attacks, as discussed e.g., in vulnerable to resource exhaustion attacks, as discussed e.g., in
[RFC2730]. [RFC2730].
8. References 8. References
8.1 Normative References 8.1. Normative References
[I-D.ietf-ipv6-link-scoped-mcast] [I-D.ietf-ipv6-link-scoped-mcast]
Park, J., "A Method for Generating Link Scoped IPv6 Park, J., "A Method for Generating Link Scoped IPv6
Multicast Addresses", draft-ietf-ipv6-link-scoped-mcast-09 Multicast Addresses", draft-ietf-ipv6-link-scoped-mcast-09
(work in progress), July 2005. (work in progress), July 2005.
[I-D.ietf-ssm-arch] [I-D.ietf-ssm-arch]
Holbrook, H. and B. Cain, "Source-Specific Multicast for Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", draft-ietf-ssm-arch-06 (work in progress), IP", draft-ietf-ssm-arch-07 (work in progress),
September 2004. October 2005.
[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23, [RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, July 1998. RFC 2365, July 1998.
[RFC3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper, [RFC3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
"IANA Guidelines for IPv4 Multicast Address Assignments", "IANA Guidelines for IPv4 Multicast Address Assignments",
BCP 51, RFC 3171, August 2001. BCP 51, RFC 3171, August 2001.
[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.
skipping to change at page 13, line 5 skipping to change at page 13, line 10
[RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast [RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Addresses", RFC 3307, August 2002. Addresses", RFC 3307, August 2002.
[RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6 [RFC3513] Hinden, R. and S. Deering, "Internet Protocol Version 6
(IPv6) Addressing Architecture", RFC 3513, April 2003. (IPv6) Addressing Architecture", RFC 3513, April 2003.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous [RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", Point (RP) Address in an IPv6 Multicast Address",
RFC 3956, November 2004. RFC 3956, November 2004.
8.2 Informative References 8.2. Informative References
[I-D.ietf-malloc-aap] [I-D.ietf-malloc-aap]
Handley, M. and S. Hanna, "Multicast Address Allocation Handley, M. and S. Hanna, "Multicast Address Allocation
Protocol (AAP)", June 2000. Protocol (AAP)", June 2000.
[I-D.ietf-mboned-addrdisc-problems] [I-D.ietf-mboned-addrdisc-problems]
Savola, P., "Lightweight Multicast Address Discovery Savola, P., "Lightweight Multicast Address Discovery
Problem Space", draft-ietf-mboned-addrdisc-problems-00 Problem Space", draft-ietf-mboned-addrdisc-problems-00
(work in progress), March 2005. (work in progress), March 2005.
skipping to change at page 14, line 35 skipping to change at page 14, line 41
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003. IPv6 (DHCPv6)", RFC 3315, July 2003.
[RITVANEN] [RITVANEN]
Ritvanen, K., "Multicast Routing and Addressing", HUT Ritvanen, K., "Multicast Routing and Addressing", HUT
Report, Seminar on Internetworking, May 2004, Report, Seminar on Internetworking, May 2004,
<http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>. <http://www.tml.hut.fi/Studies/T-110.551/2004/papers/>.
Author's Address
Pekka Savola
CSC - Scientific Computing Ltd.
Espoo
Finland
Email: psavola@funet.fi
Appendix A. Changes Appendix A. Changes
(To be removed prior to publication as an RFC.) (To be removed prior to publication as an RFC.)
A.1 Changes since -01 A.1. Changes since -01
o Mention the mechanisms which haven't been so succesful: eGLOP and o Mention the mechanisms which haven't been so succesful: eGLOP and
MZAP. MZAP.
o Remove the appendices on multicast address discovery (a separate o Remove the appendices on multicast address discovery (a separate
draft now) and IPv4 unicast-prefix based multicast addressing. draft now) and IPv4 unicast-prefix-based multicast addressing.
o Add a note on scope-relative address space and the expansion o Add a note on scope-relative address space and the expansion
ambiguity. ambiguity.
o Remove the references to draft-ietf-mboned-ipv6-issues-xx.txt o Remove the references to draft-ietf-mboned-ipv6-issues-xx.txt
o Minor editorial cleanups. o Minor editorial cleanups.
Intellectual Property Statement Author's Address
Pekka Savola
CSC - Scientific Computing Ltd.
Espoo
Finland
Email: psavola@funet.fi
Full Copyright Statement
Copyright (C) The Internet Society (2005).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
skipping to change at page 16, line 29 skipping to change at page 16, line 18
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
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The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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