draft-ietf-mboned-addrarch-05.txt   draft-ietf-mboned-addrarch-06.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 October 16, 2006 Obsoletes: 2908 (if approved) August 3, 2009
(if approved) Intended status: Informational
Intended status: Best Current Expires: February 4, 2010
Practice
Expires: April 19, 2007
Overview of the Internet Multicast Addressing Architecture Overview of the Internet Multicast Addressing Architecture
draft-ietf-mboned-addrarch-05.txt draft-ietf-mboned-addrarch-06.txt
Status of this Memo Status of this Memo
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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 . . . . . . . . . . . . . . . . . 4 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. Administratively Scoped Allocation . . . . . . . . . . . . 5 2.2. Administratively Scoped 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 . . . . . . . . . . . . . . . . . 7
3.1. Derived Assignment . . . . . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . . . . . 8 3.4. Static IANA Assignment . . . . . . . . . . . . . . . . . . 8
3.4.1. Global IANA Assignment . . . . . . . . . . . . . . . . 8 3.4.1. Global IANA Assignment . . . . . . . . . . . . . . . . 8
3.4.2. Scope-relative IANA Assignment . . . . . . . . . . . . 8 3.4.2. Scope-relative IANA Assignment . . . . . . . . . . . . 8
3.5. Dynamic Assignments . . . . . . . . . . . . . . . . . . . 9 3.5. Dynamic Assignments . . . . . . . . . . . . . . . . . . . 8
4. Summary and Future Directions . . . . . . . . . . . . . . . . 10 4. Summary and Future Directions . . . . . . . . . . . . . . . . 9
4.1. Prefix Allocation . . . . . . . . . . . . . . . . . . . . 10 4.1. Prefix Allocation . . . . . . . . . . . . . . . . . . . . 10
4.2. Address Assignment . . . . . . . . . . . . . . . . . . . . 11 4.2. Address Assignment . . . . . . . . . . . . . . . . . . . . 11
4.3. Future Actions . . . . . . . . . . . . . . . . . . . . . . 11 4.3. Future Actions . . . . . . . . . . . . . . . . . . . . . . 11
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . . 13 8.1. Normative References . . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix A. Changes . . . . . . . . . . . . . . . . . . . . . . . 15
A.1. Changes between -04 and -05 . . . . . . . . . . . . . . . 15 A.1. Changes between -05 and -06 . . . . . . . . . . . . . . . 15
A.2. Changes between -03 and -04 . . . . . . . . . . . . . . . 16 A.2. Changes between -04 and -05 . . . . . . . . . . . . . . . 15
A.3. Changes between -02 and -03 . . . . . . . . . . . . . . . 16 A.3. Changes between -03 and -04 . . . . . . . . . . . . . . . 16
A.4. Changes between -01 and -02 . . . . . . . . . . . . . . . 16 A.4. Changes between -02 and -03 . . . . . . . . . . . . . . . 16
A.5. Changes between -01 and -02 . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . . . . 17
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 about IP [RFC2908]. The consequence is that those who wish to learn about 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
skipping to change at page 3, line 26 skipping to change at page 3, line 26
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)
[RFC4607] does not have these addressing problems because SSM group [RFC4607] does not have these addressing problems because SSM group
addresses have only local significance; hence, this document focuses addresses have only local significance; hence, this document focuses
on the Any Source Multicast (ASM) model. on the Any Source Multicast (ASM) model.
This memo obsoletes RFCs 2776, 2908, and 2909 and re-classifies them This memo obsoletes and re-classifies to Historic RFC 2908, and re-
Historic. classifies to Historic RFCs 2776 and 2909.
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 terms for two and address management communities use these terms for two
conceptually different processes. conceptually different processes.
In unicast operations, address allocations refer to leasing a large In unicast operations, address allocations refer to leasing a large
skipping to change at page 4, line 37 skipping to change at page 4, line 37
sufficient for multicast testing or small scale use, it might not be sufficient for multicast testing or small scale use, it might not be
sufficient in all cases for extensive multicast use. sufficient in all cases for 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 when the AS number is greater than 255, but has to be prefix when the AS number is greater than 255, but has to be
calculated (e.g., from [RFC3180], AS 5662 maps to 233.22.30.0/24). A calculated (e.g., from [RFC3180], AS 5662 maps to 233.22.30.0/24). A
usage issue is that GLOP addresses are not tied to any prefix but to usage issue is that GLOP addresses are not tied to any prefix but to
routing domains, so they cannot be used or calculated automatically. routing domains, so they cannot be used or calculated automatically.
GLOP allocation algorithm has not been defined for IPv6 multicast GLOP mapping is not available with 4-byte AS numbers [RFC4893].
Unicast-prefix-based Allocation or an IANA allocation from "AD-HOC
Block III" (the previous so-called "eGLOP" block) could be used
instead as needed.
The GLOP allocation algorithm has not been defined for IPv6 multicast
because the unicast-prefix -based allocation (described below) because the unicast-prefix -based allocation (described below)
addresses the same need in a simpler fashion. GLOP hasn't been (and addresses the same need in a simpler fashion.
likely never will be) specified for 4-byte AS numbers
[I-D.ietf-idr-as4bytes].
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 high- RFC 3306 [RFC3306] describes a mechanism which embeds up to 64 high-
order bits of an IPv6 unicast address in the prefix part of the IPv6 order 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 A similar IPv4 mapping is described in
[I-D.ietf-mboned-ipv4-uni-based-mcast], but it provides a rather low [I-D.ietf-mboned-ipv4-uni-based-mcast], but it provides a limited
amount of addresses (e.g., 1 per an IPv4 /24 block). Although large number of addresses (e.g., 1 per an IPv4 /24 block).
networks without an AS number do exist, this technique has not been
seen to add value compared to GLOP addressing.
The IPv6 unicast-prefix-based allocations are an extremely useful way The IPv6 unicast-prefix-based allocations are an extremely useful way
to allow each network operator, even each subnet, to obtain multicast to allow each network operator, even each subnet, to obtain multicast
addresses easily, through an easy computation. Further, as the IPv6 addresses easily, through an easy computation. Further, as the IPv6
multicast header also includes the scope value [RFC3513], multicast multicast header also includes the scope value [RFC4291], multicast
groups of smaller scope can also be used with the same mapping. groups of smaller scope can also be used with the same 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 from RFC 3306 is, however, that the hosts operation. A difference from 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, prefix depends on the decisions of the operator setting up the RP,
but instead requires an assignment method. but instead 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 network operators.
operators.
2.2. Administratively Scoped Allocation 2.2. Administratively Scoped Allocation
Administratively scoped multicast address allocation [RFC2365] is Administratively scoped multicast address allocation [RFC2365] is
provided by two different means: under 239.0.0.0/8 in IPv4 or by provided by two different means: under 239.0.0.0/8 in IPv4 or by
4-bit encoding in the IPv6 multicast address prefix [RFC3513]. 4-bit encoding in the IPv6 multicast address prefix [RFC4291].
Since IPv6 administratively scoped allocations can be handled with Since IPv6 administratively scoped allocations can be handled with
unicast-prefix-based multicast addressing as described in unicast-prefix-based multicast addressing as described in
Section 2.1.2, we'll just discuss IPv4 in this section. Section 2.1.2, we'll only discuss IPv4 in this section.
The IPv4 administratively scoped prefix 239.0.0.0/8 is further The IPv4 administratively scoped prefix 239.0.0.0/8 is further
divided to Local Scope (239.255.0.0/16) and Organization Local Scope divided into Local Scope (239.255.0.0/16) and Organization Local
(239.192.0.0/14); other parts of the administrative scopes are either Scope (239.192.0.0/14); other parts of the administrative scopes are
reserved for expansion or undefined [RFC2365]. However, RFC 2365 is either reserved for expansion or undefined [RFC2365]. However, RFC
ambiguous as to whether the enterprises or the IETF are allowed to 2365 is ambiguous as to whether the enterprises or the IETF are
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 (even if not need to be shared between multiple routing domains (even if not
propagated through the Internet) are more problematic and typically propagated through the Internet) are more problematic and typically
need an assignment of a global multicast address because their scope need an assignment of a global multicast address because their scope
is 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, and it is Ghost") which are restricted either to a link or a site, and it is
extremely undesirable to propagate them further (beyond the link or extremely undesirable to propagate them further (beyond the link or
the site). Typically many such applications have been given or have the site). Typically many such applications have been given or have
hijacked a static IANA address assignment. The fact that assignments hijacked a static IANA address assignment. Given the fact that
to typically locally used applications come from the same range as assignments to typically locally used applications come from the same
global applications, implementing proper propagation limiting is range as global applications, implementing proper propagation
challenging. Filtering would be easier if such applications would in limiting is challenging. Filtering would be easier if a separate,
future be assigned specific administratively scoped addresses identifiable range would be used for such assignments in the future;
instead. This is an area of further future work. this is an area of further future work.
There has also been work on a protocol to automatically discover There has also been work on a protocol to automatically discover
multicast scope zones [RFC2776], but it has never been widely 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, organizations may have been able to obtain static
static multicast address allocations (of up to 256 addresses) multicast address allocations (of up to 256 addresses) directly from
directly from IANA. Typically these have been meant as a block of IANA. Typically these have been meant as a block of static
static assignments to multicast applications, as described in assignments to multicast applications, as described in Section 3.4.1.
Section 3.4.1. In principle, IANA should not and does not allocate If another means of obtaining addresses is available that approach is
multicast address blocks to the operators but GLOP or Unicast-prefix- preferable.
based allocations should be used instead.
Especially for those operators that only have a 32-bit AS number and
need IPv4 addresses, an IANA allocation from "AD-HOC Block III" (the
previous so-called "eGLOP" block) is an option
[I-D.ietf-mboned-rfc3171bis].
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.
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It can be concluded that dynamic multicast address allocation It can be concluded that dynamic multicast address allocation
protocols provide no benefit beyond GLOP/unicast-prefix-based protocols provide no benefit beyond GLOP/unicast-prefix-based
mechanisms and have been abandoned. mechanisms and have been abandoned.
3. Multicast Address Assignment 3. Multicast Address Assignment
There are a number of possible ways for an application, node or set There are a number of possible ways for an application, node or set
of nodes to learn a multicast address as described below. of nodes to learn a multicast address as described 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 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 [RFC4489], where only been specified for IPv6 link-scoped multicast [RFC4489], where
the EUI64 is embedded in the multicast address, providing a node with the EUI64 is embedded in the multicast address, providing a node with
unique multicast addresses for link-local ASM communications. unique multicast addresses for link-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 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 IP address. addresses between the applications running on the same 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 these 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, a 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 that wants to use a multicast
address for particular application requests an address from the address for a 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
the application to use the assigned multicast address. the application to use the assigned multicast address.
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 an assignment for the static IANA assignment refers to getting an assignment for the
particular application directly from IANA. There are two main forms particular application directly from IANA. There are two main forms
of IANA assignment: global and scope-relative. Guidelines for IANA of IANA assignment: global and scope-relative. Guidelines for IANA
are described in [RFC3171][I-D.ietf-mboned-rfc3171bis]. are described in [I-D.ietf-mboned-rfc3171bis].
3.4.1. Global IANA Assignment 3.4.1. Global IANA Assignment
Globally unique address assignment is seen as lucrative because it's Globally unique address assignment is seen as lucrative because it's
the simplest approach for application developers since they can then the simplest approach for application developers since they can then
hard-code the multicast address. Hard-coding requires no lease of hard-code the multicast address. Hard-coding requires no lease of
the usable multicast address, and likewise the client applications do the usable multicast address, and likewise the client applications do
not need to perform any kind of service discovery (but depending on not need to perform any kind of service discovery (but depending on
hard-coded addresses). However, there is an architectural scaling hard-coded addresses). However, there is an architectural scaling
problem with this approach, as it encourages a "land-grab" of the problem with this approach, as it encourages a "land-grab" of the
limited multicast address space. limited multicast address space.
[RFC3138] describes how to handle those GLOP assignments (called
"eGLOP") which use the private-use AS number space (233.252.0.0/14).
It was envisioned that IANA would delegate the responsibility of
these to RIRs, which would assign or allocate addresses as best
seemed fit. However, this was never carried out as IANA did not make
these allocations to RIRs due to procedural reasons.
In summary, there are applications which have obtained a global
static IANA assignment and while some of the assignments were really
needed, others 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.
3.4.2. Scope-relative IANA Assignment 3.4.2. Scope-relative IANA Assignment
IANA also assigns numbers as an integer offset from the highest IANA also assigns numbers as an integer offset from the highest
address in each IPv4 administrative scope as described in [RFC2365]. address in each IPv4 administrative scope as described in [RFC2365].
For example, the SLPv2 discovery scope-relative offset is "2", so For example, the SLPv2 discovery scope-relative offset is "2", so
SLPv2 discovery address within IPv4 Local-Scope (239.255.0.0/16) is SLPv2 discovery address within IPv4 Local-Scope (239.255.0.0/16) is
"239.255.255.253", within the IPv4 Organization Local-Scope "239.255.255.253", within the IPv4 Organization Local-Scope
(239.192.0.0/14) it is "239.195.255.253", and so on. (239.192.0.0/14) it is "239.195.255.253", and so on.
Similar scope-relative assignments also exist with IPv6 [RFC2375]. Similar scope-relative assignments also exist with IPv6 [RFC2375].
As IPv6 multicast addresses have much more flexible scoping, scope- As IPv6 multicast addresses have much more flexible scoping, scope-
relative assignments are also applicable to global scopes. The relative assignments are also applicable to global scopes. The
assignment policies are described in [RFC3307]. assignment policies are described in [RFC3307].
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, other mechanisms have
proposal for DHCPv6 assignment also been proposed (e.g., DHCPv6 assignment
[I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6]. [I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6]) but these have not
gained traction.
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
prefix to the applications wishing to use multicast. However, only prefix to applications wishing to use multicast. However, only few
few have implemented MADCAP, and it hasn't been significantly have implemented MADCAP, and it hasn't been significantly deployed.
deployed. So, it is not clear if the lack of deployment is due to a So, it is not clear if the lack of deployment is due to a currently
currently missing need. Moreover, it is not clear how widely for missing need. Moreover, it is not clear how widely for example the
example the APIs for communication between the multicast application APIs for communication between the multicast application and the
and the MADCAP client operating at the host have been implemented MADCAP client operating at the host have been implemented [RFC2771].
[RFC2771].
An entirely different approach is Session Announcement Protocol (SAP) An entirely different approach is Session Announcement Protocol (SAP)
[RFC2974]. In addition to advertising global multicast sessions, the [RFC2974]. In addition to advertising global multicast sessions, the
protocol also has associated ranges of addresses for both IPv4 and protocol also has associated ranges of addresses for both IPv4 and
IPv6 which can be used by SAP-aware applications to create new groups IPv6 which can be used by SAP-aware applications to create new groups
and new group addresses. Creating a session (and obtaining an and new group addresses. Creating a session (and obtaining an
address) is a rather tedious process which is why it isn't done all address) is a rather tedious process which is why it isn't done all
that often. (Note that the IPv6 SAP address is unroutable in the that often. It is also worth noting that the IPv6 SAP address is
inter-domain multicast.) unroutable in the inter-domain multicast.
A conclusion about dynamic assignment protocols is that: A conclusion about dynamic assignment protocols is that:
1. multicast is not significantly attractive in the first place, 1. multicast is not significantly attractive in the first place,
2. most applications have a static IANA assignment and thus require 2. most applications have a static IANA assignment and thus require
no dynamic or manual assignment, no dynamic or manual assignment,
3. those that cannot be easily satisfied with IANA or manual 3. those that cannot be easily satisfied with IANA or manual
assignment (i.e., where dynamic assignment would be desirable) assignment (i.e., where dynamic assignment would be desirable)
skipping to change at page 10, line 12 skipping to change at page 10, line 7
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. A summary of prefix allocation methods for ASM is shown 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 | Yes | | 2.1.2 | Derived: Unicast-prefix-based | No | Yes |
| 2.2 | Administratively scoped | Yes | NoNeed*| | 2.2 | Administratively scoped | Yes | NoNeed*|
| 2.3 | Static IANA allocation | No | No | | 2.3 | Static IANA allocation | Yes** | No |
| 2.4 | Dynamic allocation protocols | No | No | | 2.4 | Dynamic allocation protocols | No | No |
+-------+--------------------------------+--------+--------+ +-------+--------------------------------+--------+--------+
* = the need satisfied by IPv6 unicast-prefix-based allocation. * = the need satisfied by IPv6 unicast-prefix-based allocation.
** = mainly using the AD-HOC block III (former "eGLOP")
Figure 1 Figure 1
o Only ASM is affected by the assignment/allocation issues (however, o Only ASM is affected by the assignment/allocation issues.
both ASM and SSM have roughly the same address discovery issues).
o GLOP allocations seem to provide a sufficient IPv4 multicast
allocation mechanism for now, but could be extended in future.
Administratively scoped allocations provide the opportunity for
internal IPv4 allocations.
o Unicast-prefix-based addresses and the derivatives provide good o With IPv4, GLOP allocations provide a sufficient IPv4 multicast
allocation strategy with IPv6, also for scoped multicast allocation mechanism for those that have 16-bit AS number. IPv4
addresses. unicast-prefix based allocation offers some addresses. IANA is
also allocating from the AD-HOC block III (former "eGLOP") with
especially 32-bit AS number holders in mind. Administratively
scoped allocations provide the opportunity for internal IPv4
allocations.
o Dynamic allocations are a too complex and unnecessary mechanism. o With IPv6, unicast-prefix-based addresses and the derivatives
provide a good allocation strategy and this also works for scoped
multicast addresses.
o Static IANA allocations are generally an architecturally o Dynamic allocations are too complex and unnecessary a mechanism.
unacceptable approach.
4.2. Address Assignment 4.2. Address Assignment
Summary of address assignment methods is in Figure 2. A summary of address assignment methods is shown 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 |
| 3.4.1 | Global IANA/RIR assignment |LastResort|LastResort| | 3.4.1 | Global IANA/RIR assignment |LastResort|LastResort|
| 3.4.2 | Scope-relative IANA assignment | Yes | Yes | | 3.4.2 | Scope-relative IANA assignment | Yes | Yes |
| 3.5 | Dynamic assignment protocols | Yes | Yes | | 3.5 | Dynamic assignment protocols | Yes | Yes |
+--------+--------------------------------+----------+----------+ +--------+--------------------------------+----------+----------+
Figure 2 Figure 2
o Manually configured assignment is what's typically done today, and o Manually configured assignment is typical today, and works to a
works to a sufficient degree in smaller scale. sufficient degree in smaller scale.
o Global IANA assignment has been done extensively in the past, but o Global IANA assignment has been done extensively in the past.
it needs to be tightened down to prevent problems caused by "land- Scope-relative IANA assignment is acceptable but the size of the
grabbing". Scope-relative IANA assignment is acceptable but the pool is not very high. Inter-domain routing of IPv6 IANA-assigned
size of the pool is not very high. Inter-domain routing of IPv6 prefixes is likely going to be challenging and as a result that
IANA-assigned prefixes is likely going to be challenging. approach is not very appealing.
o Dynamic assignment, e.g., MADCAP has been implemented, but there o Dynamic assignment, e.g., MADCAP has been implemented, but there
is no wide deployment. So, either there are other gaps in the is no wide deployment. Therefore, either there are other gaps in
multicast architecture or there is no sufficient demand for it in the multicast architecture or there is no sufficient demand for it
the first place when manual and static IANA assignments are in the first place when manual and static IANA assignments are
available. Assignments using SAP also exist but are not common; available. Assignments using SAP also exist but are not common;
global SAP assignment is unfeasible with IPv6. global SAP assignment is unfeasible with 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. See
needs to be written down to be shown to the IANA static assignment [I-D.ietf-mboned-addrdisc-problems] and
requestors. See [I-D.ietf-mboned-addrdisc-problems] for more. [I-D.ietf-mboned-session-announcement-req] for more.
o IPv6 multicast DAD and/or multicast prefix communication
mechanisms should be analyzed (e.g.,
[I-D.jdurand-ipv6-multicast-ra]): whether there is demand or not,
and specify if yes.
o The IETF should consider whether to specify more ranges of the o The IETF should consider whether to specify more ranges of the
IPv4 administratively scoped address space for static allocation IPv4 administratively scoped address space for static allocation
for applications which should not be routed over the Internet for applications which should not be routed over the Internet
(such as backup software, etc. -- so that these wouldn't need to (such as backup software, etc. -- so that these wouldn't need to
use global addresses which should never leak in any case). use global addresses which should never leak in any case).
o The IETF should seriously consider its static IANA allocations o The IETF should consider its static IANA allocations policy, e.g.,
policy, e.g., "locking it down" to a stricter policy (like "IETF "locking it down" to a stricter policy (like "IETF Consensus") and
Consensus") and looking at developing the discovery/rendezvous looking at developing the discovery/rendezvous functions, if
functions, if necessary. necessary.
5. Acknowledgements 5. Acknowledgements
Tutoring a couple multicast-related papers, the latest by Kaarle Tutoring a couple of multicast-related papers, the latest by Kaarle
Ritvanen [RITVANEN] convinced the author that updated multicast Ritvanen [RITVANEN] convinced the author that updated multicast
address assignment/allocation documentation is needed. address assignment/allocation documentation is needed.
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, feedback for the preliminary version of this memo. Myung-Ki Shin,
Jerome Durand, John Kristoff, Dave Price, and Spencer Dawkins also Jerome Durand, John Kristoff, Dave Price, Spencer Dawkins, and Alfred
suggested improvements. Hoenes 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.
assignment of multicast addresses are related to IANA functions, it
wouldn't hurt if the IANA reviewed this entire memo.
IANA considerations in sections 4.1.1 and 4.1.2 of [RFC2908] still
apply to the administratively scoped prefixes.
IANA may be interested in reviewing the accuracy of the statement on IANA considerations in sections 4.1.1 and 4.1.2 of obsoleted and now
eGLOP address assignments in Section 3.4.1. Historic [RFC2908] were never implemented in IANA registry. No
update is necessary.
(RFC-editor: please remove this section at publication.) (RFC-editor: This section may be removed prior to publication;
alternatively, the second paragraph may be left intact.)
7. Security Considerations 7. Security Considerations
This memo only describes different approaches to allocating and This memo only describes different approaches to allocating and
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-mboned-ipv4-uni-based-mcast]
Thaler, D., "Unicast-Prefix-based IPv4 Multicast
Addresses", draft-ietf-mboned-ipv4-uni-based-mcast-06
(work in progress), March 2009.
[I-D.ietf-mboned-rfc3171bis]
Cotton, M., Vegoda, L., and D. Meyer, "IANA Guidelines for
IPv4 Multicast Address Assignments",
draft-ietf-mboned-rfc3171bis-07 (work in progress),
April 2009.
[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,
"IANA Guidelines for IPv4 Multicast Address Assignments",
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.
[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.
[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
(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.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4489] Park, J-S., Shin, M-K., and H-J. Kim, "A Method for [RFC4489] Park, J-S., Shin, M-K., and H-J. Kim, "A Method for
Generating Link-Scoped IPv6 Multicast Addresses", Generating Link-Scoped IPv6 Multicast Addresses",
RFC 4489, April 2006. RFC 4489, April 2006.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006. IP", RFC 4607, August 2006.
8.2. Informative References 8.2. Informative References
[I-D.ietf-idr-as4bytes]
Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
Number Space", draft-ietf-idr-as4bytes-12 (work in
progress), November 2005.
[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-02 Problem Space", draft-ietf-mboned-addrdisc-problems-02
(work in progress), March 2006. (work in progress), March 2006.
[I-D.ietf-mboned-ipv4-uni-based-mcast] [I-D.ietf-mboned-session-announcement-req]
Thaler, D., "Unicast-Prefix-based IPv4 Multicast Asaeda, H. and V. Roca, "Requirements for IP Multicast
Addresses", draft-ietf-mboned-ipv4-uni-based-mcast-02 Session Announcement in the Internet",
(work in progress), October 2004. draft-ietf-mboned-session-announcement-req-01 (work in
progress), March 2009.
[I-D.ietf-mboned-rfc3171bis]
Albanna, Z., Almeroth, K., Cotton, M., and D. Meyer, "IANA
Guidelines for IPv4 Multicast Address Assignments",
draft-ietf-mboned-rfc3171bis-02 (work in progress),
March 2004.
[I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6] [I-D.jdurand-assign-addr-ipv6-multicast-dhcpv6]
Durand, J., "IPv6 multicast address assignment with Durand, J., "IPv6 multicast address assignment with
DHCPv6", DHCPv6",
draft-jdurand-assign-addr-ipv6-multicast-dhcpv6-01 (work draft-jdurand-assign-addr-ipv6-multicast-dhcpv6-01 (work
in progress), February 2005. in progress), February 2005.
[I-D.jdurand-ipv6-multicast-ra]
Durand, J. and P. Savola, "Route Advertisement Option for
IPv6 Multicast Prefixes",
draft-jdurand-ipv6-multicast-ra-00 (work in progress),
February 2005.
[MBONED-IETF59] [MBONED-IETF59]
"MBONED WG session at IETF59", "MBONED WG session at IETF59",
<http://www.ietf.org/proceedings/04mar/172.htm>. <http://www.ietf.org/proceedings/04mar/172.htm>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997. RFC 2131, March 1997.
[RFC2375] Hinden, R. and S. Deering, "IPv6 Multicast Address [RFC2375] Hinden, R. and S. Deering, "IPv6 Multicast Address
Assignments", RFC 2375, July 1998. Assignments", RFC 2375, July 1998.
[RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day,
"Service Location Protocol, Version 2", RFC 2608,
June 1999.
[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.
[RFC2771] Finlayson, R., "An Abstract API for Multicast Address [RFC2771] Finlayson, R., "An Abstract API for Multicast Address
Allocation", RFC 2771, February 2000. Allocation", RFC 2771, February 2000.
[RFC2776] Handley, M., Thaler, D., and R. Kermode, "Multicast-Scope [RFC2776] Handley, M., Thaler, D., and R. Kermode, "Multicast-Scope
Zone Announcement Protocol (MZAP)", RFC 2776, Zone Announcement Protocol (MZAP)", RFC 2776,
February 2000. February 2000.
skipping to change at page 15, line 23 skipping to change at page 14, line 50
Multicast Address Allocation Architecture", RFC 2908, Multicast Address Allocation Architecture", RFC 2908,
September 2000. September 2000.
[RFC2909] Radoslavov, P., Estrin, D., Govindan, R., Handley, M., [RFC2909] Radoslavov, P., Estrin, D., Govindan, R., Handley, M.,
Kumar, S., and D. Thaler, "The Multicast Address-Set Claim Kumar, S., and D. Thaler, "The Multicast Address-Set Claim
(MASC) Protocol", RFC 2909, September 2000. (MASC) Protocol", RFC 2909, September 2000.
[RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session [RFC2974] Handley, M., Perkins, C., and E. Whelan, "Session
Announcement Protocol", RFC 2974, October 2000. Announcement Protocol", RFC 2974, October 2000.
[RFC3138] Meyer, D., "Extended Assignments in 233/8", RFC 3138,
June 2001.
[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.
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS
Number Space", RFC 4893, May 2007.
[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/>.
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 between -04 and -05 A.1. Changes between -05 and -06
o Editorial updates.
o Obsolete only RFC2908; the rest only move to Historic.
o Category is Informational instead of BCP (in line with the routing
architecture.
o Move 3171bis and v4-uni-based to Normative references in order to
make sure we don't go forward until they're resolved.
o Resolve pending issues per IETF75 discussion, in particular major
changes to eGLOP and IANA policy discussions.
A.2. Changes between -04 and -05
o Editorial updates. These and the following are from Spencer o Editorial updates. These and the following are from Spencer
Dawkins. Dawkins.
o New text explictly stating that GLOP for v6 is not needed and GLOP o New text explicitly stating that GLOP for v6 is not needed and
for 4byte ASNs isn't (and likely won't be) defined. GLOP for 4byte ASNs isn't (and likely won't be) defined.
o Expand reasons for filtering difficulties with global IANA o Expand reasons for filtering difficulties with global IANA
assignments for local apps, and that it would be easier if these assignments for local apps, and that it would be easier if these
were done from the local pool. were done from the local pool.
o Explicitly mention dynamic allocations protocols' lack of benefit o Explicitly mention dynamic allocations protocols' lack of benefit
and abandonment. and abandonment.
A.2. Changes between -03 and -04 A.3. Changes between -03 and -04
o S/scope-relative/administratively scoped/ and expand Static IANA o S/scope-relative/administratively scoped/ and expand Static IANA
Assignment section to two subsections; mainly from Dave Price. Assignment section to two subsections; mainly from Dave Price.
o Mention the routing challenges of IPv6 IANA assigned prefixes in o Mention the routing challenges of IPv6 IANA assigned prefixes in
section 4.2 section 4.2
A.3. Changes between -02 and -03 A.4. Changes between -02 and -03
o Reword architectural implications of Static IANA and editorial o Reword architectural implications of Static IANA and editorial
improvements; mainly from John Kristoff. improvements; mainly from John Kristoff.
A.4. Changes between -01 and -02 A.5. Changes between -01 and -02
o Mention the mechanisms which haven't been so succesful: eGLOP and o Mention the mechanisms which haven't been so successful: 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 administratively scoped address space and the o Add a note on administratively scoped address space and the
expansion ambiguity. expansion 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.
Author's Address Author's Address
Pekka Savola Pekka Savola
CSC - Scientific Computing Ltd. CSC - Scientific Computing Ltd.
Espoo Espoo
Finland Finland
Email: psavola@funet.fi Email: psavola@funet.fi
Full Copyright Statement
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