draft-ietf-ipv6-link-scoped-mcast-07.txt   draft-ietf-ipv6-link-scoped-mcast-08.txt 
IPv6 Working Group J-S. Park IPv6 Working Group J-S. Park
INTERNET DRAFT ETRI INTERNET DRAFT ETRI
Expires: June 2005 M-K. Shin Expires: June 2005 M-K. Shin
ETRI/NIST ETRI/NIST
H-J. Kim H-J. Kim
ETRI ETRI
December 2004 December 2004
Link Scoped IPv6 Multicast Addresses Link Scoped IPv6 Multicast Addresses
<draft-ietf-ipv6-link-scoped-mcast-07.txt> <draft-ietf-ipv6-link-scoped-mcast-08.txt>
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
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and any of which I become aware will be disclosed, in accordance and any of which I become aware will be disclosed, in accordance
with RFC 3668. with RFC 3668.
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for creating link-local multicast addresses over a known method for creating link-local multicast addresses over a known method
like unicast-prefix-based IPv6 multicast addresses. It is preferred like unicast-prefix-based IPv6 multicast addresses. It is preferred
to use this method for link-local scope rather than unicast- to use this method for link-local scope rather than unicast-
prefix-based IPv6 multicast addresses. This memo update RFC3306. prefix-based IPv6 multicast addresses. This memo update RFC3306.
Table of Contents: Table of Contents:
1. Introduction................................................2 1. Introduction................................................2
2. Applicability...............................................2 2. Applicability...............................................2
3. Link Scoped Multicast Address Format........................3 3. Link Scoped Multicast Address Format........................3
4. Example ....................................................4 4. Example ....................................................3
5. Consideration of Lifetime ..................................4 5. Consideration of Lifetime ..................................3
6. Security Considerations.....................................4 6. Security Considerations.....................................4
7. Acknowledgments.............................................4 7. Acknowledgments.............................................4
8. References..................................................5 8. References..................................................4
Author's Addresses.............................................5 Author's Addresses.............................................5
1. Introduction 1. Introduction
This document defines an extension to the multicast portion of the This document defines an extension to the multicast portion of the
IPv6 addressing architecture [RFC 3513]. The current architecture IPv6 addressing architecture [RFC 3513]. The current architecture
does not contain any built-in support for dynamic address does not contain any built-in support for dynamic address
allocation. The extension allows for use of IIDs to allocate allocation. The extension allows for use of IIDs to allocate
multicast addresses. When a link-local unicast address is multicast addresses. When a link-local unicast address is
configured at each interface of a node, an IID is uniquely configured at each interface of a node, an IID is uniquely
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(Duplicate Address Detection) has completed. (Duplicate Address Detection) has completed.
Basically, it is preferred to use this method for the link-local Basically, it is preferred to use this method for the link-local
scope rather than unicast-prefix-based IPv6 multicast addresses scope rather than unicast-prefix-based IPv6 multicast addresses
[RFC 3306]. This document restricts the usage of defined fields [RFC 3306]. This document restricts the usage of defined fields
such as scop, plen and network prefix fields of [RFC 3306]. such as scop, plen and network prefix fields of [RFC 3306].
Therefore, this document specifies encoded information for link- Therefore, this document specifies encoded information for link-
local scope in multicast addresses. local scope in multicast addresses.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "June", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC 2119]. this document are to be interpreted as described in [RFC 2119].
2. Applicability 2. Applicability
The allocation technique in this document is designed to be used in The allocation technique in this document is designed to be used in
any environment in which link-local scope IPv6 multicast addresses any environment in which link-local scope IPv6 multicast addresses
are assigned or selected. Especially, this method goes well with are assigned or selected. Especially, this method goes well with
nodes supplying multicast services in a zeroconf/serverless nodes supplying multicast services in a zeroconf/serverless
environment. For example, multicast addresses less than or equal environment. For example, multicast addresses less than or equal
to link-local scope are themselves generated by nodes supplying to link-local scope are themselves generated by nodes supplying
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multicast addresses of multicast servers using ND (address multicast addresses of multicast servers using ND (address
resolution) and well-known group IDs. resolution) and well-known group IDs.
Consequently, this technique MUST only be used for link scoped Consequently, this technique MUST only be used for link scoped
multicast addresses. If you want to use multicast addresses multicast addresses. If you want to use multicast addresses
greater than link-local scope, you need to use other methods as greater than link-local scope, you need to use other methods as
described in [RFC 3306]. described in [RFC 3306].
3. Link Scoped Multicast Address Format 3. Link Scoped Multicast Address Format
This document specifies a new format that incorporates IID This document specifies a new format that incorporates IID in the
information in the multicast addresses. The idea of delegating link-local scope multicast addresses.
multicast addresses can be applicable to link-local scope.
Figure 1 illustrates the new format for link scoped multicast Figure 1 illustrates the new format for link scoped multicast
addresses. addresses.
| 8 | 4 | 4 | 8 | 8 | 64 | 32 | | 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+ +--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| LSM | IID | group ID | |11111111|flgs|scop|reserved| plen | IID | group ID |
+--------+----+----+--------+--------+----------------+----------+ +--------+----+----+--------+--------+----------------+----------+
Figure 1: Link scoped multicast IPv6 address format Figure 1: Link scoped multicast IPv6 address format
flgs MUST be "0011". (The first two bits set to zero by the Flgs, scop, and plen fields are used to identify whether an address
sending node and ignored on receipt). "flgs" MUST use the same is a multicast address as specified in this document as follows:
flag defined in section 4 of [RFC 3306]. 1. flgs MUST be "0011".
2. scop MUST be <= 2.
scop MUST be <= 2. It is preferred to use this method for the 3. The reserved field MUST be zero.
link-local scope rather than unicast-prefix-based IPv6 multicast 4. "plen" field is a special value "1111 1111" (decimal 255).
addresses [RFC 3306]. But, the users can choose whichever they
wish and deem appropriate.
The reserved field MUST be zero.
LSM field MUST be "1111 1111" which maps to the plen field in [RFC
3306], whereas the plen field in [RFC 3306] MUST NOT be greater
than 64.
That is, flgs, scop, and plen fields are used to identify whether
an address is a multicast address as specified in this document.
The IID field is used to distinguish each node from others. And The IID field (replacing the 64-bit prefix field from [RFC 3306])
this value is obtained from the IEEE EUI-64 based interface is used to distinguish each node from others. This value is
identifier of the link-local unicast IPv6 address. Given the use obtained from the IEEE EUI-64 based interface identifier of the
of this method for link-local scope, the IID embedded in the link-local unicast IPv6 address. Given the use of this method for
multicast address MUST only come from the IID of the link-local link-local scope, the IID embedded in the multicast address MUST
unicast address on the interface after DAD has completed. That is, only come from the IID of the link-local unicast address on the
the creation of the multicast address MUST only occur after DAD has interface after DAD has completed. That is, the creation of the
completed as part of the auto-configuration process. multicast address MUST only occur after DAD has completed as part
of the auto-configuration process.
Group ID is generated to indicate a multicast application and is Group ID is generated to indicate a multicast application and is
used to guarantee its uniqueness only in the host. It June also be used to guarantee its uniqueness only in the host. It may also be
set on the basis of the guidelines outlined in [RFC 3307]. set on the basis of the guidelines outlined in [RFC 3307].
4. Example 4. Example
This is an example of link scoped IPv6 multicast addresses. For This is an example of link scoped IPv6 multicast addresses. For
example in an ethernet environment, if the link-local unicast example in an ethernet environment, if the link-local unicast
address is FE80::A12:34FF:FE56:7890, the link scoped multicast address is FE80::A12:34FF:FE56:7890, the link scoped multicast
prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96. prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96.
5. Consideration of Lifetime 5. Consideration of Lifetime
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set on the basis of the guidelines outlined in [RFC 3307]. set on the basis of the guidelines outlined in [RFC 3307].
4. Example 4. Example
This is an example of link scoped IPv6 multicast addresses. For This is an example of link scoped IPv6 multicast addresses. For
example in an ethernet environment, if the link-local unicast example in an ethernet environment, if the link-local unicast
address is FE80::A12:34FF:FE56:7890, the link scoped multicast address is FE80::A12:34FF:FE56:7890, the link scoped multicast
prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96. prefix of the node is FF32:00FF:A12:34FF:FE56:7890::/96.
5. Consideration of Lifetime 5. Consideration of Lifetime
Generally, Link scoped multicast addresses have no lifetime because Generally, Link scoped multicast addresses have no lifetime because
link-local unicast addresses also have no lifetime. But, it is not link-local unicast addresses also have no lifetime. But, it is not
true in environment of mobile. Even though multicast addresses are true in environment of mobile. Even though multicast addresses are
created from the unique IID of unicast address, their useful created from the unique IID of unicast address, their useful
lifetime is linked to the period during which the IID is known to lifetime is linked to the period during which the IID is known to
be unique. Thus, it is possible to conflict between IIDs, due to a be unique. Thus, it is possible to conflict between IIDs, due to a
new node in merged network that uses the same IID and a powered new node in merged network that uses the same IID as a powered
node. The document does not consider this case at this phase. It node.
is another challenging issue and out of scope of this document.
This is a scenario where DAD also fails to guarantee the uniqueness
of the unicast address, so this document does not try to address
this issue.
6. Security Considerations 6. Security Considerations
The uniqueness of multicast addresses using this method is The uniqueness of multicast addresses using this method is
guaranteed by the DAD process. So, it is needed to get a secure guaranteed by the DAD process. So, it is needed to get a secure
DAD process for stability of this method. This document proposes DAD process for stability of this method. This document proposes
the mechanism in [RFC 3041] for this purpose. the mechanism in [RFC 3041] for this purpose.
[RFC 3041] describes the privacy extension to IPv6 stateless [RFC 3041] describes the privacy extension to IPv6 stateless
address autoconfiguration for an IID and how to configure the address autoconfiguration to how to configure the IID of non-link-
global-scope unicast addresses. The privacy extension method in local scope unicast addresses. [RFC 3041] can not be used for
[RFC 3041] is triggered when a host receives a router advertisement making a link-local unicast address, and hence it cannot be used to
with a prefix information option carrying a global-scope prefix for create an IID for link-scoped multicast address. However, as [RFC
the purpose of address auto-configuration. That is, [RFC 3041] can 3041] does not protect the privacy of link-local unicast addresses,
not be used for making a link-local unicast address. Since the IID it does not protect the privacy of link-local unicast addresses, it
embedded in the link scoped multicast address MUST only come from does not seem to be required to protect the privacy of IID-based
the IID of the link-local unicast address on the interface after link-local multicast addresses.
DAD has completed, the secure IID, generated by [RFC 3041], can not
be used for consisting of a link scoped multicast address. But, it
is possible to use secure IID for expanding the intensity of
security regardless of a difficulty of acquisition of multicast
server addresses.
7. Acknowledgements 7. Acknowledgements
We would like to thank Dave Thaler and Brian Haberman for his We would like to thank Dave Thaler and Brian Haberman for his
comments related to the consistency between the unicast prefix- comments related to the consistency between the unicast prefix-
based multicast draft and this one. Special thanks are due to Erik based multicast draft and this one. Special thanks are due to Erik
Nordmark and Pekka Savola for valuable comments. Nordmark and Pekka Savola for valuable comments.
8. References 8. References
Normative Normative
[RFC 2119] S. Bradner, "Key words for use in RFCs to indicate [RFC 2119] S. Bradner, "Key words for use in RFCs to indicate
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