Internet DRAFT - draft-ietf-6man-multicast-addr-arch-update
draft-ietf-6man-multicast-addr-arch-update
6man Working Group M. Boucadair
Internet-Draft France Telecom
Updates: 3306,3956,4291 (if approved) S. Venaas
Intended status: Standards Track Cisco
Expires: February 12, 2015 August 11, 2014
Updates to the IPv6 Multicast Addressing Architecture
draft-ietf-6man-multicast-addr-arch-update-08
Abstract
This document updates the IPv6 multicast addressing architecture by
re-defining the reserved bits as generic flag bits. The document
provides also some clarifications related to the use of these flag
bits.
This document updates RFC 3956, RFC 3306 and RFC 4291.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on February 12, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Addressing Architecture Update . . . . . . . . . . . . . . . 3
3. Flag Bits: New Processing Rules . . . . . . . . . . . . . . . 3
4. RFC Updates . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. RFC 3306 . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1.1. Update #1 . . . . . . . . . . . . . . . . . . . . . . 4
4.1.2. Update #2 . . . . . . . . . . . . . . . . . . . . . . 5
4.2. RFC 3956 . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2.1. Update #1 . . . . . . . . . . . . . . . . . . . . . . 6
4.2.2. Update #2 . . . . . . . . . . . . . . . . . . . . . . 7
4.2.3. Update #3 . . . . . . . . . . . . . . . . . . . . . . 8
4.2.4. Update #4 . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document updates the IPv6 addressing architecture [RFC4291] by
re-defining reserved bits as generic flag bits (Section 2). The
document provides also some clarifications related to the use of
these flag bits (Section 3).
This document updates [RFC3956], [RFC3306], and [RFC4291]. These
updates are logical consequences of the new processing rules in
Section 3.
Textual representation of IPv6 addresses included in the RFC updates
follows the recommendation in [RFC5952].
2. Addressing Architecture Update
Bits 17-20 of a multicast address, where bit 1 is the most
significant bit, are defined in [RFC3956] and [RFC3306] as reserved
bits. This document defines these bits as generic flag bits so that
they apply to any multicast address. These bits are referred to as
ff2 (flag field 2) while the flgs bits in [RFC4291][RFC3956] are
renamed to ff1 (flag field 1).
Within this document, flag bits denote both ff1 and ff2.
Defining the bits 17-20 as flags for all IPv6 multicast addresses
allows addresses to be treated in a more uniform and generic way, and
allows for these bits to be defined in the future for different
purposes, irrespective of the specific type of multicast address.
For the record, this design choice was initially triggered by the
specification in [I-D.ietf-mboned-64-multicast-address-format] which
proposed for associating a meaning with one of the reserved bits.
Moreover, [I-D.ietf-mboned-64-multicast-address-format] considered
also the use of the last remaining flag in ff1 but that approach was
abandoned because it is not clear at this stage whether there is
other usage scenarios of the flag.
Section 4 specifies the updated structure of the addressing
architecture.
Further specification documents may define a meaning for these flag
bits.
3. Flag Bits: New Processing Rules
Some implementations and specification documents do not treat the
flag bits as separate bits but tend to use their combined value as a
4-bit integer. This practice is a hurdle for assigning a meaning to
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the remaining flag bits. Below are listed some examples for
illustration purposes:
o the reading of [RFC3306] may lead to conclude that ff3x::/32 is
the only allowed Source Specific Multicast (SSM) IPv6 prefix
block.
o [RFC3956] states only ff70::/12 applies to Embedded-RP.
Particularly, implementations should not treat the fff0::/12 range
as Embedded-RP.
To avoid such confusion and to unambiguously associate a meaning with
the remaining flags, the following requirement is made:
Implementations MUST treat flag bits as separate bits.
4. RFC Updates
4.1. RFC 3306
4.1.1. Update #1
This document changes Section 4 of [RFC3306] as follows:
OLD:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|flgs|scop|reserved| plen | network prefix | group ID |
+--------+----+----+--------+--------+----------------+----------+
+-+-+-+-+
flgs is a set of 4 flags: |0|0|P|T|
+-+-+-+-+
o P = 0 indicates a multicast address that is not assigned
based on the network prefix. This indicates a multicast
address as defined in [ADDRARCH].
o P = 1 indicates a multicast address that is assigned based
on the network prefix.
o If P = 1, T MUST be set to 1, otherwise the setting of the T
bit is defined in Section 2.7 of [ADDRARCH].
The reserved field MUST be zero.
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Note: [ADDRARCH] is a reference listed in [RFC3306]. [ADDRARCH]
has been since obsoleted by [RFC4291].
NEW:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+--------+----------------+----------+
|11111111|ff1 |scop|ff2 |rsvd| plen | network prefix | group ID |
+--------+----+----+----+----+--------+----------------+----------+
+-+-+-+-+
ff1 (flag field 1) is a set of 4 flags: |X|Y|P|T|
+-+-+-+-+
X and Y may each be set to 0 or 1. Note, X is for future assignment
while a meaning is associated with Y in RFC3956.
o P = 0 indicates a multicast address that is not assigned
based on the network prefix. This indicates a multicast
address as defined in [RFC4291].
o P = 1 indicates a multicast address that is assigned based
on the network prefix.
o If P = 1, T MUST be set to 1, otherwise the setting of the T
bit is defined in Section 2.7 of [RFC4291].
+-+-+-+-+
ff2 (flag field 2) is a set of 4 flags: |r|r|r|r|
+-+-+-+-+
where "rrrr" are for future assignment as additional flag bits.
r bits MUST each be sent as zero and MUST be ignored on receipt.
Flag bits denote both ff1 and ff2.
4.1.2. Update #2
This document changes Section 6 of [RFC3306] as follows:
OLD:
These settings create an SSM range of FF3x::/32 (where 'x' is any
valid scope value). The source address field in the IPv6 header
identifies the owner of the multicast address.
NEW:
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If the flag bits in ff1 are set to 0011, these settings create an
SSM range of ff3x::/32 (where 'x' is any valid scope value). The
source address field in the IPv6 header identifies the owner of
the multicast address. ff3x::/32 is not the only allowed SSM
prefix range. For example if the most significant flag bit in ff1
is set, then we would get the SSM range ffbx::/32.
4.2. RFC 3956
4.2.1. Update #1
This document changes Section 2 of [RFC3956] as follows:
OLD:
As described in [RFC3306], the multicast address format is as
follows:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+----+----------------+----------+
|11111111|flgs|scop|reserved|plen| network prefix | group ID |
+--------+----+----+--------+----+----------------+----------+
Where flgs are "0011". (The first two bits are as yet undefined,
sent as zero and ignored on receipt.)
NEW:
The multicast address format is as follows:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+----+----------------+----------+
|11111111|ff1 |scop|ff2 |rsvd|plen| network prefix | group ID |
+--------+----+----+----+----+----+----------------+----------+
+-+-+-+-+
ff1 (flag field 1) is a set of four flags: |X|R|P|T|
+-+-+-+-+
where X is for future assignment as additional flag bit. X may be
set to 0 or 1.
+-+-+-+-+
ff2 (flag field 2) is a set of 4 flags: |r|r|r|r|
+-+-+-+-+
where "rrrr" are for future assignment as additional flag bits.
r bits MUST each be sent as zero and MUST be ignored on receipt.
Flag bits denote both ff1 and ff2.
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4.2.2. Update #2
This document changes Section 3 of [RFC3956] as follows:
OLD:
| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+----+----------------+----------+
|11111111|flgs|scop|rsvd|RIID|plen| network prefix | group ID |
+--------+----+----+----+----+----+----------------+----------+
+-+-+-+-+
flgs is a set of four flags: |0|R|P|T|
+-+-+-+-+
When the highest-order bit is 0, R = 1 indicates a multicast address
that embeds the address on the RP. Then P MUST be set to 1, and
consequently T MUST be set to 1, as specified in [RFC3306]. In
effect, this implies the prefix FF70::/12. In this case, the last 4
bits of the previously reserved field are interpreted as embedding
the RP interface ID, as specified in this memo.
The behavior is unspecified if P or T is not set to 1, as then the
prefix would not be FF70::/12. Likewise, the encoding and the
protocol mode used when the two high-order bits in "flgs" are set to
11 ("FFF0::/12") is intentionally unspecified until such time that
the highest-order bit is defined. Without further IETF
specification, implementations SHOULD NOT treat the FFF0::/12 range
as Embedded-RP.
NEW:
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| 8 | 4 | 4 | 4 | 4 | 8 | 64 | 32 |
+--------+----+----+----+----+----+----------------+----------+
|11111111|ff1 |scop|ff2 |RIID|plen| network prefix | group ID |
+--------+----+----+----+----+----+----------------+----------+
+-+-+-+-+
ff1 is a set of four flags: |X|R|P|T|
+-+-+-+-+
where X is for future assignment as additional flag bit. X may be
set to 0 or 1.
R = 1 indicates a multicast address that embeds the address of the
RP. Then P MUST be set to 1, and consequently T MUST be set to 1,
according to [RFC3306], as this is a special case of unicast-prefix
based addresses. This implies that, for instance, prefixes ff70::/12
and fff0::/12 are embedded RP prefixes. When the R-bit is set, the
last 4 bits of the field that were reserved in [RFC3306] are
interpreted as embedding the RP interface ID, as specified in this
memo.
4.2.3. Update #3
This document changes Section 4 of [RFC3956] as follows:
OLD:
It MUST be a multicast address with "flgs" set to 0111, that is,
to be of the prefix FF70::/12,
NEW:
It MUST be a multicast address with R-bit set to 1.
It MUST have P-bit and T-bit both set to 1 when using the
embedding in this document as it is a prefix-based address.
4.2.4. Update #4
This document changes Section 7.1 of [RFC3956] as follows:
OLD:
To avoid loops and inconsistencies, for addresses in the range
FF70::/12, the Embedded-RP mapping MUST be considered the longest
possible match and higher priority than any other mechanism.
NEW:
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To avoid loops and inconsistencies, for addresses with R-bit set
to 1, the Embedded-RP mapping MUST be considered the longest
possible match and higher priority than any other mechanism.
5. IANA Considerations
This document does not require any action from IANA.
6. Security Considerations
The same security considerations as those discussed in [RFC3956],
[RFC3306] and [RFC4291] are to be taken into account.
7. Acknowledgements
Special thanks to Brian Haberman for the discussions prior to the
publication of this document.
Many thanks to Jouni Korhonen, Tatuya Jinmei, Charlie Kaufman, and
Ben Campbell for their review.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6
Multicast Addresses", RFC 3306, August 2002.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", RFC
3956, November 2004.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC5952] Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
Address Text Representation", RFC 5952, August 2010.
8.2. Informative References
[I-D.ietf-mboned-64-multicast-address-format]
Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and
M. Xu, "IPv6 Multicast Address With Embedded IPv4
Multicast Address", draft-ietf-mboned-64-multicast-
address-format-05 (work in progress), April 2013.
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Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Stig Venaas
Cisco
USA
Email: stig@cisco.com
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