Network Working Group C. Bao
Internet-Draft CERNET Center/Tsinghua University
Obsoletes: 2765 (if approved) C. Huitema
-Intended status: Standards Track Microsoft Corporation
-Expires: September 15, 2010 M. Bagnulo
- UC3M
+Updates: 4291 (if approved) Microsoft Corporation
+Intended status: Standards Track M. Bagnulo
+Expires: September 28, 2010 UC3M
M. Boucadair
France Telecom
X. Li
CERNET Center/Tsinghua University
- March 14, 2010
+ March 27, 2010
IPv6 Addressing of IPv4/IPv6 Translators
- draft-ietf-behave-address-format-05.txt
+ draft-ietf-behave-address-format-06.txt
Abstract
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
- This Internet-Draft will expire on September 15, 2010.
+ This Internet-Draft will expire on September 28, 2010.
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Applicability Scope . . . . . . . . . . . . . . . . . . . 3
- 1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
+ 1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
- 2. IPv4-Embedded IPv6 Address Format . . . . . . . . . . . . . . 4
- 2.1. Address Translation Algorithms . . . . . . . . . . . . . . 6
- 2.2. Text Representation . . . . . . . . . . . . . . . . . . . 6
+ 2. IPv4-Embedded IPv6 Address Prefix and Format . . . . . . . . . 4
+ 2.1. Well Known Prefix . . . . . . . . . . . . . . . . . . . . 4
+ 2.2. IPv4-Embedded IPv6 Address Format . . . . . . . . . . . . 4
+ 2.3. Address Translation Algorithms . . . . . . . . . . . . . . 6
+ 2.4. Text Representation . . . . . . . . . . . . . . . . . . . 6
3. Deployment Guidelines and Choices . . . . . . . . . . . . . . 7
3.1. Restrictions on the use of the Well-Known Prefix . . . . . 7
3.2. Impact on Inter-Domain Routing . . . . . . . . . . . . . . 8
-
-
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reference this document for algorithmic mapping of the addresses
themselves.
- This document reserves a "Well-Known Prefix" for use in an
- algorithmic mapping. The value of this IPv6 prefix is:
+ Section 2 describes the prefixes and the format of "IPv4-Embedded
+ IPv6 addresses", i.e., IPv6 addresses in which 32 bits contain an
+ IPv4 address. This format is common to both "IPv4-Converted" and
+ "IPv4-Translatable" IPv6 addresses. This section also defines the
+ algorithms for translating addresses, and the text representation of
+ IPv4-Embedded IPv6 addresses.
- 64:FF9B::/96
-
- Section 2 describes the format of "IPv4-Embedded IPv6 addresses",
- i.e., IPv6 addresses in which 32 bits contain an IPv4 address. This
- format is common to both "IPv4-Converted" and "IPv4-Translatable"
- IPv6 addresses. This section also defines the algorithms for
- translating addresses, and the text representation of IPv4-Embedded
- IPv6 addresses.
-
- Section 3 discusses the choice of prefixes, the conditions of use of
- the Well-Known Prefix and Network-Specific Prefixes, and the use of
- IPv4-Embedded IPv6 addresses with stateless and stateful translation.
+ Section 3 discusses the choice of prefixes, the conditions in which
+ they can be used, and the use of IPv4-Embedded IPv6 addresses with
+ stateless and stateful translation.
Section 4 discusses security concerns.
the IETF, we expect that their descriptions will document their
specific use of IPv4-Embedded IPv6 addresses.
+1.2. Conventions
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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-1.2. Conventions
-
- 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].
1.3. Terminology
for use in algorithmic mapping. Options for the Network Specific
Prefix are discussed in Section 3.3 and Section 3.4.
IPv4-Embedded IPv6 addresses: IPv6 addresses in which 32 bits
- contain an IPv4 address. Their format is described in Section 2.
+ contain an IPv4 address. Their format is described in
+ Section 2.2.
IPv4-Converted IPv6 addresses: IPv6 addresses used to represent IPv4
nodes in an IPv6 network. They are a variant of IPv4-Embedded
- IPv6 addresses, and follow the format described in Section 2.
+ IPv6 addresses, and follow the format described in Section 2.2.
IPv4-Translatable IPv6 addresses: IPv6 addresses assigned to IPv6
nodes for use with stateless translation. They are a variant of
IPv4-Embedded IPv6 addresses, and follow the format described in
- Section 2.
+ Section 2.2.
-2. IPv4-Embedded IPv6 Address Format
+2. IPv4-Embedded IPv6 Address Prefix and Format
- IPv4-Converted IPv6 addresses and IPv4-Translatable IPv6 addresses
- follow the same format, described here as the IPv4-Embedded IPv6
- address Format. IPv4-Embedded IPv6 addresses are composed of a
- variable length prefix, the embedded IPv4 address, and a variable
- length suffix, as presented in the following diagram, in which PL
- designates the prefix length:
+2.1. Well Known Prefix
+
+ This document reserves a "Well-Known Prefix" for use in an
+ algorithmic mapping. The value of this IPv6 prefix is:
+ 64:FF9B::/96
+2.2. IPv4-Embedded IPv6 Address Format
+ IPv4-Converted IPv6 addresses and IPv4-Translatable IPv6 addresses
+ follow the same format, described here as the IPv4-Embedded IPv6
+ address Format. IPv4-Embedded IPv6 addresses are composed of a
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+ variable length prefix, the embedded IPv4 address, and a variable
+ length suffix, as presented in the following diagram, in which PL
+ designates the prefix length:
+
+
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
|PL| 0-------------32--40--48--56--64--72--80--88--96--104-112-120-|
+--+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
In these addresses, the prefix shall be either the "Well-Known
Prefix", or a "Network-Specific Prefix" unique to the organization
- deploying the address translators. (The Well-Known prefic is 96 bits
- long, and can only be used in the last form of the table.)
+ deploying the address translators. The prefixes can only have one of
+ the following lengths: 32, 40, 48, 56, 64 or 96. (The Well-Known
+ prefic is 96 bits long, and can only be used in the last form of the
+ table.)
Various deployments justify different prefix lengths with Network-
Specific prefixes. The tradeoff between different prefix lengths are
bits first. Depending of the prefix length, the 4 octets of the
address may be separated by the reserved octet "u", whose 8 bits MUST
be set to zero. In particular:
+
+
+
+
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+
o When the prefix is 32 bits long, the IPv4 address is encoded in
positions 32 to 63.
o When the prefix is 40 bits long, 24 bits of the IPv4 address are
o When the prefix is 48 bits long, 16 bits of the IPv4 address are
encoded in positions 48 to 63, with the remaining 16 bits in
position 72 to 87.
-
-
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-
-
o When the prefix is 56 bits long, 8 bits of the IPv4 address are
encoded in positions 56 to 63, with the remaining 24 bits in
position 72 to 95.
constitute the suffix. These bits are reserved for future
extensions, and SHOULD be set to zero.
-2.1. Address Translation Algorithms
+2.3. Address Translation Algorithms
IPv4-Embedded IPv6 addresses are composed according to the following
algorithm:
o Concatenate the prefix, the 32 bits of the IPv4 address and the
null suffix if needed to obtain a 128 bit address.
- o If the prefix length is less than 96 bits, remove the last octet
- and insert the null octet "u" at the appropriate position, as
- documented in Figure 1.
+ o If the prefix length is less than 96 bits, insert the null octet
+ "u" at the appropriate position, thus causing the least
+ significant octet to be excluded, as documented in Figure 1.
The IPv4 addresses are extracted from the IPv4-Embedded IPv6
addresses according to the following algorithm:
o for the other prefix lengths, extract the "u" octet to obtain a
120 bit sequence, then extract the 32 bits following the prefix.
-2.2. Text Representation
+2.4. Text Representation
IPv4-Embedded IPv6 addresses will be represented in text in
conformity with section 2.2 of [RFC4291]. IPv4-Embedded IPv6
-
-
-
-
-
-
-
-
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The Network-Specific Prefix examples in Table 1 are derived from the
IPv6 prefix reserved for documentation in [RFC3849]. The IPv4
address 192.0.2.33 is part of the subnet 192.0.2.0/24 reserved for
- documentation in [RFC3330].
+ documentation in [RFC5735].
3. Deployment Guidelines and Choices
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Organizations deploying stateless IPv4/IPv6 translation SHOULD assign
a Network-Specific Prefix to their IPv4/IPv6 translation service.
IPv4-Translatable and IPv4-Converted IPv6 addresses MUST be
- constructed as specified in Section 2. IPv4-Translatable IPv6
+ constructed as specified in Section 2.2. IPv4-Translatable IPv6
addresses MUST use the selected Network-Specific Prefix. Both IPv4-
Translatable IPv6 addresses and IPv4-Converted IPv6 addresses SHOULD
use the same prefix.
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router anycast address in IPv6 and network identifier in IPv4, the
last IPv4-translatable address is the subnet broadcast addresses in
- IPv4. Both of them SHOULD not be used for IPv6 nodes. In addition,
+ IPv4. Both of them SHOULD NOT be used for IPv6 nodes. In addition,
the minimum IPv4 subnet can be used for hosts is /30 (the router
interface needs a valid address for the same subnet) and this rule
SHOULD also be applied to the corresponding subnet of the IPv4-
When these services are used, IPv6 nodes are addressed through
standard IPv6 addresses, while IPv4 nodes are represented by IPv4-
- Converted IPv6 addresses, as specified in Section 2.
+ Converted IPv6 addresses, as specified in Section 2.2.
The stateful nature of the translation creates a potential stability
issue when the organization deploys multiple translators. If several
3.5. Choice of Suffix
- The address format described in Section 2 recommends a zero suffix.
+ The address format described in Section 2.2 recommends a zero suffix.
Before making this recommendation, we considered different options:
checksum neutrality; the encoding of a port range; and a value
different than 0.
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5. IANA Considerations
- The Well Known Prefix falls into the range ::/8 reserved by the IETF.
- The prefix definition does not require an IANA action.
+ The IANA is requested to add a note to the documentation of the
+ 0000::/8 address block in
+ http://www.iana.org/assignments/ipv6-address-space to document the
+ assignment by the IETF of the Well Known Prefix. For example:
+
+ The "Well Known Prefix" 64:FF9B::/96 used in an algorithmic
+ mapping between IPv4 to IPv6 addresses is defined out of the
+ 0000::/8 address block, per (this document).
6. Acknowledgements
-
-
-
-
-
-
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E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
- [RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330,
- September 2002.
-
[RFC3484] Draves, R., "Default Address Selection for Internet
Protocol version 6 (IPv6)", RFC 3484, February 2003.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
+ [RFC5735] Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
+ BCP 153, RFC 5735, January 2010.
+
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projects / thirdparty / bind9.git / commitdiff
