Network Working Group O. Troan, Ed.
Internet-Draft cisco
Intended status: Standards Track November 25, 2011
Expires: May 28, 2012
Mapping of Address and Port (MAP)
draft-mdt-softwire-mapping-address-and-port-02
Abstract
This document describes a generic mechanism for mapping between an
IPv4 prefix, address or parts thereof, and transport layer ports and
an IPv6 prefix or address.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Mapping Rules . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Port mapping algorithm . . . . . . . . . . . . . . . . . . 7
4.1.1. Bit Representation of the Algorithm . . . . . . . . . 8
4.1.2. GMA examples . . . . . . . . . . . . . . . . . . . . . 9
4.1.3. GMA Provisioning Considerations . . . . . . . . . . . 9
4.1.4. Features of the Algorithm . . . . . . . . . . . . . . 10
4.2. Basic mapping rule (BMR) . . . . . . . . . . . . . . . . . 10
4.3. Forwarding mapping rule (FMR) . . . . . . . . . . . . . . 12
4.4. Default mapping rule (DMR) . . . . . . . . . . . . . . . . 13
5. The IPv6 Interface Identifier . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . . 16
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
The mechanism of mapping IPv4 addresses in IPv6 address has been
described in numerous mechanisms dating back to 1996 [RFC1933]. The
Automatic tunneling mechanism described in RFC1933, assigned a
globally unique IPv6 address to a host by combining the host's IPv4
address with a well known IPv6 prefix. Given an IPv6 packet with an
destination address with an embedded IPv4 address, a node could
automatically tunnel this packet by extracting the IPv4 tunnel end-
point address from the IPv6 destination address.
There are numerous variations of this idea, described in 6over4
[RFC2529], 6to4 [RFC3056], ISATAP [RFC5214], and 6rd [RFC5969]. The
differences are the use of well known IPv6 prefixes, or Service
Provider assigned IPv6 prefixes, and the exact position of the IPv4
bits embedded in the IPv6 address. Teredo [RFC4380] added a twist to
this to achieve NAT traversal by also encoding transport layer ports
into the IPv6 address. 6rd, to achieve more efficient encoding,
allowed for only the suffix of an IPv4 address to be embedded, with
the IPv4 prefix being deducted from other provisioning mechanisms.
NAT-PT [RFC2766](deprecated) combined with a DNS ALG used address
mapping to put NAT state, namely the IPv6 to IPv4 binding encoded in
an IPv6 address. This characteristic has been inherited by NAT64
[RFC6146] and DNS64 [RFC6147] which rely on an address format defined
in [RFC6052]. [RFC6052] specifies the algorithmic translation of an
IPv6 address to IPv4 address. In particular, [RFC6052] specifies the
address format to build IPv4-converted and IPv4-translatable IPv6
addresses. RFC6052 discusses the transport of the port set
information in an IPv4-embedded IPv6 address but the conclusion was
the following (excerpt from [RFC6052]):
"There have been proposals to complement stateless translation with a
port range feature. Instead of mapping an IPv4 address to exactly
one IPv6 prefix, the options would allow several IPv6 nodes to share
an IPv4 address, with each node managing a different set of ports.
If a port set extension is needed, could be defined later, using bits
currently reserved as null in the suffix."
The commonalities of all these mechanisms are:
o Provisions an IPv6 address for a host or an IPv6 prefix for a site
o Algorithmic or implicit address resolution for tunneling or
encapsulation. Given an IPv6 destination address, an IPv4 tunnel
endpoint address can be calculated. Likewise for translation, an
IPv4 address can be calculated from an IPv6 destination address
and vice versa.
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o Embedding of an IPv4 address or part thereof and optionally
transport layer ports into an IPv6 address.
In phases of IPv4 to IPv6 migration, IPv6 only networks will be
common, while there will still be a need for residual IPv4
deployment. This document describes a more generic mapping of IPv4
to IPv6 that can be used both for encapsulation (IPv4 over IPv6) and
for translation between the two protocols.
Just as the IPv6 over IPv4 mechanisms refereed to above, the residual
IPv4 over IPv6 mechanisms must be capable of:
o Provisioning an IPv4 prefix, an IPv4 address or a shared IPv4
address.
o Algorithmically map between an IPv4 prefix, IPv4 address or a
shared IPv4 address and an IPv6 address.
The unified mapping scheme described here supports translation mode,
encapsulation mode, in both mesh and hub and spoke topologies.
This document describes delivery of IPv4 unicast service across an
IPv6 infrastructure. IPv4 multicast is not considered further in
this document.
In particular the architecture of a shared IPv4 address by
distributing the port space is described in [RFC6346]. The
corresponding stateful solution DS-lite is described in [RFC6333].
The motivation for work is described in
[I-D.ietf-softwire-stateless-4v6-motivation].
A companion document defines a DHCPv6 option for provisioning of MAP
[I-D.mdt-softwire-map-dhcp-option].
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].
3. Terminology
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MAP domain: A set of MAP CEs and BRs connected to the same
virtual link. A service provider may deploy a
single MAP domain, or may utilize multiple MAP
domains.
MAP Rule A set of parameters describing the mapping
between an IPv4 prefix, IPv4 address or shared
IPv4 address and an IPv6 prefix or address.
Each MAP node in the domain has the same set of
rules.
MAP Border Relay (BR): A MAP enabled router managed by the service
provider at the edge of a MAP domain. A Border
Relay router has at least an IPv6-enabled
interface and an IPv4 interface connected to
the native IPv4 network. A MAP BR may also be
referred to simply as a "BR" within the context
of MAP.
MAP Customer Edge (CE): A device functioning as a Customer Edge
router in a MAP deployment. A typical MAP CE
adopting MAP rules will serve a residential
site with one WAN side interface, and one or
more LAN side interfaces. A MAP CE may also be
referred to simply as a "CE" within the context
of MAP.
Shared IPv4 address: An IPv4 address that is shared among multiple
CEs. Each node has a separate part of the
transport layer port space; denoted as a port
set. Only ports that belong to the assigned
port set can be used for communication.
End-user IPv6 prefix: The IPv6 prefix assigned to an End-user CE by
other means than MAP itself.
MAP IPv6 address: The IPv6 address used to reach the MAP function
of a CE from other CE's and from BR's.
Port-set ID (PSID): Algorithmically identifies a set of ports
exclusively assigned to the CE.
Rule IPv6 prefix: An IPv6 prefix assigned by a Service Provider
for a mapping rule.
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Rule IPv4 prefix: An IPv4 prefix assigned by a Service Provider
for a mapping rule.
IPv4 Embedded Address (EA) bits: The IPv4 EA-bits in the IPv6
address identify an IPv4 prefix/address (or
part thereof) or a shared IPv4 address (or part
thereof and a port set identifier.
4. Mapping Rules
A MAP node is provisioned with one or more mapping rules.
Mapping rules are used differently depending on their function.
Every MAP node must be provisioned with a Basic mapping rule. This
is used by the node to configure itself with an IPv4 address, IPv4
prefix or shared IPv4 address from an End-user IPv6 prefix. This
same basic rule can also be used for forwarding, where an IPv4
destination address and optionally a destination port is mapped into
an IPv6 address or prefix. Additional mapping rules can be specified
to allow for e.g. multiple different IPv4 subnets to exist within the
domain. Additional mapping rules are recognized by having a Rule
IPv6 prefix different from the base End-user IPv6 prefix.
Traffic outside of the domain (IPv4 address not matching (using
longest matching prefix) any Rule IPv4 prefix in the Rules database)
will be forward using the Default Rule. The Default Rule maps
outside destinations to the BR's IPv6 address or prefix.
There are three types of mapping rules:
1. Basic Mapping Rule - used for IPv4 prefix, address or port set
assignment. There can only be one Basic Mapping Rule per End-
user IPv6 prefix. The Basic Mapping Rule is used to configure
the MAP IPv6 address or prefix.
* Rule IPv6 prefix (including prefix length)
* Rule IPv4 prefix (including prefix length)
* Rule EA-bits length (in bits)
* Rule Port Parameters (optional)
2. Forwarding Mapping Rule - used for forwarding. The Basic Mapping
Rule is also a Forwarding Mapping Rule. Each Forwarding Mapping
Rule will result in a route in a conceptual routing table for the
Rule IPv4 prefix.
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* Rule IPv6 prefix (including prefix length)
* Rule IPv4 prefix (including prefix length)
* Rule EA-bits length (in bits)
* Rule Port Parameters (optional)
3. Default Mapping Rule - used for destinations outside the MAP
domain. A 0.0.0.0/0 route is installed in the conceptual routing
table for this rule.
* Rule IPv6 prefix (including prefix length)
* Rule BR IPv4 address
A MAP node finds its Basic Mapping Rule by doing a longest match
between the End-user IPv6 prefix and the Rule IPv6 prefix in the
Mapping Rule database. The rule is then used for IPv4 prefix,
address or shared address assignment.
A MAP IPv6 address (or prefix) is formed from the BMR Rule IPv6
prefix. This address MUST be assigned to an interface of the MAP
node and is used as to terminate all MAP traffic being sent or
received to the node.
Routes in the conceptual routing table are installed for all the
Forwarding Mapping Rules and an IPv4 default route for the Default
Mapping Rule.
In the hub and spoke mode, all traffic should be forwarded using the
Default Mapping Rule. Hub and spoke mode is achieved with a BMR IPv4
rule prefix length of 32 and no further Forwarding Mapping Rules.
4.1. Port mapping algorithm
Different Port Set Identificators (PSID) MUST have non-overlapping
port sets. The two extreme cases are: (1) the port number is not
contiguous for each PSID, but uniformly distributed across the whole
port range (0-65535); (2) the port number is contiguous in a single
range for each PSID. The port mapping algorithm proposed here is
called the Generalized Modulus Algorithm (GMA) and supports both
these cases.
For a given sharing ratio (R) and the maximum number of contiguous
ports (M), the GMA algorithm is defined as:
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1. The port number (P) of a given PSID (K) is composed of:
P = R * M * j + M * K + i
Where:
* PSID: K = 0 to R - 1
* Port range index: j = (4096 / M) / R to ((65536 / M) / R) - 1,
if the well-known port numbers (0 - 4096) are excluded.
* Contiguous Port index: i = 0 to M - 1
2. The PSID (K) of a given port number (P) is determined by:
K = (floor(P/M)) % R
Where:
* % is the modulus operator
* floor(arg) is a function that returns the largest integer not
greater than arg.
4.1.1. Bit Representation of the Algorithm
Given a sharing ratio (R=2^k), the maximum number of contiguous ports
(M=2^m), for any PSID (K) and available ports (P) can be represented
as:
0 8 15
+---------------+----------+------+-------------------+
| P |
----------------+-----------------+-------------------+
| A (j) | PSID (K) | M (i) |
+---------------+----------+------+-------------------+
|<----a bits--->|<-----k bits---->|<------m bits----->|
|k-c |<--c bits-->|<------m bits----->|
Figure 1: Bit representation
Where j and i are the same indexes defined in the port mapping
algorithm.
For any port number, the PSID can be obtained by bit mask operation.
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For a > 0, A MUST be larger than 0. This ensures that the algorithm
excludes the well known ports. For a = 0, A MAY be 0 to allow for
the provisioning of the well known ports.
When m = 0, GMA becomes a modulo operation. When a = 0, GMA becomes
division operation.
4.1.2. GMA examples
For example, for R = 1024, a = 4 (PSID offset = 4 and PSID length =
10 bits):
Port set-1 Port set-2
PSID=0 | 4096, 4097, 4098, 4099, | 8192, 8193, 8194, 8195, | 12288
PSID=1 | 4100, 4101, 4102, 4103, | 8196, 8197, 8198, 8199, | ....
PSID=2 | 4104, 4105, 4106, 4107, | 8200, 8201, 8202, 8203, | ....
PSID=3 | 4108, 4109, 4110, 4111, | 8204, 8205, 8206, 8207, | ....
...
PSID=127 | 4604, 4605, 4606, 4607, | 8700, 8701, 8702, 8703, | ....
Figure 2: Example
For example, for R = 64, a = 0 (PSID offset = 0 and PSID length = 6
bits):
Port set
PSID=0 | [ 0 - 1023]
PSID=1 | [1024 - 2047]
PSID=2 | [2048 - 3071]
PSID=3 | [3072 - 4095]
...
PSID=63 | [64512 - 65535]
Figure 3: Example with offset = 0 (a = 0)
4.1.3. GMA Provisioning Considerations
The sharing ratio (R), the PSID (K) and the PSID length are derived
from existing information.
The number of offset bits (A) and excluded ports are optionally
provisioned via the "Rule Port Mapping Parameters" in the Basic
Mapping Rule.
The defaults are:
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o Excluded ports : 0-4095
o Offset bits (A) : 4
4.1.4. Features of the Algorithm
The GMA algorithm has the following features:
1. There is no waste of the port numbers, except the well-known
ports.
2. The algorithm is flexible, the control parameters are PSID offset
(a) and PSID length (c) / Sharing ratio.
3. The algorithm is simple to perform effectively.
4. It allows Service Providers to define their own address sharing
ratio, the theoretical value is from 1:1 to 1:65536 and a more
practical value is from 1:1 to 1:4096.
5. It supports differentiated port ranges per mapping rule.
6. It support exclusion of the well-known ports.
7. It supports assigning the well-known ports to a CE.
8. It supports legacy RTP/RTCP compatibility.
4.2. Basic mapping rule (BMR)
| n bits | o bits | m bits | 128-n-o-m bits |
+--------------------+-----------+---------+------------+----------+
| Domain IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
Figure 4: IPv6 address format
The Embedded Address bits (EA bits) are unique per end user within a
Domain IPv6 prefix. The Domain IPv6 prefix is the part of the End-
user IPv6 prefix that is common among all CEs using the same Basic
Mapping Rule within the MAP domain. There MUST be a Basic Mapping
Rule with a Rule IPv6 prefix equal to the Domain IPv6 prefix. The EA
bits encode the CE specific IPv4 address and port information. The
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EA bits can contain a full or part of an IPv4 prefix or address, and
in the shared IPv4 address case contains a Port Set Identifier
(PSID).
The MAP IPv6 address is created by concatenating the End-user IPv6
prefix with the MAP subnet-id ~0 and the interface-id as specified in
the Interface-id section.
Shared IPv4 address:
| r bits | p bits | | q bits |
+-------------+---------------------+ +------------+
| Domain IPv4 | IPv4 Address suffix | |Port Set ID |
+-------------+---------------------+ +------------+
| 32 bits |
Figure 5
Complete IPv4 address:
| r bits | p bits |
+-------------+---------------------+
| Domain IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| 32 bits |
Figure 6
IPv4 prefix:
| r bits | p bits |
+-------------+---------------------+
| Domain IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| < 32 bits |
Figure 7
If only a part of the IPv4 address/prefix is encoded in the EA bits,
the Domain IPv4 prefix is provisioned to the CE by other means (e.g.
a DHCPv6 option). To create a complete IPv4 address (or prefix), the
IPv4 address suffix from the EA bits, are concatenated with the
Domain IPv4 prefix (r bits).
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The offset of the EA bits field in the IPv6 address is equal to the
BMR Rule IPv6 prefix length. The length of the EA bits field (o) is
given in the Rule EA-bits length parameter.
If o + r < 32, then an IPv4 prefix is assigned. The IPv4 prefix
length is equal to r bits + Rule EA-bits length.
If o + r is equal to 32, then a full IPv4 address is to be assigned.
The address is created by concatenating the Domain IPv4 prefix and
the EA-bits.
If o + r is > 32, then a shared IPv4 address is to be assigned. The
number of IPv4 address bits (p) in the EA bits is given by 32 - r
bits. The PSID bits are used to create a port set. The length of
the PSID bit field within EA bits is: o - p.
Example:
Given:
End-user IPv6 prefix: 2001:db8:0012:34::/56
Domain IPv6 prefix: 2001:db8:00::/40
IPv4 prefix: 192.0.2.0/24
Basic Mapping Rule: {2001:db8:00::/40, 192.0.2.0/24, 256, 6}
We get IPv4 address and port set:
EA bits offset: 40
IPv4 suffix bits (p): 32 - 24 = 8
IPv4 address: 192.0.2.18
PSID start: 40 + p = 40 + 8 = 48
PSID length: o - p = log2(256) - 8 = 8.
PSID: 0x34.
4.3. Forwarding mapping rule (FMR)
On adding a FMR rule an IPv4 route is installed the conceptual
routing table for the Rule IPv4 prefix.
On forwarding an IPv4 packet a lookup is done in the routing table
and the correct FMR is used.
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| 32 bits | | 16 bits |
+--------------------------+ +-------------------+
| IPv4 destination address | | IPv4 dest port |
+--------------------------+ +-------------------+
: : ___/ :
| p bits | / q bits :
+----------+ +------------+
|IPv4 sufx| |Port Set ID |
+----------+ +------------+
\ / ____/ ________/
\ : __/ _____/
\ : / /
| n bits | o bits | m bits | 128-n-o-m bits |
+--------------------+-----------+---------+------------+----------+
| Domain IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
Figure 8
The subnet ID for MAP is defined to be ~0. I.e. the last subnet in
an End-user IPv6 prefix allocation is used for MAP. A MAP node MUST
reserve the topmost IPv6 prefix in a End-user IPv6 prefix for the
purpose of MAP. This prefix MUST NOT be used for native IPv6
traffic.
Example:
Given:
IPv4 destination address: 192.0.2.18
IPv4 destination port: 1232
Forwarding Mapping Rule: {2001:db8:00::/40, 192.0.2.0/24,
Sharing ratio: 256, PSID offset: 4}
We get IPv6 address:
IPv4 suffix bits (p): 32 - 24 = 8 (18)
PSID length: 8 (sharing ratio)
PSID: 0x17 (1232)
EA bits: 0x1217
IPv6 address: 2001:db8:0012:17FF:<interface-identifier>
4.4. Default mapping rule (DMR)
The Default Mapping rule is used to reach IPv4 destinations outside
of the MAP domain. Traffic using this rule will be sent from a CE to
a BR.
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The Rule IPv4 prefix in the DMR is: 0.0.0.0/0. The Rule IPv6 prefix
is the IPv6 address or prefix of the BR. Which is used is dependent
on the mode used. For example translation requires that the IPv4
destination address is encoded in the BR IPv6 address, so only a
prefix is used in the DMR to allow for a generated interface
identifier. For the encapsulation mode the Rule IPv6 prefix can be
the full IPv6 address of the BR.
There MUST be only one Default Mapping Rule within a MAP domain.
An example of a DMR is:
Default Mapping Rule: {2001:db8:0001:0000:<interface-id>:/128,
0.0.0.0/0, BR IPv4 address: 192.0.2.1, }
In most implementations of a routing table, the next-hop address must
be of the same address family as the prefix. To satisfy this
requirement a BR IPv4 address is included in the rule. Giving a
default route in the routing table:
0.0.0.0 -> 192.0.2.1, MAP-Interface0
5. The IPv6 Interface Identifier
In an encapsulation solution, an IPv4 address and port is mapped to
an IPv6 address. This is the address of the tunnel end point of the
receiving MAP CE. For traffic outside the MAP domain, the IPv6
tunnel end point address is the IPv6 address of the BR. The
interface-id used for all MAP nodes in the domain MUST be
deterministic.
When translating, the destination IPv4 address is translated into a
corresponding IPv6 address. In the case of traffic outside of the
MAP domain, it is translated to the BR's IPv6 prefix. For the BR to
be able to reverse the translation, the full destination IPv4 address
must be encoded in the IPv6 address. The same thing applies if an
IPv4 prefix is encoded in the IPv6 address, then the reverse
translator needs to know the full destination IPv4 address, which has
to be encoded in the interface-id.
The encoding of the full IPv4 address into the interface identifier,
both for the source and destination IPv6 addresses have been shown to
be useful for troubleshooting.
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<-8-><-------- L>=32 -------><48-L><8->
+---+----------------+------+-----+---+
| u | IPv4 address | PSID | 0 | L |
+---+----------------+------+-----+---+
Figure 9
The L field denotes the length of the IPv4 address, IPv4 prefix or
shared IPv4 address. In the case of an full IPv4 address L = 32, in
case of an IPv4 prefix L < 32, in the case of an shared IPv4 address
32 < L <= 48.
If the End-user IPv6 prefix length is larger than 64, the most
significant parts of the interface identifier is overwritten by the
prefix. For translation mode the End-user IPv6 prefix MUST be 64 or
shorter.
6. IANA Considerations
This specification does not require any IANA actions.
7. Security Considerations
There are no new security considerations pertaining to this document.
8. Contributors
The members of the MAP design team are:
Congxiao Bao, Mohamed Boucadair, Gang Chen, Maoke Chen, Wojciech
Dec, Xiaohong Deng, Jouni Korhonen, Xing Li, Satoru Matsushima,
Tomasz Mrugalski, Tetsuya Murakami, Jacni Qin, Necj Scoberne,
Qiong Sun, Tina Tsou, Dan Wing, Leaf Yeh and Jan Zorz.
9. Acknowledgements
The authors would like to thank Guillaume Gottard.
10. References
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10.1. Normative References
[I-D.mdt-softwire-map-dhcp-option]
Mrugalski, T., Boucadair, M., Troan, O., Deng, X., and C.
Bao, "DHCPv6 Options for Mapping of Address and Port",
draft-mdt-softwire-map-dhcp-option-01 (work in progress),
October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6346] Bush, R., "The Address plus Port (A+P) Approach to the
IPv4 Address Shortage", RFC 6346, August 2011.
10.2. Informative References
[I-D.ietf-softwire-stateless-4v6-motivation]
Boucadair, M., Matsushima, S., Lee, Y., Bonness, O.,
Borges, I., and G. Chen, "Motivations for Stateless IPv4
over IPv6 Migration Solutions",
draft-ietf-softwire-stateless-4v6-motivation-00 (work in
progress), September 2011.
[RFC1933] Gilligan, R. and E. Nordmark, "Transition Mechanisms for
IPv6 Hosts and Routers", RFC 1933, April 1996.
[RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766,
February 2000.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, February 2001.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380,
February 2006.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
Infrastructures (6rd) -- Protocol Specification",
RFC 5969, August 2010.
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Internet-Draft MAP November 2011
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, August 2011.
Author's Address
Ole Troan (editor)
cisco
Oslo
Norway
Email: ot@cisco.com
Troan Expires May 28, 2012 [Page 17]