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draft-ietf-softwire-map.xml~
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draft-ietf-softwire-map.xml~
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<?xml version="1.0" encoding="US-ASCII"?>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
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<!ENTITY rfc5383 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5383.xml">
<!ENTITY I-D.mdt-softwire-map-dhcp-option SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.mdt-softwire-map-dhcp-option.xml'>
<!ENTITY I-D.ietf-softwire-stateless-4v6-motivation SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-softwire-stateless-4v6-motivation.xml'>
<!ENTITY I-D.ietf-tsvwg-iana-ports SYSTEM 'http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-tsvwg-iana-ports.xml'>
<!ENTITY I-D.xli-behave-divi SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.xli-behave-divi.xml">
<!ENTITY I-D.murakami-softwire-4v6-translation SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.murakami-softwire-4v6-translation.xml">
<!ENTITY I-D.dec-stateless-4v6 SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.dec-stateless-4v6.xml">
]>
<?rfc toc="yes" ?>
<?rfc tocompact="yes" ?>
<?rfc compact="yes" ?>
<?rfc subcompact="no" ?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes" ?>
<?rfc comments="yes" ?>
<?rfc inline="yes" ?>
<rfc category="std" docName="draft-ietf-softwire-map-00"
ipr="trust200902">
<front>
<title abbrev="MAP">Mapping of Address and Port (MAP)</title>
<author fullname="Ole Troan" initials="O" surname="Troan">
<organization>Cisco Systems</organization>
<address>
<postal>
<street></street>
<city>Oslo</city>
<country>Norway</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Wojciech Dec" initials="W" surname="Dec">
<organization>Cisco Systems</organization>
<address>
<postal>
<street>Haarlerbergpark Haarlerbergweg 13-19</street>
<city>Amsterdam, NOORD-HOLLAND</city>
<code>1101 CH</code>
<country>Netherlands</country>
</postal>
<phone></phone>
<email>[email protected]</email>
</address>
</author>
<author fullname="Xing Li" initials="X" surname="Li">
<organization abbrev="">CERNET Center/Tsinghua University</organization>
<address>
<postal>
<street>Room 225, Main Building, Tsinghua University</street>
<city>Beijing 100084</city>
<country>CN</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Congxiao Bao" initials="C" surname="Bao">
<organization abbrev="">CERNET Center/Tsinghua University</organization>
<address>
<postal>
<street>Room 225, Main Building, Tsinghua University</street>
<city>Beijing 100084</city>
<country>CN</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Yu Zhai" initials="Y." surname="Zhai">
<organization>CERNET Center/Tsinghua University</organization>
<address>
<postal>
<street>Room 225, Main Building, Tsinghua University</street>
<city>Beijing 100084</city>
<country>CN</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Satoru Matsushima" initials="S" surname="Matsushima">
<organization abbrev="">SoftBank Telecom</organization>
<address>
<postal>
<street>1-9-1 Higashi-Shinbashi, Munato-ku</street>
<city>Tokyo</city>
<country>Japan</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<author fullname="Tetsuya Murakami" initials="T" surname="Murakami">
<organization abbrev="">IP Infusion</organization>
<address>
<postal>
<street>1188 East Arques Avenue</street>
<city>Sunnyvale</city>
<country>USA</country>
</postal>
<email>[email protected]</email>
</address>
</author>
<date year="2012" />
<area>Internet</area>
<workgroup>Network Working Group</workgroup>
<!-- SECTION 0: Abstract -->
<abstract>
<t>This document describes a mechanism for transporting IPv4
packets across an IPv6 network, and a generic mechanism for
mapping between IPv6 addresses and IPv4 addresses and transport
layer ports.</t>
</abstract>
</front>
<middle>
<!-- SECTION 1: Introduction -->
<section title="Introduction">
<t>Mapping IPv4 addresses in IPv6 addresses has been described
in numerous mechanisms dating back to 1996 <xref
target="RFC1933"></xref>. 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 a 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.</t>
<t>There are numerous variations of this idea, described in
6over4 <xref target="RFC2529"></xref>, 6to4 <xref
target="RFC3056"></xref>, ISATAP <xref target="RFC5214"></xref>,
and 6rd <xref target="RFC5969"></xref>.</t>
<!--
The differences between
these are the use of well-known IPv6 prefixes, or Service
Provider assigned IPv6 prefixes, and the position of the
embedded IPv4 bits in the IPv6 address. Teredo <xref
target="RFC4380"></xref> 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 deduced from other provisioning mechanisms.</t>
<t>NAT-PT <xref target="RFC2766"></xref>(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 <xref
target="RFC6146"></xref> and DNS64 <xref
target="RFC6147"></xref> which rely on an address format defined
in <xref target="RFC6052"></xref>. <xref
target="RFC6052"></xref> specifies the algorithmic translation
of an IPv6 address to IPv4 address. In particular, <xref
target="RFC6052"></xref> 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]):</t>
<t>"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, it could be defined later, using bits currently reserved
as null in the suffix."</t>
-->
<t>The commonalities of all these IPv6 over IPv4 mechanisms are:
<list style="symbols">
<t>Automatically provisions an IPv6 address for a host or an
IPv6 prefix for a site</t>
<t>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.</t>
<t>Embedding of an IPv4 address or part thereof and optionally
transport layer ports into an IPv6 address.</t>
</list></t>
<t>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 generic mapping of IPv4 to
IPv6, and mechanisms for encapsulation (IPv4 over IPv6) and
translation between the two protocols that use this mapping.</t>
<t>Just as the IPv6 over IPv4 mechanisms referred to above, the
residual IPv4 over IPv6 mechanisms must be capable of:</t>
<t><list style="symbols">
<t>Provisioning an IPv4 prefix, an IPv4 address or a shared IPv4
address.</t>
<t>Algorithmically map between an IPv4 prefix, IPv4 address or
a shared IPv4 address and an IPv6 address.</t>
</list></t>
<t>The unified mapping scheme described here supports
translation mode, encapsulation mode, in both mesh and hub and
spoke topologies, including 1:1 address mappings with full
independence between the IPv6 and IPv4 addressing.</t>
<t>This document describes delivery of IPv4 unicast service
across an IPv6 infrastructure. IPv4 multicast is not considered
further in this document.</t>
<t>The A+P (Address and Port) architecture of sharing an IPv4
address by distributing the port space is described in <xref
target="RFC6346"></xref>. Specifically section 4 of <xref
target="RFC6346"/> covers stateless mapping. The corresponding
stateful solution DS-lite is described in <xref
target="RFC6333"></xref>. The motivation for the work is
described in <xref
target="I-D.ietf-softwire-stateless-4v6-motivation"></xref>.</t>
<t>A companion document defines a DHCPv6 option for provisioning
of MAP <xref
target="I-D.mdt-softwire-map-dhcp-option"></xref>. Other means
of provisioning is possible. Deployment considerations are
described in [I-D.mdt-softwire-map-deployment].</t>
<t>MAP relies on IPv6 and is designed to deliver
production-quality dual-stack service while allowing IPv4 to be
phased out within the SP network. The phasing out of IPv4 within
the SP network is independent of whether the end user disables
IPv4 service or not. Further, "Greenfield"; IPv6-only networks
may use MAP in order to deliver IPv4 to sites via the IPv6
network.</t>
</section>
<!-- SECTION 2: REQUIREMENTS LANGUAGE -->
<section anchor="conventions" title="Conventions">
<t>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 <xref
target="RFC2119"></xref>.</t>
</section>
<!-- conventions -->
<section title="Terminology">
<t><list hangIndent="24" style="hanging">
<t hangText="MAP domain:">One or more 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.</t>
<t hangText="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 domain uses a
different mapping rule set.</t>
<t hangText="MAP node">A device that implements MAP.</t>
<t hangText="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.</t>
<t hangText="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.</t>
<t hangText="Port-set:">Each node has a separate part of the
transport layer port space; denoted as a port-set.</t>
<t hangText="Port-set ID (PSID):">Algorithmically identifies a
set of ports exclusively assigned to the CE.</t>
<t hangText="Shared IPv4 address:">An IPv4 address that is
shared among multiple CEs. Only ports that belong to the
assigned port-set can be used for communication. Also known as
a Port-Restricted IPv4 address.</t>
<t hangText="End-user IPv6 prefix:">The IPv6 prefix assigned
to an End-user CE by other means than MAP
itself. E.g. provisioned using DHCPv6 PD <xref
target="RFC3633"/> or configured manually. It is unique for
each CE.</t>
<t hangText="MAP IPv6 address:">The IPv6 address used to reach
the MAP function of a CE from other CEs and from BRs.</t>
<t hangText="Rule IPv6 prefix:">An IPv6 prefix assigned by
a Service Provider for a mapping rule.</t>
<t hangText="Rule IPv4 prefix:">An IPv4 prefix assigned by a
Service Provider for a mapping rule.</t>
<t hangText="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.</t>
<t hangText="MRT:">MAP Rule table. Address and Port aware
data structure, supporting longest match lookups. The MRT is
used by the MAP forwarding function.</t>
<t hangText="MAP-T:">Mapping of Address and Port –
Translation mode. MAP-T utilizes IPv4/IPv6 translation as per
<xref target="RFC6145"/>.</t>
<t hangText="MAP-E:">Mapping of Address and Port –
Encapsulation mode. MAP-E utilizes a simple IPv4-in-IPv6
tunneling <xref target="RFC2473"/>.</t>
</list></t>
</section>
<!-- SECTION 3: DESCRIPTION -->
<section title="Architecture">
<t>The MAP mechanism is largely built up using existing standard
building blocks. The existing NAT44 on the CE is used with
additional support for restricting transport protocol ports,
ICMP identifiers and fragment identifiers to the configured port
set. MAP supports two forwarding modes, one using stateless
NAT64 as specified in <xref target="RFC6145"/> and one
encapsulation mode specified in <xref target="RFC2473"/>. In
addition MAP specifies an algorithm to do "address resolution"
from an IPv4 address and port to an IPv6 address. This
algorithmic mapping is specified in section 5.</t>
<t>A full IPv4 address or IPv4 prefix can be used like today,
e.g. for identifying an interface or as a DHCP pool. A shared
IPv4 address on the other hand, MUST NOT be used to identify an
interface. While it is theoretically possible to make host
stacks and applications port-aware, that is considered a too
drastic change to the IP model <xref target="RFC6250"/>.</t>
<t>The MAP architecture described here, restricts the use of the
shared IPv4 address to only be used as the global address
(outside) of the NAPT <xref target="RFC2663"/> running on the
CE. The NAPT MUST in turn be connected to a MAP aware forwarding
function, that does encapsulation/decapsulation or translation
to IPv6.</t>
<t>When MAP is used to provision a full IPv4 address or an IPv4
prefix to the CE, these restrictions do not apply.</t>
<t>For packets outbound from the private IPv4 network, the CE
NAPT MUST translate transport identifiers (e.g. TCP and UDP port
numbers) so that they fall within the assigned CE's
port-range.</t>
<t>The forwarding function uses the Mapping Rule Table (MRT) to
make forwarding decisions. The table consist of the mapping
rules. An entry in the table consists of an IPv4 prefix and
PSID. The normal best matching prefix algorithm is used. With a
maximum key length of 48 (Length of IPv4 address (32) + Length
of Transport layer port field (16)). E.g. with a sharing ratio
of 64 (6 bit PSID length) a "host route" for this CE would be a
/38 (32 + 6).</t>
<figure align="center" anchor="topology" title="Network Topology">
<preamble></preamble>
<artwork align="center">
<![CDATA[
User N
Private IPv4
| Network
|
O--+---------------O
| | MAP CE |
| +-----+--------+ |
| NAPT44| MAP | |
| +-----+ | | |\ ,-------. .------.
| +--------+ | \ ,-' `-. ,-' `-.
O------------------O / \ O---------O / Public \
/ IPv6 only \ | MAP |/ IPv4 \
( Network --+ Border +- Network )
\ (MAP Domain) / | Relay |\ /
O------------------O \ / O---------O \ /
| MAP CE | /". ,-' `-. ,-'
| +-----+--------+ | / `----+--' ------'
| NAPT44| MAP | |/
| +-----+ | |
| | +--------+ |
O---.--------------O
|
User M
Private IPv4
Network
]]></artwork>
</figure>
<t>The MAP BR is responsible for connecting external IPv4 networks to
all devices in one or more MAP domains.</t>
<t>The translation mode allows communication between both
IPv4-only and any IPv6 enabled end hosts, with native IPv6-only
servers which are using IPv4-mapped IPv6 address based on DMR in
the MAP-T domain. In this mode, the IPv6-only servers SHOULD
have both A and AAAA records in the authorities DNS server <xref
target="RFC6219"></xref>. DNS64 <xref target="RFC6147"></xref>
become required only when IPv6 servers in the MAP-T domain are
expected themselves to initiate communication to external
IPv4-only hosts.</t>
<t>MAP can also be provisioned in 1:1 mode. In 1:1 mode the BR
has a MAP domain per subscriber, and the CE is configured in hub
and spoke mode, with only a DMR and no other mapping rules. This
allows for a mode where the BR has one rule per subscriber and
the provisioning of IPv4 address or prefix and port sets is
independent of the End-User IPv6 prefix.</t>
</section>
<section title="Mapping Algorithm">
<t>A MAP node is provisioned with one or more mapping rules.</t>
<t>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 its IPv4
address, IPv4 prefix or shared IPv4 address. 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 are specified to
allow for e.g. multiple different IPv4 subnets to exist within
the domain and optimize forwarding between them.</t>
<t>Traffic outside of the domain (i.e. when the destination IPv4
address does not match (using longest matching prefix) any Rule
IPv4 prefix in the Rules database) will be forward using the
Default mapping rule. The Default mapping rule maps outside
destinations to the BR's IPv6 address or prefix.</t>
<t>There are three types of mapping rules:
<list style="numbers">
<t>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.
<list style="symbols">
<t>Rule IPv6 prefix (including prefix length)</t>
<t>Rule IPv4 prefix (including prefix length)</t>
<t>Rule EA-bits length (in bits)</t>
<t>Rule Port Parameters (optional)</t>
<t>Forwarding mode</t>
</list></t>
<t>Forwarding Mapping Rule - used for forwarding. The Basic
Mapping Rule is also a Forwarding Mapping Rule. Each
Forwarding Mapping Rule will result in an entry in the MRT for
the Rule IPv4 prefix. The FMR consists of the same parameters
as the BMR.</t>
<t>Default Mapping Rule - used for destinations outside the
MAP domain. A 0.0.0.0/0 entry is installed in the MRT for this
rule.
<list style="symbols">
<t>IPv6 prefix of address of BR</t>
<t>Forwarding mode</t>
</list></t>
</list></t>
<t>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.</t>
<t>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 to terminate all MAP traffic being sent
or received to the node.</t>
<t>Port-aware IPv4 entries in the MRT are installed for all the
Forwarding Mapping Rules and an IPv4 default route for the
Default Mapping Rule.</t>
<t>In hub and spoke mode, all traffic MUST be forwarded using
the Default Mapping Rule.</t>
<section title="Port mapping algorithm">
<t>The port mapping algorithm is used in domains whose rules
allow IPv4 address sharing. Different Port-Set Identifiers
(PSID) MUST have non-overlapping port-sets. The two extreme
cases are: (1) the port numbers are not contiguous for each
PSID, but uniformly distributed across the port range
(0-65535); (2) the port numbers are 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.</t>
<t>For a given sharing ratio (R) and the maximum number of
contiguous ports (M), the GMA algorithm is defined as:</t>
<t><list style="numbers">
<t>The port number (P) of a given PSID (K) is composed of:
<figure><artwork>
P = R * M * j + M * K + i
</artwork></figure>
Where:<list style="symbols">
<t>PSID: K = 0 to R - 1</t>
<t>Port range index: j = (4096 / M) / R to ((65536 / M) / R) - 1, if the
port numbers (0 - 4095) are excluded.</t>
<t>Contiguous Port index: i = 0 to M - 1</t>
</list></t>
<t>The PSID (K) of a given port number (P) is determined by:
<figure><artwork>
K = (floor(P/M)) % R
</artwork></figure>
Where:<list style="symbols">
<t>% is the modulus operator</t>
<t>floor(arg) is a function that returns the largest integer
not greater than arg.</t>
</list></t>
</list></t>
<section title="Bit Representation of the Algorithm">
<t>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:</t>
<t><figure align="left" title="Bit representation" anchor="bitrepresentation-fig">
<preamble></preamble>
<artwork align="left"><![CDATA[
0 8 15
+---------------+----------+------+-------------------+
| P |
----------------+-----------------+-------------------+
| A (j) | PSID (K) | M (i) |
+---------------+----------+------+-------------------+
|<----a bits--->|<-----k bits---->|<------m bits----->|
]]></artwork></figure></t>
<t>Where j and i are the same indexes defined in the port
mapping algorithm.</t>
<t>For any port number, the PSID can be obtained by bit mask
operation.</t>
<t>For a > 0, j MUST be larger than 0. This ensures that the
algorithm excludes the system ports (<xref
target="I-D.ietf-tsvwg-iana-ports"/>). For a = 0, j MAY be 0
to allow for the provisioning of the system ports.</t>
</section>
<section title="GMA examples">
<t><figure align="left" title="Example 1: with offset = 4 (a = 4)">
<preamble>For example, for R = 1024, PSID offset: a = 4 and
PSID length: k = 10 bits</preamble>
<artwork align="left">
Port-set-1 Port-set-2
PSID=0 | 4096, 4097, 4098, 4099, | 8192, 8193, 8194, 8195, | ...
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=1023| 8188, 8189, 8190, 8191, | 12284, 12285, 12286, 12287,| ...
</artwork></figure></t>
<t><figure align="left" title="Example 2: with offset = 0 (a = 0)">
<preamble>For example, for R = 64, a = 0 (PSID offset = 0
and PSID length = 6 bits):</preamble>
<artwork align="left">
Port-set
PSID=0 | [ 0 - 1023]
PSID=1 | [1024 - 2047]
PSID=2 | [2048 - 3071]
PSID=3 | [3072 - 4095]
...
PSID=63 | [64512 - 65535]
</artwork></figure></t>
</section>
<section title="GMA Provisioning Considerations">
<t>The number of offset bits (a) and excluded ports are
optionally provisioned via the "Rule Port Mapping
Parameters" in the Basic Mapping Rule.</t>
<t>The defaults are:
<list style="symbols">
<t>Excluded ports : 0-4095</t>
<t>Offset bits (a) : 4</t>
</list></t>
<t>To simplify the GMA port mapping algorithm the defaults
are chosen so that the PSID field starts on a nibble
boundary and the excluded port range (0-1023) is extended to
0-4095.</t>
</section>
</section>
<section title="Basic mapping rule (BMR)">
<t><figure align="center" title="IPv6 address format"
anchor="addressallocation-fig">
<preamble></preamble>
<artwork align="center"><![CDATA[
| n bits | o bits | s bits | 128-n-o-s bits |
+--------------------+-----------+---------+------------+----------+
| Rule IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
]]></artwork>
</figure></t>
<t>The Embedded Address bits (EA bits) are unique per end user
within a Rule IPv6 prefix. The Rule 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. The EA bits
encode the CE specific IPv4 address and port information. The
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).</t>
<t>The MAP IPv6 address is created by concatenating the
End-user IPv6 prefix with the MAP subnet-id and the
interface-id as specified in <xref target="interface-id"/>.</t>
<t>The MAP subnet ID is defined to be the first subnet (all
bits set to zero). A MAP node MUST reserve the first IPv6
prefix in a End-user IPv6 prefix for the purpose of MAP.</t>
<t>The MAP IPv6 is created by combining the End-User IPv6
prefix with the all zeros subnet-id and the MAP IPv6 interface
identifier.</t>
<t><figure align="center" anchor="addressallocation2-fig" title="Shared IPv4 address">
<preamble>Shared IPv4 address:</preamble>
<artwork align="center"><![CDATA[
| r bits | p bits | | q bits |
+-------------+---------------------+ +------------+
| Rule IPv4 | IPv4 Address suffix | |Port-Set ID |
+-------------+---------------------+ +------------+
| 32 bits |
]]></artwork>
</figure></t>
<t><figure align="center" anchor="addressallocation3-fig" title="Complete IPv4 address">
<preamble>Complete IPv4 address:</preamble>
<artwork align="center"><![CDATA[
| r bits | p bits |
+-------------+---------------------+
| Rule IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| 32 bits |
]]></artwork>
</figure></t>
<t><figure align="center" anchor="addressallocation4-fig" title="IPv4 prefix">
<preamble>IPv4 prefix:</preamble>
<artwork align="center"><![CDATA[
| r bits | p bits |
+-------------+---------------------+
| Rule IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| < 32 bits |
]]></artwork>
</figure></t>
<t>The length of r MAY be zero, in which case the complete
IPv4 address or prefix is encoded in the EA bits. If only a
part of the IPv4 address/prefix is encoded in the EA bits, the
Rule 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 (p) from the EA bits, are
concatenated with the Rule IPv4 prefix (r bits).</t>
<t>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 by the BMR Rule EA-bits length. The
sum of the Rule IPv6 Prefix length and the Rule EA-bits length
MUST be less or equal than the End-user IPv6 prefix length.</t>
<t>If o + r < 32 (length of the IPv4 address in bits), then
an IPv4 prefix is assigned.</t>
<t>If o + r is equal to 32, then a full IPv4 address is
to be assigned. The address is created by concatenating the
Rule IPv4 prefix and the EA-bits.</t>
<t>If o + r is > 32, then a shared IPv4 address is to be
assigned. The number of IPv4 address suffix 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.</t>
<t>The length of r MAY be 32, with no part of the IPv4 address
embedded in the EA bits. This results in a mapping with no
dependence between the IPv4 address and the IPv6 address. In
addition the length of o MAY be zero (no EA bits embedded in
the End-User IPv6 prefix), meaning that also the PSID is
provisioned using e.g. the DHCP option.</t>
<t>In the following examples, only the suffix (last 8 bits) of
the IPv4 address is embedded in the EA bits (r = 24), while
the IPv4 prefix (first 24 bits) is given in the BMR Rule IPv4
prefix.</t>
<t><figure>
<preamble>Example:</preamble>
<artwork align="left"><![CDATA[
Given:
End-user IPv6 prefix: 2001:db8:0012:3400::/56
Basic Mapping Rule: {2001:db8:0000::/40 (Rule IPv6 prefix),
192.0.2.0/24 (Rule IPv4 prefix),
16 (Rule EA-bits length)}
Sharing ratio: 256 (16 - (32 - 24) = 8. 2^8 = 256)
PSID offset: 4 (default value as per section 5.1.3)
We get IPv4 address and port-set:
EA bits offset: 40
IPv4 suffix bits (p): Length of IPv4 address (32) -
IPv4 prefix length (24) = 8
IPv4 address: 192.0.2.18 (0x12)
PSID start: 40 + p = 40 + 8 = 48
PSID length: o - p = 16 (56 - 40) - 8 = 8
PSID: 0x34
Port-set-1: 4928, 4929, 4930, 4931, 4932, 4933, 4934, 4935,
4936, 4937, 4938, 4939, 4940, 4941, 4942, 4943
Port-set-2: 9024, 9025, 9026, 9027, 9028, 9029, 9030, 9031,
9032, 9033, 9034, 9035, 9036, 9037, 9038, 9039
...
Port-set-15: 62272, 62273, 62274, 62275,
62276, 62277, 62278, 62279,
62280, 62281, 62282, 62283,
62284, 62285, 62286, 62287,
]]></artwork>
</figure>
</t>
</section>
<section title="Forwarding mapping rule (FMR)">
<t>On adding an FMR rule, an IPv4 route is installed in the
MRT for the Rule IPv4 prefix.</t>
<t>On forwarding an IPv4 packet, a best matching prefix lookup
is done in the MRT and the correct FMR is chosen.</t>
<t>
<figure align="left" anchor="aplusptoipv6-fig" title="Deriving of MAP IPv6 address">
<preamble></preamble>
<artwork align="left"><![CDATA[
| 32 bits | | 16 bits |
+--------------------------+ +-------------------+
| IPv4 destination address | | IPv4 dest port |
+--------------------------+ +-------------------+
: : ___/ :
| p bits | / q bits :
+----------+ +------------+
|IPv4 sufx| |Port-Set ID |
+----------+ +------------+
\ / ____/ ________/
\ : __/ _____/
\ : / /
| n bits | o bits | s bits | 128-n-o-s bits |
+--------------------+-----------+---------+------------+----------+
| Rule IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
]]></artwork>
</figure>
</t>
<t><figure>
<preamble>Example:</preamble>
<artwork align="left"><![CDATA[
Given:
IPv4 destination address: 192.0.2.18
IPv4 destination port: 9030
Forwarding Mapping Rule: {2001:db8:0000::/40 (Rule IPv6 prefix),
192.0.2.0/24 (Rule IPv4 prefix),
16 (Rule EA-bits length)}
PSID offset: 4 (default value as per section 5.1.3)
We get IPv6 address:
IPv4 suffix bits (p): 32 - 24 = 8 (18 (0x12))
PSID length: 8
PSID: 0x34 (9030 (0x2346))
EA bits: 0x1234
MAP IPv6 address: 2001:db8:0012:3400:00c0:0002:1200:3400
]]></artwork>
</figure>
</t>
</section>
<section title="Default mapping rule (DMR)">
<t>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.</t>
<t>The DMR consist of the IPv6 address or IPv6 prefix of the
BR. Which is used, is dependent on the forwarding mode
used. Translation mode 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 complete IPv6
address of the BR is used.</t>
</section>
</section>
<section title="The IPv6 Interface Identifier" anchor="interface-id">
<t>The Interface identifier format of a MAP node is based on the
format specified in section 2.2 of <xref target="RFC6052"/>,
with the added PSID field if present, as shown in figure <xref
target="interfaceid2-fig"/>.</t>
<t><figure align="left" anchor="interfaceid2-fig" title="">
<preamble></preamble>
<artwork align="left"><![CDATA[
+--+---+---+---+---+---+---+---+---+
|PL| 8 16 24 32 40 48 56 |
+--+---+---+---+---+---+---+---+---+
|64| u | IPv4 address | PSID | 0 |
+--+---+---+---+---+---+---+---+---+
]]></artwork>
</figure>
</t>
<t>For traffic destined outside of a MAP domain (i.e. for
traffic following the default mapping rule), the destination
IPv4 address is mapped to the IPv6 address or prefix of the
BR. For MAP-E this is the IPv6 tunnel end point address of the
BR, while for MAP-T this is the IPv6 converted representation of
the IPv6 address per RFC6052, shown in the form of an example in
figure <xref target="interfaceid3-fig"/> below. Note that the BR
prefix-length is variable and can be both shorter or longer than
64 bits, up to 96 bits.</t>
<t><figure anchor="interfaceid3-fig" title="">
<preamble></preamble>
<artwork><![CDATA[
<---------- 64 ------------>< 8 ><----- 32 -----><--- 24 --->
+--------------------------+----+---------------+-----------+
| BR prefix | u | IPv4 address | 0 |
+--------------------------+----+---------------+-----------+
]]></artwork>
</figure></t>
<t>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.</t>
<t>In the case of an IPv4 prefix, the IPv4 address field is
right-padded with zeroes up to 32 bits. The PSID field is
left-padded to create a 16 bit field. For an IPv4 prefix or a
complete IPv4 address, the PSID field is zero.</t>
<t>If the End-user IPv6 prefix length is larger than 64, the
most significant parts of the interface identifier is
overwritten by the prefix.</t>
</section>
<section title="MAP Configuration">
<t>For a given MAP domain, the BR and CE MUST be configured with
the following MAP elements. The configured values for these
elements are identical for all CEs and BRs within a given MAP
domain.</t>
<t><list style="symbols">
<t>The End-User IPv6 prefix (Part of the normal IPv6
provisioning).</t>
<t>The Basic Mapping Rule and optionally the Forwarding
Mapping Rules, including the Rule IPv6 prefix, Rule IPv4
prefix, Length of EA bits, and Forwarding mode</t>
<t>The Default Mapping Rule with the BR IPv6 prefix or address</t>
<t>Hub and spoke mode or Mesh mode. (If all traffic should be
sent to the BR, or if direct CE to CE traffic should be
supported).</t>
</list></t>
<section title="MAP CE">
<t>The MAP elements are set to values that are the same
across all CEs within a MAP domain. The values may be
configured in a variety of manners, including provisioning
methods such as the Broadband Forum's "TR-69" Residential
Gateway management interface, an XML-based object retrieved
after IPv6 connectivity is established, or manual
configuration by an administrator. This document describes how
to configure the necessary parameters via a single DHCPv6
option. A CE that allows IPv6 configuration by DHCP SHOULD
implement this option. Other configuration and management
methods may use the format described by this option for
consistency and convenience of implementation on CEs that
support multiple configuration methods.</t>
<t>The only remaining provisioning information the CE requires