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draft-ietf-softwire-map-00.txt
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Network Working Group O. Troan
Internet-Draft W. Dec
Intended status: Standards Track Cisco Systems
Expires: December 3, 2012 X. Li
C. Bao
Y. Zhai
CERNET Center/Tsinghua
University
S. Matsushima
SoftBank Telecom
T. Murakami
IP Infusion
June 1, 2012
Mapping of Address and Port (MAP)
draft-ietf-softwire-map-00
Abstract
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.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 3, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
Troan, et al. Expires December 3, 2012 [Page 1]
Internet-Draft MAP June 2012
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Troan, et al. Expires December 3, 2012 [Page 2]
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Mapping Algorithm . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Port mapping algorithm . . . . . . . . . . . . . . . . . . 10
5.1.1. Bit Representation of the Algorithm . . . . . . . . . 11
5.1.2. GMA examples . . . . . . . . . . . . . . . . . . . . . 11
5.1.3. GMA Provisioning Considerations . . . . . . . . . . . 12
5.2. Basic mapping rule (BMR) . . . . . . . . . . . . . . . . . 12
5.3. Forwarding mapping rule (FMR) . . . . . . . . . . . . . . 15
5.4. Default mapping rule (DMR) . . . . . . . . . . . . . . . . 16
6. The IPv6 Interface Identifier . . . . . . . . . . . . . . . . 17
7. MAP Configuration . . . . . . . . . . . . . . . . . . . . . . 18
7.1. MAP CE . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.2. MAP BR . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.3. Backwards compatibility . . . . . . . . . . . . . . . . . 19
8. Forwarding Considerations . . . . . . . . . . . . . . . . . . 19
8.1. Receiving rules . . . . . . . . . . . . . . . . . . . . . 20
8.2. MAP BR . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.2.1. IPv6 to IPv4 . . . . . . . . . . . . . . . . . . . . . 20
8.2.2. IPv4 to IPv6 . . . . . . . . . . . . . . . . . . . . . 21
9. ICMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.1. Translating ICMP/ICMPv6 Headers . . . . . . . . . . . . . 21
10. Fragmentation and Path MTU Discovery . . . . . . . . . . . . . 22
10.1. Fragmentation in the MAP domain . . . . . . . . . . . . . 22
10.2. Receiving IPv4 Fragments on the MAP domain borders . . . . 23
10.3. Sending IPv4 fragments to the outside . . . . . . . . . . 23
11. NAT44 Considerations . . . . . . . . . . . . . . . . . . . . . 23
12. Deployment Considerations . . . . . . . . . . . . . . . . . . 23
12.1. Choice of forwarding mode . . . . . . . . . . . . . . . . 23
12.2. Use cases . . . . . . . . . . . . . . . . . . . . . . . . 24
12.2.1. Hub and spoke with per subscriber rules . . . . . . . 24
12.2.2. Communication with IPv6 servers in the MAP-T domain . 24
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
14. Security Considerations . . . . . . . . . . . . . . . . . . . 24
15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 25
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
17.1. Normative References . . . . . . . . . . . . . . . . . . . 26
17.2. Informative References . . . . . . . . . . . . . . . . . . 27
Appendix A. Example of MAP-T translation . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32
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1. Introduction
Mapping IPv4 addresses in IPv6 addresses 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 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.
There are numerous variations of this idea, described in 6over4
[RFC2529], 6to4 [RFC3056], ISATAP [RFC5214], and 6rd [RFC5969].
The commonalities of all these IPv6 over IPv4 mechanisms are:
o Automatically 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.
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 generic mapping of IPv4 to
IPv6, and mechanisms for encapsulation (IPv4 over IPv6) and
translation between the two protocols that use this mapping.
Just as the IPv6 over IPv4 mechanisms referred 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,
including 1:1 address mappings with full independence between the
IPv6 and IPv4 addressing.
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This document describes delivery of IPv4 unicast service across an
IPv6 infrastructure. IPv4 multicast is not considered further in
this document.
The A+P (Address and Port) architecture of sharing an IPv4 address by
distributing the port space is described in [RFC6346]. Specifically
section 4 of [RFC6346] covers stateless mapping. The corresponding
stateful solution DS-lite is described in [RFC6333]. The motivation
for the 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]. Other means of provisioning is
possible. Deployment considerations are described in [I-D.mdt-
softwire-map-deployment].
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.
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
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.
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.
MAP node A device that implements MAP.
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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.
Port-set: Each node has a separate part of the
transport layer port space; denoted as a
port-set.
Port-set ID (PSID): Algorithmically identifies a set of ports
exclusively assigned to the CE.
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.
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 [RFC3633] or
configured manually. It is unique for each
CE.
MAP IPv6 address: The IPv6 address used to reach the MAP
function of a CE from other CEs and from BRs.
Rule IPv6 prefix: An IPv6 prefix assigned by a Service Provider
for a mapping rule.
Rule IPv4 prefix: An IPv4 prefix assigned by a Service Provider
for a mapping rule.
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.
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MRT: MAP Rule table. Address and Port aware data
structure, supporting longest match lookups.
The MRT is used by the MAP forwarding
function.
MAP-T: Mapping of Address and Port - Translation
mode. MAP-T utilizes IPv4/IPv6 translation
as per [RFC6145].
MAP-E: Mapping of Address and Port - Encapsulation
mode. MAP-E utilizes a simple IPv4-in-IPv6
tunneling [RFC2473].
4. Architecture
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 [RFC6145] and one encapsulation mode specified in [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.
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
[RFC6250].
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 [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.
When MAP is used to provision a full IPv4 address or an IPv4 prefix
to the CE, these restrictions do not apply.
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.
The forwarding function uses the Mapping Rule Table (MRT) to make
forwarding decisions. The table consist of the mapping rules. An
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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).
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
Figure 1: Network Topology
The MAP BR is responsible for connecting external IPv4 networks to
all devices in one or more MAP domains.
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 [RFC6219]. DNS64 [RFC6147] become
required only when IPv6 servers in the MAP-T domain are expected
themselves to initiate communication to external IPv4-only hosts.
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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.
5. Mapping Algorithm
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 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.
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.
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)
* Forwarding mode
2. 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.
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The FMR consists of the same parameters as the BMR.
3. 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.
* IPv6 prefix of address of BR
* Forwarding mode
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 to terminate all MAP traffic being sent or received
to the node.
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.
In hub and spoke mode, all traffic MUST be forwarded using the
Default Mapping Rule.
5.1. Port mapping algorithm
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.
For a given sharing ratio (R) and the maximum number of contiguous
ports (M), the GMA algorithm is defined as:
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
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* Port range index: j = (4096 / M) / R to ((65536 / M) / R) - 1,
if the port numbers (0 - 4095) 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.
5.1.1. 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----->|
Figure 2: 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.
For a > 0, j MUST be larger than 0. This ensures that the algorithm
excludes the system ports ([I-D.ietf-tsvwg-iana-ports]). For a = 0,
j MAY be 0 to allow for the provisioning of the system ports.
5.1.2. GMA examples
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For example, for R = 1024, PSID offset: a = 4 and PSID length: k = 10
bits
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,| ...
Example 1: with offset = 4 (a = 4)
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]
Example 2: with offset = 0 (a = 0)
5.1.3. GMA Provisioning Considerations
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:
o Excluded ports : 0-4095
o Offset bits (a) : 4
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.
5.2. Basic mapping rule (BMR)
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| n bits | o bits | s bits | 128-n-o-s bits |
+--------------------+-----------+---------+------------+----------+
| Rule IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
Figure 3: IPv6 address format
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).
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
Section 6.
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.
The MAP IPv6 is created by combining the End-User IPv6 prefix with
the all zeros subnet-id and the MAP IPv6 interface identifier.
Shared IPv4 address:
| r bits | p bits | | q bits |
+-------------+---------------------+ +------------+
| Rule IPv4 | IPv4 Address suffix | |Port-Set ID |
+-------------+---------------------+ +------------+
| 32 bits |
Figure 4: Shared IPv4 address
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Complete IPv4 address:
| r bits | p bits |
+-------------+---------------------+
| Rule IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| 32 bits |
Figure 5: Complete IPv4 address
IPv4 prefix:
| r bits | p bits |
+-------------+---------------------+
| Rule IPv4 | IPv4 Address suffix |
+-------------+---------------------+
| < 32 bits |
Figure 6: IPv4 prefix
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).
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.
If o + r < 32 (length of the IPv4 address in bits), then an IPv4
prefix is assigned.
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.
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.
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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.
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.
Example:
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,
5.3. Forwarding mapping rule (FMR)
On adding an FMR rule, an IPv4 route is installed in the MRT for the
Rule IPv4 prefix.
On forwarding an IPv4 packet, a best matching prefix lookup is done
in the MRT and the correct FMR is chosen.
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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 | s bits | 128-n-o-s bits |
+--------------------+-----------+---------+------------+----------+
| Rule IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
Figure 7: Deriving of MAP IPv6 address
Example:
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
5.4. 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.
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
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interface identifier. For the encapsulation mode the complete IPv6
address of the BR is used.
6. The IPv6 Interface Identifier
The Interface identifier format of a MAP node is based on the format
specified in section 2.2 of [RFC6052], with the added PSID field if
present, as shown in figure Figure 8.
+--+---+---+---+---+---+---+---+---+
|PL| 8 16 24 32 40 48 56 |
+--+---+---+---+---+---+---+---+---+
|64| u | IPv4 address | PSID | 0 |
+--+---+---+---+---+---+---+---+---+
Figure 8
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 Figure 9 below. Note that
the BR prefix-length is variable and can be both shorter or longer
than 64 bits, up to 96 bits.
<---------- 64 ------------>< 8 ><----- 32 -----><--- 24 --->
+--------------------------+----+---------------+-----------+
| BR prefix | u | IPv4 address | 0 |
+--------------------------+----+---------------+-----------+
Figure 9
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.
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.
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If the End-user IPv6 prefix length is larger than 64, the most
significant parts of the interface identifier is overwritten by the
prefix.
7. MAP Configuration
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.
o The End-User IPv6 prefix (Part of the normal IPv6 provisioning).
o 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
o The Default Mapping Rule with the BR IPv6 prefix or address
o 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).
7.1. MAP CE
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.
The only remaining provisioning information the CE requires in order
to calculate the MAP IPv4 address and enable IPv4 connectivity is the
IPv6 prefix for the CE. The End-user IPv6 prefix is configured as
part of obtaining IPv6 Internet access.
A single MAP CE MAY be connected to more than one MAP domain, just as
any router may have more than one IPv4-enabled service provider
facing interface and more than one set of associated addresses
assigned by DHCP. Each domain a given CE operates within would