One document matched: draft-mdt-softwire-map-encapsulation-00.xml
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<rfc category="std" docName="draft-mdt-softwire-map-encapsulation-00"
ipr="trust200902">
<!-- ***** FRONT MATTER ***** -->
<front>
<title abbrev="MAP Encapsulation (MAP-E)">MAP Encapsulation (MAP-E) -
specification</title>
<author fullname="Tetsuya Murakami" initials="T." surname="Murakami" role="editor">
<organization>IP Infusion</organization>
<address>
<postal>
<street>1188 East Arques Avenue</street>
<city>Sunnyvale</city>
<country>USA</country>
</postal>
<email>tetsuya@ipinfusion.com</email>
</address>
</author>
<author fullname="Ole Troan" initials="O." surname="Troan">
<organization>cisco</organization>
<address>
<postal>
<street></street>
<city>Oslo</city>
<country>Norway</country>
</postal>
<email>ot@cisco.com</email>
</address>
</author>
<!--
<author fullname="Remi Despres" initials="R." surname="Despres">
<organization>RD-IPtech</organization>
<address>
<postal>
<street>3 rue du President Wilson</street>
<city>Levallois</city>
<country>France</country>
</postal>
<email>remi.despres@free.fr</email>
</address>
</author>
-->
<author fullname="Satoru Matsushima" initials="S." surname="Matsushima">
<organization>SoftBank</organization>
<address>
<postal>
<street>1-9-1 Higashi-Shinbashi, Munato-ku</street>
<city>Tokyo</city>
<country>Japan</country>
</postal>
<email>satoru.matsushima@tm.softbank.co.jp</email>
</address>
</author>
<date month="January" year="2012" />
<area>Internet</area>
<workgroup>Internet Engineering Task Force</workgroup>
<keyword></keyword>
<abstract>
<t>This document specifies the “Mapping of Address and Port“
(MAP) encapsulation based solution (MAP-E) with an automatic tunneling
mechanism for providing IPv4 connectivity service to end users over a
service provider's IPv6 network.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>MAP-E is a protocol mechanism of the &ldque;Mapping of Address
and Port“ (MAP) encapsulation based solution to deploy IPv4
to sites via a service provider's (SP's) IPv6 network with the
automatic tunneling mechanism (IPv4-in-IPv6). Similar to Dual-Stack
Lite <xref target="I-D.ietf-softwire-dual-stack-lite"></xref>,
MAP-E is designed to allow IPv4 traffic to be delivered over
an IPv6 network without the direct provisioning of IPv4
addresses. Like 6rd <xref target="RFC5969"></xref>, MAP-E is
operated in a fully stateless manner within the SP network.</t>
<t>MAP-E 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,
&ldque;Greenfield&ldque; IPv6-only networks may use MAP-E in order to
deliver IPv4 to sites via the IPv6 network in a way that does not
require protocol translation between IPv4 and IPv6.</t>
<t>MAP-E utilizes an algorithmic mapping, defined in MAP
<xref target="I-D.mdt-softwire-mapping-address-and-port"></xref>,
between the IPv6 and IPv4 addresses that are assigned for use
within the SP network. This mapping can provide automatic determination
of IPv6 tunnel endpoints from IPv4 destination addresses, allowing the
stateless operation of MAP-E. MAP-E views the IPv6 network as a link
layer for IPv4 and supports an automatic tunneling abstraction
similar to the Non-Broadcast Multiple Access (NBMA) <xref
target="RFC2491"></xref> model.</t>
<t>The MAP algorithmic mapping is also used to automatically
provision IPv4 addresses and allocating a set of non-overlapping
ports for each MAP-E CE. The "SP-facing" (i.e., "WAN") side of the
MAP-E CE, operate as native IPv6 interface with no need for IPv4
operation or support. On the "end-user-facing" (i.e., "LAN") side
of a CE, IPv6 and IPv4 might be implemented as for any native
dual-stack service delivered by the SP.</t>
<t>A MAP-E domain consists of MAP-E Customer Edge (CE) routers and
one or more MAP-E Border Relays (BRs). IPv4 packets encapsulated
by MAP-E follow the IPv6 routing topology within the SP network
between CEs and among CEs and BRs. CE to CE traffic is direct,
while BRs are traversed only for IPv4 packets that are destined
to or are arriving from outside a given MAP-E domain. As MAP-E is
stateless, BRs may be reached using anycast for failover and
resiliency.</t>
<t>MAP-E does not require any stateful NAPT <xref target="RFC3022">
</xref> functions at the BRs or elsewhere within the SP network.
Instead, MAP-E allows for sharing of IPv4 addresses among multiple
sites by automatically allocating a set of non-overlapping ports
for each CE as part of the stateless mapping function. It is
expected that the CE will, in turn, perform local IPv4 Network
Address and Port Translation (NAPT) <xref target="RFC3022">
</xref> functions for the site as is commonly performed today,
except avoiding ports outside of the allocated port set. Although
MAP-E is designed primarily to support IPv4 deployment to a customer
site (such as a residential home network) by an SP, it can equally
be applied to an individual host acting as a CE router.</t>
</section>
<section title="Requirements Language">
<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 <xref target="RFC2119">
RFC 2119</xref>.</t>
</section>
<section title="Terminology">
<t><list hangIndent="22" style="hanging">
<t hangText="MAP-E:">Mapping of Address and Port – Encapsulation
mode. MAP-E utilizes a simple IPv4-in-IPv6 tunneling along with the
MAP extensions for mapping between IPv4 and IPv6 defined in
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>
and this draft.</t>
<t hangText="MAP-E domain (Domain):">A set of MAP-E CEs and BRs
connected to the same virtual MAP-E link. A service provider may
deploy MAP-E with a single MAP-E domain, or may utilize multiple
MAP-E domains. Each domain requires a separate MAP-E rule set.</t>
<t hangText="MAP-E Border Relay (BR):">A MAP-E enabled router
managed by the service provider at the edge of a MAP-E domain.
A Border Relay router has at least one of each of the
following: an IPv6-enabled interface, a MAP-E virtual interface
acting as an endpoint for the MAP-E IPv4 in IPv6 tunnel, and an
IPv4 interface connected to the native IPv4 network. A MAP-E BR
may also be referred to simply as a "BR" within the context of
MAP-E.</t>
<t hangText="MAP-E Customer Edge (CE):">A device functioning as
a Customer Edge router in a MAP-E deployment. In a residential
broadband deployment, this type of device is sometimes
referred to as a "Residential Gateway" (RG) or "Customer
Premises Equipment" (CPE). A typical MAP-E CE serving a
residential site has one WAN side interface, one or more LAN
side interfaces, and a MAP-E virtual interface. A MAP-E CE may
also be referred to simply as a "CE" within the context of
MAP-E.</t>
<t hangText="Shared IPv4 address:">An IPv4 address that is
shared among multiple nodes. Each node has a separate part of
the transport layer port space.</t>
<t hangText="MAP-E Rule:">A MAP rule defining the mapping relationship
for a given MAP-E domain between IPv4 and IPv6, defined in
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>
</t>
</list></t>
</section>
<section title="MAP-E Configuration">
<t>The IPv4 prefix, IPv4 address or shared IPv4 address for use
at a customer site is automatically obtained based on BMR defined
in MAP
<xref target="I-D.mdt-softwire-mapping-address-and-port"></xref>
from the IPv6 prefix delegated to the site.</t>
<t>For a given MAP-E domain, the BR and CE MUST be configured with
a set of mapping rules (BMR, FMR and DMR) defined in
<xref target="I-D.mdt-softwire-mapping-address-and-port"></xref>
. The configured values for these elements MUST be consistent
for all CEs and BRs within a given MAP-E domain.</t>
<t>The configuration elements in the set of mapping rules (BMR, FMR
and DMR) may be provisioned via IPv6 DHCP defined in
<xref target="I-D.mdt-softwire-map-dhcp-option"></xref> or manually.
</t>
<t>The only remaining provisioning information in order to enable
MAP-E is an IPv6 prefix. This IPv6 prefix is configured as part of
obtaining IPv6 Internet access (i.e., configured via SLAAC, DHCPv6,
DHCPv6 PD, manual or otherwise).</t>
</section>
<section anchor="behavior" title="MAP-E Node Behavior">
<section anchor="br-provisioning" title="Provisioning of MAP-E BR">
<t>The MAP-E BR needs to be provisioned with information for the MAP-E
domain or domains it is expected to handle, along with any necessary
routing processes. For each MAP-E domain, the BR will have the
following parameters:</t>
<t>o The MAP Domain IPv4 and IPv6 prefix, and their lengths (Basic
Mapping Rule)</t>
<t>o The MAP EA-bits (CE index), including IPv4 suffix, length and
any port-range (including any excluded ports and the port number
continuity parameter)</t>
<t>o The BR prefix and its length (Default Mapping Rule)</t>
<t>o The subnet ID</t>
<t>A BR when configured for BMR, FMR and DMR, and performs the
following functions:</t>
<t>o Configures the IPv4/IPv6 stateless encapsulation parameters
(BMR, FMR and DMR)</t>
<t>Based on the above configuration, the IPv4-in-IPv6 encapsulation
function can be performed by the BR.</t>
<t>o Derive IPv4 address along with any applicable port-range from
IPv4-translatable address (BMR)</t>
<t>o Derive IPv4-translatable address from IPv4 address and port
number (FMR)</t>
</section>
<section anchor="br-behavior" title="Packet Forwarding Behavior on MAP-E BR">
<t>(a) BR reception of an IPv4 packet</t>
<t><list hangIndent="22" style="hanging">
<t hangText="Step 1">BR looks up an appropriate mapping rule (FMR)
with a specific Domain IPv4 prefix which has the longest match with
an IPv4 destination address in the received IPv4 packet. If the FMR
is not found, the received packet should be discarded. If the length
of Domain IPv4 prefix plus EA-bits associated with the FMR does not
exceed 32 bits, BR proceeds to step 2. If the length exceeds 32 bits,
BR checks that the received packet contains a complete IPv4 datagram.
If the packet is fragmented, BR should reassemble the packet. Once BR
can obtain the complete IPv4 datagram, BR proceeds to step 2 as though
the datagram has been received in a single packet.</t>
<t hangText="Step 2">BR generates a CE IPv6 address from the IPv4
destination address or the IPv4 destination address and the destination
port based on the FMR found in step 1. If the CE IPv6 address can be
successfully generated, BR encapsulates the IPv4 packet in IPv6 and
forwards the IPv6 packet via the IPv6 interface. If the length of the
IPv6 encapsulated packet exceeds the MTU of the IPv6 interface, the
fragmentation should be done in IPv6.</t>
</list></t>
<t>(b) BR reception of an IPv6 packet</t>
<t><list hangIndent="22" style="hanging">
<t hangText="Step 1">If the received IPv6 packet is fragmented, the
reassembly should be done in IPv6 at first. Once BR obtains a complete
IPv6 packet, BR looks up an appropriate mapping rule (BMR) with a specific
Domain IPv6 prefix which has the longest match with an IPv6 source address
in the received IPv6 packet. If the BMR rule is not found, the received
IPv6 packet should be discarded. BR derives a CE IPv6 address from the
IPv4 source address or the IPv4 source address and the source port in
the encapsulated IPv4 packet based on the BMR. If the CE IPv6 address is
eqaul to the IPv6 source address in the received IPv6 packet, BR decapsulates
the IPv4 packet and then forward it via the IPv4 interface.</t>
</list></t>
</section>
<section anchor="ce-provisioning" title="Provisioning of MAP-E CE">
<t>A MAP-E CE requires the following parameters for provisioning:</t>
<t>o The MAP Domain IPv4 and IPv6 prefix, and their lengths (Basic
Mapping Rule)</t>
<t>o The MAP EA-bits (CE index), including IPv4 suffix, length and
any port-range (including any excluded ports and the port number
continuity parameter)</t>
<t>o The BR prefix and its length (Default Mapping Rule)</t>
<t>A MAP-E CE that receives a MAP DHCP option
<xref target="I-D.mdt-softwire-map-dhcp-option"></xref> for BMR,
FMR and DMR and performs the following (MAP initialization)
functions:</t>
<t>o Configures the NAT44 port-range mapping function parameters
(BMR)</t>
<t>o Configures the IPv4/IPv6 stateless encapsulation parameters
(BMR, FMR and DMR) Based on the above configuration, the IPv4/IPv6
encapsulation function can be performed in CE.</t>
<t>o Derives IPv4 address along with any applicable port-range from
IPv4-translatable address (BMR)</t>
<t>o Derives IPv4-translatable address from IPv4 address (FMR)</t>
</section>
<section anchor="ce-behavior" title="Packet Forwarding Behavior on MAP-E CE">
<t>(a) CE reception of an IPv4 packet</t>
<t><list hangIndent="22" style="hanging">
<t hangText="Step 1">CE looks up an appropriate mapping rule (FMR)
with a specific Doamin IPv4 prefix which has the longest match with an
IPv4 destination address in the received IPv4 packet. If the FMR
is found, the length of Domain IPv4 prefix plus EA-bits must be checked.
If the length does not exceeds 32 bits, CE proceeds to step 2. If the
length exceeds 32 bits, CE checks that the received IPv4 packet contains
a complete IPv4 datagram. If the packet is fragmented, CE should reassemble
the packet. Once CE can obtain the complete IPv4 datagram, CE proceeds
to step 2 as though the datagram has been received in a single packet.
If the FMR is not found, CE proceeds to step 2.</t>
<t hangText="Step 2">If the FMR is found in step 1, CE derives a IPv6
destination address from the IPv4 destination address or the IPv4
destination address and the destination port based on the FMR. If the
IPv6 destination address can be derived successfully, CE encapsulates
the IPv4 packet in IPv6 whose destination address is set to the derived
IPv6 address. If the FMR is not found in step 1, CE uses the DMR and then
CE encapsulates the IPv4 packet in IPv6 whose destination address is set
to the BR IPv6 address. Then CE forwards the IPv6 packet via IPv6 interface.
If the length of the IPv6 packet exceeds the MTU of the IPv6 interface,
the fragmentation should be done in IPv6. Moreover, if using IPv4 shared
address, a Datagram ID in the received IPv4 header must be over-written
before encapsulating the IPv4 packet in IPv6. In case of shared IPv4 address,
the Datagram ID must be unique among CEs sharing the same IPv4 address.
Hence, CE should assign the unique value and set this value to the datagram
ID in IPv4 header. This value may be generated from the port-range assigned
to the CE to keep the uniqueness among CEs sharing same IPv4 address.</t>
</list></t>
<t>(b) CE reception of an IPv6 packet</t>
<t><list hangIndent="22" style="hanging">
<t hangText="Step 1">If the received IPv6 packet is fragmented, the
reassembly should be done in IPv6 at first. Once CE obtains a complete
IPv6 packet, CE looks up an appropriate mapping rule (BMR) with a
specific Domain IPv6 prefix which has the longest match with an IPv6
source address in the recieved IPv6 packet. If the BMR is found, the
CE derives a CE IPv6 address from the IPv4 source address or the IPv4
source address and the source port based on the BMR and then checks
that the IPv6 source address of the received IPv6 packet is matched
to it. If the BMR is not found, CE checks that the IPv6 source address
is matched to the BR IPv6 address. In case of success, the CE can
decapsulate the IPv4 packet and forward it via the IPv4 interface.</t>
</list></t>
</section>
</section>
<section title="Deriving IPv6 address from IPv4">
<section title="Deriving IPv6 address from IPv4 Address and Port Number at the BR">
<t>IPv6 Source Address and Source Port Number:</t>
<t>At the BR, the IPv6 source address MUST be set to the BR IPv6
address as per DMR
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>.
The source Layer 4 port number MUST be unchanged.</t>
<t>IPv6 Destination Address and Destination Port Number:</t>
<t>At the BR, the IPv6 destination address (IPv4-translatable address)
MUST be derived from the IPv4 destination address and the destination
port number per FMR
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>.
The destination Layer 4 port number MUST be unchanged.</t>
</section>
<section title="Deriving IPv6 address from IPv4 Address and Port Number at the CE">
<t>IPv6 Source Address and Source Port Number:</t>
<t>At the CE, the IPv6 source address (IPv4-translatable address) MUST
be derived from the IPv4 source address as per BMR
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>.
The source port number MUST be unchanged.</t>
<t>IPv6 Destination Address and Destination Port Number:</t>
<t>At the CE, if Forwarding Mapping Rules (FMRs) are enabled, the IPv4
packet MUST be checked to see if the IPv4 destination address matches
the FMR. If matching, the IPv6 destination address (IPv4-converted
address) MUST be derived from the IPv4 destination address and the
destination port number as per FMR. Otherwise, the IPv6 destination
address MUST be set to the BR IPv6 address per DMR
<xref target="I-D.mdt-softwire-mapping-address-and-port">MAP</xref>.
The destination port number MUST be unchanged.</t>
</section>
</section>
<section anchor="fragmentation" title="Encapsulation and Fragmentation Considerations">
<!-- <section title="Maximum Transmission Unit"> -->
<t>Maximum transmission unit (MTU) and fragmentation issues
for IPv4 in IPv6 tunneling are discussed in detail in Section
7.2 of <xref target="RFC2473"></xref>. MAP-E's scope is limited to
a service provider network. IPv6 Path MTU discovery MAY be used
to adjust the MTU of the tunnel as described in Section 7.2 of
<xref target="RFC2473"></xref>, or the MAP-E Tunnel MTU might be
explicitly configured.</t>
<t>The use of an anycast source address could lead to any ICMP
error message generated on the path being sent to a different
BR. Therefore, using dynamic tunnel MTU Section 7.2 of
<xref target="RFC2473"></xref> is subject to IPv6 Path MTU
blackholes.</t>
<t>Multiple BRs using the same anycast source address could
send fragmented packets to the same MAP-E CE at the same time.
If the fragmented packets from different BRs happen to use the
same fragment ID, incorrect reassembly might occur. For this
reason, a BR using an anycast source address MUST NOT fragment
the IPv6 encapsulated packet unless BR's having identical rules
are required to use disjoint ranges of fragment ID.</t>
<t>If the MTU is well-managed such that the IPv6 MTU on the CE
WAN side interface is set so that no fragmentation occurs
within the boundary of the SP, then the MAP-E Tunnel MTU should
be set to the known IPv6 MTU minus the size of the
encapsulating IPv6 header (40 bytes). For example, if the
IPv6 MTU is known to be 1500 bytes, the MAP-E Tunnel MTU might
be set to 1460 bytes. Absent more specific information, the
MAP-E Tunnel MTU SHOULD default to 1280 bytes.</t>
<t>Alternatively, if BR's having identical rule are required
to use disjoint ranges of fragment ID, a BR using an anycast
source address SHOULD fragment the IPv6 encapsulated packet
correctly.</t>
<t>For MAP-E domain traversal, IPv4 packets are encapsulated in
IPv6 packets whose Next header is set to 4 (i.e. IPv4). If
fragmentation of IPv6 packets is needed, it is performed
according to <xref target="RFC2460"></xref>. Absent more specific
information, the path MTU of a MAP-E Domain has to be set to 1280
<xref target="RFC2460"></xref>.</t>
<t>In domains where IPv4 addresses are not shared, IPv6 destinations
are derived from IPv4 addresses alone. Thus, each IPv4 packet can be
encapsulated and decapsulated independently of each other. MAP-E
processing is completely stateless.</t>
<t>On the other hand, in domains where IPv4 addresses are shared, BR's
and CE's can have to encapsulate IPv4 packets whose IPv6 destinations
depend on destination ports. Precautions are needed, due to the fact
that the destination port of a fragmented datagram is available only
in its first fragment. A sufficient precaution consists in
reassembling each datagram received in multiple packets, and to treat
it as though it would have been received in single packet. This
function is such that MAP-E is in this case stateful at the IP layer.
(This is common with DS-lite and NAT64/DNS64 which, in addition, are
stateful at the transport layer.) At Domain entrance, this ensures
that all pieces of all received IPv4 datagrams go to the right IPv6
destinations.</t>
<t>Another peculiarity of shared IPv4 addresses is that, without
precaution, a destination could simultaneously receive from different
sources fragmented datagrams that have the same Datagram ID (the
Identification field of <xref target="RFC0791"></xref>. This would
disturb the reassembly process. To eliminate this risk, CE MUST rewrite
the datagram ID to an unique value among CEs having same shared IPv4
address upon sending the packets over MAP-E tunnel. This value SHOULD be
generated locally within the port-range assigned to a given CE. Note that
replacing a Datagram ID in an IPv4 header implies an update of its
Header-checksum fieald, by adding to it the one's complement difference
between the old and the new values.</t>
</section>
<section anchor="forwarding" title="Packet Forwarding Considerations">
<section anchor="mesh" title="Mesh model">
<t>Basically, MAP-E should allow the mesh model in order for all CEs
to communicate each others directly. If one mapping rules is applied
to a given MAP-E domain, all CEs can communicate each others directly.
If multiple mapping rules are applied to a given MAP-E domain, or if
multiple MAP-E domains are existed, CE can communicate each others
directly only if all CEs know all mapping rules. When a CE receives
an IPv4 packet from its LAN side, the CE looks up a mapping rule
corresponding to an IPv4 destination address in the received IPv4
packet. If the corresponding mapping rule is found, CE can communicate
to another CE directly based on the mapping rule defined as Forwarding
mapping rule (FMR) in
<xref target="I-D.mdt-softwire-mapping-address-and-port"></xref>
. If the corresponding mapping rule is not found, CE must forward the
packet to a given BR.</t>
</section>
<section anchor="hub-spoke" title="Hub & Spoke model">
<t>In order to allow the mesh topology so that all CEs can communicate
each others directly, all CE should know all mapping rules applied to
a given MAP-E domain or MAP-E domains. However, if a CE knows only subset
of mapping rules applied to a given MAP-E domain or MAP-E domains, a CE can
not communicate to some CEs due to the lack of mapping rules. In this
case, an IPv4 packet toward to these CEs must be forwarded to a given
BR. In order to achieve the hub & spoke mode fully, Forwarding mapping
rule (FMR) defined in
<xref target="I-D.mdt-softwire-mapping-address-and-port"></xref>
should be disabled. In this case, all CEs do not look up the mapping
rules upon receiving an IPv4 packet from its LAN side and then CE must
encapsulate the IPv4 packet with IPv6 whose destination must be a given
BR.</t>
</section>
</section>
<section title="NAT Considerations">
<t>NAT44 should be implemented in CPE which has MAP-E CE function. The
NAT44 must conform that best current practice documented in <xref
target="RFC4787"></xref>, <xref target="RFC5508"></xref> and <xref
target="RFC5382"></xref>. When there are restricted available port
numbers in a given MAP-E CE, the NAT44 must restrict mapping ports
within the port-set.</t>
</section>
<section title="ICMP Considerations">
<t>ICMP message should be supported in MAP-E domain. Hence, the
NAT44 in MAP-E CE must implement the behavior for ICMP message
conforming to the best current practice documented in
<xref target="RFC5508"></xref>.</t>
<t> If a MAP-E CE receives an ICMP message having ICMP identifier
field in ICMP header, NAT44 in the MAP-E CE must rewrite this
field to a specific value assigned from the port-set. BR and other
CEs must handle this field similar to the port number in tcp/udp
header upon receiving the ICMP message with ICMP identifier field.</t>
<t>If a MAP-E BR and CE receives an ICMP error message without
ICMP identifier field for some errors that is detected inside
a IPv6 tunnel, a MAP-E BR and CE should replay the ICMP error
message to the original source. This behavior should be
implemented conforming to the section 8 of
<xref target="RFC2473"></xref>. The MAP-E BR and CE obtain the
origianl IPv6 tunnel packet storing in ICMP payload and then
decapsulate IPv4 packet. Finally the MAP-E BR and CE generate
a new ICMP error message from the decapsulated IPv4 packet
and then forward it.</t>
<t>If a MAP-E BR receives an ICMP error message on its IPv4 interface,
the MAP-E BR should replay the ICMP message to an appropriate MAP-E
CE. If IPv4 address is not shared, the MAP-E BR generates a CE IPv6
address from the IPv4 destination address in the ICMP error message
and encapsulates the ICMP message in IPv6. If IPv4 address is shared,
the MAP-E BR derives an original IPv4 packet from the ICMP payload and
generates a CE IPv6 address from the source address and the source
port in the original IPv4 packet. If the MAP-E BR can generate the CE
IPv6 address, the MAP-E BR encapsulates the ICMP error message in IPv6
and then forward it to its IPv6 interface.</t>
</section>
<section anchor="security" title="Security Considerations">
<t><list hangIndent="22" style="hanging">
<t hangText="Spoofing attacks:">
With consistency checks between IPv4 and IPv6 sources that are
performed on IPv4/IPv6 packets received by BR's and CE's (<xref
target="behavior"></xref>), MAP-E does not introduce any
opportunity for spoofing attack that would not pre-exist in
IPv6.</t>
<t hangText="Denial-of-service attacks:">
In MAP-E domains where IPv4 addresses are shared, the fact that
IPv4 datagram reassembly may be necessary introduces an
opportunity for DOS attacks. This is inherent to address sharing,
and is common with other address sharing approaches such as DS-lite
and NAT64/DNS64. The best protection against such attacks is to
accelerate IPv6 enablement in both clients and servers so that,
where MAP-E is supported, it is less and less used.</t>
<t hangText="Routing-loop attacks:">
This attack may exist in some automatic-tunneling scenarios
are documented in
<xref target="I-D.ietf-v6ops-tunnel-loops"></xref>. They cannot
exist with MAP-E because each BRs checks that the IPv6 source
address of a received IPv6 packet is a CE address.</t>
<t hangText="Attacks facilitated by restricted port set:">
From hosts that are not subject to ingress filtering of <xref
target="RFC2827"></xref>, some attacks are possible by intervening
with faked packets during ongoing transport connections (<xref
target="RFC4953"></xref>, <xref target="RFC5961"></xref>, <xref
target="RFC6056"></xref>. The attacks depend on guessing which
ports are currently used by target hosts. Using unrestricted port
set which mean that are IPv6 is exactly preferable. To avoid this
attacks using restricted port set, NAT44 filtering behavior SHOULD
be "Address-Dependent Filtering".</t>
</list></t>
</section>
<section anchor="iana" title="IANA Consideration">
<t>This document makes no request of IANA.</t>
</section>
<section anchor="acknowledgements" title="Acknowledgements">
<t>This draft is based on original idea described in <xref
target="I-D.despres-softwire-sam"></xref>. The authors would like
to thank Remi Despres, Mark Townsley, Wojciech Dec and Olivier
Vautrin.</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<references title="Normative References">
&I-D.mdt-softwire-mapping-address-and-port;
&I-D.mdt-softwire-map-dhcp-option;
&RFC0791;
&RFC2119;
&RFC2460;
&RFC3315;
&RFC4291;
&RFC2491;
</references>
<references title="Informative References">
&I-D.despres-softwire-sam;
&I-D.ietf-softwire-dual-stack-lite;
&I-D.ietf-v6ops-tunnel-loops;
&RFC2473;
&RFC2827;
&RFC3022;
&RFC4787;
&RFC4953;
&RFC5382;
&RFC5508;
&RFC5961;
&RFC5969;
&RFC6056;
&I-D.operators-softwire-stateless-4v6-motivation;
</references>
<!-- Change Log
v00 2012-01-08 TM Initial version
-->
</back>
</rfc>
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