One document matched: draft-mrugalski-softwire-dhcpv4-over-v6-option-01.xml
<?xml version='1.0' ?>
<?rfc toc="yes"?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes"?> <?rfc subcompact="no"?>
<?rfc symrefs="yes"?>
<!DOCTYPE rfc SYSTEM 'rfc2629bis.dtd' [
]>
<rfc ipr="trust200902" category="std"
docName="draft-mrugalski-softwire-dhcpv4-over-v6-option-01">
<front>
<title abbrev="DHCPv4 over IPv6 DHCPv6 Option">Dynamic Host
Configuration Protocol for IPv6 (DHCPv6) Option for DHCPv4 over
IPv6 Endpoint</title>
<author fullname="Tomasz Mrugalski" initials="T" surname="Mrugalski">
<organization abbrev="ISC">Internet Systems Consortium, Inc.</organization>
<address>
<postal>
<street>950 Charter Street</street>
<city>Redwood City</city>
<region>CA</region>
<code>94063</code>
<country>USA</country>
</postal>
<phone>+1 650 423 1345</phone>
<email>tomasz.mrugalski@gmail.com</email>
</address>
</author>
<author initials="P." surname="Wu" fullname="Peng Wu">
<organization>Tsinghua University</organization>
<address>
<postal>
<city>Beijing</city>
<code>100084</code>
<country>P.R.China</country>
</postal>
<email>pengwu.thu@gmail.com</email>
</address>
</author>
<date />
<area>Internet</area>
<workgroup>Dynamic Host Configuration WG</workgroup>
<keyword>DHCPv6</keyword>
<keyword>Softwire</keyword>
<keyword>DHCPv4 over IPv6</keyword>
<abstract>
<t><xref target="I-D.ietf-dhc-dhcpv4-over-ipv6"/>
defines a way for communication between legacy DHCPv4 clients
with DHCPv4 servers over IPv6-only transport. It requires
deployment of Client Relay Agent (CRA) that transmits messages
to IPv6-Transport Server (TSV) or IPv6-Transport Relay Agent
(TRA). Deployed CRA must know an address of TSV or TRA to
forward incoming client's messages. This document defines a
DHCPv6 option that may be used to provision TSV or TRA location
to CRAs.</t>
</abstract>
</front>
<middle>
<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="Introduction">
<t><xref target="I-D.ietf-dhc-dhcpv4-over-ipv6"/> defines a way
for communication between legacy DHCPv4 clients with DHCPv4
servers (defined in <xref target="RFC2131"/>) over IPv6-only
transport. It requires deployment of Client Relay Agent (CRA)
that transmits messages to IPv6-Transport Server (TSV) or
IPv6-Transport Relay Agent (TRA). Although there are several
scenarios envisaged, all of them assume that CRA needs to know
the recipient address of the DHCPv4-over-IPv6 traffic. In a
typical deployment as
<xref target="I-D.cui-softwire-b4-translated-ds-lite"/>
or <xref target="I-D.ietf-softwire-public-4over6"/>,
CRA functionality will be a part of a Lightweight B4 element
(Basic Bridging BroadBand element) implementation.</t>
<t>Depending on the scenario discussed, the DHCPv4 over IPv6
transport endpoint could be either an IPv6-Transport Server (TSV)
or an IPv6-Transport Relay Agent (TRA). Both cases are
indistinguishable from CRA perspective. CRA needs to know TSV's
or TRA's IPv6 address in advance to relay traffic. Again, the
typical envisaged use would be the Lightweight 4over6
architecture, where TSV or TRA could be part of Lightweight
AFTR implementation.</t>
<t>As CRA uplink is IPv6-only (otherwise there would be no need
to deploy DHCPv4 over IPv6), the only feasible way to provision
information to CRA is over DHCPv6. Therefore this document specifies
a DHCPv6 option that conveys necessary information.</t>
<t>To provide the conveyance of the configuration information, a
single <xref target="RFC3315">DHCPv6</xref> option is used,
expressing the TRA's or TSV's IPv6 address to the CRA.</t>
</section>
<section title='The DHCPv4-Over-IPv6 Endpoint DHCPv6 Option' anchor='option-addr'>
<t>The DHCPv4-over-IPv6 option is a DHCPv6 option. It consists
of an option-code and option-len fields (as all DHCPv6 options
have), and a fixed-length dhcpv4-over-ipv6-endpoint-addr
field containing an IPv6 address that refers to
the DHCPv4 over IPv6 transport endpoint to which the CRA MAY
transport DHCPv4 traffic. This address represents TRA or TSV,
depending on deployment scenario.</t>
<t>The DHCPv4-over-IPv6 option SHOULD NOT appear in any other
than the following DHCPv6 messages: Solicit, Advertise, Request,
Renew, Rebind, Information-Request and Reply.</t>
<t>The format of the DHCPv4 over IPv6 option is shown in the
following figure:</t>
<figure align="center" anchor="option-format-addr"
title="AFTR-Name DHCPv6 Option Format">
<artwork>
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
| OPTION_DHCP4_OVER_V6: (TBD) | option-len |
+-------------------------------+-------------------------------+
| |
| dhcpv4-over-ipv6-endpoint-addr |
| |
+---------------------------------------------------------------+
OPTION_DHCP4_OVER_V6: (TBD)
option-len: 16
dhcpv4-over-ipv6-endpoint-addr: An IPv6 address of the
DHCPv4-over-IPv6 transport endpoint.
</artwork>
</figure>
<t>The option is validated by confirming that all of the
following conditions are met:
<list style="numbers">
<t>the option-len is exactly 16;</t>
<t>the dhcpv4-over-ipv6-endpoint-addr contains valid unicast address.
In particular any address (::), multicast (ff::/8) or IPv4-mapped IPv6 address
is invalid and MUST be rejected.</t>
</list>
</t>
</section>
<section title="DHCPv6 Server Behavior">
<t>A DHCPv6 server SHOULD NOT send more than one DHCPv4-over-IPv6
option. It SHOULD NOT permit the configuration of multiple
addresses within one DHCPv4-over-IPv6 option. Both of these
conditions are handled as errors by the client, so an
operator using software that does not perform these validations
should be careful not to configure multiple addresses.</t>
<t><xref target="RFC3315">RFC 3315 Section 17.2.2</xref>
describes how a DHCPv6 client and server negotiate configuration
values using the Option Request Option (OPTION_ORO). As a
convenience to the reader, we mention here that a server will
not reply with a DHCPv4-over-IPv6 option if the client has not
explicitly enumerated it on its Option Request Option. In other
words, server SHOULD send this option only if client explicitly
requested it in ORO.</t>
</section>
<section title="DHCPv6 Client Behavior">
<t>A client that supports the DHCPv4 over IPv6 functionality of
and conforms to this specification MUST include OPTION_DHCP4_OVER_V6
on its OPTION_ORO.</t>
<t>If the client receives the DHCPv4-over-IPv6 option, it MUST verify the
option contents as described in <xref target="option-addr"/>.</t>
<t>If the CRA entity receives more than one DHCPv4-over-IPv6 option, it
MUST use only one instance of that option.</t>
<t>If the DHCPv4-over-IPv6 option contains more than one address,
the CRA entity system MUST ignore the option. It SHOULD
warn its operator about such condition.</t>
<t>Note that a CRA system may have multiple network interfaces,
and these interfaces may be configured differently; some may be
connected to networks that call for DHCPv4-over-IPv6, and some
may be connected to networks that are using normal dual stack or
other means. The CRA entity should approach this specification
on an interface-by-interface basis. For example, if the CRA
entity is attached to multiple networks that provide the
DHCPv4-over-IPv6 option, then the CRA entity MUST configure a
DHCPv4 over IPv6 transport for each interface separately as each
transport provides IPv4 connectivity for each distinct
interface.
</t>
</section>
<section title="Security Considerations">
<t>This document does not present any new security issues, but
as with all DHCPv6-derived configuration state, it is completely
possible that the configuration is being delivered by a third
party (Man In The Middle). As such, there is no basis to trust
that the access the DHCPv4-over-IPv6 connection provides can be
trusted. It should be protected by available security mechanisms
such as IP firewalls.</t>
<t>It should be noted that DHCPv4 over IPv6 traffic may bypass
existing firewalls that are typically configured to drop
incoming outside DHCPv4 over IPv4 and DHCPv6 over IPv6 traffic.</t>
<t><xref target="RFC3315">RFC 3315</xref> discusses DHCPv6-related
security issues.</t>
<t><xref target="I-D.ietf-dhc-dhcpv4-over-ipv6"></xref>
discusses DHCPv4-over-IPv6 related security issues.</t>
</section>
<section title="IANA Considerations">
<t>IANA is kindly requested to allocate DHCPv6 option code TBD
to the OPTION_DHCP4_OVER_V6. The value should be added to the
DHCPv6 option code space defined in Section 24.3 of <xref
target="RFC3315"/>.</t>
</section>
<section title="Acknowledgements">
<t>Authors would like to thank nobody so far, as we have not received
any comments yet.</t>
<t>This work has been partially supported by the Polish Ministry
of Science and Higher Education under the European Regional Development
Fund, Grant No. POIG.01.01.02-00-045/09-00 (Future Internet Engineering
Project).</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.3315"?>
<?rfc include="reference.RFC.2131"?>
<?rfc include="reference.I-D.ietf-dhc-dhcpv4-over-ipv6"?>
</references>
<references title="Informative References">
<?rfc include="reference.I-D.cui-softwire-b4-translated-ds-lite"?>
<?rfc include="reference.I-D.ietf-softwire-public-4over6"?>
</references>
</back>
</rfc>
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