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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft <rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
-ietf-dhc-dhcpv4-over-dhcpv6-ra-06" category="std" consensus="true" submissionTy -ietf-dhc-dhcpv4-over-dhcpv6-ra" category="std" consensus="true" submissionType=
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<link href="https://datatracker.ietf.org/doc/draft-ietf-dhc-dhcpv4-over-dhcpv6
-ra" rel="prev"/>
<front> <front>
<title abbrev="DHCP 4o6 Relay Agent">DHCPv4-over-DHCPv6 with Relay Agent Sup <title abbrev="DHCP 4o6 Relay Agent">DHCPv4 over DHCPv6 with Relay Agent Sup
port</title> port</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-dhc-dhcpv4-over-dhcpv6-r <seriesInfo name="RFC" value="9928"/>
a-06"/>
<author initials="C." surname="Porfiri" fullname="Claudio Porfiri"> <author initials="C." surname="Porfiri" fullname="Claudio Porfiri">
<organization>Ericsson</organization> <organization>Ericsson</organization>
<address> <address>
<email>claudio.porfiri@ericsson.com</email> <email>claudio.porfiri@ericsson.com</email>
</address> </address>
</author> </author>
<author initials="S." surname="Krishnan" fullname="Suresh Krishnan"> <author initials="S." surname="Krishnan" fullname="Suresh Krishnan">
<organization>Cisco</organization> <organization>Cisco</organization>
<address> <address>
<email>suresh.krishnan@gmail.com</email> <email>suresh.krishnan@gmail.com</email>
skipping to change at line 39 skipping to change at line 40
<address> <address>
<email>jari.arkko@ericsson.com</email> <email>jari.arkko@ericsson.com</email>
</address> </address>
</author> </author>
<author initials="M." surname="Kühlewind" fullname="Mirja Kühlewind"> <author initials="M." surname="Kühlewind" fullname="Mirja Kühlewind">
<organization>Ericsson</organization> <organization>Ericsson</organization>
<address> <address>
<email>mirja.kuehlewind@ericsson.com</email> <email>mirja.kuehlewind@ericsson.com</email>
</address> </address>
</author> </author>
<date year="2025" month="August" day="26"/> <date year="2026" month="February"/>
<area>Internet</area> <area>INT</area>
<workgroup>Dynamic Host Configuration</workgroup> <workgroup>dhc</workgroup>
<keyword>dhcp</keyword> <keyword>dhcp</keyword>
<abstract> <abstract>
<?line 59?> <?line 54?>
<t>This document describes a mechanism for networks <t>This document describes a mechanism for networks
with legacy IPv4-only clients to use services provided by with legacy IPv4-only clients to use services provided by
DHCPv4-over-DHCPv6 in a Relay Agent. DHCPv4 over DHCPv6 in a Relay Agent.
RFC7341 specifies use of DHCPv4-over-DHCPv6 in the client only. RFC 7341 specifies the use of DHCPv4 over DHCPv6 in the client only.
This document specifies a RFC7341-based approach that This document specifies an approach based on RFC 7341 that
allows a Relay Agent to implement the DHCP 4o6 encapsulation and allows a Relay Agent to implement the DHCPv4-over-DHCPv6 encapsulation and
decapsulation of DHCPv4 messages in DHCPv6 messages on behalf of a decapsulation of DHCPv4 messages in DHCPv6 messages on behalf of a
DHCPv4 client.</t> DHCPv4 client.</t>
</abstract> </abstract>
<note removeInRFC="true">
<name>About This Document</name>
<t>
Status information for this document may be found at <eref target="https
://datatracker.ietf.org/doc/draft-ietf-dhc-dhcpv4-over-dhcpv6-ra/"/>.
</t>
<t>Source for this draft and an issue tracker can be found at
<eref target="https://github.com/mirjak/draft-dhc-dhcpv4-over-dhcpv6-ra"
/>.</t>
</note>
</front> </front>
<middle> <middle>
<?line 71?> <?line 66?>
<section anchor="introduction"> <section anchor="introduction">
<name>Introduction</name> <name>Introduction</name>
<t><xref target="RFC7341"/> describes a transport mechanism for carrying D HCPv4 <xref target="RFC2131"/> <t><xref target="RFC7341"/> describes a transport mechanism for carrying D HCPv4 <xref target="RFC2131"/>
messages using DHCPv6 <xref target="draft-ietf-dhc-rfc8415bis"/> for dynamic pro messages using DHCPv6 <xref target="RFC9915"/> for dynamic provisioning
visioning of IPv4 addresses and other DHCPv4-specific configuration parameters
of IPv4 addresses and other DHCPv4 specific configuration parameters
across IPv6-only networks. The deployment of <xref target="RFC7341"/> requires s upport in across IPv6-only networks. The deployment of <xref target="RFC7341"/> requires s upport in
DHCP clients and at the DHCPv6 server. DHCP clients and at the DHCPv6 server.
However, if a client is embedded in a host that only supports IPv4 However, if a client is embedded in a host that only supports IPv4
and cannot easily be replaced or updated (which could be due to any and cannot easily be replaced or updated (which could be due to any
number of technical or business reasons), this approach does not number of technical or business reasons), this approach does not
work.</t> work.</t>
<t>Similarly, the specifications for DHCPv6 Relay Agents such as Lightweig <t>Similarly, the DHCPv6 Relay Agent specification defined in <xref target
ht ="RFC9915"/>,
DHCPv6 Relay Agent (LDRA) <xref target="RFC6221"/> or DHCPv6 Relay Agent (L3RA) which also refers to <xref target="RFC6221"/> for the Lightweight DHCPv6 Relay A
<xref target="draft-ietf-dhc-rfc8415bis"/> do not foresee the possibility to han gent
dle legacy DHCPv4, (LDRA) behavior, does not provide any mechanism to handle legacy DHCPv4,
other than implementing DHCP 4o6 in the client.</t> except by requiring the client to implement the DHCPv4-over-DHCPv6
<t>This document specifies an <xref target="RFC7341"/> based solution that encapsulation and decapsulation.</t>
can be <t>This document specifies a solution based on <xref target="RFC7341"/> th
at can be
implemented in intermediate nodes such as switches or routers, implemented in intermediate nodes such as switches or routers,
without putting any requirements on clients. No new protocols or extensions are needed; without putting any requirements on clients. No new protocols or extensions are needed;
instead, this document specifies a new use case for <xref target="RFC7341"/> tha t allows instead, this document specifies a new use case for <xref target="RFC7341"/> tha t allows
a Relay Agent to perform the DHCP 4o6 encapsulation and decapsulation instead of a Relay Agent to perform the DHCPv4-over-DHCPv6 encapsulation and decapsulation instead of
the client.</t> the client.</t>
<section anchor="applicability"> <section anchor="applicability">
<name>Applicability Scope</name> <name>Applicability Scope</name>
<t>The mechanisms described in this document apply to the configuration phase <t>The mechanisms described in this document apply to the configuration phase
of hosts that need to receive an IPv4 address when a DHCP server for IPv4 <xref target="RFC2131"/> is not of hosts that need to receive an IPv4 address when a DHCP server for IPv4 <xref target="RFC2131"/> is not
reachable directly from the host. Furthermore, the host is unable to implement reachable directly from the host. Furthermore, the host is unable to implement
a DHCP client conformant to <xref target="RFC7341"/> as it is connected to an IP a DHCP client conformant to <xref target="RFC7341"/>, as it is connected to an I
v4-only Pv4-only
network. But there is a DHCPv6 server that can provide IPv4 addresses by means o network. However, there is a DHCPv6 server that can provide IPv4 addresses by me
f ans of
the mechanisms specified in <xref target="RFC7341"/>.</t> the mechanisms specified in <xref target="RFC7341"/>.</t>
</section> </section>
</section> </section>
<section anchor="conventions-and-definitions"> <section anchor="conventions-and-definitions">
<name>Conventions and Definitions</name> <name>Conventions and Definitions</name>
<t>The following terms and acronyms are used in this document:</t> <t>The following terms and abbreviations are used in this document:</t>
<ul spacing="normal"> <dl newline="true">
<li> <dt>DHCP:</dt>
<t>DHCP: <dd>
If not otherwise specified, DHCP refers to DHCPv4 and/or DHCPv6.</t> <t>Refers to DHCPv4 and/or DHCPv6 if not otherwise specified.</t>
</li> </dd>
<li> <dt>DHCP Relay Agent:</dt>
<t>DHCPv4: <dd>
DHCP as defined in <xref target="RFC2131"/>.</t> <t>Refers to a common concept in all of the following protocols, altho
</li> ugh the details differ
<li> between them: the Bootstrap Protocol (BOOTP) <xref target="RFC0951"/> <xref targ
<t>DHCPv4 over DHCPv6 (or 4o6): et="RFC1542"/>, DHCPv4
The architecture, the procedures, and the protocols specified in the <xref target="RFC2131"/> <xref target="RFC2132"/>, and DHCPv6 <xref target="RFC9
DHCPv4-over-DHCPv6 document <xref target="RFC7341"/>.</t> 915"/>.</t>
</li> </dd>
<li> <dt>DHCPv4:</dt>
<t>DHCP Relay Agent: <dd>
This is a concept in all of the following protocols, although the details diffe <t>Refers to DHCP as defined in <xref target="RFC2131"/>.</t>
r </dd>
between them: BOOTP <xref target="RFC951"/> <xref target="RFC1542"/>, DHCPv4 <dt>DHCPv4 over DHCPv6 (DHCP 4o6):</dt>
<xref target="RFC2131"/> <xref target="RFC2132"/>, and DHCPv6 <xref target="dra <dd>
ft-ietf-dhc-rfc8415bis"/>.</t> <t>Refers to the architecture, the procedures, and the protocols speci
</li> fied in the
<li> DHCPv4-over-DHCPv6 document <xref target="RFC7341"/>.</t>
<t>Lightweight DHCPv6 Relay Agent (or LDRA): </dd>
This is an extension of the original DHCPv6 Relay Agent specification, to allow <dt>DHCPv4-over-DHCPv6 Relay Agent (4o6RA):</dt>
layer-2-only devices to perform a Relay Agent function <xref target="RFC6221"/> <dd>
.</t> <t>Refers to a Relay Agent that implements the DHCP 4o6
</li> transport as specified in this document.</t>
<li> </dd>
<t>DHCPv4 over DHCPv6 Relay Agent (or 4o6RA): <dt>Layer 3 Relay Agent (L3RA):</dt>
Refers to a Relay Agent that implements the 4o6 <dd>
transport as specified in this document.</t> <t>Refers to a DHCP Relay Agent as specified in <xref target="RFC9915"
</li> /> that is not a LDRA.</t>
</ul> </dd>
<dt>Lightweight DHCPv6 Relay Agent (LDRA):</dt>
<dd>
<t>Refers to an extension of the original DHCPv6 Relay Agent specifica
tion, to allow
Layer 2 (L2) only devices to perform a Relay Agent function <xref target="RFC622
1"/>.</t>
</dd>
</dl>
<t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14 >REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL <t>The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14 >REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECO MMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>", NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECO MMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be i nterpreted as "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to be i nterpreted as
described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they
appear in all capitals, as shown here.</t> appear in all capitals, as shown here.</t>
<?line -18?> <?line -18?>
</section> </section>
<section anchor="dhcpv4-over-dhcpv6-relay-agent-4o6ra"> <section anchor="dhcpv4-over-dhcpv6-relay-agent-4o6ra">
<name>DHCPv4 over DHCPv6 Relay Agent (4o6RA)</name> <name>DHCPv4-over-DHCPv6 Relay Agent (4o6RA)</name>
<t>This document assumes a network, where IPv4-only hosts are connected <t>This document assumes a network where IPv4-only hosts are connected
to a network that supports IPv6 and limited IPv4 services.</t> to a network that supports IPv6 and limited IPv4 services.</t>
<t>To address such a network setup, this document extends <t>To address such a network setup, this document extends
DHCPv6 Relay Agents with DHCPv4-over-DHCPv6, as shown in <xref target="fig_4o6RA "/>.</t> DHCPv6 Relay Agents with DHCPv4 over DHCPv6, as shown in <xref target="fig_4o6RA "/>.</t>
<figure anchor="fig_4o6RA"> <figure anchor="fig_4o6RA">
<name>Architecture Example with Legacy DHCP Client</name> <name>Architecture Example with Legacy DHCP Client</name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="208" width="480" viewBox="0 0 480 208" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="208" width="480" viewBox="0 0 480 208" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round">
<path d="M 8,64 L 8,128" fill="none" stroke="black"/> <path d="M 8,64 L 8,128" fill="none" stroke="black"/>
<path d="M 80,48 L 80,64" fill="none" stroke="black"/> <path d="M 80,48 L 80,64" fill="none" stroke="black"/>
<path d="M 80,128 L 80,144" fill="none" stroke="black"/> <path d="M 80,128 L 80,144" fill="none" stroke="black"/>
<path d="M 96,64 L 96,128" fill="none" stroke="black"/> <path d="M 96,64 L 96,128" fill="none" stroke="black"/>
<path d="M 176,64 L 176,128" fill="none" stroke="black"/> <path d="M 176,64 L 176,128" fill="none" stroke="black"/>
<path d="M 192,48 L 192,64" fill="none" stroke="black"/> <path d="M 192,48 L 192,64" fill="none" stroke="black"/>
skipping to change at line 219 skipping to change at line 217
+--------+-+ +-+-----------+-+ +-+--------+ +--------+-+ +-+-----------+-+ +-+--------+
| | | | | | | |
'-----------' '-----------' '-----------' '-----------'
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>This document specifies the encapsulation <t>This document specifies the encapsulation
and decapsulation specified in <xref target="RFC7341"/> to be performed in the R elay Agent and decapsulation specified in <xref target="RFC7341"/> to be performed in the R elay Agent
without requiring any changes on the DHCPv4 client. without requiring any changes on the DHCPv4 client.
In this case it is up to the Relay Agent to provide the full DHCP In this case, it is up to the Relay Agent to provide the full DHCP
4o6 support and the legacy DHCPv4 client is not aware that it is being served 4o6 support, and the legacy DHCPv4 client is not aware that it is being served
via a DHCP 4o6 service. via a DHCP 4o6 service.
As the 4o6RA acts as a DHCP 4o6 client, all prerequisites and configuration As the 4o6RA acts as a DHCP 4o6 client, all prerequisites and configurations
that apply to the DHCP client in <xref section="5" sectionFormat="of" target="RF C7341"/> are also applied to the 4o6RA.</t> that apply to the DHCP client in <xref section="5" sectionFormat="of" target="RF C7341"/> are also applied to the 4o6RA.</t>
<t>As the 4o6RA takes the role of the client in respect to <xref target="R FC7341"/>, <t>As the 4o6RA takes the role of the client in respect to <xref target="R FC7341"/>,
it is responsible for determining a suitable interface where it acts as a it is responsible for determining a suitable interface where it acts as a
DHCPv6 client, and it is responsible for locating a suitable DHCPv6 DHCPv6 client, and it is responsible for locating a suitable DHCPv6
server or relay agent and obtain the necessary IPv6 configuration.. server or Relay Agent and obtaining the necessary IPv6 configuration.
As specified in <xref target="RFC7341"/>, the 4o6RA, acting as 4o6 client, there As specified in <xref target="RFC7341"/>, the 4o6RA, acting as DHCP 4o6 client,
fore has to request therefore has to request
the DHCP 4o6 Server Address option from the server by sending the the DHCP 4o6 Server Address option from the server by sending the
Option Request option as described in <xref target="draft-ietf-dhc-rfc8415bis"/> Option Request option as described in <xref target="RFC9915"/>
before it can use the 4o6 transport.</t> before it can use the DHCP 4o6 transport.</t>
<t>To maintain interoperability with existing DHCPv6 relays and servers, <t>To maintain interoperability with existing DHCPv6 relays and servers,
the message format is unchanged from <xref target="draft-ietf-dhc-rfc8415bis"/>. the message format is unchanged from <xref target="RFC9915"/>. The 4o6RA impleme
The 4o6RA implements nts
the same message types as a DHCPv6 Relay Agent <xref section="6" sectionFormat=" the same message types as a DHCPv6 Relay Agent (see <xref section="6" sectionFor
of" target="RFC7341"/>.</t> mat="of" target="RFC7341"/>).</t>
<t>However, in this specification, the 4o6RA, instead of the client, creat <t>However, in this specification, the 4o6RA, instead of the client, creat
es the DHCPV4-QUERY Message es the DHCPV4-QUERY message
and encapsulates the DHCP request message received from the legacy DHCPv4 client .</t> and encapsulates the DHCP request message received from the legacy DHCPv4 client .</t>
<t>When DHCPV4-RESPONSE Message is received by the 4o6 Relay Agent, <t>When the DHCPV4-RESPONSE message is received by the DHCP 4o6 Relay Agen
it looks for the DHCPv4 Message option within this message. t,
it looks for the DHCPv4 message option within this message.
If this option is not found or the DHCPv4-RESPONSE message is not well-formed, If this option is not found or the DHCPv4-RESPONSE message is not well-formed,
it <bcp14>MUST</bcp14> be discarded. it <bcp14>MUST</bcp14> be discarded.
If the DHCPv4 Message option is present and correct, the 4o6RA <bcp14>MUST</bcp1 If the DHCPv4 message option is present and correct, the 4o6RA <bcp14>MUST</bcp1
4> extract the DHCPv4 4> extract the DHCPv4
message and forward the encapsulated DHCPv4-response to the requesting DHCPv4 message and forward the encapsulated DHCPv4-RESPONSE to the requesting DHCPv4
client, given that the encapsulated DHCPv4-response is correct and can be client, given that the encapsulated DHCPv4-RESPONSE is correct and can be
actually forwarded.</t> actually forwarded.</t>
<t>Layer-2 Relay Agents receiving DHCPV4-QUERY or DHCPV4-RESPONSE messages <t>Layer 2 (L2) Relay Agents receiving DHCPV4-QUERY or DHCPV4-RESPONSE mes sages
<bcp14>MUST</bcp14> handle them as specified in <xref section="6" sectionFormat= "of" target="RFC6221"/>.</t> <bcp14>MUST</bcp14> handle them as specified in <xref section="6" sectionFormat= "of" target="RFC6221"/>.</t>
<t>In any given environment, DHCPv6 servers to which DHCPV4-QUERY <t>In any given environment, DHCPv6 servers to which DHCPV4-QUERY
requests are routed are expected to be compliant with 4o6 according requests are routed are expected to be compliant with DHCP 4o6 according
to <xref target="RFC7341"/>. No additional requirements on DHCPv6 servers are s et to <xref target="RFC7341"/>. No additional requirements on DHCPv6 servers are s et
by this specification.</t> by this specification.</t>
<section anchor="intermediate-relays"> <section anchor="intermediate-relays">
<name>Intermediate relays</name> <name>Intermediate Relays</name>
<t>Intermediate relays shall behave according to section 10 of <xref tar <t>Intermediate relays shall behave according to <xref section="10" sect
get="RFC7341"/>.</t> ionFormat="of" target="RFC7341"/>.</t>
</section> </section>
<section anchor="topology_considerations"> <section anchor="topology_considerations">
<name>4o6RA and Topology Discovery</name> <name>4o6RA and Topology Discovery</name>
<t>In some networks, the configuration of a host may depend on the topol ogy. <t>In some networks, the configuration of a host may depend on the topol ogy.
However, when a new host attaches to a network, it may be unaware However, when a new host attaches to a network, it may be unaware
of the topology and, consequently, how it has to be configured.</t> of the topology and, consequently, how it has to be configured.</t>
<t>DHCPv4 <xref target="RFC2131"/> and DHCPv6 <xref target="draft-ietf-d <t>DHCPv4 <xref target="RFC2131"/> and DHCPv6 <xref target="RFC9915"/> s
hc-rfc8415bis"/> specifications pecifications
describe how addresses can be allocated to clients based on network describe how addresses can typically be allocated to clients based on network
topology information provided by a DHCP relay, typically.</t> topology information provided by a DHCP relay.</t>
<t>Address/prefix allocation decisions are integral to the allocation of <t>Address/prefix allocation decisions are integral to the allocation of
addresses and prefixes in DHCP, as described in detail addresses and prefixes in DHCP, as described in detail
in <xref target="RFC7969"/>. This specification aims to guarantee that the 4o6RA does not in <xref target="RFC7969"/>. This specification aims to guarantee that the 4o6RA does not
break any legacy capability when used for topology discovery.</t> break any legacy capability when used for topology discovery.</t>
<t>Topology discovery as described in <xref target="RFC7969"/> differs b etween <t>Topology discovery as described in <xref target="RFC7969"/> differs b etween
IPv4 and IPv6:</t> IPv4 and IPv6 as follows:</t>
<ul spacing="normal"> <ul spacing="normal">
<li> <li>
<t>IPv4: <t>IPv4: When using DHCP on IPv4, only the first Relay Agent <bcp14>
when using DHCP on IPv4 only the first Relay Agent <bcp14>SHOULD</bcp14> SHOULD</bcp14>
set the giaddr field (section 3.1 of <xref target="RFC7969"/>). Thus, in a set the giaddr field (<xref section="3.1" sectionFormat="of" target="RFC7969"/>)
network that has more than one Relay Agent only part of the topology . Thus, in a
network that has more than one Relay Agent, only part of the topology
is transported via DHCPv4.</t> is transported via DHCPv4.</t>
</li> </li>
<li> <li>
<t>IPv6: <t>IPv6: When using DHCPv6, all Relay Agents <bcp14>SHOULD</bcp14> s
when using DHCPv6, all Relay Agents <bcp14>SHOULD</bcp14> send end
link-address and Interface-ID options, that provide link-address and Interface-ID options that provide
information about the complete path information about the complete path
between the DHCPv6 client and the DHCPv6 server to the DHCPv6 server.</t> between the DHCPv6 client and the DHCPv6 server to the DHCPv6 server.</t>
</li> </li>
</ul> </ul>
<t>In Layer-2 networks, Lightweight DHCPv6 Relay Agents <xref target="RF C6221"/> <t>In Layer 2 networks, Lightweight DHCPv6 Relay Agents (LDRAs) <xref ta rget="RFC6221"/>
can be used.</t> can be used.</t>
<t>When provided, the topology information is available at the DHCPv6 <t>When provided, the topology information is available at the DHCPv6
server in the form of a sequence of the link-address field and Interface-ID opti on.</t> server in the form of a sequence of the link-address field and Interface-ID opti on.</t>
<t>Then, topology information for the given IP address <t>Then, topology information for the given IP address
can be obtained from the DHCPv6 server and used for configuration can be obtained from the DHCPv6 server and used for configuration
or other purposes.</t> or other purposes.</t>
<t><xref target="RFC7341"/> enables the client to use DHCPv6 for topolog y discovery <t><xref target="RFC7341"/> enables the client to use DHCPv6 for topolog y discovery
even within a DHCPv4 context, as the DHCPv6 Relay Agent knows even within a DHCPv4 context, as the DHCPv6 Relay Agent knows
the interface where the encapsulated DHCP request is received. the interface where the encapsulated DHCP request is received.
As shown in <xref target="fig_4o6RA_RA"/>, however, the introduction of 4o6 at However, as shown in <xref target="fig_4o6RA_RA"/>, the introduction of DHCP 4o6
the edge of the IPv6 network hides the Layer-2 network from the DHCPv6 RA. at
As such, moving 4o6 to a intermediate node rather than performing it at the clie the edge of the IPv6 network hides the Layer 2 network from the DHCPv6 RA.
nt breaks As such, moving DHCP 4o6 to an intermediate node rather than performing it at th
the topology propagation, as 4o6RA-only solutions does not provide any interface e client breaks
the topology propagation, as 4o6RA-only solutions do not provide any interface
information in the encapsulated message.</t> information in the encapsulated message.</t>
<figure anchor="fig_4o6RA_RA"> <figure anchor="fig_4o6RA_RA">
<name>Broken topology information</name> <name>Broken Topology Information</name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="208" width="576" viewBox="0 0 576 208" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="208" width="576" viewBox="0 0 576 208" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round">
<path d="M 8,64 L 8,128" fill="none" stroke="black"/> <path d="M 8,64 L 8,128" fill="none" stroke="black"/>
<path d="M 80,48 L 80,64" fill="none" stroke="black"/> <path d="M 80,48 L 80,64" fill="none" stroke="black"/>
<path d="M 80,128 L 80,144" fill="none" stroke="black"/> <path d="M 80,128 L 80,144" fill="none" stroke="black"/>
<path d="M 96,64 L 96,128" fill="none" stroke="black"/> <path d="M 96,64 L 96,128" fill="none" stroke="black"/>
<path d="M 120,64 L 120,128" fill="none" stroke="black"/> <path d="M 120,64 L 120,128" fill="none" stroke="black"/>
<path d="M 200,64 L 200,128" fill="none" stroke="black"/> <path d="M 200,64 L 200,128" fill="none" stroke="black"/>
<path d="M 224,64 L 224,128" fill="none" stroke="black"/> <path d="M 224,64 L 224,128" fill="none" stroke="black"/>
<path d="M 240,48 L 240,64" fill="none" stroke="black"/> <path d="M 240,48 L 240,64" fill="none" stroke="black"/>
skipping to change at line 385 skipping to change at line 381
| | | | | Agent | | Agent | | | | | | | | Agent | | Agent | | |
+--------+-+ +---------+ +-+---+---+ +--------+ +-+--------+ +--------+-+ +---------+ +-+---+---+ +--------+ +-+--------+
| | | | | | | |
'-----------------' '-------------------------' '-----------------' '-------------------------'
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>In order to provide full topology information, it is <bcp14>RECOMMEND ED</bcp14> that <t>In order to provide full topology information, it is <bcp14>RECOMMEND ED</bcp14> that
any implementation of 4o6RA be combined any implementation of 4o6RA be combined
with an LDRA implementation <xref target="RFC6221"/> in a back-to-back structure , and that the with an LDRA implementation <xref target="RFC6221"/> in a back-to-back structure and that the
LDRA implementation includes a mechanism to obtain interface information that LDRA implementation includes a mechanism to obtain interface information that
can be used to provide the Interface-ID option to outgoing can be used to provide the Interface-ID option to outgoing
DHCPV4-QUERY messages, as specified in Section 5.3.2 of <xref target="RFC6221"/> .</t> DHCPV4-QUERY messages, as specified in <xref section="5.3.2" sectionFormat="of" target="RFC6221"/>.</t>
<t>The internal mechanisms to exchange interface information, <t>The internal mechanisms to exchange interface information,
their format and whether the interface information contains an indication that a their format, and whether the interface information contains an indication that
4o6RA a 4o6RA
is involved are out of the scope for this document.</t> is involved, are out of the scope for this document.</t>
<t>The resulting architecture is shown in <xref target="fig_4o6LDRA"/> w here <t>The resulting architecture is shown in <xref target="fig_4o6LDRA"/> w here
the Relay Agent is implementing 4o6RA and LDRA, and has an internal interface to the Relay Agent is implementing 4o6RA and LDRA and has an internal interface to
propagate topology information from 4o6RA to LDRA.</t> propagate topology information from 4o6RA to LDRA.</t>
<figure anchor="fig_4o6LDRA"> <figure anchor="fig_4o6LDRA">
<name>Topology information preserved with LDRA</name> <name>Topology Information Preserved with LDRA</name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="224" width="528" viewBox="0 0 528 224" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="224" width="528" viewBox="0 0 528 224" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round">
<path d="M 8,80 L 8,144" fill="none" stroke="black"/> <path d="M 8,80 L 8,144" fill="none" stroke="black"/>
<path d="M 80,48 L 80,80" fill="none" stroke="black"/> <path d="M 80,48 L 80,80" fill="none" stroke="black"/>
<path d="M 80,144 L 80,160" fill="none" stroke="black"/> <path d="M 80,144 L 80,160" fill="none" stroke="black"/>
<path d="M 96,80 L 96,144" fill="none" stroke="black"/> <path d="M 96,80 L 96,144" fill="none" stroke="black"/>
<path d="M 120,80 L 120,144" fill="none" stroke="black"/> <path d="M 120,80 L 120,144" fill="none" stroke="black"/>
<path d="M 200,80 L 200,144" fill="none" stroke="black"/> <path d="M 200,80 L 200,144" fill="none" stroke="black"/>
<path d="M 224,80 L 224,144" fill="none" stroke="black"/> <path d="M 224,80 L 224,144" fill="none" stroke="black"/>
<path d="M 240,48 L 240,80" fill="none" stroke="black"/> <path d="M 240,48 L 240,80" fill="none" stroke="black"/>
skipping to change at line 445 skipping to change at line 441
<path d="M 96,176 C 87.16936,176 80,168.83064 80,160" fill="none " stroke="black"/> <path d="M 96,176 C 87.16936,176 80,168.83064 80,160" fill="none " stroke="black"/>
<path d="M 224,176 C 232.83064,176 240,168.83064 240,160" fill=" none" stroke="black"/> <path d="M 224,176 C 232.83064,176 240,168.83064 240,160" fill=" none" stroke="black"/>
<path d="M 288,176 C 279.16936,176 272,168.83064 272,160" fill=" none" stroke="black"/> <path d="M 288,176 C 279.16936,176 272,168.83064 272,160" fill=" none" stroke="black"/>
<path d="M 472,176 C 480.83064,176 488,168.83064 488,160" fill=" none" stroke="black"/> <path d="M 472,176 C 480.83064,176 488,168.83064 488,160" fill=" none" stroke="black"/>
<g class="text"> <g class="text">
<text x="108" y="52">L2</text> <text x="108" y="52">L2</text>
<text x="152" y="52">Network</text> <text x="152" y="52">Network</text>
<text x="196" y="52">or</text> <text x="196" y="52">or</text>
<text x="348" y="52">IPv6</text> <text x="348" y="52">IPv6</text>
<text x="400" y="52">Network</text> <text x="400" y="52">Network</text>
<text x="136" y="68">IPv6-only</text> <text x="136" y="68">IPv6-Only</text>
<text x="196" y="68">link</text> <text x="196" y="68">Link</text>
<text x="52" y="100">DHCPv4</text> <text x="52" y="100">DHCPv4</text>
<text x="156" y="100">L2</text> <text x="156" y="100">L2</text>
<text x="256" y="100">4o6</text> <text x="256" y="100">4o6</text>
<text x="332" y="100">LDRA</text> <text x="332" y="100">LDRA</text>
<text x="460" y="100">DHCP</text> <text x="460" y="100">DHCP</text>
<text x="496" y="100">4o6</text> <text x="496" y="100">4o6</text>
<text x="52" y="116">Client</text> <text x="52" y="116">Client</text>
<text x="156" y="116">Switch</text> <text x="156" y="116">Switch</text>
<text x="264" y="116">Relay</text> <text x="264" y="116">Relay</text>
<text x="336" y="116">RFC6221</text> <text x="320" y="116">RFC</text>
<text x="356" y="116">6221</text>
<text x="476" y="116">Server</text> <text x="476" y="116">Server</text>
<text x="264" y="132">Agent</text> <text x="264" y="132">Agent</text>
</g> </g>
</svg> </svg>
</artwork> </artwork>
<artwork type="ascii-art" align="center"><![CDATA[ <artwork type="ascii-art" align="center"><![CDATA[
.-----------------. .------------------------. .-----------------. .------------------------.
| L2 Network or | | IPv6 Network | | L2 Network or | | IPv6 Network |
| IPv6-only link | | | | IPv6-Only Link | | |
+--------+-+ +---------+ +-+---+--+---------+ +------+---+ +--------+-+ +---------+ +-+---+--+---------+ +------+---+
| DHCPv4 | | L2 | | 4o6 | LDRA | | DHCP 4o6 | | DHCPv4 | | L2 | | 4o6 | LDRA | | DHCP 4o6 |
| Client +--+ Switch +--+ Relay + RFC6221 +------+ Server | | Client +--+ Switch +--+ Relay + RFC 6221+------+ Server |
| | | | | Agent | | | | | | | | | Agent | | | |
+--------+-+ +---------+ +-+---+--+---------+ +------+---+ +--------+-+ +---------+ +-+---+--+---------+ +------+---+
| | | | | | | |
'-----------------' '------------------------' '-----------------' '------------------------'
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>In a simple case, where the same node hosts the 4o6RA and the DHCP4o6 <t>In a simple case, where the same node hosts the 4o6RA and the DHCP 4o
server, 6 server,
it might be enough to only use 4o6RA, as shown in <xref target="fig_4o6RAserver" it might be enough to only use 4o6RA, as shown in <xref target="fig_4o6RAserver"
/>.</t> />, where
CPE stands for "Customer Premises Equipment".</t>
<figure anchor="fig_4o6RAserver"> <figure anchor="fig_4o6RAserver">
<name>Topology information preserved by 4o6 Relay Agent in DHCP server </name> <name>Topology Information Preserved by 4o6 Relay Agent in DHCP Server </name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="208" width="344" viewBox="0 0 344 208" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/200 0/svg" version="1.1" height="208" width="344" viewBox="0 0 344 208" class="diagr am" text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap ="round">
<path d="M 8,64 L 8,128" fill="none" stroke="black"/> <path d="M 8,64 L 8,128" fill="none" stroke="black"/>
<path d="M 80,48 L 80,64" fill="none" stroke="black"/> <path d="M 80,48 L 80,64" fill="none" stroke="black"/>
<path d="M 80,128 L 80,144" fill="none" stroke="black"/> <path d="M 80,128 L 80,144" fill="none" stroke="black"/>
<path d="M 96,64 L 96,128" fill="none" stroke="black"/> <path d="M 96,64 L 96,128" fill="none" stroke="black"/>
<path d="M 176,64 L 176,128" fill="none" stroke="black"/> <path d="M 176,64 L 176,128" fill="none" stroke="black"/>
<path d="M 192,48 L 192,64" fill="none" stroke="black"/> <path d="M 192,48 L 192,64" fill="none" stroke="black"/>
<path d="M 192,128 L 192,144" fill="none" stroke="black"/> <path d="M 192,128 L 192,144" fill="none" stroke="black"/>
<path d="M 248,64 L 248,128" fill="none" stroke="black"/> <path d="M 248,64 L 248,128" fill="none" stroke="black"/>
skipping to change at line 546 skipping to change at line 544
<name>Deployment Considerations</name> <name>Deployment Considerations</name>
<t>As clients are unaware of the presence of 4o6RA, the network <t>As clients are unaware of the presence of 4o6RA, the network
deployment needs to ensure that all DHCPv4 broadcast and unicast messages to and deployment needs to ensure that all DHCPv4 broadcast and unicast messages to and
from clients are steered via a 4o6RA. from clients are steered via a 4o6RA.
This can be achieved by placing the 4o6RA in a central position This can be achieved by placing the 4o6RA in a central position
that can intercept all traffic from the clients or by using Network Address that can intercept all traffic from the clients or by using Network Address
Translation (NAT) with the 4o6RA address for unicast messages.</t> Translation (NAT) with the 4o6RA address for unicast messages.</t>
</section> </section>
<section anchor="seccons"> <section anchor="seccons">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>This document specifies the applicability of 4o6 DHCP in a scenario whe <t>This document specifies the applicability of DHCP 4o6 in a scenario whe
re legacy IPv4 clients are re legacy IPv4 clients are
connected to 4o6 DHCP Relay Agents that perform the encapsulation and decapsulat connected to DHCP 4o6 Relay Agents that perform the encapsulation and decapsulat
ion. This document ion.
does not change anything else in the 4o6 DHCP specification and therefore the This document does not change anything else in the DHCP 4o6 specification <xref
security considerations of <xref target="RFC7341"/> still apply. target="RFC7341"/>;
therefore, the security considerations of that document still apply.
Specifically, since the legacy IPv4 client is not aware of the encapsulation and decapsulation, Specifically, since the legacy IPv4 client is not aware of the encapsulation and decapsulation,
it is 4o6RA has to provide the protections that are specficed in the security 4o6RA has to provide the protections that are specified in the security
considerations in <xref section="12" sectionFormat="of" target="RFC7341"/>.</t> considerations in <xref section="12" sectionFormat="of" target="RFC7341"/>.</t>
<t>The mechanisms defined here differ from <xref target="RFC7341"/> as the y allow the DHCP client <t>The mechanisms defined here differ from <xref target="RFC7341"/> as the y allow the DHCP client
to send and receive DHCPv4 messages, whereas in <xref target="RFC7341"/> the cli ent to send and receive DHCPv4 messages, whereas in <xref target="RFC7341"/>, the cl ient
only sends DHCPv6 messages. This makes it possible that in improperly configured only sends DHCPv6 messages. This makes it possible that in improperly configured
networks where the client is located on the same Layer-2 scope of a DHCPv4 serve r, networks where the client is located on the same Layer 2 scope of a DHCPv4 serve r,
DHCPv4 messages could reach a DHCPv4 server without using the 4o6RA. DHCPv4 messages could reach a DHCPv4 server without using the 4o6RA.
While this can cause erroneous state in both clients and servers While this can cause erroneous state in both clients and servers
and potentially even lead to misconfigurations that impact reachability, and potentially even lead to misconfigurations that impact reachability,
this is seen as a deployment error rather than a security concern. this is seen as a deployment error rather than a security concern.
Further, even though this mechanism may be used for attacks from within the netw ork, Further, even though this mechanism may be used for attacks from within the netw ork,
this is not a new concern introduced by this specification.</t> this is not a new concern introduced by this specification.</t>
<t>More generally, legacy IPv4 clients are not aware of this mechanism, ho wever, even <t>More generally, legacy IPv4 clients are not aware of this mechanism; ho wever, even
when DHCP 4o6 is used, the client does not have any control about the when DHCP 4o6 is used, the client does not have any control about the
information provided by the Relay agent. information provided by the Relay Agent.
As such this change does not raise any additional security concerns.</t> As such, this change does not raise any additional security concerns.</t>
</section> </section>
<section anchor="iana-considerations"> <section anchor="iana-considerations">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>This document has no IANA actions.</t> <t>This document has no IANA actions.</t>
</section> </section>
</middle> </middle>
<back> <back>
<references anchor="sec-combined-references"> <references anchor="sec-combined-references">
<name>References</name> <name>References</name>
<references anchor="sec-normative-references"> <references anchor="sec-normative-references">
<name>Normative References</name> <name>Normative References</name>
<reference anchor="RFC6221"> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.6
<front> 221.xml"/>
<title>Lightweight DHCPv6 Relay Agent</title> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7
<author fullname="D. Miles" initials="D." role="editor" surname="Mil 341.xml"/>
es"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.9
<author fullname="S. Ooghe" initials="S." surname="Ooghe"/> 915.xml"/>
<author fullname="W. Dec" initials="W." surname="Dec"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2
<author fullname="S. Krishnan" initials="S." surname="Krishnan"/> 119.xml"/>
<author fullname="A. Kavanagh" initials="A." surname="Kavanagh"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.8
<date month="May" year="2011"/> 174.xml"/>
<abstract>
<t>This document proposes a Lightweight DHCPv6 Relay Agent (LDRA)
that is used to insert relay agent options in DHCPv6 message exchanges identifyi
ng client-facing interfaces. The LDRA can be implemented in existing access node
s (such as Digital Subscriber Link Access Multiplexers (DSLAMs) and Ethernet swi
tches) that do not support IPv6 control or routing functions. [STANDARDS-TRACK]<
/t>
</abstract>
</front>
<seriesInfo name="RFC" value="6221"/>
<seriesInfo name="DOI" value="10.17487/RFC6221"/>
</reference>
<reference anchor="RFC7341">
<front>
<title>DHCPv4-over-DHCPv6 (DHCP 4o6) Transport</title>
<author fullname="Q. Sun" initials="Q." surname="Sun"/>
<author fullname="Y. Cui" initials="Y." surname="Cui"/>
<author fullname="M. Siodelski" initials="M." surname="Siodelski"/>
<author fullname="S. Krishnan" initials="S." surname="Krishnan"/>
<author fullname="I. Farrer" initials="I." surname="Farrer"/>
<date month="August" year="2014"/>
<abstract>
<t>IPv4 connectivity is still needed as networks migrate towards I
Pv6. Users require IPv4 configuration even if the uplink to their service provid
er supports IPv6 only. This document describes a mechanism for obtaining IPv4 co
nfiguration information dynamically in IPv6 networks by carrying DHCPv4 messages
over DHCPv6 transport. Two new DHCPv6 messages and two new DHCPv6 options are d
efined for this purpose.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7341"/>
<seriesInfo name="DOI" value="10.17487/RFC7341"/>
</reference>
<reference anchor="draft-ietf-dhc-rfc8415bis" target="https://datatracke
r.ietf.org/doc/draft-ietf-dhc-rfc8415bis/">
<front>
<title>Dynamic Host Configuration Protocol for IPv6 (DHCPv6)</title>
<author>
<organization/>
</author>
<date year="2025" month="June"/>
</front>
</reference>
<reference anchor="RFC2119">
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit
le>
<author fullname="S. Bradner" initials="S." surname="Bradner"/>
<date month="March" year="1997"/>
<abstract>
<t>In many standards track documents several words are used to sig
nify the requirements in the specification. These words are often capitalized. T
his document defines these words as they should be interpreted in IETF documents
. This document specifies an Internet Best Current Practices for the Internet Co
mmunity, and requests discussion and suggestions for improvements.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC8174">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author fullname="B. Leiba" initials="B." surname="Leiba"/>
<date month="May" year="2017"/>
<abstract>
<t>RFC 2119 specifies common key words that may be used in protoco
l specifications. This document aims to reduce the ambiguity by clarifying that
only UPPERCASE usage of the key words have the defined special meanings.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
</reference>
</references> </references>
<references anchor="sec-informative-references"> <references anchor="sec-informative-references">
<name>Informative References</name> <name>Informative References</name>
<reference anchor="RFC951"> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.0
<front> 951.xml"/>
<title>Bootstrap Protocol</title> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.1
<author fullname="W.J. Croft" initials="W.J." surname="Croft"/> 542.xml"/>
<author fullname="J. Gilmore" initials="J." surname="Gilmore"/> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2
<date month="September" year="1985"/> 131.xml"/>
<abstract> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.2
<t>This RFC describes an IP/UDP bootstrap protocol (BOOTP) which a 132.xml"/>
llows a diskless client machine to discover its own IP address, the address of a <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7
server host, and the name of a file to be loaded into memory and executed. The 969.xml"/>
bootstrap operation can be thought of as consisting of TWO PHASES. This RFC desc
ribes the first phase, which could be labeled `address determination and bootfil
e selection'. After this address and filename information is obtained, control p
asses to the second phase of the bootstrap where a file transfer occurs. The fil
e transfer will typically use the TFTP protocol, since it is intended that both
phases reside in PROM on the client. However BOOTP could also work with other pr
otocols such as SFTP or FTP. This RFC suggests a proposed protocol for the ARPA-
Internet community, and requests discussion and suggestions for improvements.</t
>
</abstract>
</front>
<seriesInfo name="RFC" value="951"/>
<seriesInfo name="DOI" value="10.17487/RFC0951"/>
</reference>
<reference anchor="RFC1542">
<front>
<title>Clarifications and Extensions for the Bootstrap Protocol</tit
le>
<author fullname="W. Wimer" initials="W." surname="Wimer"/>
<date month="October" year="1993"/>
<abstract>
<t>Some aspects of the BOOTP protocol were rather loosely defined
in its original specification. In particular, only a general description was pro
vided for the behavior of "BOOTP relay agents" (originally called "BOOTP forward
ing agents"). The client behavior description also suffered in certain ways. Thi
s memo attempts to clarify and strengthen the specification in these areas. [STA
NDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="1542"/>
<seriesInfo name="DOI" value="10.17487/RFC1542"/>
</reference>
<reference anchor="RFC2131">
<front>
<title>Dynamic Host Configuration Protocol</title>
<author fullname="R. Droms" initials="R." surname="Droms"/>
<date month="March" year="1997"/>
<abstract>
<t>The Dynamic Host Configuration Protocol (DHCP) provides a frame
work for passing configuration information to hosts on a TCPIP network. DHCP is
based on the Bootstrap Protocol (BOOTP), adding the capability of automatic allo
cation of reusable network addresses and additional configuration options. [STAN
DARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="2131"/>
<seriesInfo name="DOI" value="10.17487/RFC2131"/>
</reference>
<reference anchor="RFC2132">
<front>
<title>DHCP Options and BOOTP Vendor Extensions</title>
<author fullname="S. Alexander" initials="S." surname="Alexander"/>
<author fullname="R. Droms" initials="R." surname="Droms"/>
<date month="March" year="1997"/>
<abstract>
<t>This document specifies the current set of DHCP options. Future
options will be specified in separate RFCs. The current list of valid options i
s also available in ftp://ftp.isi.edu/in-notes/iana/assignments. [STANDARDS-TRAC
K]</t>
</abstract>
</front>
<seriesInfo name="RFC" value="2132"/>
<seriesInfo name="DOI" value="10.17487/RFC2132"/>
</reference>
<reference anchor="RFC7969">
<front>
<title>Customizing DHCP Configuration on the Basis of Network Topolo
gy</title>
<author fullname="T. Lemon" initials="T." surname="Lemon"/>
<author fullname="T. Mrugalski" initials="T." surname="Mrugalski"/>
<date month="October" year="2016"/>
<abstract>
<t>DHCP servers have evolved over the years to provide significant
functionality beyond that described in the DHCP base specifications. One aspect
of this functionality is support for context-specific configuration information
. This memo describes some such features and explains their operation.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7969"/>
<seriesInfo name="DOI" value="10.17487/RFC7969"/>
</reference>
</references> </references>
</references> </references>
<?line 379?> <?line 376?>
<section anchor="usecase"> <section anchor="usecase">
<name>Example Use Case: Topology Discovery for IPv4-only Radio Unit in 3GP <name>Example Use Case: Topology Discovery for IPv4-Only Radio Unit in 3GP
P RAN with Switched Fronthaul</name> P RAN with Switched Fronthaul</name>
<t>In 3GPP mobile network architecture, the User Equipments (UE) are conne <t>In 3GPP mobile network architecture, the User Equipment (UE) is
cted connected via a Radio Access Network (RAN). RAN is built up with
via Radio Access Network (RAN). RAN is built up with Baseband Units (BB) Baseband Units (BBUs) and Radio Units (RUs). A radio Fronthaul (FH) network
and Radio Units (RU). Radio Fronthaul Network (FH) connects RU and BB, each of connects RUs and BBUs. Each RU and BBU is an IP host, and they may
RU and BB is an IP host, they may support IPv4 only, IPv6 only or both support IPv4 only, IPv6 only, or both, depending on the vendor and the
depending on the vendor and the model. model.
Each RU is unique as it is tied to a set of antennas, and each antenna Each RU is unique as it is tied to a set of antennas, and each antenna
is serving a specific Cell and Sector. is serving a specific Cell and Sector.
Each RU is configured by the BB depending on the Cell and Sectors it serves. Each RU is configured by the BBU depending on the Cell and Sectors it serves.
However, that dependency is only specified by the cabling between RU and antenna However, that dependency is only specified by the cabling between RUs and antenn
s. as.
BB can be cabled to RU directly or via a Layer-2 switched network.</t> BBUs can be cabled to RUs directly or via a Layer 2 switched network.</t>
<figure anchor="bb_connected_to_ru"> <figure anchor="bb_connected_to_ru">
<name>3GPP RAN where RU are cabled directly to BB</name> <name>3GPP RAN Where RUs Are Cabled Directly to BBUs</name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="368" width="256" viewBox="0 0 256 368" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="368" width="256" viewBox="0 0 256 368" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round">
<path d="M 8,32 L 8,80" fill="none" stroke="black"/> <path d="M 8,32 L 8,80" fill="none" stroke="black"/>
<path d="M 8,112 L 8,160" fill="none" stroke="black"/> <path d="M 8,112 L 8,160" fill="none" stroke="black"/>
<path d="M 8,208 L 8,256" fill="none" stroke="black"/> <path d="M 8,208 L 8,256" fill="none" stroke="black"/>
<path d="M 8,288 L 8,336" fill="none" stroke="black"/> <path d="M 8,288 L 8,336" fill="none" stroke="black"/>
<path d="M 80,32 L 80,80" fill="none" stroke="black"/> <path d="M 80,32 L 80,80" fill="none" stroke="black"/>
<path d="M 80,112 L 80,160" fill="none" stroke="black"/> <path d="M 80,112 L 80,160" fill="none" stroke="black"/>
<path d="M 80,208 L 80,256" fill="none" stroke="black"/> <path d="M 80,208 L 80,256" fill="none" stroke="black"/>
<path d="M 80,288 L 80,336" fill="none" stroke="black"/> <path d="M 80,288 L 80,336" fill="none" stroke="black"/>
skipping to change at line 797 skipping to change at line 676
| | | +-----------+ | | | +-----------+
+--------+ | +--------+ |
| |
+--------+ | +--------+ |
| RU2 +-----+ | RU2 +-----+
| | | |
+--------+ +--------+
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>In <xref target="bb_connected_to_ru"/> BB is directly cabled to a set o <t>In <xref target="bb_connected_to_ru"/>, the BBU is directly cabled to a
f RUs, the set of RUs, and the
BB can recognize the relationship between RUs and Cell/Sectors BBU can recognize the relationship between RUs and Cell/Sectors
based on the cabling between the RUs and antennas.</t> based on the cabling between the RUs and antennas.</t>
<t>When BBs and RUs are connected via a Layer-2 switched network, <t>When BBUs and RUs are connected via a Layer 2 switched network,
the added level of complexity requires the BBs to have a deeper the added level of complexity requires the BBUs to have a deeper
knowledge of the topology in order to properly configure the RUs, knowledge of the topology in order to properly configure the RUs,
involving knowledge of all the cabling in the switched network.</t> involving knowledge of all the cabling in the switched network.</t>
<t>Examples for switched networks are shown in section 3 of <xref target=" RFC7969"/> <t>Examples for switched networks are shown in <xref section="3" sectionFo rmat="of" target="RFC7969"/>
and demonstrate the different levels of complexity. and demonstrate the different levels of complexity.
An example of a FH is depicted in <xref target="l2_switched_fh"/>.</t> An example of a FH is depicted in <xref target="l2_switched_fh"/>.</t>
<figure anchor="l2_switched_fh"> <figure anchor="l2_switched_fh">
<name>3GPP RAN with Layer-2 Switched Fronthaul Example</name> <name>3GPP RAN with Layer 2 Switched Fronthaul Example</name>
<artset> <artset>
<artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="352" width="544" viewBox="0 0 544 352" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round"> <artwork type="svg" align="center"><svg xmlns="http://www.w3.org/2000/ svg" version="1.1" height="352" width="544" viewBox="0 0 544 352" class="diagram " text-anchor="middle" font-family="monospace" font-size="13px" stroke-linecap=" round">
<path d="M 8,32 L 8,80" fill="none" stroke="black"/> <path d="M 8,32 L 8,80" fill="none" stroke="black"/>
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skipping to change at line 873 skipping to change at line 752
<path d="M 152,304 L 224,304" fill="none" stroke="black"/> <path d="M 152,304 L 224,304" fill="none" stroke="black"/>
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<g class="text"> <g class="text">
<text x="40" y="52">RU1</text> <text x="40" y="52">RU1</text>
<text x="132" y="52">P1</text> <text x="132" y="52">P1</text>
<text x="196" y="68">L2RA</text> <text x="196" y="68">L2RA</text>
<text x="364" y="84">L3RA</text> <text x="364" y="84">L3RA</text>
<text x="180" y="100">L2</text> <text x="180" y="100">L2</text>
<text x="132" y="116">P2</text> <text x="132" y="116">P2</text>
<text x="188" y="116">switch</text> <text x="188" y="116">Switch</text>
<text x="40" y="132">RU2</text> <text x="40" y="132">RU2</text>
<text x="180" y="132">#1</text> <text x="180" y="132">#1</text>
<text x="348" y="132">Router</text> <text x="348" y="132">Router</text>
<text x="484" y="180">DHCP</text> <text x="484" y="180">DHCP</text>
<text x="492" y="196">Server</text> <text x="492" y="196">Server</text>
<text x="40" y="212">RU3</text> <text x="40" y="212">RU3</text>
<text x="132" y="212">P1</text> <text x="132" y="212">P1</text>
<text x="492" y="212">#1</text> <text x="492" y="212">#1</text>
<text x="196" y="228">L2RA</text> <text x="196" y="228">L2RA</text>
<text x="180" y="260">L2</text> <text x="180" y="260">L2</text>
<text x="340" y="260">Baseband</text> <text x="340" y="260">Baseband</text>
<text x="132" y="276">P2</text> <text x="132" y="276">P2</text>
<text x="188" y="276">switch</text> <text x="188" y="276">Switch</text>
<text x="340" y="276">Unit</text> <text x="340" y="276">Unit</text>
<text x="40" y="292">RU4</text> <text x="40" y="292">RU4</text>
<text x="180" y="292">#2</text> <text x="180" y="292">#2</text>
</g> </g>
</svg> </svg>
</artwork> </artwork>
<artwork type="ascii-art" align="center"><![CDATA[ <artwork type="ascii-art" align="center"><![CDATA[
+--------+ +--------+
| RU1 | P1 +-+------+ | | | RU1 | P1 +-+------+ | |
| +--------| | L2RA | | +----+------+ | | +--------| | L2RA | | +----+------+ |
+--------+ | +------+ | | | L3RA | | +--------+ | +------+ | | | L3RA | |
| L2 | +--| +------+ | | L2 | +--| +------+ |
+--------+ P2 | switch | | | | | +--------+ P2 | Switch | | | | |
| RU2 +--------| #1 +-----| | Router +----| | RU2 +--------| #1 +-----| | Router +----|
| | +--------+ | +-----------+ | +---------+ | | +--------+ | +-----------+ | +---------+
+--------+ | | | | +--------+ | | | |
| +--| DHCP | | +--| DHCP |
+--------+ | | | Server | +--------+ | | | Server |
| RU3 | P1 +-+------+ | | | #1 | | RU3 | P1 +-+------+ | | | #1 |
| +--------| | L2RA | | +-----------+ | +---------+ | +--------| | L2RA | | +-----------+ | +---------+
+--------+ | +------+ | | | | +--------+ | +------+ | | | |
| L2 | +--| Baseband | | | L2 | +--| Baseband | |
+--------+ P2 | switch | | | Unit | | +--------+ P2 | Switch | | | Unit | |
| RU4 +--------| #2 +-----| | +----| | RU4 +--------| #2 +-----| | +----|
| | +--------+ | +-----------+ | | | +--------+ | +-----------+ |
+--------+ | | +--------+ | |
]]></artwork> ]]></artwork>
</artset> </artset>
</figure> </figure>
<t>If IPv6 is used and all RU are capable of DHCPv6 in <xref target="l2_sw itched_fh"/>, <t>If IPv6 is used and all RUs are capable of DHCPv6 in <xref target="l2_s witched_fh"/>,
DHCP topology knowledge can be used for solving the RU configuration problem. DHCP topology knowledge can be used for solving the RU configuration problem.
Such solution would use the topology discovery mechanisms described in section 3 Such solution would use the topology discovery mechanisms described in <xref sec
.2 tion="3.2" sectionFormat="of" target="RFC7969"/>.</t>
of <xref target="RFC7969"/>.</t> <t>If RUs are capable of IPv4 only but implement a DHCP 4o6 client accordi
<t>If RU are capable of IPv4 only but implement a 4o6 client according to ng to <xref target="RFC7341"/>, the same topology discovery mechanisms are appli
<xref target="RFC7341"/>, the same topology discovery mechanisms are applicable. cable.</t>
</t> <t>If RUs are capable of IPv4 only and cannot implement a DHCP 4o6 client
<t>If RU are capable of IPV4 only and cannot implement a 4o6 client accord according to <xref target="RFC7341"/>,
ing to <xref target="RFC7341"/>, the topology discovery mechanisms described in <xref section="3.2" sectionFormat
the topology discovery mechanisms described in section 3.2 ="of" target="RFC7969"/> can be used by introducing 4o6RA in the switches as des
of <xref target="RFC7969"/> can be used by introducing 4o6RA in the switches as cribed in this document.</t>
decribed in this document.</t>
</section> </section>
<section numbered="false" anchor="acknowledgments"> <section numbered="false" anchor="acknowledgments">
<name>Acknowledgments</name> <name>Acknowledgments</name>
<t>The authors would also like to acknowledge interesting discussions in <t>The authors would like to acknowledge interesting discussions in
this problem space with Sarah Gannon, Ines Ramadza, and Siddharth Sharma this problem space with <contact fullname="Sarah Gannon"/>, <contact fullname="I
as well as reviews and comments provided by Eric Vyncke, Mohamed Boucadair, nes Ramadza"/>, and <contact fullname="Siddharth Sharma"/>,
David Lamparter, Michael Richardson, Alan DeKok, Dale Worley, Paul Wouters, as well as reviews and comments provided by <contact fullname="Éric Vyncke"/>, <
Deb Cooley, Erik Kline, Ketan Talaulikar, Mike Bishop and Roman Danyliw.</t> contact fullname="Mohamed Boucadair"/>,
<contact fullname="David Lamparter"/>, <contact fullname="Michael Richardson"/>,
<contact fullname="Alan DeKok"/>, <contact fullname="Dale Worley"/>, <contact f
ullname="Paul Wouters"/>,
<contact fullname="Deb Cooley"/>, <contact fullname="Erik Kline"/>, <contact ful
lname="Ketan Talaulikar"/>, <contact fullname="Mike Bishop"/>, and <contact full
name="Roman Danyliw"/>.</t>
</section> </section>
</back> </back>
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