One document matched: draft-ietf-pcp-dhcp-07.xml
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<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="5"?>
<?rfc tocindent="yes"?>
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<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std" docName="draft-ietf-pcp-dhcp-07" ipr="trust200902">
<front>
<title abbrev="PCP DHCP Options">DHCP Options for the Port Control
Protocol (PCP)</title>
<author fullname="Mohamed Boucadair" initials="M." surname="Boucadair">
<organization>France Telecom</organization>
<address>
<postal>
<street></street>
<city>Rennes</city>
<region></region>
<code>35000</code>
<country>France</country>
</postal>
<email>mohamed.boucadair@orange.com</email>
</address>
</author>
<author fullname="Reinaldo Penno" initials="R." surname="Penno">
<organization>Cisco</organization>
<address>
<postal>
<street></street>
<code></code>
<country>USA</country>
</postal>
<email>repenno@cisco.com</email>
</address>
</author>
<author fullname="Dan Wing" initials="D." surname="Wing">
<organization abbrev="Cisco">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>170 West Tasman Drive</street>
<city>San Jose</city>
<region>California</region>
<code>95134</code>
<country>USA</country>
</postal>
<email>dwing@cisco.com</email>
</address>
</author>
<date day="26" month="March" year="2013" />
<workgroup>PCP Working Group</workgroup>
<keyword>PCP Server discovery, Port Mapping, Shared Address</keyword>
<abstract>
<t>This document specifies DHCP (IPv4 and IPv6) options to configure
hosts with Port Control Protocol (PCP) Server names. The use of DHCPv4
or DHCPv6 depends on the PCP deployment scenario.</t>
</abstract>
<note 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>
</note>
</front>
<middle>
<section title="Introduction">
<t>This document defines DHCPv4 <xref target="RFC2131"></xref> and
DHCPv6 <xref target="RFC3315"></xref> options which can be used to
provision PCP Server <xref target="I-D.ietf-pcp-base"></xref> names.
Motivations for not expressing the PCP option as a 32 or 128-bit binary
address are discussed in <xref target="rationale"></xref>.</t>
<t>In order to make use of these options, this document assumes
appropriate name resolution means (e.g., Section 6.1.1 of <xref
target="RFC1123"></xref>) are available on the host client.</t>
<t>The use of DHCPv4 or DHCPv6 depends on the PCP deployment
scenarios.</t>
</section>
<section title="Terminology">
<t>This document makes use of the following terms:<?rfc subcompact="yes" ?></t>
<t><list style="symbols">
<t>PCP Server denotes a functional element which receives and
processes PCP requests from a PCP Client. A PCP Server can be
co-located with or be separated from the function (e.g., NAT,
Firewall) it controls. Refer to <xref
target="I-D.ietf-pcp-base"></xref>.</t>
<t>PCP Client denotes a PCP software instance responsible for
issuing PCP requests to a PCP Server. Refer to <xref
target="I-D.ietf-pcp-base"></xref>.</t>
<t>DHCP refers to both DHCPv4 <xref target="RFC2131"></xref> and
DHCPv6 <xref target="RFC3315"></xref>.</t>
<t>DHCP client (or client) denotes a node that initiates requests to
obtain configuration parameters from one or more DHCP servers.</t>
<t>DHCP server (or server) refers to a node that responds to
requests from DHCP clients.</t>
<t>Name is a domain name (as per Section 8 of <xref
target="RFC3315"></xref>) that contains one or more labels. In
particular, a PCP name may be structured as DNS qualified name or be
composed of strings such as can be passed to getaddrinfo (Section
6.1 of <xref target="RFC3493"></xref>), including address literals,
etc. </t>
</list><?rfc subcompact="no" ?></t>
</section>
<section title="DHCPv6 PCP Server Option">
<t>This DHCPv6 option conveys a name to be used to retrieve the IP
addresses of PCP Server(s). Appropriate name resolution queries should
be issued to resolve the conveyed name.</t>
<section title="Format">
<t>The format of the DHCPv6 PCP Server option is shown in <xref
target="dhcpv6_name_option"></xref>.</t>
<t><figure anchor="dhcpv6_name_option"
title="PCP Server Name DHCPv6 Option">
<preamble></preamble>
<artwork><![CDATA[ 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_PCP_SERVER | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: PCP Server Domain Name(s) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<postamble></postamble>
</figure>The fields of the option shown in <xref
target="dhcpv6_name_option"></xref> are as follows:<?rfc subcompact="yes" ?></t>
<t><list style="symbols">
<t>Option-code: OPTION_PCP_SERVER (TBA, see <xref
target="iana6"></xref>)</t>
<t>Option-length: Length of the 'PCP Server Domain Name' field in
octets.</t>
<t>PCP Server Domain Name(s): The domain name (s) of the PCP
Server to be used by the PCP Client. The OPTION_PCP_SERVER option
can include multiple PCP Server Domain Names; each name is treated
as a separate PCP Server. The domain name is encoded as specified
in <xref target="RFC3315">Section 8 of</xref>.</t>
</list></t>
<t><?rfc subcompact="no" ?></t>
</section>
<section title="Client Behavior">
<t>To discover a PCP Server <xref target="I-D.ietf-pcp-base"></xref>,
the DHCPv6 client MUST include an Option Request Option (ORO)
requesting the DHCPv6 PCP Server Name option as described in Section
22.7 of <xref target="RFC3315"></xref> (i.e., include
OPTION_PCP_SERVER on its OPTION_ORO).</t>
<t>If the DHCPv6 client receives an OPTION_PCP_SERVER option from the
DHCPv6 server, it extracts the name(s) conveyed in the
OPTION_PCP_SERVER option and proceeds to validate it. The DHCPv6
client MUST verify the name(s) is properly encoded as detailed in
Section 8 of <xref target="RFC3315"></xref>.</t>
<t>Once each name conveyed in the OPTION_PCP_SERVER option is
validated, the DHCPv6 client MUST follow the procedure specified in
<xref target="usename"></xref>.</t>
</section>
</section>
<section title="DHCPv4 PCP Option">
<t></t>
<section title="Format">
<t>The PCP Server Name DHCPv4 option can be used to configure a name
to be used by the PCP Client to contact a PCP Server. The format of
this option is illustrated in <xref target="dhcppcp"></xref>.</t>
<t></t>
<t><figure anchor="dhcppcp" title="PCP Server Name DHCPv4 Option">
<preamble></preamble>
<artwork><![CDATA[
Code Length PCP Server Domain Name
+-----+-----+-----+-----+-----+-----+-----+--
| TBA | n | s1 | s2 | s3 | s4 | s5 | ...
+-----+-----+-----+-----+-----+-----+-----+--
]]></artwork>
<postamble></postamble>
</figure></t>
<t>The description of the fields is as follows:<?rfc subcompact="yes" ?><list
style="symbols">
<t>Code: OPTION_PCP_SERVER (TBA, see <xref
target="iana4"></xref>);</t>
<t>Length: Includes the length of the "PCP Server Domain Name"
field in octets; The maximum length is 255 octets.</t>
<t>PCP Server Domain Name(s): The domain name(s) of the PCP Server
to be used by the PCP Client when issuing PCP messages. The
OPTION_PCP_SERVER option can include multiple PCP Server Domain
Names; each name is treated as a separate PCP Server. The encoding
of the domain name is described in Section 8 of <xref
target="RFC3315"></xref>.</t>
</list></t>
<t><?rfc subcompact="no" ?>The OPTION_PCP_SERVER DHCPv4 option is a
concatenation-requiring option. As such, the mechanism specified in
<xref target="RFC3396"></xref> MUST be used if the PCP Server Name
option exceeds the maximum DHCPv4 option size of 255 octets.</t>
</section>
<section title="Client Behavior">
<t>DHCPv4 client expresses the intent to get OPTION_PCP_SERVER by
specifying it in Parameter Request List Option <xref
target="RFC2132"></xref>.</t>
<t>If the DHCPv4 client receives an OPTION_PCP_SERVER option from the
DHCPv4 server, it extracts the name(s) conveyed in the option and
proceeds to validate it. The DHCPv4 client MUST verify the name(s) is
properly encoded as detailed in Section 8 of <xref
target="RFC3315"></xref>.</t>
<t>Once each name conveyed in the OPTION_PCP_SERVER option is
validated, the DHCPv4 client MUST follow the procedure specified in
<xref target="usename"></xref>.</t>
</section>
</section>
<section anchor="usename" title="Use of PCP Server Names">
<t>If the OPTION_PCP_SERVER option conveys IP address literals, the
trailing dot MUST be removed. </t>
<t>Each configured PCP Server Name is passed to the name resolution
library (e.g., Section 6.1.1 of <xref target="RFC1123"></xref> or <xref
target="RFC6055"></xref>) to retrieve the corresponding IP address(es)
(IPv4 or IPv6). It is out of scope of this document to specify how the
PCP Client selects the PCP Server(s) to contact.</t>
<t>Multiple PCP Server Names may be configured to a PCP Client in some
deployment contexts such as multi-homing. It is out of scope of this
document to enumerate all deployment scenarios which require multiple
Names to be configured.</t>
<t>A host may have multiple network interfaces (e.g, 3G, WiFi, etc.);
each configured differently. Each PCP Server learned MUST be associated
with the interface via which it was learned.</t>
</section>
<section title="Dual-Stack Hosts">
<t>In some deployment contexts, the PCP Server may be reachable with an
IPv4 address but DHCPv6 is used to provision the PCP Client. In such
scenarios, a plain IPv4 address or an IPv4-mapped IPv6 address can be
configured to reach the PCP Server.</t>
<t>A Dual-Stack host may receive OPTION_PCP_SERVER via both DHCPv4 and
DHCPv6. The content of these OPTION_PCP_SERVER options may refer to the
same or distinct PCP Servers. This is deployment-specific and as such it
is out of scope of this document.</t>
</section>
<section title="Guidance to Administrators">
<t>If IPv4 address literals are to be returned in the OPTION_PCP_SERVER
option, administrators should not configure ambiguous strings such as
"10.0.258", "0xA000001", and "012.0x102"; the strict form is recommended
instead. Refer to Section 3.1.1 and Section 3.1.2 of <xref
target="I-D.iab-identifier-comparison"></xref> for a more generic
discussion on IP address literals. </t>
</section>
<section anchor="Security" title="Security Considerations">
<t>The security considerations in <xref target="RFC2131"></xref>, <xref
target="RFC3315"></xref> and <xref target="I-D.ietf-pcp-base"></xref>
are to be considered.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t></t>
<section anchor="iana6" title="DHCPv6 Option">
<t>IANA is requested to assign the following new DHCPv6 Option Code in
the registry maintained in http://www.iana.org/assignments/
dhcpv6-parameters:</t>
<texttable style="headers">
<ttcol align="right">Option Name</ttcol>
<ttcol>Value</ttcol>
<c>OPTION_PCP_SERVER</c>
<c>TBA</c>
</texttable>
</section>
<section anchor="iana4" title="DHCPv4 Option">
<t>IANA is requested to assign the following new DHCPv4 Option Code in
the registry maintained in
http://www.iana.org/assignments/bootp-dhcp-parameters/:</t>
<texttable style="headers">
<ttcol align="right">Option Name</ttcol>
<ttcol>Value</ttcol>
<c>OPTION_PCP_SERVER</c>
<c>TBA</c>
</texttable>
<t></t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler, T.
Mrugalski, T. Reddy, S. Cheshire and M. Wasserman for their review and
comments.</t>
<t>Special thanks to T. Lemon for the review and his continuous effort
to enhance this specification.</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.RFC.2132'?>
<?rfc include='reference.RFC.3396'?>
<?rfc include='reference.I-D.ietf-pcp-base'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.6333'?>
<?rfc include='reference.RFC.3493'?>
<?rfc include='reference.RFC.1123'?>
<?rfc include='reference.RFC.6055'?>
<?rfc include='reference.RFC.6146'?>
<?rfc include='reference.RFC.6334'?>
<?rfc include='reference.I-D.ietf-behave-lsn-requirements'?>
<?rfc include='reference.I-D.iab-identifier-comparison'?>
<?rfc include='reference.I-D.ietf-dhc-option-guidelines'?>
</references>
<section anchor="rationale" title="Rationale">
<t>Distinct IP-Address and Name DHCP options have been considered in
early stages of this specification. This flexibility aims to let service
providers make their own engineering choices and use the most convenient
option according to their deployment context. Nevertheless, the DHC WG's
position is this flexibility has some drawbacks such as inducing errors
(See Section 7 of <xref
target="I-D.ietf-dhc-option-guidelines"></xref>). Therefore, only the
Name option is maintained within this document.</t>
<t>This choice is motivated by operational considerations: In
particular, some Service Providers are considering two levels of
redirection:</t>
<t><?rfc subcompact="yes" ?><list style="format (%d)">
<t>The first level is national-wise and undertaken by DHCP: a
regional-specific Name will be returned;</t>
<t>The second level is done during the resolution of the
regional-specific Name to redirect the customer to a regional PCP
server among a pool deployed regionally.</t>
</list><?rfc subcompact="no" ?></t>
<t></t>
<t>Distinct operational teams are responsible for each of the above
mentioned levels. A clear separation between the functional perimeter of
each team is a sensitive task for the maintenance of the offered
services. Regional teams will require to introduce new resources (e.g.,
new PCP-controlled devices such as Carrier Grade NATs (CGNs, <xref
target="I-D.ietf-behave-lsn-requirements"></xref>)) to meet an increase
in customer base. Operations related to the introduction of these new
devices (e.g., addressing, redirection, etc.) are implemented locally.
Having this regional separation provides flexibility to manage portions
of network operated by dedicated teams. This two-level redirection can
not be met by the IP Address option.</t>
<t>In addition to the operational considerations:<?rfc subcompact="yes" ?><list
style="symbols">
<t>The use of the Name for NAT64 <xref target="RFC6146"></xref>
might be suitable for load-balancing purposes;</t>
<t>For the DS-Lite case <xref target="RFC6333"></xref>, if the
encapsulation mode is used to send PCP messages, an IP address may
be used since the AFTR selection is already done via the AFTR_NAME
DHCPv6 option <xref target="RFC6334"></xref>. Of course, this
assumes that the PCP Server is co-located with the AFTR function. If
these functions are not co-located, conveying the Name would be more
convenient.</t>
</list></t>
<t><?rfc subcompact="no" ?>Returning a Name requires the host to embed a
name resolution service. Some may present this as an argument against
defining a Name option. Nevertheless, this argument may be objected as
implementing a name resolution library (e.g., embed a DNS resolver) is
cheap and devices which don't embed DNS resolver are uncommon.</t>
</section>
</back>
</rfc>
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