One document matched: draft-ietf-pcp-dhcp-06.xml
<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="5"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std" docName="draft-ietf-pcp-dhcp-06" 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="19" month="February" 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 expressing the PCP option as a textual string rather
than 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
scenario.</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 UTF-8 <xref target="RFC3629"></xref> string that can be
passed to getaddrinfo (Section 6.1 of <xref
target="RFC3493"></xref>), such as a DNS name, address literals,
etc. The name MUST NOT contain spaces or nulls. A name may be a
fully qualified domain name (e.g., "myservice.example.com."), IPv4
address in dotted-decimal form (e.g., 192.0.2.33) or textual
representation of an IPv6 address (e.g., 2001:db8::1) <xref
target="RFC4291"></xref><xref target="RFC5952"></xref>.</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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Name-length | |
+-+-+-+-+-+-+-+-+ |
: PCP Server Name :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| Name-length | | |
+-+-+-+-+-+-+-+-+ | O
: PCP Server Name : P
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ T
. I
. O
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N
| Name-length | | A
+-+-+-+-+-+-+-+-+ | L
: PCP Server Name : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
]]></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: includes total length of all following option
data in octets.</t>
<t>Name-length (one-octet field): Includes the length of the PCP
Server Name, in octets.</t>
<t>PCP Server Name (variable): The name of the PCP Server to be
used by the PCP Client. The name is encoded as a UTF-8 <xref
target="RFC3629"></xref> string.</t>
</list></t>
<t><?rfc subcompact="no" ?>The OPTION_PCP_SERVER option can include
multiple PCP Server names; each name is treated as a separate PCP
Server. When several names are to be included, "Name-length" and "PCP
Server Name" fields are repeated.</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. A name is considered as valid if it is a
legal UTF-8 string which does not contain any spaces or nulls. Below
are listed some additional validation rules:<list style="symbols">
<t>The trailing dot is optional when a domain name is conveyed in
the option.</t>
<t>IPv6 addresses MUST NOT be enclosed in brackets.</t>
<t>A domain name is structured as one or more labels concatenated
with dots. A label MUST have no more than 63 characters.</t>
</list></t>
<t>The DHCPv6 client MUST silently ignore invalid names.</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[ Option- Name-
Code length length PCP Server Name
+-----+-----+-----+-----+-----+-----+-----+--
| TBA | n | m | name ...
+-----+-----+-----+-----+-----+-----+-----+--
]]></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>Option-length: includes total length of all following option
data in octets. The maximum length is 255 octets.</t>
<t>Name-length (one-octet field): Includes the length of the PCP
Server Name, in octets.</t>
<t>PCP Server Name (variable): The name of the PCP Server to be
used by the PCP Client when issuing PCP messages. The name is
encoded as a UTF-8 <xref target="RFC3629"></xref> string.</t>
</list></t>
<t><?rfc subcompact="no" ?>The OPTION_PCP_SERVER option can include
multiple PCP Server names; each name is treated as a separate PCP
Server. When several names are to be included, "Name-length" and "PCP
Server Name" fields are repeated.</t>
<t>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. A name
is considered as valid if it is a legal UTF-8 string which does not
contain any spaces or nulls. Below are listed some additional
validation rules:<list style="symbols">
<t>The trailing dot is optional when a domain name is conveyed in
the option.</t>
<t>A domain name is structured as one or more labels concatenated
with dots. A label MUST have no more than 63 characters.</t>
</list></t>
<t>The DHCPv4 client MUST silently discard non valid names.</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>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 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>Authors of this document request the following DHCPv6 option
code:</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>Authors of this document request the following DHCPv4 option
code:</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. Lemon, S. Cheshire and M. Wasserman for their review and
comments.</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.RFC.3629'?>
<?rfc include='reference.RFC.5952'?>
<?rfc include='reference.RFC.4291'?>
<?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.2181'?>
<?rfc include='reference.RFC.6334'?>
<?rfc include='reference.I-D.ietf-behave-lsn-requirements'?>
<?rfc include='reference.I-D.ietf-dhc-option-guidelines'?>
</references>
<section anchor="rationale" title="Rationale">
<t>The pcp WG consensus is to define a DHCP option which contains a
string that can be passed to APIs (e.g., getaddrinfo()). In particular,
the option should be designed to include a name (e.g., domain name <xref
target="RFC2181"></xref>) or IP address literal string. In such design,
DHCP clients are expected to pass the conveyed string to any supported
name resolution library (DNS is a name resolution service among others).
The underlying name resolution library is responsible for validating the
name.</t>
<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" ?></t>
<section title="Dependency on Name Resolution">
<t>The approach adopted in this document allows for an IP address or a
Name to be returned in the specified DHCP option. In particular, a
server can resolve first the name and return in the option the
resolved IP address(es). For deployments where this is not possible,
the server can return a name which will be resolved by the host
embedding the client. This document does not have any requirement on
the underlying name resolution library (in particular, DNS is not
assumed as the only available name resolution service). </t>
<t>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>
</section>
</back>
</rfc>
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