One document matched: draft-ietf-pcp-dhcp-04.xml
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<?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-04" 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="6" month="August" year="2012" />
<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.</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>DHCPv4 refers to the Dynamic Host Configuration Protocol <xref
target="RFC2131"></xref> for IPv4.</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 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="Rationale">
<t>Both IP Address and Name DHCP options have been considered in early
stages of this specification. This flexibility aims to let service
providers to make their own engineering choices and use the convenient
option according to their deployment context. Nevertheless, 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 document defines an option to carry a name rather than an IP
address. 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
of 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>
<section title="DHCPv6 PCP Server Option">
<t>This DHCPv6 option conveys a domain 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(s) is encoded as string.
When several names are included, a space character is used as
separator.</t>
</list></t>
<t><?rfc subcompact="no" ?></t>
</section>
<section title="Client Behaviour">
<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. </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 domain
name(s) is encoded as strings. When several names are included, a
space character is used as separator.</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 Behaviour">
<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 validating it.</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>This section specifies the behavior to be followed by the PCP Client
to contact its PCP Server(s) when receiving one or several PCP Names.
This section is not specific to DHCP; it is applicable to any mechanism
that configures server names.</t>
<t>Multiple 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>
<section title="Name Resolution">
<t>Each configured 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). Then, the PCP Client MUST follow the procedure
specified in <xref target="selection"></xref> to contact its PCP
Server(s).</t>
<t>It is RECOMMENDED to associate a validity lifetime (e.g., TTL of
DNS record if the Name is resolved using DNS) with any address
resulting from resolving the PCP Server Name when stored in a local
name resolution cache. Considerations on how to flush out a local
cache are out of the scope of this document.</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 anchor="selection" title="IP Address Selection">
<t>This section specifies the behavior to be followed by the PCP
Client to contact its PCP Server(s) when receiving one or several PCP
Names:</t>
<t><?rfc subcompact="yes" ?></t>
<t><list style="numbers">
<t>If only one PCP Name is configured: if a list of IP addresses
is returned as a result of resolving the PCP Server Name, the PCP
Client follows the procedure specified in <xref
target="series"></xref>.</t>
<t>If several PCP Names are configured: each Name is treated as a
separate PCP Server. Moreover, each Name may be resolved into one
IP address or a list of IP addresses. The PCP Client contacts in
parallel the first IP address of each Name and follows the
procedure specified in <xref target="series"></xref> for the list
of IP addresses returned for each Name. <xref
target="examples"></xref> provides some examples to illustrate
this procedure.</t>
</list></t>
<t><?rfc subcompact="no" ?></t>
<t><!--Various use cases may be envisaged:
(1) Multiple PCP-controlled devices (e.g, IPv6 FW, NAT64 and NPTv6): these functions may be embedded in distinct devices:
"Procedure 2" is to be followed. But still the question is how the PCP Client
is aware about the capabilities of each PCP-controlled device and how to bound an IP address to a PCP function?
(2) Co-located model (e.g., FW and NATxy functions): one single IP address is needed; "Procedure 1" is to be followed.
(3) When several IP addresses pointing to the same function are retrieved: "Procedure 1" is to be followed.
* case: chain of PCP Servers: FW+NAT/NPT, two addresses may be used: capabilities of the PCP-controlled device
* Capabilities OPTION (see extension): to distinguish between these devices; how to associate capabilities/IP address
*** Do we need to indicate the capabilities in the DHCP option? See http://tools.ietf.org/html/draft-boucadair-pcp-extensions-02#section-4
-->The discovery procedure may result in a PCP Client instantiating multiple
mappings maintained by distinct PCP Servers. The decision to use all
these mappings or delete some of them is deployment-specific. Only the
client can decide whether all the mappings are needed or only a subset
of them.</t>
<section anchor="series" title="Serial Queries">
<t>The PCP Client initializes its retransmission timer, RETRY_TIMER,
to 2 seconds. The PCP Client sends its PCP message to the PCP Server
and waits 2 seconds for a response. If no response is received, it
doubles the value of RETRY_TIMER, sends another (identical) PCP
message and waits 2*RETRY_TIMER. This procedure is repeated three
(3) times, doubling the value of RETRY_TIMER each time. If no
response is received after four (4) attempts, the PCP Client tries
with the next IP address in its list of PCP Server addresses. If it
has exhausted its list, the procedure is repeated every fifteen
minutes until the PCP request is successfully answered. If, when
sending PCP requests the PCP Client receives an ICMP error (e.g.,
port unreachable, network unreachable) it SHOULD immediately try the
next IP address in the list. Once the PCP Client has successfully
received a response from a PCP Server address on that interface, it
sends subsequent PCP requests to that same server address until that
PCP Server becomes non-responsive, which causes the PCP client to
attempt to re-iterate the procedure starting with the first PCP
Server address on its list.</t>
</section>
<section anchor="examples" title="Examples">
<t>The following sub-sections provide three examples to illustrate
the procedure.</t>
<t>For all these examples, let's suppose pcpserver-x, pcpserver-y
and pcpserver-z are configured as PCP Names.</t>
<section title="Example 1">
<t>Let's also suppose:</t>
<t><figure>
<artwork><![CDATA[* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is reachable]]></artwork>
</figure></t>
<t>The procedure to contact the PCP Servers is as follows:</t>
<t><figure>
<artwork><![CDATA[* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* Responses are received from IPy1 and IPz1 but not from IPx1
- The request is re-sent to IPx1
- If no response is received after four attempts, the request
is sent to IPx2
]]></artwork>
</figure></t>
</section>
<section title="Example 2">
<t>Now, if the following conditions are made:</t>
<t><figure>
<artwork><![CDATA[* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is not reachable]]></artwork>
</figure></t>
<t>The procedure to contact the PCP Servers lead to the
following:</t>
<t><figure>
<artwork><![CDATA[* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* A response is received from IPy1 but not from IPx1 and IPz1
- the requests are re-sent to IPx1 and IPz1
- If no response is received after four attempts, the request
is then sent to IPx2 and IPz2
]]></artwork>
</figure></t>
</section>
<section title="Example 3">
<t>Let's suppose now that:</t>
<t><figure>
<artwork><![CDATA[* IPx1 and IPx2 are returned for pcpserver-x; IPx1 is not reachable.
* IPy1 and IPy2 are returned for pcpserver-y; IPy1 is not reachable
* IPz1 and IPz2 are returned for pcpserver-z; IPz1 is not reachable]]></artwork>
</figure></t>
<t>The procedure to contact the PCP Servers is as follows:</t>
<t><figure>
<artwork><![CDATA[* Send PCP requests to all servers: IPx1, IPy1 and IPz1
* No answer is received for all requests
- the requests are re-sent to IPx1, IPy1 and IPz1
- If no response is received after four attempts, the request
is then sent to IPx2, IPy2 and IPz2]]></artwork>
</figure></t>
<t></t>
</section>
</section>
</section>
</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 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.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.ietf-dhc-option-guidelines'?>
</references>
</back>
</rfc>
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