One document matched: draft-ietf-dime-nat-control-16.xml
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<rfc category="std" docName="draft-ietf-dime-nat-control-16" ipr="trust200902">
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<!-- ***** FRONT MATTER ***** -->
<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<title abbrev="Diameter NAT Control Application">Diameter Network Address
and Port Translation Control Application</title>
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<author fullname="Frank Brockners" initials="F." surname="Brockners">
<organization>Cisco</organization>
<address>
<postal>
<street>Hansaallee 249, 3rd Floor</street>
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<region>NORDRHEIN-WESTFALEN</region>
<code>40549</code>
<country>Germany</country>
</postal>
<email>fbrockne@cisco.com</email>
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</address>
</author>
<author fullname="Shwetha Bhandari" initials="S." surname="Bhandari">
<organization>Cisco</organization>
<address>
<postal>
<street>Cessna Business Park, Sarjapura Marathalli Outer Ring
Road</street>
<city>Bangalore, KARNATAKA 560 087</city>
<country>India</country>
</postal>
<email>shwethab@cisco.com</email>
</address>
</author>
<author fullname="Vaneeta Singh" initials="V." surname="Singh">
<organization></organization>
<address>
<postal>
<street>18, Cambridge Road</street>
<city>Bangalore 560008</city>
<country>India</country>
</postal>
<email>vaneeta.singh@gmail.com</email>
</address>
</author>
<author fullname="Victor Fajardo" initials="V." surname="Fajardo">
<organization>Telcordia Technologies</organization>
<address>
<postal>
<street>1 Telcordia Drive #1S-222</street>
<city>Piscataway, NJ 08854</city>
<country>USA</country>
</postal>
<email>vf0213@gmail.com</email>
</address>
</author>
<date day="20" month="April" year="2012" />
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<area>General</area>
<workgroup>Internet Engineering Task Force</workgroup>
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<keyword>diameter</keyword>
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<abstract>
<t>This document describes the framework, messages, and procedures for
the Diameter Network address and port translation Control Application.
This Diameter application allows per endpoint control of Network Address
Translators and Network Address and Port Translators, which are added to
networks to cope with IPv4-address space depletion. This Diameter
application allows external devices to configure and manage a Network
Address Translator device - expanding the existing Diameter-based AAA
and policy control capabilities with a Network Address Translators and
Network Address and Port Translators control component. These external
devices can be network elements in the data plane such as a Network
Access Server, or can be more centralized control plane devices such as
AAA-servers. This Diameter application establishes a context to commonly
identify and manage endpoints on a gateway or server, and a Network
Address Translator and Network Address and Port Translator device. This
includes, for example, the control of the total number of Network
Address Translator bindings allowed or the allocation of a specific
Network Address Translator binding for a particular endpoint. In
addition, it allows Network Address Translator devices to provide
information relevant to accounting purposes.</t>
</abstract>
</front>
<middle>
<section title="Introduction" toc="default">
<t>Internet service providers deploy Network Address Translators (NATs)
and Network Address and Port Translators (NAPTs) <xref
target="RFC3022"></xref> in their networks. A key motivation for doing
so is the depletion of available public IPv4 addresses. This document
defines a Diameter application allowing providers to control the
behavior of NAT and NAPT devices that implement IPv4-to-IPv4 network
address and port translation <xref target="RFC2663"></xref> as well as
stateful IPv6-to-IPv4 address family translation as defined in <xref
target="RFC2663"></xref>, <xref target="RFC6145"></xref>, and <xref
target="RFC6146"></xref>. The use of a Diameter application allows for
simple integration into the existing Authentication, Authorization and
Accounting (AAA) environment of a provider.</t>
<t>The Diameter Network address and port translation Control Application
(DNCA) offers the following capabilities:</t>
<t><list style="numbers">
<t>Limits or defines the number of NAPT/NAT bindings made available
to an individual endpoint. The main motivation for restricting the
number of bindings on a per endpoint basis is to protect the service
of the service provider against denial of service attacks. If
multiple endpoints share a single public IP address, these endpoints
can share fate. If one endpoint would (either intentionally, or due
to mis-behavior, mis-configuration, mal-ware, etc.) be able to
consume all available bindings for a given single public IP address,
service would be hampered (or might even become unavailable) for
those other endpoints sharing the same public IP address. The
efficiency of a NAPT deployment depends on the maximum number of
bindings an endpoint could use. Given that the typical number of
bindings an endpoint uses depends on the type of endpoint (e.g. a
personal computer of a broadband user is expected to use a higher
number of bindings than a simple mobile phone) and a NAPT device is
often shared by different types of endpoints, it is desirable to
actively manage the maximum number of bindings. This requirement is
specified in REQ-3 of <xref
target="I-D.ietf-behave-lsn-requirements"></xref></t>
<t>Supports the allocation of specific NAPT/NAT bindings. Two types
of specific bindings can be distinguished:<list style="symbols">
<t>Allocation of a pre-defined NAT binding: Both the internal
and external IP address and port pair are specified within the
request. Some deployment cases, such as access to a web-server
within a user’s home network with IP address and port,
benefit from statically configured bindings.</t>
<t>Allocation of an external IP address for a given internal IP
address: The allocated external IP address is reported back to
the requestor. In some deployment scenarios, the application
requires immediate knowledge of the allocated binding for a
given internal IP address but does not control the allocation of
the external IP address; for example, SIP-proxy server
deployments.</t>
</list></t>
<t>Defines the external address pool(s) to be used for allocating an
external IP address: External address pools can either be
pre-assigned at the NAPT/NAT device, or specified within a request.
If pre-assigned address pools are used, a request needs to include a
reference to identify the pool. Otherwise, the request contains a
description of the IP address pool(s) to be used; for example, a
list of IP-subnets. Such external address pools can be used to
select the external IP address in NAPT/NAT bindings for multiple
subscribers.</t>
<t>Generates reports and accounting records: Reports established
bindings for a particular endpoint. The collected information is
used by accounting systems for statistical purposes.</t>
<t>Queries and retrieves details about bindings on demand: This
feature complements the previously mentioned accounting
functionality (see item 4). This feature can be used by an entity to
find NAT-bindings belonging to one or multiple endpoints on the
NAT-device. The entity is not required to create a DNCA control
session to perform the query, but would obviously still need to
create a Diameter session complying to the security
requirements.</t>
<t>Identifies a subscriber or endpoint on multiple network devices
(NAT/NAPT device, the AAA-server, or the Network Access Server
(NAS)): Endpoint identification is facilitated through a Global
Endpoint ID. Endpoints are identified through a single or a set of
classifiers, such as IP address, Virtual Local Area Network (VLAN)
identifier, or interface identifier which uniquely identify the
traffic associated with a particular global endpoint.</t>
</list></t>
<t>With the above capabilities, DNCA qualifies as a MIDCOM protocol
<xref target="RFC3303"></xref>, <xref target="RFC3304"></xref>, <xref
target="RFC5189"></xref> for middle boxes which perform NAT. The MIDCOM
protocol evaluation <xref target="RFC4097"></xref> evaluated Diameter as
a candidate protocol for MIDCOM. DNCA provides the extensions to the
Diameter base protocol <xref target="RFC3588"></xref> following the
MIDCOM protocol requirements, such as the support of NAT-specific rule
transport, support for oddity of mapped ports, as well as support for
consecutive range port numbers. DNCA adds to the MIDCOM protocol
capabilities in that it allows to maintain the reference to an endpoint
representing a user or subscriber in the control operation, enabling the
control of the behavior of a NAT-device on a per endpoint basis.
Following the requirements of different operators and deployments,
different management protocols are employed. Examples include e.g. SNMP
<xref target="RFC3411"></xref> and NETCONF <xref
target="RFC6241"></xref> which can both be used for device
configuration. Similarly, DNCA is complementing existing MIDCOM
implementations, offering a MIDCOM protocol option for operators with an
operational environment that is Diameter-focused which desire to use
Diameter to perform per endpoint NAT control. Note that in case an
operator uses multiple methods and protocols to configure a NAT-device,
such as for example command line interface, SNMP, NETCONF, or PCP, along
with DNCA specified in this document, the operator MUST ensure that the
configurations performed using the different methods and protocols do
not conflict in order to ensure a proper operation of the NAT
service.</t>
<t>This document is structured as follows: Section 2 lists terminology,
while Section 3 provides an introduction to DNCA and its overall
deployment framework. Sections 4 to 8 cover DNCA specifics, with Section
4 describing session management, Section 5 the use of the Diameter base
protocol, Section 6 new commands, Section 7 Attribute Value Pairs(AVPs)
used, and Section 8 accounting aspects. Section 9 presents AVP
occurrence tables. IANA and security considerations are addressed in
Sections 10 and 11.</t>
</section>
<section anchor="Conventions" title="Conventions">
<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"></xref>.</t>
<t>Abbreviations used in this document:</t>
<t><list style="empty">
<t>AAA: Authentication, Authorization, Accounting</t>
<t>DNCA: Diameter Network address and port translation Control
Application</t>
<t>Endpoint: Managed entity of the DNCA. An endpoint represents a
network element or device, associated with a subscriber, a user or a
group of users. An endpoint is represented by a single
access-session on a NAS. DNCA assumes a 1:1 relationship between an
endpoint, the access-session it represents, and the associated DNCA
session.</t>
<t>NAPT: Network Address and Port Translation, see also <xref
target="RFC3022"></xref></t>
<t>NAT: Network Address Translation (NAT and NAPT are used in this
document interchangeably)</t>
<t>NAT-binding or binding: Association of two IP address/port pairs
(with one IP address typically being private and the other one
public) to facilitate NAT</t>
<t>NAT binding predefined template: Is a policy template or
configuration that is predefined at the NAT-device. It may contain
NAT-bindings, IP-address pools for allocating the external
IP-address of a NAT-binding, the maximum number of allowed
NAT-bindings for end-points, etc.</t>
<t>NAT-device: Network Address Translator or Network Address and
Port Translator: An entity performing NAT or NAPT.</t>
<t>NAT-controller: Entity controlling the behavior of a
NAT-device.</t>
<t>NAS: Network Access Server</t>
<t>NCR: NAT Control Request</t>
<t>NCA: NAT Control Answer</t>
<t>NAT44: IPv4 to IPv4 network address and port translation, see
<xref target="RFC2663"></xref></t>
<t>NAT64: IPv6 to IPv4 address family translation, see <xref
target="RFC6145"></xref> and <xref target="RFC6146"></xref></t>
<t>PPP: Point-to-Point Protocol <xref target="RFC1661"></xref></t>
</list></t>
</section>
<section anchor="framework" title="Deployment Framework">
<section title="Deployment Scenario">
<t><xref target="fig-network-deployment"></xref> shows a typical
network deployment for IPv4-Internet access. A user’s IPv4 host
(i.e. endpoint) gains access to the Internet though a NAS, which
facilitates the authentication of the endpoint and configures the
endpoints’s connection according to the authorization and
configuration data received from the AAA-server upon successful
authentication. Public IPv4 addresses are used throughout the network.
DNCA manages an endpoint that represents a network element or device
or IPv4 host, associated with a subscriber, a user or a group of
users. An endpoint is represented by a single access-session on a NAS.
DNCA assumes a 1:1 relationship between an endpoint, the
access-session it represents, and the associated DNCA session.</t>
<figure anchor="fig-network-deployment"
title="Typical network deployment for internet access">
<artwork><![CDATA[
+---------+
| |
| AAA |
| |
+---------+
|
|
|
|
+---------+ +---------+ +----------+
| IPv4 | | | | IPv4 |
| Host |----------| NAS |-------------| Internet |
| | | | | |
+---------+ +---------+ +----------+
<-------------------- Public IPv4 ---------------------->
]]></artwork>
</figure>
<t><xref target="fig-NAT-deployment"></xref> depicts the deployment
scenario where a service provider places a NAT between the host and
the public Internet. The objective is to provide the customer with
connectivity to the public IPv4 Internet. The NAT-device performs
network address and port (and optionally address family) translation,
depending on whether the access network uses private IPv4 addresses or
public IPv6 addresses, to public IPv4 addresses. Note that there may
be more than one NAS, NAT-device, or AAA-entity in a deployment,
although the figures only depict one entity each for clarity.</t>
<t>If the NAT-device would be put in place without any endpoint
awareness, the service offerings of the service provider could be
impacted as detailed in <xref
target="I-D.ietf-behave-lsn-requirements"></xref>. This includes cases
like:</t>
<t><list style="symbols">
<t>Provisioning static NAT bindings for particular endpoints</t>
<t>Using different public IP address pools for different set of
endpoints (for example, residential or business customers)</t>
<t>Reporting allocated bindings on a per endpoint basis</t>
<t>Integrate control of the NAT-device into the already existing
per endpoint management infrastructure of the service provider</t>
</list></t>
<figure anchor="fig-NAT-deployment"
title="Access network deployment with NAT">
<artwork><![CDATA[
+---------+
| |
| AAA |
| |
+---------+
|
|
|
|
+--------+ +---------+ +--------+ +----------+
| IPv4 |----| |----| NAT- |----| IPv4- |
| Host | | NAS | | device | | Internet |
| | | | | | | |
+--------+ +---------+ +--------+ +----------+
For NAT44 deployments (IPv4 host):
<----- Private IPv4 ----------><--- Public IPv4 --->
For NAT64 deployments (IPv6 host):
<----- Public IPv6 ----------><--- Public IPv4 --->
]]></artwork>
</figure>
<t><xref target="fig-NAT-deployment"></xref> shows a typical
deployment for IPv4-Internet access involving a NAT-device within the
service provider network. The figure describes two scenarios: One
where an IPv4-host (with a private IPv4 address) accesses the
IPv4-Internet, as well as one where an IPv6-host accesses the
IPv4-Internet.</t>
</section>
<section title="Diameter NAPT Control Application Overview">
<t>DNCA runs between two DNCA Diameter peers. One DNCA Diameter peer
resides within the NAT-device, the other DNCA Diameter peer resides
within a NAT-controller (discussed in Section 3.3). DNCA allows per
endpoint control and management of NAT within the NAT-device. Based on
Diameter, DNCA integrates well with the suite of Diameter applications
deployed for per endpoint authentication, authorization, accounting,
and policy control in service provider networks.</t>
<t>DNCA offers:<list style="symbols">
<t>Request and answer commands to control the allowed number of
NAT bindings per endpoint to request the allocation of specific
bindings for an endpoint, to define the address pool to be used
for an endpoint.</t>
<t>Provides per endpoint reporting of the allocated NAT
bindings.</t>
<t>Provides unique identification of an endpoint on NAT-device,
AAA-server and NAS, to simplify correlation of accounting data
streams.</t>
</list></t>
<t>DNCA allows controlling the behavior of a NAT-device on a per
endpoint basis during initial session establishment and at later
stages by providing an update procedure for already established
sessions. Using DNCA, per endpoint NAT binding information can be
retrieved either using accounting mechanisms or through an explicit
session query to the NAT.</t>
</section>
<section title="Deployment Scenarios For DNCA">
<t>DNCA can be deployed in different ways. DNCA supports deployments
with "n" NAT-controllers and "m" NAT-devices, with n and m equal to or
greater than 1. From a DNCA perspective an operator should ensure that
the session representing a particular endpoint is atomic. Any
deployment MUST ensure that for any given endpoint only a single DNCA
NAT-controller and is active at any point in time. This is to ensure
that NAT-devices controlled by multiple NAT-controllers do not receive
conflicting control requests for a particular endpoint, or would be
unclear which NAT-controller to send accounting information to.
Operational considerations MAY require an operator to use alternate
control mechanisms or protocols such as SNMP or manual configuration
via a Command-Line-Interface to apply per-endpoint NAT-specific
configuration, like for example static NAT-bindings. For these cases,
the NAT-device MUST allow the operator to configure a policy how
configuration conflicts are resolved. Such a policy could for example
specify that manually configured NAT-bindings using the
Command-Line-Interface always take precedence over those configured
using DNCA.</t>
<t>Two common deployment scenarios are outlined in <xref
target="fig-NAT-integrated-deployment"></xref> (“integrated
deployment”) and <xref
target="fig-NAT-autonomous-deployment"></xref> (“autonomous
deployment”). Per the note above, multiple instances of
NAT-controllers and NAT-devices could be deployed. The figures only
show single instances for reasons of clarity. The two shown scenarios
differ in which entity fulfills the role of the NAT-controller. Within
the figures (C) denotes the network element performing the role of the
NAT-controller.</t>
<t>The integrated deployment approach hides the existence of the
NAT-device from external servers, such as the AAA-server. It is suited
for environments where minimal changes to the existing AAA deployment
are desired. The NAS and the NAT-device are Diameter peers supporting
the DNCA. The Diameter peer within the NAS, performing the role of the
NAT-controller, initiates and manages sessions with the NAT-device,
exchanges NAT specific configuration information and handles reporting
and accounting information. The NAS receives reporting and accounting
information from the NAT-device. With this information, the NAS can
provide a single accounting record for the endpoint. A system
correlating the accounting information received from the NAS and
NAT-device would not be needed.</t>
<t>An example network attachment for an integrated NAT deployment can
be described as follows: An endpoint connects to the network, with the
NAS being the point of attachment. After successful authentication,
the NAS receives endpoint related authorization data from the
AAA-server. A portion of the authorization data applies to per
endpoint configuration on the NAS itself, another portion describes
authorization and configuration information for NAT control aimed at
the NAT-device. The NAS initiates a DNCA session to the NAT-device and
sends relevant authorization and configuration information for the
particular endpoint to the NAT-device. This can comprise NAT-bindings,
which have to be pre-established for the endpoint, or management
related configuration, such as the maximum number of NAT-bindings
allowed for the endpoint. The NAT-device sends its per endpoint
accounting information to the NAS, which aggregates the accounting
information received from the NAT-device with its local accounting
information for the endpoint into a single accounting stream towards
the AAA-server.</t>
<figure anchor="fig-NAT-integrated-deployment"
title="NAT control deployment: Integrated deployment">
<artwork><![CDATA[
+---------+
| |
| AAA |
| |
+---------+
|
|
|
+--------+ +---------+ +--------+ +----------+
| | | (C) | | | | |
| Host |----| NAS |----| NAT- |----| IPv4- |
| | | | | device | | Internet |
+--------+ +---------+ +--------+ +----------+
For NAT44 deployments (IPv4 host):
<----- Private IPv4 ----------><--- Public IPv4 --->
For NAT64 deployments (IPv6 host):
<----- Public IPv6 ----------><--- Public IPv4 --->
]]></artwork>
</figure>
<t><xref target="fig-NAT-integrated-deployment"></xref> shows examples
of integrated deployments. The figure describes two scenarios: One
where an IPv4-host (with a private IPv4 address) accesses the
IPv4-Internet, as well as one where an IPv6-host accesses the
IPv4-Internet.</t>
<t>The autonomous deployment approach decouples endpoint management on
the NAS and NAT-device. In the autonomous deployment approach, the
AAA-system and the NAT-device are the Diameter peers running the DNCA.
The AAA-system also serves as NAT-controller. It manages the
connection to the NAT-device, controls the per endpoint configuration,
and also receives accounting and reporting information from the
NAT-device. Different from the integrated deployment scenario, the
autonomous deployment scenario does not “hide” the
existence of the NAT-device from the AAA infrastructure. Here two
accounting streams are received by the AAA-server for one particular
endpoint, one from the NAS, and one from the NAT-device.</t>
<figure anchor="fig-NAT-autonomous-deployment"
title="NAT control deployment: Autonomous deployment">
<artwork><![CDATA[
+---------+
| (C) |
| AAA |---------
| | |
+---------+ |
| |
| |
| |
+--------+ +---------+ +---------+ +----------+
| IPv4/ | | | | | | IPv4 |
| IPv6 |----| NAS |----| NAT- |----| Internet |
| Host | | | | device | | |
+--------+ +---------+ +---------+ +----------+
For NAT44 deployments (IPv4 host):
<----- Private IPv4 ----------><--- Public IPv4 --->
For NAT64 deployments (IPv6 host):
<----- Public IPv6 ----------><--- Public IPv4 --->]]></artwork>
</figure>
<t><xref target="fig-NAT-autonomous-deployment"></xref> shows examples
of autonomous deployments. The figure describes two scenarios: One
where an IPv4-host (with a private IPv4 address) accesses the
IPv4-Internet, as well as one where an IPv6-host accesses the
IPv4-Internet.</t>
</section>
</section>
<section anchor="sec-dnca"
title="DNCA Session Establishment and Management">
<t>Note that this section forward references some of the commands and
AVPs defined for DNCA. Please refer to <xref
target="sec-dnca-commands"></xref> and <xref
target="sec-dnca-avps"></xref> for details. DNCA runs between a Diameter
peer residing in a NAT-controller and a Diameter peer residing in a
NAT-device. Note that, per what was already mentioned above, each DNCA
session between Diameter peers in a NAT-controller and a NAT-device
represents a single endpoint, with an endpoint being either a network
element, a device or an IPv4 host associated with a subscriber, a user,
or a group of users. The Diameter peer within the NAT-controller is
always the control requesting entity: It initiates, updates, or
terminates the sessions. Sessions are initiated when the NAT-controller
learns about a new endpoint (i.e., host) that requires a NAT service.
This could for example be due to the entity hosting the NAT-controller
receiving authentication, authorization, or accounting requests for or
from the endpoint. Alternate methods that could trigger session setup
include local configuration, receipt of a packet from a formerly unknown
IP-address, etc.</t>
<section title="Session Establishment">
<t>The DNCA Diameter peer within the NAT-controller establishes a
session with the DNCA Diameter peer within the NAT-device to control
the behavior of the NAT function within the NAT-device. During session
establishment, the DNCA Diameter peer within the NAT-controller passes
along configuration information to DNCA Diameter peer within the
NAT-device. The session configuration information comprises the
maximum number of bindings allowed for the endpoint associated with
this session, a set of pre-defined NAT bindings to be established for
this endpoint, or a description of the address pool, that external
addresses are to be allocated from.</t>
<t>The DNCA Diameter peer within the NAT-controller generates a
NAT-Control Request (NCR) message to the DNCA Diameter peer within the
NAT-device with NC-Request-Type AVP set to INITIAL_REQUEST to initiate
a Diameter NAT control session. On receipt of a NCR the DNCA Diameter
peer within the NAT-device sets up a new session for the endpoint
associated with the endpoint classifier(s) contained in the NCR. The
DNCA Diameter peer within the NAT-device notifies its DNCA Diameter
peer within the NAT-controller about successful session setup using a
NAT-Control Answer (NCA) message with Result-Code set to
DIAMETER_SUCCESS. <xref target="fig-session-establishment"></xref>
shows the initial protocol interaction between the two DNCA Diameter
peers.</t>
<t>The initial NAT-Control-Request MAY contain configuration
information for the session, which specifies the behavior of the
NAT-device for the session. The configuration information that MAY be
included, comprises: <list style="symbols">
<t>A list of NAT bindings, which should be pre-allocated for the
session; for example, in case an endpoint requires a fixed
external IP-address/port pair for an application. </t>
<t>The maximum number of NAT-bindings allowed for an endpoint.</t>
<t>A description of the external IP-address pool(s) to be used for
the session.</t>
<t>A reference to a NAT Binding Predefined template on the
NAT-device, which is applied to the session. Such a NAT Binding
Predefined template on the NAT-device may contain, for example,
the name of the IP-address pool that external IP-addresses should
be allocated from, the maximum number of bindings permitted for
the endpoint, etc.</t>
</list>In certain cases, the NAT-device may not be able to perform
the tasks requested within the NCR. These include the following: <list
style="symbols">
<t>If a DNCA Diameter peer within the NAT-device receives a NCR
from a DNCA Diameter peer within a NAT-controller with
NC-Request-Type AVP set to INITIAL_REQUEST that identifies an
already existing session; that is endpoint identifier match an
already existing session, the DNCA Diameter peer within the
NAT-device MUST return an NCA with Result-Code set to
SESSION_EXISTS, and provide the Session-Id of the existing session
in the Duplicate-Session-Id AVP.</t>
<t>If a DNCA Diameter peer within the NAT-device receives a NCR
from a DNCA Diameter peer within a NAT-controller with
NC-Request-Type AVP set to INITIAL_REQUEST that matches more than
one of the already existing sessions; that is, DNCA Diameter peer
and endpoint identifier match already existing sessions, the DNCA
Diameter peer within the NAT-device MUST return an NCA with
Result-Code set to INSUFFICIENT-CLASSIFIERS. In case a DNCA
Diameter peer receives a NCA that reports
Insufficient-Classifiers, it MAY choose to retry establishing a
new session using additional or more specific classifiers.</t>
<t>If the NCR contains a NAT Binding predefined template not
defined on the NAT-device, the DNCA Diameter peer within the
NAT-device MUST return an NCA with Result-Code AVP set to
UNKNOWN_BINDING_TEMPLATE_NAME.</t>
<t>In case the NAT-device is unable to establish all of the
bindings requested in the NCR, the DNCA Diameter peer MUST return
an NCA with Result-Code set to BINDING_FAILURE. A DNCA Diameter
peer within a NAT-device MUST treat a NCR as an atomic operation;
hence none of the requested bindings will be established by the
NAT-device. Either all requested actions within a NCR MUST be
completed successfully, or the entire request fails.</t>
<t>If a NAT-device cannot conform to a request to set the maximum
number of NAT bindings allowed for a session, the DNCA Diameter
peer in the NAT-device MUST return an NCA with Result-Code AVP set
to MAX_BINDINGS_SET_FAILURE. Such a condition can for example
occur if the operator specified the maximum number of NAT bindings
through another mechanism, which per the operator's policy, takes
precedence over DNCA.</t>
<t>If a NAT-device does not have sufficient resources to process a
request, the DNCA Diameter peer MUST return an NCA with
Result-Code set to RESOURCE_FAILURE.</t>
<t>In case Max-NAT-Bindings, NAT-Control-Definition as well as
NAT-Control-Binding-Template are included in the NCR, and the
values in Max-NAT-Bindings and NAT-Control-Definition contradict
those specified in the pre-provisioned template on the NAT-device
which NAT-Control-Binding-Template references, Max-NAT-Bindings
and NAT-Control-Definition MUST override the values specified in
the template that NAT-Control-Binding-Template refers to.</t>
</list></t>
<figure anchor="fig-session-establishment"
title="Initial NAT control request and session establishment ">
<artwork><![CDATA[
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
Trigger |
| |
| NCR |
|------------------------------------------>|
| |
| |
| |
| |
| If Able to comply
| with Request then
| Create session state
| |
| |
| NCA |
|<------------------------------------------|
| |
| |]]></artwork>
</figure>
<t>Note: The DNCA Diameter peer within the NAT-device creates session
state only if it is able to comply with the NCR. On success it will
reply with an NCA with Result-Code set to DIAMETER_SUCCESS.</t>
</section>
<section title="Session Update">
<t>Session update is performed if the NAT-controller desires to change
the behavior of the NAT-device for an existing session. Session update
could be used, for example, to change the number of allowed bindings
for a particular session, or establish or remove a pre-defined
binding.</t>
<t>The DNCA Diameter peer within the NAT-controller generates a NCR
message to the DNCA Diameter peer within the NAT-device with
NC-Request-Type AVP set to UPDATE_REQUEST upon receiving a trigger
signal. If the session is updated successfully, the DNCA Diameter peer
within the NAT-device notifies the DNCA Diameter peer within the
NAT-controller about the successful session update using a NAT-Control
Answer (NCA) message with Result-Code set to DIAMETER_SUCCESS.<xref
target="fig-session-update"> </xref> shows the protocol interaction
between the two DNCA Diameter peers.</t>
<t>In certain cases, the NAT-device may not be able to perform the
tasks requested within the NCR. These include the following: <list
style="symbols">
<t>If DNCA Diameter peer within a NAT-device receives an NCR
update or query request for a non-existent session, it MUST set
Result-Code in the answer to DIAMETER_UNKNOWN_SESSION_ID.</t>
<t>If the NCR contains a NAT Binding Predefined template not
defined on the NAT-device, an NCA with Result-Code AVP set to
UNKNOWN_BINDING_TEMPLATE_NAME MUST be returned.</t>
<t>If the NAT-device cannot establish the requested binding
because the maximum number of allowed bindings has been reached
for the endpoint classifier, an NCA with Result-Code AVP set to
MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT MUST be returned to the DNCA
Diameter peer.</t>
<t>If the NAT-device cannot establish some or all of the bindings
requested in an NCR, but has not yet reached the maximum number of
allowed bindings for the endpoint, an NCA with Result-Code set to
BINDING_FAILURE MUST be returned. As already noted, the DNCA
Diameter peer in a NAT-device MUST treat an NCR as an atomic
operation. Hence none of the requested bindings will be
established by the NAT-device in case of failure. Actions
requested within a NCR are either all successful or all fail.</t>
<t>If the NAT-device cannot conform to a request to set the
maximum number of bindings allowed for a session as specified by
the Max-NAT-Bindings, the DNCA Diameter peer in the NAT-device
MUST return an NCA with Result-Code AVP set to
MAX_BINDINGS_SET_FAILURE.</t>
<t>If the NAT-device does not have sufficient resources to process
a request, an NCA with Result-Code set to RESOURCE_FAILURE MUST be
returned.</t>
<t>If an NCR changes the maximum number of NAT-bindings allowed
for the endpoint defined through an earlier NCR, the new value
MUST override any previously defined limit on the maximum number
of NAT bindings set through DNCA. Note that prior to overwriting
an existing value, the NAT-device MUST check whether the overwrite
action conforms to the locally configured policy. Deployment
dependent, an existing value could have been set by a protocol or
mechanism different from DNCA and with higher priority. In which
case, the NAT-device will refuse the change and the DNCA Diameter
peer in the NAT-device MUST return an NCA with Result-Code AVP set
to MAX_BINDINGS_SET_FAILURE. It depends on the implementation of
the NAT-device on how the NAT-device copes with a case where the
new value is lower than the actual number of allocated bindings.
The NAT-device SHOULD refrain from enforcing the new limit
immediately (that is, actively remove bindings), but rather
disallows the establishment of new bindings until the current
number of bindings is lower than the newly established maximum
number of allowed bindings.</t>
<t>If an NCR specifies a new NAT Binding Predefined template on
the NAT-device, the NAT Binding Predefined template overrides any
previously defined rule for the session. Existing NAT-bindings
SHOULD NOT be impacted by the change of templates.</t>
<t>In case Max-NAT-Binding, NAT-Control-Definition as well as
NAT-Control-Binding-Template are included in the NCR, and the
values in Max-NAT-Bindings and NAT-Control-Definition contradict
those specified in the pre-provisioned template on the NAT-device
which NAT-Control-Binding-Template references, Max-NAT-Bindings
and NAT-Control-Definition MUST override the values specified in
the template that the NAT-Control-Binding-Template refers to.</t>
</list>Note: Already established bindings for the session SHOULD NOT
be affected in case the tasks requested within the NCR cannot be
completed.</t>
<figure anchor="fig-session-update"
title="NAT control request for session update ">
<artwork><![CDATA[
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
Change of session |
attributes |
| |
| NCR |
|------------------------------------------>|
| |
| |
| If able to comply
| with the request:
| Update session state
| |
| |
| NCA |
|<------------------------------------------|
| |]]></artwork>
</figure>
</section>
<section title="Session and Binding Query">
<t>A Session and NAT-binding query MAY be used by the DNCA Diameter
peer within the NAT-controller to either retrieve information on the
current bindings for a particular session at the NAT-device or
discover the session identifier for a particular external IP
address/port pair.</t>
<t>A DNCA Diameter peer within the NAT-controller starts a session
query by sending an NCR message with NC-Request-Type AVP set to
QUERY_REQUEST. <xref target="fig-session-query"></xref> shows the
protocol interaction between the DNCA Diameter peers.</t>
<t>Two types of query requests exist. The first type of query request
uses the session ID as input parameter to the query. It is to allow
the DNCA Diameter peer within the NAT-controller to retrieve the
current set of bindings for a specific session. The second type of
query request is used to retrieve the session identifiers, along with
the associated bindings, matching a criteria. This enables the DNCA
Diameter peer within the NAT-controller to find those sessions, which
utilize a specific external or internal IP-address.</t>
<t><list style="numbers">
<t>Request a list of currently allocated NAT bindings for a
particular session: On receiving a NCR, the NAT-device SHOULD look
up the session information for the session ID contained in the
NCR, and report all currently active NAT-bindings for the session
using an NCA message with Result-Code set to DIAMETER_SUCCESS. In
this case the NCR MUST NOT contain a NAT-Control-Definition AVP.
Each NAT-binding is reported in a NAT-Control-Definition AVP. In
case the session ID is unknown, the DNCA Diameter peer within the
NAT-device MUST return an NCA message with Result-Code set to
DIAMETER_UNKNOWN_SESSION_ID.</t>
<t>Retrieve session IDs and bindings for internal IP-address or
one or multiple external IP-address/port pairs: If the DNCA
Diameter peer within the NAT-controller wishes to retrieve the
session ID(s) for internal IP-address or one or multiple external
IP-address/port pairs, it MUST include the internal IP-address as
part of Framed-IP-Address or external IP-address/port pair(s) as
part of the NAT-External-Address AVP of the NCR. The external
IP-address/port pair(s) are pre-known to the controller via
configuration, AAA interactions, or other means. The session ID is
not included in the NCR or the NCA for this type of a query. The
DNCA Diameter peer within the NAT-device SHOULD report the
NAT-bindings and associated session IDs corresponding to the
internal IP-address or external IP-address/port pairs in an NCA
message using one or multiple instances of the
NAT-Control-Definition AVP. The Result-Code is set to
DIAMETER_SUCCESS. In case an external IP-address/port pair has no
associated existing NAT-binding, the NAT-Control-Definition AVP
contained in the reply just contains the NAT-External-Address
AVP.</t>
</list></t>
<figure anchor="fig-session-query" title="Session query">
<artwork><![CDATA[
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
DNCA Session Established |
| |
| NCR |
|------------------------------------------>|
| |
| |
| |
| |
| Look up corresponding session
| and associated NAT-bindings
| |
| NCA |
|<------------------------------------------|
| |
| |
| |]]></artwork>
</figure>
</section>
<section anchor="sec-dnca-sess-term" title="Session Termination">
<t>Similar to session initiation, session tear down MUST be initiated
by the DNCA Diameter peer within the NAT-controller. The DNCA Diameter
peer sends a Session Terminate Request (STR) message to its peer
within the NAT-device upon receiving a trigger signal. The source of
the trigger signal is outside the scope of this document. As part of
STR message processing the DNCA Diameter peer within the NAT-device
MAY send an accounting stop record reporting all bindings. All the
NAT-bindings belonging to the session MUST be removed and the session
state MUST be cleaned up. The DNCA Diameter peer within the NAT-device
MUST notify its DNCA Diameter peer in the NAT-controller about
successful session termination using a Session Terminate Answer (STA)
message with Result-Code set to DIAMETER_SUCCESS. <xref
target="fig-session-terminate"></xref> shows the protocol interaction
between the two DNCA Diameter peers.</t>
<t>If a DNCA Diameter peer within a NAT-device receives a STR and
fails to find a matching session, the DNCA Diameter peer MUST return a
STA with Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.</t>
<figure anchor="fig-session-terminate"
title="Terminate NAT control session">
<artwork><![CDATA[
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
Trigger |
| |
| STR |
|------------------------------------------->|
| |
| |
| |
| |
| |
| Send accounting stop |
|<-------------------------------------------|
| reporting all session bindings |
| |
| |
| Remove NAT-bindings
| of session
| |
| Terminate session /
| Remove session state
| |
| |
| |
| STA |
|<-------------------------------------------|
| |
| |]]></artwork>
</figure>
</section>
<section title="Session Abort">
<t>An Abort-Session-Request (ASR) message is sent from the DNCA
Diameter peer within the NAT-device to the DNCA Diameter peer within
the NAT-controller when it is unable to maintain a session due to
resource limitations. The DNCA Diameter peer within the NAT-controller
MUST acknowledge successful session abort using a Abort Session Answer
(ASA) message with Result-Code set to DIAMETER_SUCCESS. <xref
target="fig-session-abort"></xref> shows the protocol interaction
between the DNCA Diameter peers. The DNCA Diameter peers will start a
session termination procedure as described in <xref
target="sec-dnca-sess-term"></xref> following an ASA with Result-Code
set to DIAMETER_SUCCESS.</t>
<t>If the DNCA Diameter peer within a NAT-controller receives an ASR
but fails to find a matching session, it MUST return an ASA with
Result-Code set to DIAMETER_UNKNOWN_SESSION_ID. If the DNCA Diameter
peer within the NAT-controller is unable to comply with the ASR for
any other reason, an ASA with Result-Code set to
DIAMETER_UNABLE_TO_COMPLY MUST be returned.</t>
<figure anchor="fig-session-abort" title="Abort NAT control session">
<artwork><![CDATA[
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| Trigger
| |
| ASR |
|<-------------------------------------------|
| |
| |
| |
| ASA |
|------------------------------------------->|
| |
| |
| |
| On successful ASA |
|<------Session Termination Procedure------->|]]></artwork>
</figure>
</section>
<section title="Failure cases of the DNCA Diameter peers">
<t>This document does not specify the behavior in case the NAT-device
and NAT-controller, or their respective DNCA Diameter peers are out of
sync or lose state. This could happen for example if one of the
entities restarts, in case of a (temporary) loss of network
connectivity etc. Example failure cases include the following:</t>
<t><list style="symbols">
<t>NAT-controller and the DNCA Diameter peer within the
NAT-controller lose state (e.g., due to a restart). In this case,
<list style="symbols">
<t>the DNCA Diameter peer within the NAT-device MAY receive an
NCR with NC-Request-Type AVP set to INITIAL_REQUEST that
matches an existing session of the DNCA Diameter peer within
the NAT-device. The DNCA Diameter peer within the NAT-device
MUST return Result-Code that contains Duplicate-Session-Id AVP
to report the Session-ID of the existing session. The DNCA
Diameter peer within the NAT-controller MAY send an explicit
Session Terminate Request (STR) for the older session, which
was lost.</t>
<t>a DNCA Diameter peer MAY receive accounting records for a
session that does not exist. The DNCA Diameter peer sends an
accounting answer with Result-Code set to
DIAMETER_UNKNOWN_SESSION_ID in response. On receiving the
response, the DNCA Diameter peer SHOULD clear the session and
remove associated session state.</t>
</list></t>
<t>NAT-device and the DNCA Diameter peer within NAT-device lose
state. In such a case, the DNCA Diameter peer MAY receive a NCR
with NC-Request-Type AVP set to UPDATE_REQUEST for a non-existent
session. The DNCA Diameter peer MUST return an NCA with
Result-Code set to DIAMETER_UNKNOWN_SESSION_ID. When DNCA
application within NAT-controller receives this NCA within
Result-Code set to DIAMETER_UNKNOWN_SESSION_ID, it MAY try to
reestablish DNCA session or disconnect corresponding access
session.</t>
<t>The DNCA Diameter peer within the NAT-controller is
unreachable, for example detected by Diameter device watchdog
messages (as defined in Section 5.5 of <xref
target="RFC3588"></xref>), or accounting requests from the DNCA
Diameter peer fail to get a response, NAT-bindings and NAT-device
state pertaining to that session MUST be cleaned up after a grace
period that is configurable on the NAT-device. The grace period
can be configured as zero or higher, depending on operator
preference. </t>
<t>The DNCA Diameter peer within the NAT-device is unreachable or
down and NCR fails to get a response. Handling of this case
depends on the actual service offering of the service provider.
The service provider could for example choose to stop offering
connectivity service.</t>
<t>A discussion of the mechanisms how a NAT-device cleans up state
in case the DNCA Diameter peer within the NAT-device crashes is
outside the scope of this document. Implementers of NAT-devices
could choose from a variety of options such as coupling the state
(e.g. NAT bindings) to timers which require periodic refresh, or
time out otherwise, operating system watchdogs for applications,
etc.</t>
</list></t>
</section>
</section>
<section anchor="sec-diameter-base-use"
title="Use of the Diameter Base Protocol">
<t>The Diameter Base Protocol defined by <xref target="RFC3588"></xref>
applies with the clarifications listed in the present specification.</t>
<section anchor="sec-diameter-messages"
title="Securing Diameter Messages ">
<t>For secure transport of Diameter messages, the recommendations in
<xref target="RFC3588"></xref> apply.</t>
<t>DNCA Diameter peers SHOULD verify their identity during the
Capabilities Exchange Request procedure.</t>
<t>A DNCA Diameter peer within the NAT-device SHOULD verify that a
DNCA Diameter peer that issues a NCR command is allowed to do so based
on: <list style="symbols">
<t>The identity of the DNCA Diameter peer</t>
<t>The type of NCR Command</t>
<t>The content of the NCR Command</t>
<t>Any combination of the above</t>
</list></t>
</section>
<section title="Accounting Functionality">
<t>Accounting functionality (accounting session state machine, related
command codes and AVPs) is defined in <xref
target="sec-accounting"></xref> below.</t>
</section>
<section title="Use of Sessions">
<t>Each DNCA session MUST have a globally unique Session-ID as defined
in <xref target="RFC3588"></xref>, which MUST NOT be changed during
the lifetime of a DNCA session. The Diameter Session-ID serves as the
global endpoint identifier. The DNCA Diameter peers maintain state
associated with the Session-ID. This globally unique Session-ID is
used for updating, accounting, and terminating the session. A DNCA
session MUST NOT have more than one outstanding request at any given
instant. A DNCA Diameter peer sends an Abort-Session-Request as
defined in <xref target="RFC3588"></xref> if it is unable to maintain
sessions due to resource limitation.</t>
</section>
<section title="Routing Considerations">
<t>It is assumed that the DNCA Diameter peer within a NAT-controller
knows the DiameterIdentity of the Diameter peer within a NAT-device
for a given endpoint. Both the Destination-Realm and Destination-Host
AVPs are present in the request from a DNCA Diameter peer within a
NAT-controller to a DNCA Diameter peer within a NAT-device.</t>
</section>
<section title="Advertising Application Support">
<t>Diameter nodes conforming to this specification MUST advertise
support for DNCA by including the value of TBD.APP-ID in the
Auth-Application-Id of the Capabilities-Exchange-Request and
Capabilities-Exchange-Answer command<xref target="RFC3588">
</xref>.</t>
</section>
</section>
<section anchor="sec-dnca-commands" title="DNCA Commands">
<t>The following commands are used to establish, maintain and query
NAT-bindings.</t>
<section anchor="sec-dnca-ncr" title="NAT-Control Request (NCR) Command">
<t>The NAT-Control Request (NCR) command, indicated by the command
field set to TBD.COM-CODE and the "R" bit set in the Command Flags
field, is sent from the DNCA Diameter peer within the NAT-controller
to the DNCA Diameter peer within the NAT-device in order to install
NAT-bindings.</t>
<t>User-Name, Logical-Access-Id, Physical-Access-ID,
Framed-IP-Address, Framed-IPv6-Prefix, Framed-Interface-Id,
EGRESS-VLANID, NAS-Port-ID, Address-Realm, Calling-Station-ID AVPs
serve as identifiers for the endpoint.</t>
<t>Message format:</t>
<figure>
<artwork><![CDATA[ < NC-Request > ::= < Diameter Header: TBD.COM-CODE, REQ, PXY>
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
{ NC-Request-Type }
[ Session-Id ]
[ Origin-State-Id ]
*1 [ NAT-Control-Remove ]
*1 [ NAT-Control-Install ]
[ NAT-External-Address ]
[ User-Name ]
[ Logical-Access-Id ]
[ Physical-Access-ID ]
[ Framed-IP-Address ]
[ Framed-IPv6-Prefix ]
[ Framed-Interface-Id ]
[ EGRESS-VLANID]
[ NAS-Port-ID]
[ Address-Realm ]
[ Calling-Station-ID ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ AVP ]
]]></artwork>
</figure>
</section>
<section anchor="sec-dnca-nca" title="NAT-Control Answer (NCA) Command">
<t>The NAT-Control-Answer (NCA) command, indicated by the Command-Code
field set to TBD.COM-CODE and the "R" bit cleared in the Command Flags
field, is sent by the DNCA Diameter peer within the NAT-device in
response to NAT-Control-Request command.</t>
<t>Message format:</t>
<figure>
<artwork><![CDATA[ <NC-Answer> ::= < Diameter Header: TBD.COM-CODE, PXY >
{ Origin-Host }
{ Origin-Realm }
{ Result-Code }
[ Session-Id ]
[ NC-Request-Type ]
* [ NAT-Control-Definition ]
[ Current-NAT-Bindings ]
[ Origin-State-Id ]
[ Error-Message ]
[ Error-Reporting-Host ]
* [ Failed-AVP ]
* [ Proxy-Info ]
[ Duplicate-Session-ID ]
* [ Redirect-Host]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
* [ Failed-AVP ]
* [ AVP ]
]]></artwork>
</figure>
</section>
</section>
<section title="NAT Control Application Session State Machine">
<t>This section contains a set of finite state machines, representing
the life cycle of a DNCA session, which MUST be observed by all
implementations of the DNCA Diameter application. The DNCA Diameter
peers are stateful and the state machine maintained is similar to the
stateful Client and Server authorization state machine described in
<xref target="RFC3588"></xref>. When a session is moved to the Idle
state, any resources that were allocated for the particular session must
be released. Any event not listed in the state machines MUST be
considered as an error condition, and an answer, if applicable, MUST be
returned to the originator of the message.</t>
<t>In the state table, the event 'Failure to send NCR' means that the
DNCA Diameter peer within the NAT-controller is unable to send the NCR
command to the desired destination. This could be due to the peer being
down, or due to the peer sending back the transient failure or temporary
protocol error notification DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED
in the Result-Code AVP of an NCA.</t>
<t>In the state table "FAILED NCA" means that the DNCA Diameter peer
within the NAT-device was not able to honor the corresponding NCR. This
can happen due to any transient and permanent error at the NAT-device or
its associated DNCA Diameter peer within indicated by the following
error Result-Code values: RESOURCE_FAILURE,
UNKNOWN_BINDING_TEMPLATE_NAME, MAX_BINDINGS_SET_FAILURE,
BINDING_FAILURE, MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT, SESSION_EXISTS,
INSUFFICIENT_CLASSIFIERS.</t>
<t>The following state machine is observed by a DNCA Diameter peer
within a NAT-controller. The state machine description uses the term
"access session" to describe the connectivity service offered to the
endpoint or host. "Access session" should not be confused with the
Diameter session ID.</t>
<t><figure>
<artwork><![CDATA[ DNCA Diameter peer within a NAT-controller
State Event Action New State
-------------------------------------------------------------
Idle New endpoint detected that Send Pending
requires NAT Control NCR
Initial
Request
Idle ASR Received Send ASA Idle
for unknown session with
Result-Code
= UNKNOWN_
SESSION_ID
Pending Successful NCA Setup Open
received complete
Pending Successful NCA Send STR Discon
received
but peer unable to provide
service
Pending Error processing successful Send STR Discon
NCA
Pending Failed Clean up Idle
NCA received
Open NAT control Send Open
update required NCR Update
Request
Open Successful Open
NCA received
Open Failed Clean up Idle
NCA received
Open Access session end detected Send STR Discon
Open ASR Received, Send ASA Discon
access session will be with
terminated Result-Code
= SUCCESS,
Send STR
Open ASR Received, Send ASA Open
access session will not with
be terminated Result-Code
!= SUCCESS
Discon ASR Received Send ASA Idle
Discon STA Received Discon. Idle
endpoint]]></artwork>
</figure></t>
<t>The following state machine is observed by a DNCA Diameter peer
within a NAT-device.</t>
<figure>
<artwork><![CDATA[
DNCA Diameter peer within a NAT-device
State Event Action New State
-------------------------------------------------------------
Idle NCR Query request Send Idle
received, and successful
able to provide requested NCA
NAT Binding report
Idle NCR received Send Open
and able to successful
provide requested NCA
NAT control service
Idle NCR request Send Idle
received, and failed
unable to provide requested NCA
NAT control service
Open NCR request Send Open
received, and successful
able to provide requested NCA
NAT control service
Open NCR request Send Idle
received, and failed
unable to provide requested NCA,
NAT control service Clean up
Open Unable to continue Send ASR Discon
providing requested
NAT control service
Open Unplanned loss of session/ Clean up Idle
connection to DNCA Diameter
peer in NAT controller
detected (e.g. due to Diameter
watchdog notification)
Discon Failure to send ASR Wait, Discon
resend ASR
Discon ASR successfully sent and Clean up Idle
ASA Received with Result-Code
Not ASA Received None No change
Discon
Any STR Received Send STA, Idle
Clean up]]></artwork>
</figure>
</section>
<section anchor="sec-dnca-avps" title="DNCA AVPs">
<t></t>
<section title="Reused Base Protocol AVPs">
<t>The following table describes the AVPs reused from Diameter Base
Protocol <xref target="RFC3588"></xref>; their AVP Code values, types,
and possible flag values; and whether the AVP MAY be encrypted. The
<xref target="RFC3588"></xref> specifies the AVP Flag rules for AVPs
in section 4.5. The Diameter AVP rules are defined in the <xref
target="RFC3588"></xref>, section 4.</t>
<figure anchor="tab-avps-from-diameter-base" suppress-title="true">
<artwork><![CDATA[ +---------+
| AVP |
| Flag |
| rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | |
| Attribute Name Code Data Type |MUST |MAY| Encr |
+-----------------------------------------------+-----+---+---------+
|Acct-Interim-Interval 85 Unsigned32 | M | P | Y |
|Auth-Application-Id 258 Unsigned32 | M | P | N |
|Destination-Host 293 DiamIdent | M | P | N |
|Destination-Realm 283 DiamIdent | M | P | N |
|Error-Message 281 UTF8String | M | P | N |
|Error-Reporting-Host 294 DiamIdent | M | P | N |
|Failed-AVP 279 Grouped | M | P | N |
|Origin-Host 264 DiamIdent | M | P | N |
|Origin-Realm 296 DiamIdent | M | P | N |
|Origin-State-Id 278 Unsigned32 | M | P | N |
|Proxy-Info 284 Grouped | M | P | N |
|Result-Code 268 Unsigned32 | M | P | N |
|Route-Record 282 DiamIdent | M | | N |
|Session-Id 263 UTF8String | M | P | Y |
|User-Name 1 UTF8String | M | P | Y |
+-----------------------------------------------+-----+---+---------+]]></artwork>
<postamble>Table 1: DIAMETER AVPs used from Diameter
base</postamble>
</figure>
<t>The Auth-Application-Id AVP (AVP Code 258) is assigned by IANA to
Diameter applications. The value of the Auth-Application-Id for the
Diameter NAT Control Application is TBD.APP-ID. Please refer to <xref
target="RFC3588"></xref> for the definition of the Diameter AVP flag
rules and the associated abbreviations used in the table.</t>
</section>
<section anchor="sec_result-codes"
title="Additional Result-Code AVP Values">
<t>This section defines new values for the Result-Code AVP that SHALL
be supported by all Diameter implementations that conform to the
present document.</t>
<section title="Success">
<t>No new Result-Code AVP value is defined within this category.</t>
</section>
<section anchor="sec_result-code-transient" title="Transient Failures">
<t>Result-Code AVP values that fall within the transient failures
category are those used to inform a peer that the request could not
be satisfied at the time that it was received. The request may be
able to be satisfied in the future.</t>
<t>The following new values of the Result-Code AVP are defined:</t>
<t><list style="empty">
<t>RESOURCE_FAILURE (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device indicates
that the binding could not be installed or a new session
could not be created due to resource shortage.</t>
</list></t>
</list></t>
</section>
<section anchor="sec_result-code-permanent"
title="Permanent Failures ">
<t>The Result-Code AVP values, which fall within the permanent
failures category are used to inform the peer that the request
failed, and should not be attempted again. The request may be able
to be satisfied in the future.</t>
<t>The following new values of the Result-Code AVP are defined:</t>
<t><list style="empty">
<t>UNKNOWN_BINDING_TEMPLATE_NAME (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device indicates
that the binding could not be installed or a new session
could not be created because the specified
NAT-Control-Binding-Template AVP, that refers to a
predefined policy template in the NAT-device, is
unknown.</t>
</list></t>
<t>BINDING_FAILURE (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device indicates
that the requested binding(s) could not be installed. For
example: Requested ports are already in use.</t>
</list>MAX_BINDINGS_SET_FAILURE (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device indicates
that it failed to conform to a request to configure the
maximum number of bindings for a session. For example: An
operator defined the maximum number of bindings on the
NAT-device using a method or protocol which takes
precendence over DNCA.</t>
</list></t>
<t>MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT (TBD.RCX)<list
style="empty">
<t>The DNCA Diameter peer within the NAT-device denies the
request because the maximum number of allowed bindings has
been reached for the specified endpoint classifier.</t>
</list></t>
<t>SESSION_EXISTS (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device denies
request to initialize a new session, if it already has a
DNCA session that uses the same set of classifiers as
indicated by the DNCA Diameter peer within the
NAT-controller in the new session initialization
request.</t>
</list></t>
<t>INSUFFICIENT_CLASSIFIERS (TBD.RCX)<list style="empty">
<t>The DNCA Diameter peer within the NAT-device requests to
initialize a new session, if the classifiers in the request
match more than one of the existing sessions on the DNCA
Diameter peer within the NAT-device.</t>
</list></t>
</list></t>
</section>
</section>
<section title="Reused NASREQ Diameter Application AVPs">
<t>The following table describes the AVPs reused from the Diameter
Network Access Server Application <xref target="RFC4005"></xref>;
their AVP Code values, types, and possible flag values; and whether
the AVP MAY be encrypted. The <xref target="RFC3588"></xref> specifies
the AVP Flag rules for AVPs in section 4.5. The Diameter AVP rules are
defined in the <xref target="RFC3588"></xref>, section 4.</t>
<figure anchor="tab-avps-from-nasreq" suppress-title="true">
<artwork><![CDATA[ +---------------------+
| AVP Flag rules |
+------------------+------+------------|----+-----+----+-----|----+
| | AVP | | | |SHLD| MUST| |
| Attribute Name | Code | Value Type|MUST| MAY | NOT| NOT|Encr|
|------------------|------|------------|----+-----+----+-----|----|
| NAS-Port | 5 | Unsigned32 | M | P | | V | Y |
| NAS-Port-Id | 87 | UTF8String | M | P | | V | Y |
| Calling-Station- | 31 | UTF8String | M | P | | V | Y |
| Id | | | | | | | |
| Framed-IP-Address| 8 | OctetString| M | P | | V | Y |
| Framed-Interface-| 96 | Unsigned64 | M | P | | V | Y |
| Id | | | | | | | |
| Framed-IPv6- | 97 | OctetString| M | P | | V | Y |
| Prefix | | | | | | | |
+------------------+------+------------|----+-----+----+-----|----+]]></artwork>
<postamble>Table 2: Reused NASREQ Diameter application AVPs. Please
refer to <xref target="RFC3588"></xref> for the definition of the
Diameter AVP flag rules and the associated abbreviations used in the
table.</postamble>
</figure>
</section>
<section title="Reused AVPs from RFC 4675 ">
<t>The following table describes the AVPs reused from "RADIUS
Attributes for Virtual LAN and Priority Support" specification <xref
target="RFC4675"></xref>; their AVP Code values, types, and possible
flag values; and whether the AVP MAY be encrypted. The <xref
target="RFC3588"></xref> specifies the AVP Flag rules for AVPs in
section 4.5. The Diameter AVP rules are defined in the <xref
target="RFC3588"></xref>, section 4.</t>
<figure anchor="tab-avps-from-rfc4675" suppress-title="true">
<artwork><![CDATA[ +---------------------+
| AVP Flag rules |
+------------------+------+------------|----+-----+----+-----|----+
| | AVP | | | |SHLD| MUST| |
| Attribute Name | Code | Value Type|MUST| MAY | NOT| NOT|Encr|
|------------------|------|------------|----+-----+----+-----|----|
| Egress-VLANID | 56 | OctetString| M | P | | V | Y |
+------------------+------+------------|----+-----+----+-----|----+]]></artwork>
<postamble>Table 3: Reused attributes from RFC 4675. Please refer to
<xref target="RFC3588"></xref> for the definition of the Diameter
AVP flag rules and the associated abbreviations used in the
table.</postamble>
</figure>
</section>
<section title="Reused AVPs from Diameter QoS Application">
<t>The following table describes the AVPs reused from the Traffic
Classification and Quality of Service (QoS) Attributes for Diameter
<xref target="RFC5777"></xref>; their AVP Code values, types, and
possible flag values; and whether the AVP MAY be encrypted. The <xref
target="RFC3588"></xref> specifies the AVP Flag rules for AVPs in
section 4.5. The Diameter AVP rules are defined in the <xref
target="RFC3588"></xref>, section 4.</t>
<figure anchor="tab-avps-from-diameter-qos" suppress-title="true">
<artwork><![CDATA[ +---------+
| AVP |
| Flag |
| rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | |
| Attribute Name Code Data Type |MUST |MAY| Encr |
+-----------------------------------------------+-----+---+---------+
|Port 530 Integer32 | M | P | Y |
|Protocol 513 Enumerated | M | P | Y |
|Direction 514 Enumerated | M | P | Y |
+-----------------------------------------------+-----+---+---------+
]]></artwork>
<postamble>Table 4: Reused QoS-attributes. Please refer to <xref
target="RFC3588"></xref> for the definition of the Diameter AVP flag
rules and the associated abbreviations used in the
table.</postamble>
</figure>
</section>
<section title="Reused AVPs from ETSI ES 283 034, e4 Diameter Application">
<t>The following table describes the AVPs reused from the Diameter e4
Application <xref target="ETSIES283034"></xref>; their AVP Code
values, types, and possible flag values; and whether the AVP MAY be
encrypted. The <xref target="RFC3588"></xref> specifies the AVP Flag
rules for AVPs in section 4.5. The Diameter AVP rules are defined in
the <xref target="RFC3588"></xref>, section 4. The Vendor-ID field in
these AVP header will be set to ETSI (13019).</t>
<figure anchor="tab-avps-from-diameter-e4" suppress-title="true">
<artwork><![CDATA[ +---------+
| AVP |
| Flag |
| rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | |
| Attribute Name Code Data Type |MUST |MAY| Encr |
+-----------------------------------------------+-----+---+---------+
|Address-Realm 301 OctetString | M,V | | Y |
|Logical-Access-Id 302 OctetString | V | M | Y |
|Physical-Access-ID 313 UTF8String | V | M | Y |
+-----------------------------------------------+-----+---+---------+
]]></artwork>
<postamble>Table 5: Reused AVPs from Diameter e4 application. Please
refer to <xref target="RFC3588"></xref> for the definition of the
Diameter AVP flag rules and the associated abbreviations used in the
table.</postamble>
</figure>
</section>
<section anchor="tab-new-avps" title="DNCA Defined AVPs">
<t>The following table describes the new Diameter AVPs defined in this
document; their AVP Code values, types, and possible flag values; and
whether the AVP MAY be encrypted. The <xref target="RFC3588"></xref>
specifies the AVP Flag rules for AVPs in section 4.5. The Diameter AVP
rules are defined in the <xref target="RFC3588"></xref>, section 4.
The AVPs defined here MUST NOT have the V bit in the AVP Flag set.</t>
<figure suppress-title="true">
<artwork><![CDATA[ +---------+
| AVP |
| Flag |
| rules |
+--------------------------------------------------|-----+---+------+
| AVP | | | |
| Attribute Name Code Data Type |MUST |MAY| Encr |
+--------------------------------------------------+-----+---+------+
|NC-Request-Type TBD.AX 8.7.1 Enumerated | M | P | Y |
|NAT-Control-Install TBD.AX 8.7.2 Grouped | M | P | Y |
|NAT-Control-Remove TBD.AX 8.7.3 Grouped | M | P | Y |
|NAT-Control-Definition TBD.AX 8.7.4 Grouped | M | P | Y |
|NAT-Internal-Address TBD.AX 8.7.5 Grouped | M | P | Y |
|NAT-External-Address TBD.AX 8.7.6 Grouped | M | P | Y |
|Max-NAT-Bindings TBD.AX 8.7.7 Unsigned32 | M | P | Y |
|NAT-Control- TBD.AX 8.7.8 OctetString| M | P | Y |
| Binding-Template | | | |
|Duplicate- TBD.AX 8.7.9 UTF8String | M | P | Y |
| Session-ID | | | |
|NAT-External-Port- TBD.AX 8.7.10 Enumerated | M | P | Y |
| Style | | | |
|NAT-Control-Record TBD.AX 9.2.1 Grouped | M | P | Y |
|NAT-Control- TBD.AX 9.2.2 Enumerated | M | P | Y |
| Binding-Status | | | |
|Current-NAT-Bindings TBD.AX 9.2.3 Unsigned32 | M | P | Y |
+--------------------------------------------------+-----+---+------+
]]></artwork>
<postamble>Table 6: New Diameter AVPs. Please refer to <xref
target="RFC3588"></xref> for the definition of the Diameter AVP flag
rules and the associated abbreviations used in the
table.</postamble>
</figure>
<section anchor="avp_NC-Request-Type" title="NC-Request-Type AVP">
<t>The NC-Request-Type AVP (AVP Code TBD.AX) is of type Enumerated
and contains the reason for sending the NAT-Control-Request command.
It shall be present in all NAT-Control-Request messages.</t>
<t>The following values are defined: <list style="empty">
<t>INITIAL_REQUEST (1)<list style="empty">
<t>An Initial Request is to initiate a Diameter NAT control
session between the DNCA Diameter peers.</t>
</list></t>
<t>UPDATE_REQUEST (2)<list style="empty">
<t>An Update Request is used to update bindings previously
installed on a given access session, to add new binding on a
given access session, or to remove one or several binding(s)
activated on a given access session.</t>
</list></t>
<t>QUERY_REQUEST (3)<list style="empty">
<t>Query Request is used to query a NAT-device about the
currently installed bindings for an endpoint classifier.</t>
</list></t>
</list></t>
</section>
<section anchor="avp_NAT-Control-Install"
title="NAT-Control-Install AVP">
<t>The NAT-Control AVP (AVP code TBD.AX) is of type Grouped, and it
is used to activate or install NAT bindings. It also contains
Max-NAT-Bindings that defines the maximum number of NAT bindings
allowed for an endpoint and the NAT-Control-Binding-Template that
references a predefined template on the NAT-device that may contain
static binding, a maximum number of bindings allowed, an IP-address
pool from which external binding addresses should be allocated, etc.
If the NAT-External-Port-Style AVP is present, then the NAT-device
MUST select the external ports for the NAT-Bindings as per the style
specified. The NAT-External-Port-Style is applicable for
NAT-Bindings defined by the NAT-Control-Definition AVPs whose
NAT-External-Address or Port AVPs within the NAT-External-Address
are unspecified.</t>
<t>AVP format:</t>
<figure>
<artwork><![CDATA[ NAT-Control-Install ::= < AVP Header: TBD.AX >
* [ NAT-Control-Definition ]
[ NAT-Control-Binding-Template ]
[ Max-NAT-Bindings ]
[ NAT-External-Port-Style ]
* [ AVP ]]]></artwork>
</figure>
</section>
<section anchor="avp_NAT-Control-Remove"
title="NAT-Control-Remove AVP">
<t>The NAT-Control-Remove AVP (AVP code TBD.AX) is of type Grouped,
and it is used to deactivate or remove NAT-bindings. At least one of
the two AVPs (NAT-Control-Definition AVP,
NAT-Control-Binding-Template AVP) SHOULD be present in the
NAT-Control-Remove AVP.</t>
<t>AVP format:</t>
<figure>
<artwork><![CDATA[ NAT-Control-Remove ::= < AVP Header: TBD.AX >
* [ NAT-Control-Definition ]
[ NAT-Control-Binding-Template ]
* [ AVP ]]]></artwork>
</figure>
</section>
<section anchor="avp_NAT-Control-Definition"
title="NAT-Control-Definition AVP">
<t>The NAT-Control-Definition AVP (AVP code TBD.AX) is of type
Grouped, and it describes a binding.</t>
<t>The NAT-Control-Definition AVP uniquely identifies the binding
between the DNCA Diameter peers.</t>
<t>If both the NAT-Internal-Address and NAT-External-Address AVP(s)
are supplied, it is a pre-defined binding.</t>
<t>If the NAT-External-Address AVP is not specified then the
NAT-device MUST select the external port as per the
NAT-External-Port-Style AVP, if present in the
NAT-Control-Definition AVP.</t>
<t>The Protocol AVP describes the transport protocol for the
binding. The NAT-Control-Definition AVP can contain either zero or
one Protocol AVP. If the Protocol AVP is omitted and if both
internal and external IP-address are specified then the binding
reserves the IP-addresses for all transport protocols.</t>
<t>The Direction AVP is of type Enumerated. It specifies the
direction for the binding. The values of the enumeration applicable
in this context are: "IN","OUT". If Direction AVP is OUT or absent,
the NAT-Internal-Address refers to the IP-address of the endpoint
that needs to be translated. If Direction AVP is "IN",
NAT-Internal-Address is the destination IP-address that has to be
translated.</t>
<t>AVP format:</t>
<figure>
<artwork><![CDATA[ NAT-Control-Definition ::= < AVP Header: TBD.AX >
{ NAT-Internal-Address }
[ Protocol ]
[ Direction ]
[ NAT-External-Address ]
[ Session-Id ]
* [ AVP ]]]></artwork>
</figure>
</section>
<section anchor="avp_NAT-Internal-Address"
title="NAT-Internal-Address AVP">
<t>The NAT-Internal-Address AVP (AVP code TBD.AX) is of type
Grouped. It describes the internal IP-address and port for a
binding. Framed-IPV6-Prefix and Framed-IP-Address AVPs are mutually
exclusive.</t>
<t>AVP format:</t>
<figure>
<artwork><![CDATA[ NAT-Internal-Address ::= < AVP Header: TBD.AX >
[ Framed-IP-Address ]
[ Framed-IPv6-Prefix ]
[ Port]
* [ AVP ]]]></artwork>
</figure>
</section>
<section anchor="avp_NAT-External-Address"
title="NAT-External-Address AVP">
<t>The NAT-External-Address AVP (AVP code TBD.AX) is of type
Grouped, and it describes the external IP-address and port for a
binding. The external IP-address specified in this attribute can be
reused for multiple endpoints by specifying the same address in the
respective NAT-External-Address AVPs. If the external IP-address is
not specified and the NAT-External-Port-Style AVP is specified in
the NAT-Control-Definition AVP then the NAT-device MUST select
external port as per the NAT-External-Port-Style AVP.</t>
<t>AVP format:</t>
<figure>
<artwork><![CDATA[ NAT-External-Address ::= < AVP Header: TBD.AX >
[ Framed-IP-Address ]
[ Port ]
* [ AVP ]]]></artwork>
</figure>
</section>
<section anchor="avp_Max-NAT-Bindings" title="Max-NAT-Bindings">
<t>The Max-NAT-Bindings AVP (AVP code TBD.AX) is of type Unsigned32.
It indicates the maximum number of NAT-bindings allowed for a
particular endpoint.</t>
</section>
<section anchor="avp_NAT-Control-Binding-Rule"
title="NAT-Control-Binding-Template AVP">
<t>The NAT-Control-Binding-Template AVP (AVP code TBD.AX) is of type
OctetString. It defines a name for a policy template that is
predefined at the NAT-device. Details on the contents and structure
of the template and configuration are outside the scope of this
document. The policy to which this AVP refers to may contain
NAT-bindings, IP-address pool for allocating the external IP-address
of a NAT-binding, and maximum number of allowed NAT-bindings. Such
policy template can be reused by specifying the same
NAT-Control-Binding-Template AVP in the corresponding
NAT-Control-Install AVPs of multiple endpoints.</t>
</section>
<section anchor="avp_Duplicate-Session-Id"
title="Duplicate-Session-Id AVP">
<t>The Duplicate-Session-Id AVP (AVP Code TBD.AX) is of type
UTF8String. It is used to report errors and contains the Session-Id
of an existing session.</t>
</section>
<section anchor="avp_NAT-External-Port-Style"
title="NAT-External-Port-Style AVP">
<t>The NAT-External-Port-Style AVP (AVP Code TBD.AX) is of type
Enumerated and contains the style to be followed while selecting the
external port for a NAT-Binding relative to the internal port.</t>
<t>The following values are defined: <list style="empty">
<t>FOLLOW_INTERNAL_PORT_STYLE (1)<list style="empty">
<t>External port numbers selected MUST follow the same
sequence and oddity as the internal ports of the
NAT-bindings. The port odditity is required to support
protocols like RTP and RTCP as defined in <xref
target="RFC3550"></xref>. If for example the internal port
in a requested NAT-binding is odd numbered then the external
port allocated MUST also be odd numbered, and vice versa for
an even numbered port. In addition, the sequence of port
numbering is maintained: If internal ports are consecutive,
then the NAT-device MUST choose consecutive external ports
for the NAT-bindings.</t>
</list></t>
</list></t>
</section>
</section>
</section>
<section anchor="sec-accounting" title="Accounting Commands">
<t>The DNCA reuses session based accounting as defined in the Diameter
Base Protocol<xref target="RFC3588"></xref> to report the bindings per
endpoint. This reporting is achieved by sending Diameter Accounting
Requests (ACR) [Start, Interim and Stop] from the DNCA Diameter peer
within the NAT-device to its associated DNCA Diameter peer within the
NAT-controller.</t>
<t>The DNCA Diameter peer within the NAT-device sends an ACR Start on
receiving a NCR with NC-Request-Type AVP set to INITIAL_REQUEST for a
session or on creation of the first binding for a session requested in
an earlier NCR. DNCA may send ACR Interim updates, if required, either
due to a change in bindings resulting from a NCR with NC-Request-Type
AVP set to UPDATE_REQUEST, or periodically as specified in
Acct-Interim-Interval by the DNCA Diameter peer within the
NAT-controller, or when it creates or tears down bindings. An ACR Stop
is sent by the DNCA Diameter peer within the NAT-device on receiving
STR.</t>
<t>The function of correlating the multiple bindings used by an endpoint
at any given time is relegated to the post processor.</t>
<t>The DNCA Diameter peer within the NAT-device may trigger an interim
accounting record when the maximum number of bindings, if received in an
NCR, is reached.</t>
<section title="NAT Control Accounting Messages">
<t>The ACR and ACA messages are reused as defined in the Diameter Base
Protocol <xref target="RFC3588"></xref> for exchanging endpoint NAT
binding details between the DNCA Diameter peers. The DNCA Application
IDs is used in the accounting commands. ACR contains one or more
optional NAT-Control-Record AVPs to report the bindings. The
NAT-device indicates the number of allocated NAT bindings to the
NAT-controller using the Current-NAT-Bindings AVP. This number needs
to match the number of bindings identified as active within the
NAT-Control-Record AVP.</t>
</section>
<section title="NAT Control Accounting AVPs">
<t>In addition to AVPs for ACR specified in <xref
target="RFC3588"></xref>, the DNCA Diameter peer within the NAT-device
must add the NAT-Control-Record AVP.</t>
<section anchor="avp_NAT-Control-Record" title="NAT-Control-Record">
<t>The NAT-Control-Record AVP (AVP code TBD.AX) is of type Grouped.
It describes a binding and its status. If NAT-Control-Binding-Status
is set to Created, Event-Timestamp indicates the binding creation
time. If NAT-Control-Binding-Status is set to Removed,
Event-Timestamp indicates the binding removal time. If
NAT-Control-Binding-Status is active, Event-Timestamp need not be
present; if a value is present, it indicates that binding is active
at the given time.</t>
<figure>
<artwork><![CDATA[ NAT-Control-Record ::= < AVP Header: TBD.AX >
{ NAT-Control-Definition }
{ NAT-Control-Binding-Status }
[ Event-Timestamp ]]]></artwork>
</figure>
</section>
<section anchor="avp_NAT-Control-Binding-Status"
title="NAT-Control-Binding-Status">
<t>The NAT-Control-Binding-Status AVP (AVP code TBD.AX) is of type
enumerated. It indicates the status of the binding - created,
removed, or active.</t>
<t>The following values are defined: <list style="empty">
<t>Created (1)<list style="empty">
<t>NAT binding is created.</t>
</list></t>
<t>Active (2)<list style="empty">
<t>NAT binding is active.</t>
</list></t>
<t>Removed (3)<list style="empty">
<t>NAT binding was removed.</t>
</list></t>
</list></t>
</section>
<section anchor="avp_Current-NAT-Bindings"
title="Current-NAT-Bindings">
<t>The Current-NAT-Bindings AVP (AVP code TBD.AX) is of type
Unsigned32. It indicates the number of NAT bindings active on the
NAT-device.</t>
</section>
</section>
</section>
<section anchor="sec-avp-occurence-table" title="AVP Occurrence Table">
<t>The following sections present the AVPs defined in this document and
specify the Diameter messages in which they can be present. Note: AVPs
that can only be present within a Grouped AVP are not represented in
this table.</t>
<t>The table uses the following symbols:</t>
<t><list style="empty">
<t><list hangIndent="10" style="hanging">
<t hangText="0">The AVP MUST NOT be present in the message.</t>
<t hangText="0+">Zero or more instances of the AVP can be
present in the message.</t>
<t hangText="0-1">Zero or one instance of the AVP can be present
in the message. It is considered an error if there is more than
one instance of the AVP.</t>
<t hangText="1">One instance of the AVP MUST be present in the
message.</t>
<t hangText="1+">At least one instance of the AVP MUST be
present in the message.</t>
</list></t>
</list></t>
<section title="DNCA AVP Table for NAT Control Initial and Update Requests">
<t>The following table lists DNCA specific AVPs that have to be
present in NCRs and NCAs with NC-Request-Type set to INITIAL_REQUEST
or UPDATE_REQUEST.</t>
<figure>
<artwork><![CDATA[ +-------------------+
| Command Code |
+-----------------------------------+-------------------+
| Attribute Name NCR NCA |
+-------------------------------------------------------+
|NC-Request-Type 1 1 |
|NAT-Control-Install 0-1 0 |
|NAT-Control-Remove 0-1 0 |
|NAT-Control-Definition 0 0 |
|Current-NAT-Bindings 0 0 |
|Duplicate-Session-Id 0 0-1 |
+-------------------------------------------------------+]]></artwork>
</figure>
<t>Note that any combination of "NAT-Control-Install" and
"NAT-Control-Remove" AVPs could be present in an update or initial
requests. Consider the following examples:</t>
<t><list style="empty">
<t>Neither "NAT-Control-Install AVP" nor "NAT-Control-Remove AVP"
are present: This could for example be the case if the
NAT-controller would only want to receive accounting information,
but not control NAT-bindings.</t>
<t>Only "NAT-Control-Install AVP" is present: This could for
example be the case if a new NAT-binding is installed for an
existing session.</t>
<t>Only "NAT-Control-Remove AVP" is present: This could for
example be the case if a new NAT-binding is removed from an
existing session.</t>
<t>Both, "NAT-Control-Install AVP" and "NAT-Control-Remove AVP"
are present: This could for example be the case if a formerly
created NAT-binding is removed and a new NAT-binding is
established within the same request.</t>
</list></t>
</section>
<section title="DNCA AVP Table for Session Query request">
<t>The following table lists DNCA specific AVPs that have to be
present in NCRs and NCAs with NC-Request-Type set to
QUERY_REQUEST.</t>
<figure>
<artwork><![CDATA[ +-------------------+
| Command Code |
+-----------------------------------+-------------------+
| Attribute Name NCR NCA |
+-------------------------------------------------------+
|NC-Request-Type 1 1 |
|NAT-Control-Install 0 0 |
|NAT-Control-Remove 0 0 |
|NAT-Control-Definition 0 0+ |
|NAT-External-Address 0+ 0 |
|Current-NAT-Bindings 0 1 |
|Duplicate-Session-Id 0 0 |
+-------------------------------------------------------+]]></artwork>
</figure>
</section>
<section title="DNCA AVP Table for Accounting Message">
<t>The following table lists DNCA specific AVPs, which may or may not
be present in ACR and ACA messages.</t>
<figure>
<artwork><![CDATA[ +-------------------+
| Command Code |
+-----------------------------------+-------------------+
| Attribute Name ACR ACA |
+-------------------------------------------------------+
|NAT-Control-Record 0+ 0 |
|Current-NAT-Bindings 1 0 |
+-------------------------------------------------------+
]]></artwork>
</figure>
</section>
</section>
<!-- -->
<!-- Possibly a 'Contributors' section ...
-->
<section anchor="IANA" title="IANA Considerations">
<t>This section contains the namespaces that have either been created in
this specification, or the values assigned to existing namespaces
managed by IANA.</t>
<t>In the subsections below, when we speak about review by a Designated
Expert, please note that the designated expert will be assigned by the
IESG. Initially, such Expert discussions take place on the AAA WG
mailing list.</t>
<section title="Application Identifier">
<t>This specification assigns the value <TBD.APP-ID>, 'Diameter
NAT Control Application', to the Application Identifier namespace
defined in <xref target="RFC3588"></xref>. See <xref
target="sec-dnca"></xref> for more information.</t>
</section>
<section title="Command Codes">
<t>This specification uses the value <TBD.COM-CODE> from the
Command code namespace defined in <xref target="RFC3588"></xref> for
the NAT-Control-Request (NCR), NAT-Control-Answer (NCA) commands. See
<xref target="sec-dnca-ncr"></xref> and <xref
target="sec-dnca-nca"></xref> for more information on these
commands.</t>
</section>
<section title="AVP Codes">
<t>This specification assigns the values <TBD.AX> from the AVP
code namespace defined in <xref target="RFC3588"></xref>. See <xref
target="tab-new-avps"></xref> for the assignment of the namespace in
this specification.</t>
</section>
<section title="Result-Code AVP Values ">
<t>This specification assigns the values <TBD.RCX> (4xxx, 5xxx,
5xxx, 5xxx, 5xxx,5xxx) from the Result-Code AVP value namespace
defined in <xref target="RFC3588"></xref>. See <xref
target="sec_result-codes"></xref> for the assignment of the namespace
in this specification.</t>
</section>
<section title="NC-Request-Type AVP">
<t>As defined in <xref target="avp_NC-Request-Type"></xref>, the
NC-Request-Type AVP includes Enumerated type values 1 - 3. IANA has
created and is maintaining a namespace for this AVP. All remaining
values are available for assignment by a Designated Expert <xref
target="RFC5226"></xref>.</t>
</section>
<section title="NAT-External-Port-Style AVP">
<t>As defined in <xref target="avp_NAT-External-Port-Style"></xref>,
the NAT-External-Port-Style AVP includes Enumerated type value 1. IANA
has created and is maintaining a namespace for this AVP. All remaining
values are available for assignment by a Designated Expert <xref
target="RFC5226"></xref>.</t>
</section>
<section title="NAT-Control-Binding-Status AVP">
<t>As defined in <xref target="avp_NC-Request-Type"></xref>, the
NAT-Control-Binding-Status AVP includes Enumerated type values 1 - 3.
IANA has created and is maintaining a namespace for this AVP. All
remaining values are available for assignment by a Designated Expert
<xref target="RFC5226"></xref>.</t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>This document describes procedures for controlling NAT related
attributes and parameters by an entity, which is non-local to the device
performing NAT. This section discusses security considerations for DNCA.
This includes the interactions between the Diameter peers within a
NAT-controller and a NAT-device as well as general considerations for
NAT-control in a service provider network.</t>
<t>Security between a NAT-controller and a NAT-device has a number of
components: authentication, authorization, integrity, and
confidentiality.</t>
<t>Authentication refers to confirming the identity of an originator for
all datagrams received from the originator. Lack of authentication of
Diameter messages between the Diameter peers can jeopardize the
fundamental service of the peering network elements. A consequence of
not authenticating the message sender by the recipient would be that an
attacker could spoof the identity of a "legitimate" authorizing entity
in order to change the behavior of the receiver. An attacker could for
example launch a denial of service attack by setting the maximum number
of bindings for a session on the NAT-device to zero; provision bindings
on a NAT-device which include IP-addresses already in use in other parts
of the network; or request session termination of the Diameter session
and hamper an endpoint's (i.e. a user's) connectivity. Lack of
authentication of a NAT-device to a NAT-controller could lead to
situations where the NAT-device could provide a wrong view of the
resources (i.e. NAT-bindings). In addition, NAT Binding Predefined
template on the NAT-device could be configured differently than expected
by the NAT-controller. Failing of any of the two DNCA Diameter peers to
provide the required credentials should be subject to logging. The
corresponding logging infrastructure of the operator SHOULD be built in
a way that it can mitigate potential denial of service attacks resulting
from large amounts of logging events. This could include proper
dimensioning of the logging infrastructure combined with policing the
maximum amount of logging events accepted by the logging system to a
threshold which the system is known to be able to handle.</t>
<t>Authorization refers to whether a particular authorizing entity is
authorized to signal a network element requests for one or more
applications, adhering to a certain policy profile. Failing the
authorization process might indicate a resource theft attempt or failure
due to administrative and/or credential deficiencies. In either case,
the network element should take the proper measures to log such
attempts.</t>
<t>Integrity is required to ensure that a Diameter message exchanged
between the Diameter peers has not been maliciously altered by
intermediate devices. The result of a lack of data integrity enforcement
in an untrusted environment could be that an impostor will alter the
messages exchanged between the peers. This could cause a change of
behavior of the peers, including the potential of a denial of
service.</t>
<t>Confidentiality protection of Diameter messages ensures that the
signaling data is accessible only to the authorized entities. When
signaling messages between the DNCA Diameter peers traverse untrusted
networks, lack of confidentiality will allow eavesdropping and traffic
analysis.</t>
<t>Diameter offers security mechanisms to deal with the functionality
demanded above. DNCA makes use of the capabilities offered by Diameter
and the underlying transport protocols to deliver these requirements
(see <xref target="sec-diameter-messages"></xref>). If the DNCA
communication traverses untrusted networks, messages between DNCA
Diameter peers SHOULD be secured using either IPsec or TLS. Please refer
to <xref target="RFC3588"></xref>, section 13 for details. DNCA Diameter
peers SHOULD perform bilateral authentication, authorization as well as
procedures to ensure integrity and confidentiality of the information
exchange. In addition the Session-Id chosen for a particular Diameter
session SHOULD be chosen in a way that it is hard to guess in order to
mitigate issues through potential message replay.</t>
<t>DNCA Diameter peers SHOULD have a mutual trust setup. This document
does not specify a mechanisms for authorization between the DNCA
Diameter peers. The DNCA Diameter peers SHOULD be provided with
sufficient information to make an authorization decision. The
information can come from various sources, for example the peering
devices could store local authentication policy, listing the identities
of authorized peers.</t>
<t>Any mechanism or protocol providing control of a NAT-device, and DNCA
is an example of such a control mechanism, could allow for misuse of the
NAT-device given that it enables the definition of per-destination or
per-source rules. Misuse could include anti-competitive practices among
providers, censorship, crime, etc. NAT-control could be used as a tool
for preventing or redirecting access to particular sites. For instance,
by controlling the NAT bindings, one could ensure that endpoints aren't
able to receive particular flows, or that those flows are redirected to
a relay that snoops or tampers with traffic instead of directly
forwarding the traffic to the intended endpoint. In addition one could
set up a binding in a way that the source IP address used is one of a
relay so that traffic coming back can be snooped on or interfered with.
The operator also needs to consider security threats resulting from
unplanned termination of the DNCA session. Unplanned session
termination, which could e.g. happen due to an attacker taking down the
NAT-controller, leads to the NAT-device cleaning up the state associated
with this session after a grace period. If the grace period is set to
zero, the endpoint will experience an immediate loss of connectivity to
services reachable through the NAT-device following the termination of
the DNCA session.The protections on DNCA and its Diameter protocol
exchanges don't prevent such abuses of NAT-control. Prevention of
mis-use or mis-configuration of a NAT-device by an authorized
NAT-controller is beyond the scope of this protocol specification. A
service provider deploying DNCA needs to make sure that higher layer
processes and procedures are put in place which allow them to detect and
mitigate misuses.</t>
</section>
<section title="Examples">
<t>This section shows example DNCA message content and exchange.</t>
<section title="DNCA Session Establishment Example">
<t><xref target="fig-session-establishment-example"></xref> depicts a
typical call flow for DNCA session establishment.</t>
<t>In this example, the NAT-controller:</t>
<t><list style="letters">
<t>requests a maximum of 100 NAT-bindings for the endpoint.</t>
<t>defines a static binding for a TCP connection which associates
the internal IP-Address:Port 192.0.2.1:80 with the external
IP-Address:Port 198.51.100.1:80 for the endpoint.</t>
<t>requests the use of a preconfigured template called
"local-policy" while creating NAT-bindings for the endpoint.</t>
</list></t>
<figure anchor="fig-session-establishment-example"
title="Initial NAT control request and session establishment example">
<artwork><![CDATA[endpoint NAT-Controller (within NAS) NAT-device
| | |
| | |
| 1. Trigger | |
|--------------------------->| |
| +-------------------------------------+ |
| | 2. Determine that NAT control | |
| | is required for the endpoint | |
| +-------------------------------------+ |
| | |
| | |
| ...................................
| .| 3. Diameter Base CER/CEA |.
| .|<----------------------------->|.
| ...................................
| | |
| | |
| | 4. NCR |
| |------------------------------>|
| | |
| | 5. DNCA session
| | established
| | |
| | 6. NCA |
| |<------------------------------|
| | |
| | |
| 7. Data traffic |
|----------------------------------------------------------->|
| | |
| | |
| | 8. NAT Bindings
| | created as per
| | directives in the
| | DNCA session
| | |
]]></artwork>
</figure>
<t>Detailed description of the steps shown in <xref
target="fig-session-establishment-example"></xref>:</t>
<t><list style="numbers">
<t>The NAT-controller (co-located with the NAS here) creates state
for an endpoint based on a trigger. This could for example be the
successful establishment of a Point-to-Point Protocol (PPP) <xref
target="RFC1661"></xref> access session.</t>
<t>Based on the configuration of the DNCA Diameter peer within the
NAT-controller, the NAT-controller determines that NAT-control is
required and is to be enforced at a NAT-device.</t>
<t>If there is no Diameter session already established with the
DNCA Diameter peer within NAT-device, a Diameter connection is
established and Diameter Base CER/CEA are exchanged.</t>
<t>The NAT-Controller creates an NCR message (see below) and sends
it to the NAT-device. This example shows IPv4 to IPv4 address and
port translation. For IPv6 to IPv4 translation, the
Framed-IP-Address AVP would be replaced by the Framed-IPv6-Address
AVP with the value set to the IPv6 address of the endpoint.
<figure anchor="fig-NAT-session-establish-example"
suppress-title="true">
<artwork><![CDATA[ < NC-Request > ::= < Diameter Header: TBD.COM-CODE, REQ, PXY>
Session-Id = "natC.example.com:33041;23432;"
Auth-Application-Id = <DNCA Application ID>
Origin-Host = "natC.example.com"
Origin-Realm = "example.com"
Destination-Realm = "example.com"
Destination-Host = "nat-device.example.com"
NC-Request-Type = INITIAL_REQUEST
User-Name = "subscriber_example1"
Framed-IP-Address = "192.0.2.1"
NAT-Control-Install = {
NAT-Control-Definition = {
Protocol = TCP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 80
}
NAT-External-Address = {
Framed-IP-Address = "198.51.100.1"
Port = 80
}
}
Max-NAT-Bindings = 100
NAT-Control-Binding-Template = "local-policy"
}]]></artwork>
</figure></t>
<t>The NAT-device establishes a DNCA session as it is able to
comply with the request.</t>
<t>The NAT-device sends an NCA to indicate the successful
completion of the request. <figure suppress-title="true">
<artwork><![CDATA[ <NC-Answer> ::= < Diameter Header: TBD.COM-CODE, PXY >
Session-Id = "natC.example.com:33041;23432;"
Origin-Host = "nat-device.example.com"
Origin-Realm = "example.com"
NC-Request-Type = INITIAL_REQUEST
Result-Code = DIAMETER_SUCCESS
]]></artwork>
</figure></t>
<t>The endpoint sends packets that reach the NAT-device.</t>
<t>The NAT-device performs NAT for traffic received from the
endpoint with source address 192.0.2.1. Traffic with source
IP-address 192.0.2.1 and port 80 are translated to the external
IP-address 198.51.100.1 and port 80. Traffic with source
IP-address 192.0.2.1 and a source port different from 80 will be
translated to IP-address 198.51.100.1 and a port chosen by the
NAT-device. Note that this example assumes that the NAT-device
follows typical binding allocation rules for endpoints, in that
only a single external IP-address is used for all traffic received
from a single IP-address of an endpoint. The NAT-device will allow
a maximum of 100 NAT-bindings be created for the endpoint.</t>
</list></t>
</section>
<section title="DNCA Session Update with Port Style Example">
<t>This section gives an example for a DNCA session update: A new set
of NAT-bindings is requested for an existing session. The request
contains a directive ( the "NAT-External-Port-Style" AVP set to
FOLLOW_INTERNAL_PORT_STYLE) that directs the NAT-device to maintain
port-sequence and port-oddity for the newly created NAT-bindings. In
the example shown, the internal ports are UDP port 1036 and 1037. The
NAT-device follows the directive selects the external ports
accordingly. The NAT-device would for example create a mapping of
192.0.2.1:1036 to 198.51.100.1:5056 and 192.0.2.1:1037 to
198.51.100.1:5057, thereby maintaining port oddity (1036->5056,
1037->5057) and sequence ( the consecutive internal ports 1036 and
1037 map to the consecutive external ports 5056 and 5057).</t>
<figure anchor="fig-NAT-session-update-example" suppress-title="true">
<artwork><![CDATA[ < NC-Request > ::= < Diameter Header: TBD.COM-CODE, REQ, PXY>
Session-Id = "natC.example.com:33041;23432;"
Auth-Application-Id = <DNCA Application ID>
Origin-Host = "natC.example.com"
Origin-Realm = "example.com"
Destination-Realm = "example.com"
Destination-Host = "nat-device.example.com"
NC-Request-Type = UPDATE_REQUEST
NAT-Control-Install = {
NAT-Control-Definition = {
Protocol = UDP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 1035
}
}
NAT-Control-Definition = {
Protocol = UDP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 1036
}
}
NAT-External-Port-
Style = FOLLOW_INTERNAL_PORT_STYLE
}]]></artwork>
</figure>
</section>
<section title="DNCA Session Query Example">
<t>This section shows an example for DNCA session query for a
subscriber whose internal IP-Address is 192.0.2.1.</t>
<figure anchor="fig-NAT-session-query-example" suppress-title="true">
<artwork><![CDATA[ < NC-Request > ::= < Diameter Header: TBD.COM-CODE, REQ, PXY>
Auth-Application-Id = <DNCA Application ID>
Origin-Host = "natC.example.com"
Origin-Realm = "example.com"
Destination-Realm = "example.com"
Destination-Host = "nat-device.example.com"
NC-Request-Type = QUERY_REQUEST
Framed-IP-Address = "192.0.2.1"]]></artwork>
</figure>
<t>The NAT-device constructs an NCA to report all currently active
NAT-bindings whose internal address is 192.0.2.1.</t>
<figure anchor="fig-NAT-session-query-answer-example"
suppress-title="true">
<artwork><![CDATA[ <NC-Answer> ::= < Diameter Header: TBD.COM-CODE, PXY >
Origin-Host = "nat-device.example.com"
Origin-Realm = "example.com"
NC-Request-Type = QUERY_REQUEST
NAT-Control-Definition = {
Protocol = TCP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 80
}
NAT-External-Address = {
Framed-IP-Address = "198.51.100.1"
Port = 80
}
Session-Id = "natC.example.com:33041;23432;"
}
NAT-Control-Definition = {
Protocol = TCP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 1036
}
NAT-External-Address = {
Framed-IP-Address = "198.51.100.1"
Port = 5056
}
Session-Id = "natC.example.com:33041;23432;"
}
NAT-Control-Definition = {
Protocol = TCP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 1037
}
NAT-External-Address = {
Framed-IP-Address = "198.51.100.1"
Port = 5057
}
Session-Id = "natC.example.com:33041;23432;"
} ]]></artwork>
</figure>
</section>
<section title="DNCA Session Termination Example">
<t>In this example the NAT-controller decides to terminate the
previously established DNCA session. This could for example be the
case as a result of an access session (e.g. a PPP session) associated
with an endpoint been torn down.</t>
<figure anchor="fig-session-teardown-example"
title=" NAT control session termination example ">
<artwork><![CDATA[
NAT-Controller NAT-device
| |
| |
+--------------+ |
| 1. Trigger | |
+--------------+ |
| |
| |
| 2. STR |
|-------------------------------------->|
| |
| 3. DNCA session
| lookup
| 4. ACR |
|<--------------------------------------|
| |
| 5. ACA |
|-------------------------------------->|
| |
| |
| 6. DNCA bindings
| and session cleanup
| |
| 7. STA |
|<--------------------------------------|
| |]]></artwork>
</figure>
<t>The following steps describe the sequence of events for tearing
down the DNCA session in the example above:</t>
<t><list style="numbers">
<t>The NAT-controller receives a trigger that a DNCA session
associated with a specific endpoint should be terminated. An
example event could be the termination of the PPP <xref
target="RFC1661"></xref> access session to an endpoint in a NAS.
The NAS correspondingly triggers the NAT-controller request
tear-down of the associated DNCA session.</t>
<t>The NAT-controller creates the required NCR message and sends
it to the NAT-device: <figure
anchor="fig-NAT-session-termination-example"
suppress-title="true">
<artwork><![CDATA[ < STR > ::= < Diameter Header: 275, REQ, PXY>
Session-Id = "natC.example.com:33041;23432;"
Auth-Application-Id = <DNCA Application ID>
Origin-Host = "natC.example.com"
Origin-Realm = "example.com"
Destination-Realm = "example.com"
Destination-Host = "nat-device.example.com"
Termination-Cause = DIAMETER_LOGOUT
]]></artwork>
</figure></t>
<t>The NAT-device looks up the DNCA session based on the
Session-Id AVP and finds a previously established active
session.</t>
<t>The NAT-device reports all NAT-bindings established for that
subscriber using an ACR: <figure
anchor="fig-NAT-session-accounting-request-example"
suppress-title="true">
<artwork><![CDATA[ < ACR > ::= < Diameter Header: 271, REQ, PXY>
Session-Id = "natC.example.com:33041;23432;"
Auth-Application-Id = <DNCA Application ID>
Origin-Host = "nat-device.example.com"
Origin-Realm = "example.com"
Destination-Realm = "example.com"
Destination-Host = "natC.example.com"
Accounting-Record-Type = STOP_RECORD
Accounting-Record-Number = 1
NAT-Control-Record = {
NAT-Control-Definition = {
Protocol = TCP
Direction = OUT
NAT-Internal-Address = {
Framed-IP-Address = "192.0.2.1"
Port = 5001
}
NAT-External-Address = {
Framed-IP-Address = "198.51.100.1"
Port = 7777
}
}
NAT-Control-Binding-Status = Removed
}
]]></artwork>
</figure></t>
<t>The NAT-controller receives and processes the ACR as per its
configuration. It responds with an ACA to the NAT-device. <figure
suppress-title="true">
<artwork><![CDATA[ <ACA> ::= < Diameter Header: 271, PXY >
Session-Id = "natC.example.com:33041;23432;"
Origin-Host = "natC.example.com"
Origin-Realm = "example.com"
Result-Code = DIAMETER_SUCCESS
Accounting-Record-Type = STOP_RECORD
Accounting-Record-Number = 1
]]></artwork>
</figure></t>
<t>On receipt of the ACA the NAT-device cleans up all NAT-bindings
and associated session state for the endpoint.</t>
<t>NAT-device sends an STA. On receipt of the STA the
NAT-controller will clean up the corresponding session state.
<figure suppress-title="true">
<artwork><![CDATA[ <STA> ::= < Diameter Header: 275, PXY >
Session-Id = "natC.example.com:33041;23432;"
Origin-Host = "nat-device.example.com"
Origin-Realm = "example.com"
Result-Code = DIAMETER_SUCCESS
]]></artwork>
</figure></t>
</list></t>
</section>
</section>
<section title="Acknowledgements">
<t>The authors would like to thank Jari Arkko, Wesley Eddy, Stephen
Farrell, Miguel A. Garcia, David Harrington, Jouni Korhonen, Matt
Lepinski, Avi Lior, Chris Metz, Pallavi Mishra, Lionel Morand, Robert
Sparks, Martin Stiemerling, Dave Thaler, Hannes Tschofenig, Sean Turner,
Shashank Vikram, Greg Weber, and Glen Zorn for their input on this
document.</t>
</section>
<section title="Change History (to be removed prior to publication as an RFC) ">
<t>Changes from -00 to -01</t>
<t><list style="letters">
<t>new values for Result-Code AVP used - instead of
Experimental-Result AVP</t>
<t>added support for transport specific binding (UDP/TCP)</t>
<t>added support for twice-NAT</t>
<t>clarified the use of the two different types of
query-requests</t>
</list></t>
<t>Changes from -01 to -02</t>
<t><list style="letters">
<t>Reference to pull mode removed, session initiation event
clarified in section 4.1</t>
<t>added Redirect-* AVPs in NCA command</t>
<t>Removed reference to Called-Station-Id AVP in NCR command</t>
<t>Editorial changes</t>
<t>added support for bindings providing AFT (NAT64)</t>
</list>Changes from -02 to -03<list style="letters">
<t>Editorial changes</t>
</list>Changes from -03 to -04<list style="letters">
<t>Editorial changes suggested in WG last call review</t>
<t>Removed NCR Request type terminate and replaced with STR</t>
<t>All references to Auth-Session-State are removed and a new
section to describe FSM for Manager and Agent has been added</t>
<t>Clarified reuse of External address and address pools among
multiple subscribers</t>
</list>Changes from -04 to -05<list style="letters">
<t>Removed references to Large Scale NAT as per review comments</t>
</list>Changes from -05 to -06<list style="letters">
<t>Editorial changes</t>
</list>Changes from -06 to -07<list style="letters">
<t>Added a note in section 4.3 stating the state of pre-existing
bindings on update failure</t>
<t>Security considerations are made consistent between sections 5.1
and 12</t>
<t>Editorial changes</t>
</list>Changes from -07 to -08<list style="letters">
<t>Added section 4.6 to describe session abort</t>
<t>Editorial changes</t>
<t>Nomenclature change: From DNCA Agent/Manager to DNCA Diameter
peers identifying the location where they reside (NAT-controller or
NAT-device)</t>
<t>IANA consideration Section format changes</t>
<t>Updated security section (included considerations directly,
rather than referring to Diameter QoS similarities).</t>
</list></t>
<t>Changes from -08 to -09</t>
<t><list style="letters">
<t>expanded on the need for an SP controlling the maximum number of
bindings of an endpoint (see introduction section)</t>
<t>added a paragraph in the security section outlining general
mis-uses of NAT-control (non specific to DNCA), with DNCA being an
example of such a NAT-control protocol</t>
<t>editorial changes</t>
</list>Changes from -09 to -10<list style="letters">
<t>Section 4 and security considerations updated with RFC 2119
language</t>
<t>NAT-External-Port-Style AVP added to aid external port oddity
requirement as per MIDCOM framework</t>
<t>NAT related RFCs added in normative reference</t>
<t>Section 13 added to provide example DNCA message exchange
flows</t>
<t>Added a description to provide DNCA comparison with MIDCOM</t>
<t>n:1 deployment model for NAT-controllers and NAT-devices
explicitly specified</t>
<t>editorial changes as per IESG DISCUSS comments</t>
</list></t>
<t>Changes from -10 to -11<list style="letters">
<t>clarified DNCA session query to be done after Diameter session is
established</t>
<t>Section 4.4 Session Termination updated to specify resource
cleanup at NAT-Device upon session termination</t>
<t>Removed Framed-IP-Netmask AVP from NAT-External-Address as
external address is fully defined by Framed-IP-Address AVP</t>
<t>Updated Section 12 to highlight Session-Id to be chosen such that
it is hard to guess</t>
<t>editorial changes as per IESG DISCUSS</t>
</list></t>
<t>Changes from -11 to -12<list style="letters">
<t>endpoint replaces references to end point and user and defines
what Endpoint means in this draft</t>
<t>editorial changes as per IESG DISCUSS</t>
</list></t>
<t>Changes from -12 to -13<list style="letters">
<t>Section 4.3 session query updated to use NAT-External-Address for
external IP-address based query</t>
</list></t>
<t>Changes from -13 to -14<list style="letters">
<t>Added NAT-External-Address in NC-request for session query by
external IP-address</t>
<t>Reordered all mandatory AVPs in NCR and NCA to appear before
optional AVPs</t>
</list></t>
<t>Changes from -14 to -15<list style="letters">
<t>As part of IESG discuss - clarified that multiple methods if used
along with DNCA for NAT control should be configured to prevent
conflict.</t>
<t>Clarified misuse of NAT-device by a Diameter authorized
NAT-controller using DNCA is beyond the scope of this protocol
specification.</t>
<t>Editorial updates.</t>
</list></t>
<t>Changes from -15 to -16<list style="letters">
<t>Extended section covering case of a single NAT-device controlled
by multiple NAT-ontrollers which use different protocols for
configuring the NAT-device.</t>
<t>Added NAT-device state cleanup in case of unexpected/unplanned
termination of Diameter session or application either on
NAT-controller or NAT-device.</t>
<t>Added MAX_BINDINGS_SET_FAILURE failure case (for those scenarios
where the maximum number of bindings cannot be set by the
controller)</t>
</list></t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
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