Internet Engineering Task Force F. Brockners
Internet-Draft S. Bhandari
Intended status: Standards Track Cisco
Expires: August 20, 2011 V. Singh
V. Fajardo
Telcordia Technologies
February 16, 2011
Diameter Network Address and Port Translation Control Application
draft-ietf-dime-nat-control-07
Abstract
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 cope with IPv4-address space
completion. 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.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 20, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Deployment Framework . . . . . . . . . . . . . . . . . . . . . 7
3.1. Deployment Scenario . . . . . . . . . . . . . . . . . . . 7
3.2. Diameter NAPT Control Application Overview . . . . . . . . 8
3.3. Deployment Scenarios For DNCA . . . . . . . . . . . . . . 9
4. DNCA Session Establishment and Management . . . . . . . . . . 11
4.1. Parties Involved . . . . . . . . . . . . . . . . . . . . . 11
4.2. Session Establishment . . . . . . . . . . . . . . . . . . 11
4.3. Session Re-Authorization . . . . . . . . . . . . . . . . . 13
4.4. Session and Binding Query . . . . . . . . . . . . . . . . 15
4.5. Session Termination . . . . . . . . . . . . . . . . . . . 17
4.6. DNCA Manager and Agent Failures . . . . . . . . . . . . . 18
5. Use Of The Diameter Base Protocol . . . . . . . . . . . . . . 18
5.1. Securing Diameter Messages . . . . . . . . . . . . . . . . 19
5.2. Accounting Functionality . . . . . . . . . . . . . . . . . 19
5.3. Use Of Sessions . . . . . . . . . . . . . . . . . . . . . 19
5.4. Routing Considerations . . . . . . . . . . . . . . . . . . 19
5.5. Advertising Application Support . . . . . . . . . . . . . 19
6. DNCA Commands . . . . . . . . . . . . . . . . . . . . . . . . 20
6.1. NAT-Control Request (NCR) Command . . . . . . . . . . . . 20
6.2. NAT-Control Answer (NCA) Command . . . . . . . . . . . . . 21
7. NAT Control Application Session State Machine . . . . . . . . 21
8. DNCA AVPs . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1. Reused Base Protocol AVPs . . . . . . . . . . . . . . . . 24
8.2. Additional Result-Code AVP Values . . . . . . . . . . . . 25
8.2.1. Success . . . . . . . . . . . . . . . . . . . . . . . 25
8.2.2. Transient Failures . . . . . . . . . . . . . . . . . . 25
8.2.3. Permanent Failures . . . . . . . . . . . . . . . . . . 26
8.3. Reused NASREQ Diameter Application AVPs . . . . . . . . . 27
8.4. Reused from RFC 4675 . . . . . . . . . . . . . . . . . . . 27
8.5. Reused from Diameter QoS Application . . . . . . . . . . . 27
8.6. Reused from ETSI ES 283 034, e4 Diameter Application . . . 28
8.7. DNCA Defined AVPs . . . . . . . . . . . . . . . . . . . . 29
8.7.1. NC-Request-Type AVP . . . . . . . . . . . . . . . . . 29
8.7.2. NAT-Control-Install AVP . . . . . . . . . . . . . . . 30
8.7.3. NAT-Control-Remove AVP . . . . . . . . . . . . . . . . 30
8.7.4. NAT-Control-Definition AVP . . . . . . . . . . . . . . 30
8.7.5. NAT-Internal-Address AVP . . . . . . . . . . . . . . . 31
8.7.6. NAT-External-Address AVP . . . . . . . . . . . . . . . 31
8.7.7. Max-NAT-Bindings . . . . . . . . . . . . . . . . . . . 32
8.7.8. NAT-Control-Binding-Rule AVP . . . . . . . . . . . . . 32
8.7.9. Duplicate-Session-Id AVP . . . . . . . . . . . . . . . 32
9. Accounting Commands . . . . . . . . . . . . . . . . . . . . . 32
9.1. NAT Control Accounting Messages . . . . . . . . . . . . . 33
9.2. NAT Control Accounting AVPs . . . . . . . . . . . . . . . 33
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9.2.1. NAT-Control-Record . . . . . . . . . . . . . . . . . . 33
9.2.2. NAT-Control-Binding-Status . . . . . . . . . . . . . . 33
9.2.3. Current-NAT-Bindings . . . . . . . . . . . . . . . . . 34
10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . . 34
10.1. DNCA AVP Table for NAT Control Initial and Update
Requests . . . . . . . . . . . . . . . . . . . . . . . . . 34
10.2. DNCA AVP Table for Session Query request . . . . . . . . . 35
10.3. DNCA AVP Table for Accounting Message . . . . . . . . . . 35
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 35
11.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 36
11.2. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 36
11.3. AVP Values . . . . . . . . . . . . . . . . . . . . . . . . 36
11.3.1. Result-Code AVP Values . . . . . . . . . . . . . . . . 37
11.4. Application IDs . . . . . . . . . . . . . . . . . . . . . 37
12. Security Considerations . . . . . . . . . . . . . . . . . . . 38
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38
14. Change History (to be removed prior to publication as an
RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
15.1. Normative References . . . . . . . . . . . . . . . . . . . 40
15.2. Informative References . . . . . . . . . . . . . . . . . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40
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1. Introduction
Internet service providers have started to deploy Network Address
Translators (NATs) and Network Address and Port Translators (NAPTs)
at the edge of their networks to deal with the depletion of available
public IPv4 addresses. This document defines a Diameter application
for providers deploying such NAT and NAPT devices. The use of a
Diameter application allows for simple integration into the existing
Authentication, Authorization and Accounting (AAA) environment of a
provider.
The Diameter Network address and port translation Control Application
(DNCA) offers the following capabilities:
1. Limits or defines the number of NAPT/NAT bindings made available
to an individual subscriber or end point.
2. Supports the allocation of specific NAPT/NAT bindings. Two types
of specific bindings can be distinguished:
* Allocation of a pre-defined NAT binding: Both the internal and
external IP address and port pair are specified within the
request. In 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.
* 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.
3. 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, 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,
list of IP-subnets. Such External address pools can be used to
select external IP address in NAPT/NAT bindings for multiple
subscribers.
4. Generates reports and accounting records: Reports established
bindings for a particular user. The collected information is
used by accounting systems for statistical purposes.
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5. Queries and retrieves details about bindings on demand: This
feature complements the previously mentioned accounting
functionality(see item 4).
6. Identifies a subscriber or endpoint on multiple network devices
(NAPT or NAT 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
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 AVPs used,
and Section 8 accounting aspects. Section 9 presents an AVP
occurance table. IANA and security considerations are addressed in
Sections 10 and 11.
2. Conventions
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 [RFC2119].
Abbreviations used in this document:
AAA: Authentication, Authorization, Accounting
DNCA: Diameter Network address and port translation Control
Application
NAPT: Network Address and Port Translation
NAT: Network Address Translation (NAT and NAPT are used in this
document interchangeably)
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
NAS: Network Access Server
NCR:NAT Control Request
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NCA:NAT Control Answer
3. Deployment Framework
3.1. Deployment Scenario
Figure 1 shows a typical network deployment for Internet access. A
user's IPv4 host gains access to the Internet though a NAS, which
facilitates the authentication of the endpoint and configures the
user'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.
+---------+
| |
| AAA |
| |
+---------+
|
|
|
|
+---------+ +---------+ +----------+
| IPv4 | | | | IPv4 |
| Host |----------| NAS |-------------| Internet |
| | | | | |
+---------+ +---------+ +----------+
<-------------------- Public IPv4 ---------------------->
Figure 1: Typical network deployment for internet access
Figure 2 depicts the deployment scenario when a service provider
introduces a NAT device to increase the efficiency of the global IPv4
address pool utilization. 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.
If the NAT device would be put in place without any endpoint
awareness, the service offerings of the service provider could be
hampered. Provisioning static NAT bindings for particular endpoints,
using different public IP address pools for different set of
endpoints; for example, residential or business customers, and
reporting allocated bindings on a per endpoint basis is burdensome
for a service provider if the NAT device is not aware of endpoints
and allows per endpoint control and management, which easily
integrates with the already existing per endpoint management
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infrastructure of the service provider.
+---------+
| |
| AAA |
| |
+---------+
|
|
|
|
+--------+ +---------+ +---------+ +----------+
| IPv4/ | | | | | | IPv4 |
| IPv6 |----| NAS |----| NAT |----| Internet |
| Host | | | | | | |
+--------+ +---------+ +---------+ +----------+
<-------- Private IPv4 -----------><--- Public IPv4 --->
<-------- Public IPv6 -----------><--- Public IPv4 --->
Figure 2: Access network deployment with NAT
3.2. Diameter NAPT Control Application Overview
DNCA runs between a DNCA Agent on the NAT and DNCA Manager. DNCA
allows per endpoint control and management of NAT. 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.
DNCA offers:
o 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.
o Provides per endpoint reporting of the allocated NAT bindings.
o Provides unique identification of an endpoint on NAT device, AAA-
server and NAS, to simplify correlation of accounting data
streams.
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.
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3.3. Deployment Scenarios For DNCA
The role of DNCA can be fulfilled by either the NAS or by an external
server, such as AAA-server. The two deployment scenarios are
outlined in Figure 3 ("integrated deployment") and Figure 4
("autonomous deployment").
Within the figures (M) denotes the network element, which takes on
DNCA Manager role. Similarly, (A) identifies the network element,
which performs DNCA Agent role.
The integrated deployment approach hides the existence of the NAT
device from external servers, such as the AAA-server as much as
possible. It is suited for environments where minimal changes to the
existing AAA deployment are desired. As DNCA Manager the NAS,
initiates and manages session with the NAT device, exchanges NAT
specific configuration information and handles reporting and
accounting information. The NAS receives reporting and accounting
information from NAT device. With this information, the NAS provides
a single accounting record for the user. This reduces the usage of
an external accounting system for correlating the information
received from multiple sources.
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,
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. NAS will initiate a DNCA session to the NAT and send
the 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 or accounting requirements. The
NAT device sends its per endpoint accounting information to the NAS,
which aggregates the accounting information received form the NAT
device with its local accounting information for the endpoint into a
single accounting stream towards the AAA-server.
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+---------+
| |
| AAA |
| |
+---------+
|
|
|
+--------+ +---------+ +---------+ +----------+
| IPv4/ | | (M) | | (A) | | IPv4 |
| IPv6 |----| NAS |----| NAT |----| Internet |
| Host | | | | | | |
+--------+ +---------+ +---------+ +----------+
<-------- Public IPv6 ----------><--- Public IPv4 ---->
<-------- Private IPv4 ----------><--- Public IPv4 ---->
Figure 3: NAT Control deployment: Integrated deployment
The autonomous deployment approach decouples user management on NAS
and NAT device. The AAA system performing the role of DNCA Manager
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.
+---------+
| (M) |
| AAA |---------
| | |
+---------+ |
| |
| |
| |
+--------+ +---------+ +---------+ +----------+
| IPv4/ | | | | (A) | | IPv4 |
| IPv6 |----| NAS |----| NAT |----| Internet |
| Host | | | | | | |
+--------+ +---------+ +---------+ +----------+
<-------- Public IPv6 ----------><---- Public IPv4 --->
<-------- Private IPv4 ----------><---- Public IPv4 --->
Figure 4: NAT Control deployment: Autonomous deployment
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4. DNCA Session Establishment and Management
Note that this section forward references some of the commands and
AVPs defined for DNCA. Please refer to Section 6 and Section 8 for
details.
4.1. Parties Involved
Authorization and control models supported by this application
include the following parties:
o DNCA Agent: DNCA Agent is part of the NAT device
o DNCA Manager
The NAT control requesting entity is always DNCA Manager. DNCA
Manager always initiates, updates, or terminates the sessions. This
mode of operation is sometimes also referred to as "push mode".
DNCA Manager can be NAS or AAA-server. DNCA Manager initiates a
session with DNCA Agent when it learns about the subscriber. DNCA
Manager may learn about a subscriber when it receives authentication,
authorization, or accounting request for that subscriber or by some
other means, such as on the box configuration to identify a
subscriber with respect to his IP packets.
4.2. Session Establishment
DNCA Manager establishes a session with DNCA Agent to control the
behavior of the NAT device. During session establishment, DNCA
Manager passes along configuration information to DNCA Agent. 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, external addresses to be allocated
from.
DNCA Manager initiates the Diameter NAT Control session to DNCA
Agent. DNCA Manager generates a NAT-Control Request (NCR) message to
DNCA Agent with NC-Request-Type AVP set to INITIAL_REQUEST. On
receipt of NCR DNCA Agent sets up a new session for the endpoint
associated with the endpoint classifier(s) contained in the NCR.
DNCA Agent notifies DNCA Manager about successful session setup using
a NAT-Control Answer (NCA) message with Result-Code set to
DIAMETER_SUCCESS. Figure 5 shows the initial protocol interaction
between DNCA Manager and DNCA Agent.
The initial NAT-Control-Request may contain configuration information
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for the session, which specifies the behavior of the NAT device for
the session. The configuration information, which may be included,
comprises:
o A list of NAT bindings, which should be pre-allocated for the
session; for example, in case a subscriber requires a fixed
external IP- address/port pair for one of the applications.
o The maximum number of NAT bindings allowed for an endpoint.
o A description of the external address pool(s) to be used for the
session.
o A reference to a predefined binding rule on DNCA Agent, which is
applied to the session. Such a predefined binding rule on DNCA
Agent may contain, for example, the name of the IP address pool
that external IP addresses should be allocated from, maximum
number of bindings permitted for the endpoint etc.
In certain cases, DNCA Agent may not be able to perform the tasks
requested within the NCR. These include the following:
o If a DNCA Agent receives a NCR from a DNCA Manager with NC-
Request-Type AVP set to INITIAL_REQUEST that identifies an already
existing session; that is, DNCA Manager and endpoint identifier
match an already existing session, DNCA Agent returns NCA with
Result-Code set to SESSION_EXISTS, and provides the Session-Id of
the existing session in Duplicate-Session-Id AVP.
o If a DNCA Agent receives an NCR from a DNCA Manager with NC-
Request-Type AVP set to INITIAL_REQUEST that matches more than one
of the already existing sessions; that is, DNCA Manager and
endpoint identifier match already existing sessions, DNCA Agent
returns a NCA with Result-Code set to INSUFFICIENT-CLASSIFIERS.
In case a DNCA Manager receives NCA that reports Insufficient-
Classifiers, it may choose to retry establishing a new session
using additional and more specific classifiers.
o If the NCR contains a binding rule not defined on the NAT device,
DNCA Agent returns NCA with Result-Code AVP set to
UNKNOWN_BINDING_RULE.
o In case DNCA Agent is unable to establish all of the bindings
requested in the NCR, it will return a NCA with Result-Code set to
BINDING_FAILURE. DNCA Agent, that is NAT device, treats 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 are completed successfully, or the entire request
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fails.
o If DNCA Agent does not have sufficient resources to process a
request, it returns NCA with Result-Code set to RESOURCE_FAILURE.
o In case Max-NAT-Binding and NAT-Control-Definition are included in
the NCR along with a reference to a binding rule; that is, a
predefined template on NAT device, and the values in Max-NAT-
Binding and NAT-Control-Definition contradict those specified in
the pre-defined binding rule, Max-NAT-Binding and NAT-Control-
Definition override the values specified in the binding rule.
DNCA Manager DNCA Agent
| |
| |
| |
Trigger |
| |
| NCR |
|------------------------------------------>|
| (INITIAL_REQUEST, endpoint classifier, |
| session id, NAT control config data) |
| |
| |
| Create session state
| |
| |
| NCA |
|<------------------------------------------|
| (result code) |
| |
| |
Figure 5: Initial NAT Control request and session establishment
4.3. Session Re-Authorization
Session re-authorization is performed if DNCA Manager desires to
change the behavior of the NAT for an existing session. Re-
authorization could be used, for example, to change the number of
allowed bindings for a particular session, or establish or remove a
pre-defined binding.
DNCA Manager generates a NCR message to DNCA Agent with NC-Request-
Type AVP set to UPDATE_REQUEST upon receiving a trigger signal. In
case the session is updated successfully, DNCA Agent notifies DNCA
Manager about successful session update using a NAT-Control Answer
(NCA) message with Result-Code set to DIAMETER_SUCCESS. Figure 6
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shows the protocol interaction between DNCA Manager and DNCA Agent.
In certain cases, DNCA Agent may not be able to perform the tasks
requested within the NCR. These include the following:
o If DNCA Agent receives a NCR update or query request for a non-
existent session, it sets Result-Code in the answer to
DIAMETER_UNKNOWN_SESSION_ID.
o If the NCR contains a binding rule not defined on the NAT device,
DNCA Agent returns NCA with Result-Code AVP set to
UNKNOWN_BINDING_RULE.
o If DNCA Agent cannot establish the requested binding because the
maximum number of allowed bindings has been reached for the
Endpoint Classifier, it returns NCA with Result-Code AVP set to
MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT.
o If DNCA Agent cannot establish some or all of the bindings
requested in a NCR, but has not yet reached the maximum number of
allowed bindings for the subscriber, it returns a NCA with Result-
Code set to BINDING_FAILURE. DNCA Agent (i.e., NAT device) treats
a NCR as an atomic operation. Hence none of the requested
bindings will be established by NAT device. Either all requested
actions within a NCR are either successful or failed completely.
o If DNCA Agent does not have sufficient resources to process a
request, it returns NCA with Result-Code set to RESOURCE_FAILURE.
o If a NCR redefines the maximum number of NAT bindings allowed for
the endpoint, the new value will override any previously defined
limit on NAT bindings. 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.
Typically the NAT device refrains from enforcing the new limit
immediately; that is, actively remove bindings, but rather
disallow the establishment of new bindings until the current
number of bindings is lower than the newly established maximum
number of allowed bindings.
o If a NCR specifies a new binding rule, predefined on DNCA Agent,
the binding rule overrides any previously defined rules for the
session.
o If Max-NAT-Binding and NAT-Control-Definition AVPs are included in
the NCR along with a reference to a binding rule (a predefined
template on NAT device) and the values in Max-NAT-Binding and NAT-
Control-Definition AVPs contradict those specified in the pre-
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defined binding rule, Max-NAT-Binding and NAT-Control-Definition
AVPs override the values specified in the binding rule.
Note: Already established bindings for the session will not be
affected.
DNCA Manager DNCA Agent
| |
| |
| |
Change of session |
attributes |
| |
| NCR |
|------------------------------------------>|
| (UPDATE_REQUEST session id, |
| NAT control config data) |
| |
| |
| Update session state
| |
| |
| NCA |
|<------------------------------------------|
| (result code) |
| |
| |
Figure 6: NAT Control request for session update
4.4. Session and Binding Query
Session query can be used by DNCA Manager 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.
DNCA Manager initiates a session query by sending a NCR message to
DNCA Agent with NC-Request-Type AVP set to QUERY_REQUEST. Figure 7
shows the protocol interaction between DNCA Manager and DNCA Agent.
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
DNCA Manager 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 DNCA Manager to find the sessions, which
utilize a specific external IP address.
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1. Request a list of currently allocated NAT bindings for a
particular session: DNCA Agent on receiving NCR, looks up session
information for the session ID contained in the NCR, and reports
all currently active NAT bindings for the session using 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, DNCA Agent returns NCA with Result-Code
set to DIAMETER_UNKNOWN_SESSION_ID.
2. Retrieve session IDs and internal IP address/port pairs for one
or multiple external IP address/port pairs: If DNCA Manager
wishes to retrieve the session ID(s) for one or multiple external
IP address/port pairs, it MUST include the external IP address/
port pair(s) as part of the NAT-Control-Definition AVP of the
NCR. The session ID is not included in the NCR or the NCA for
this type of a query. DNCA Agent reports the NAT bindings and
associated session IDs corresponding to the external IP address/
port pairs in a NCA message with Result-Code set to
DIAMETER_SUCCESS with the same session ID, which is used in NCR.
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.
DNCA Manager DNCA Agent
| |
| |
| |
DNCA Session Established |
| |
| NCR |
|------------------------------------------>|
| (QUERY_REQUEST) |
| |
| |
| |
| Look up corresponding session
| and associated NAT Bindings
| |
| NCA |
|<------------------------------------------|
| (Result-Code) |
| |
| |
Figure 7: Session Query
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4.5. Session Termination
DNCA Manager generates a Session Terminate Request (STR) message to
DNCA Agent upon receiving a trigger signal. The source of the
trigger signal is outside the scope of this document. DNCA Agent
sends accounting stop record reporting all the bindings and notifies
DNCA Manager about successful session termination using a Session
Terminate Answer (STA) message with Result-Code set to
DIAMETER_SUCCESS. Figure 8 shows the protocol interaction between
DNCA Manager and DNCA Agent.
If a DNCA Agent receives STR from a DNCA Manager and fails to find a
matching session, DNCA Agent returns STA with Result-Code set to
DIAMETER_UNKNOWN_SESSION_ID.
DNCA Manager DNCA Agent
| |
| |
Trigger |
| |
| STR |
|------------------------------------------->|
| (session id) |
| |
| |
| Remove NAT bindings
| of session
| |
| |
| Send accounting stop |
|<-------------------------------------------|
| for all session bindings |
| |
| Terminate Session /
| Remove session state
| |
| |
| |
| STA |
|<-------------------------------------------|
| (Result-Code) |
| |
Figure 8: Terminate NAT Control session
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4.6. DNCA Manager and Agent Failures
This document does not cover details in case DNCA Manager and DNCA
Agent are out of sync. This happens when DNCA Manager or DNCA Agent
restart, (temporary) loss of network connectivity etc. DNCA Manager
and DNCA Agent MUST have builtin redundancy support to recover state
in case of failure.
Example failure cases include the following:
o DNCA Manager loses session state (e.g. due to a restart). In this
case,
* DNCA Agent may receive a NCR with NC-Request-Type AVP set to
INITIAL_REQUEST that matches an existing session of DNCA Agent.
DNCA Agent returns a Result-Code that contains Duplicate-
Session-Id AVP to report the Session-ID of existing session.
DNCA Manager may send an explicit Sesstion Terminate Request
(STR) for the older session, which was lost.
* DNCA Manager may receive accounting records for a session that
does not exist. DNCA Manager sends an accounting answer with
Result-Code set to DIAMETER_UNKNOWN_SESSION_ID. On receiving
this, DNCA Agent clears the session and removes the associated
session state.
o DNCA Agent loses session state. In such a case, DNCA Agent may
receive a NCR with NC-Request-Type AVP set to UPDATE_REQUEST for a
non-existent session. DNCA Agent returns NCA with Result-Code set
to DIAMETER_UNKNOWN_SESSION_ID.
o DNCA Manager is unreachable, for example detected by Diameter
watchdog, or down and accounting request from DNCA Agent fails to
get a response. The mechanism to ensure that a DNCA Manager no
longer has associated state for a session being cleared by a DNCA
Agent is beyond the scope of this document.
o DNCA Agent is unreachable or down and NCR requests fail to get a
response. Handling of this case depends on the actual service
offering of the service provider. The service provider can choose
to terminate the access session to the endpoint.
5. Use Of The Diameter Base Protocol
The Diameter Base Protocol defined by [RFC3588] applies with the
clarifications listed in the present specification.
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5.1. Securing Diameter Messages
For secure transport of Diameter messages recommendations in
[RFC3588] apply.
DNCA Agent MAY verify the identity of DNCA Manager during the
Capabilities Exchange Request procedure.
DNCA Agent MAY verify if DNCA Manager that issues a NCR command is
allowed and it is based on:
o The identity of DNCA Manager
o The type of NCR Command
o The content of the NCR Command
o Any combination of the above
5.2. Accounting Functionality
Accounting functionality (accounting session state machine, related
command codes and AVPs) is defined in Section 9 below.
5.3. Use Of Sessions
Each DNCA session MUST have a globally unique Session-ID as defined
in [RFC3588], which MUST NOT be changed during the lifetime of a DNCA
session. The Diameter Session-ID serves as the global endpoint
identifier. DNCA Agent and DNCA Manager maintain state associated
with the Session-ID. This globally unique Session-ID is used for
updating, accounting, and terminating the session. DNCA session MUST
NOT have more than one outstanding request at any given instant.
DNCA Agent sends an Abort-Session-Request as defined in [RFC3588] if
it is unable to maintain sessions due to resource limitation.
5.4. Routing Considerations
It is assumed that DNCA Manager knows the DiameterIdentity of DNCA
Agent for a given endpoint. Both the Destination-Realm and
Destination-Host AVPs are present in the request from DNCA Manager to
DNCA Agent.
5.5. Advertising Application Support
Diameter nodes conforming to this specification MUST advertise
support for DNCA by including the value of TBD in the Auth-
Application-Id of the Capabilities-Exchange-Request and Capabilities-
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Exchange-Answer command[RFC3588].
6. DNCA Commands
The following commands are used to establish, maintain and query NAT
bindings.
6.1. NAT-Control Request (NCR) Command
The NAT-Control Request (NCR) command, indicated by the command field
set to TBD and the "R" bit set in the Command Flags field, is sent
from DNCA Manager to DNCA Agent in order to install NAT bindings.
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
subscriber.
Message Format:
< NC-Request > ::= < Diameter Header: TBD, REQ, PXY>
[ Session-Id ]
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Destination-Host }
{ NC-Request-Type }
[ Origin-State-Id ]
*1 [ NAT-Control-Remove ]
*1 [ NAT-Control-Install ]
[ 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 ]
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6.2. NAT-Control Answer (NCA) Command
The NAT-Control-Answer (NCA) command, indicated by the Command-Code
field set to TBD and the "R" bit cleared in the Command Flags field,
is sent by DNCA Agent in response to NAT-Control-Request command.
Message Format:
<NC-Answer> ::= < Diameter Header: TBD, PXY >
[ Session-Id ]
{ Origin-Host }
{ Origin-Realm }
{ NC-Request-Type }
[ Result-Code ]
* [ 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 ]
* [ AVP ]
7. NAT Control Application Session State Machine
This section contains a set of finite state machines, representing
the life cycle of DNCA session, which MUST be observed by all
implementations of DNCA Diameter application. DNCA Agent and Manager
are stateful and the state machine maintained is similar to the
stateful Client and Server authorization state machine described in
[RFC3588]. 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.
In the state table, the event 'Failure to send NCR' means that DNCA
Manager is unable to send command NCR to the desired destination.
This could be due to the peer being down, or due to the peer sending
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back a transient failure or temporary protocol error notification
DIAMETER_TOO_BUSY or DIAMETER_LOOP_DETECTED in the Result-Code AVP of
NCA.
In the state table "FAILED NCA" means that DNCA Agent was not able to
honor corresponding NCR. This can happen due to any of the transient
and permanent error at DNCA Agent indicated by the following error
Result-Code values - RESOURCE_FAILURE, UNKNOWN_BINDING_RULE_NAME,
BINDING_FAILURE, MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT,
SESSION_EXISTS, INSUFFICIENT_CLASSIFIERS
The following state machine is observed by a DNCA Manager:
MANAGER
State Event Action New State
-------------------------------------------------------------
Idle New Host 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 Sent STR Discon
received
but Agent unable to provide
service
Pending Error processing successful Sent STR Discon
NCA
Pending Failed Cleanup Idle
NCA received
Open NAT control Send Open
update required NCR Update
Request
Open Successful Open
NCA received
Open Failed Cleanup Idle
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NCA received.
Open Access Session end detected Send STR Discon
Open ASR Received, Send ASA Discon
client will comply with with
request to end the session Result-Code
= SUCCESS,
Send STR.
Open ASR Received, Send ASA Open
client will not comply with with
request to end the session Result-Code
!= SUCCESS
Discon ASR Received Send ASA Idle
Discon STA Received Discon. Idle
user/device
The following state machine is observed by a DNCA Agent:
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AGENT
State Event Action New State
-------------------------------------------------------------
Idle NCR request Send Open
received, and successful
able to 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 Cleanup
Open Unable to continue Send ASR Discon
providing requested
NAT control service
Discon Failure to send ASR Wait, Discon
resend ASR
Discon ASR successfully sent and Cleanup Idle
ASA Received with Result-Code
Not ASA Received None No Change.
Discon
Any STR Received Send STA, Idle
Cleanup.
8. DNCA AVPs
8.1. Reused Base Protocol AVPs
AVPs reused from Diameter Base Protocol [RFC3588] are listed below.
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+-------------------+
| AVP Flag rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | May |
| Attribute Name Code Data Type |MUST |MAY| encrypt |
+-----------------------------------------------+-----+---+---------+
|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 |
+-----------------------------------------------+-----+---+---------+
|M - Mandatory bit. An AVP with "M" bit set and its value MUST be |
| supported and recognized by a Diameter entity in order the |
| message, which carries this AVP, to be accepted. |
|P - Indicates the need for encryption for end-to-end security. |
+-------------------------------------------------------------------+
Figure 9: DIAMETER AVPs used from Diameter base
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.
8.2. Additional Result-Code AVP Values
This section defines new values for the Result-Code AVP which SHALL
be supported by all Diameter implementations that conform to the
present document.
8.2.1. Success
No new Result-Code AVP value is defined within this category.
8.2.2. Transient Failures
Result-Code AVP values that fall within the transient failures
category are those used to inform a peer that the request could not
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be satisfied at the time that it was received. The request may be
able to be satisfied in the future.
The following new values of the Result-Code AVP are defined:
RESOURCE_FAILURE (TBD)
DNCA Agent indicates that the binding could not be installed or
a new session could not be created due to resource shortage.
8.2.3. Permanent Failures
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.
The following new values of the Result-Code AVP are defined:
UNKNOWN_BINDING_RULE_NAME (TBD)
DNCA Agent indicates that the binding could not be installed or
a new session could not be created due to resource shortage.
BINDING_FAILURE (TBD)
DNCA indicates that the requested binding(s) could not be
installed.
MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT (TBD)
DNCA Agent denies the request because the maximum number of
allowed bindings has been reached for the specified Endpoint
Classifier.
SESSION_EXISTS (TBD)
DNCA Agent denies request to initialize a new session, if it
already has a DNCA session that uses the same set of
classifiers as indicated by DNCA Manager in the new session
initialization request.
INSUFFICIENT_CLASSIFIERS (TBD)
DNCA Agent defines request to initialize a new session, if the
classifiers in the request match more than one of the existing
sessions on DNCA Agent.
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8.3. Reused NASREQ Diameter Application AVPs
The following AVPs are reused from Diameter Network Access Server
Application [RFC4005].
+---------------------+
| 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 | | | | | | | |
+------------------+------+------------|----+-----+----+-----|----+
Figure 10: Reused NASREQ Diameter application AVPs
8.4. Reused from RFC 4675
The following AVPs are reused from "RADIUS Attributes for Virtual LAN
and Priority Support" specification [RFC4675].
+---------------------+
| AVP Flag rules |
+------------------+------+------------|----+-----+----+-----|----+
| | AVP | | | |SHLD| MUST| |
| Attribute Name | Code | Value Type|MUST| MAY | NOT| NOT|Encr|
|------------------|------|------------|----+-----+----+-----|----|
| Egress-VLANID | 56 | OctetString| M | P | | V | Y |
+------------------+------+------------|----+-----+----+-----|----+
Figure 11: Reused attributes from RFC 4675
8.5. Reused from Diameter QoS Application
The following AVPs are reused from the Traffic Classification and
Quality of Service (QoS) Attributes for Diameter [RFC5777].
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+-------------------+
| AVP Flag rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | May |
| Attribute Name Code Data Type |MUST |MAY| encrypt |
+-----------------------------------------------+-----+---+---------+
|Port TBD Integer32 | M | P | Y |
|IP-Address-Mask TBD Grouped | M | P | Y |
|Protocol TBD Enumerated | M | P | Y |
|Direction TBD Enumerated | M | P | Y |
+-----------------------------------------------+-----+---+---------+
|M - Mandatory bit. An AVP with "M" bit set and its value MUST be |
| supported and recognized by a Diameter entity in order the |
| message, which carries this AVP, to be accepted. |
|P - Indicates the need for encryption for end-to-end security. |
+-------------------------------------------------------------------+
Figure 12: Reused QoS-attributes
8.6. Reused from ETSI ES 283 034, e4 Diameter Application
The following AVPs are reused from the Diameter e4 Application
[ETSIES283034].
+-------------------+
| AVP Flag rules |
+-----------------------------------------------|-----+---+---------+
| AVP | | | May |
| Attribute Name Code Data Type |MUST |MAY| encrypt |
+-----------------------------------------------+-----+---+---------+
|Address-Realm 301 OctetString | M,V | | Y |
|Logical-Access-Id 302 OctetString | V | M | Y |
|Physical-Access-ID 313 UTF8String | V | M | Y |
+-----------------------------------------------+-----+---+---------+
|M - Mandatory bit. An AVP with "M" bit set and its value MUST be |
| supported and recognized by a Diameter entity in order the |
| message, which carries this AVP, to be accepted. |
|P - Indicates the need for encryption for end-to-end security. |
|V - Indicates whether the optional Vendor-ID field is present |
| in the AVP header. Vendor-Id header of all AVPs in |
| this table will be set to ETSI (13019). |
+-------------------------------------------------------------------+
Figure 13: Reused AVPs from Diameter e4 application
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8.7. DNCA Defined AVPs
The following table describes the new Diameter AVPs used in this
document.
+-------------------+
| AVP Flag rules |
+-----------------------------------------------|-----+---+---------+
| AVP Section | | | May |
| Attribute Name Code Defined Data Type |MUST |MAY| encrypt |
+-----------------------------------------------+-----+---+---------+
|NC-Request-Type TBD 7.7.1 Enumerated | M | P | Y |
|NAT-Control-Install TBD 7.7.2 Grouped | M | P | Y |
|NAT-Control-Remove TBD 7.7.3 Grouped | M | P | Y |
|NAT-Control-Definition TBD 7.7.4 Grouped | M | P | Y |
|NAT-Internal-Address TBD 7.7.5 Grouped | M | P | Y |
|NAT-External-Address TBD 7.7.6 Grouped | M | P | Y |
|Max-NAT-Bindings TBD 7.7.7 Unsigned32 | M | P | Y |
|NAT-Control- TBD 7.7.8 OctetString| M | P | Y |
| Binding-Rule | | | |
|Duplicate- TBD 7.7.9 UTF8String | M | P | Y |
| Session-ID | | | |
|NAT-Control-Record TBD 8.2.1 Grouped | M | P | Y |
|NAT-Control- TBD 8.2.2 Enumerated | M | P | Y |
| Binding-Status | | | |
|Current-NAT-Bindings TBD 8.2.3 Unsigned32 | M | P | Y |
+-----------------------------------------------+-----+---+---------+
|M - Mandatory bit. An AVP with "M" bit set and its value MUST be |
| supported and recognized by a Diameter entity in order the |
| message, which carries this AVP, to be accepted. |
|P - Indicates the need for encryption for end-to-end security. |
|V - Vendor specific bit that indicates whether the optional |
| Vendor-ID field is present in the AVP header. |
+-------------------------------------------------------------------+
Figure 14: New Diameter AVPs
8.7.1. NC-Request-Type AVP
The NC-Request-Type AVP (AVP Code TBD) 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.
The following values are defined:
INITIAL_REQUEST (1)
An Initial Request is used to install binding at DNCA Agent on
a successful access session setup.
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UPDATE_REQUEST (2)
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.
QUERY_REQUEST (4)
Query Request is used to query DNCA Agent about the currently
installed bindings for an endpoint classifier.
8.7.2. NAT-Control-Install AVP
The NAT-Control AVP (AVP code TBD) is of type Grouped, and it is used
to activate or install NAT bindings. It also contains Max-NAT-
Bindings that defines maximum number of NAT bindings to be allowed
for a subscriber and NAT-Control-Binding-Rule that references
predefined policy template on DNCA Agent that may contain static
bindings, maximum number of bindings to be allowed, address pool from
which external binding address should be allocated.
AVP format:
NAT-Control-Install ::= < AVP Header: TBD >
* [ NAT-Control-Definition ]
[ NAT-Control-Binding-Rule ]
[ Max-NAT-Bindings]
* [ AVP ]
8.7.3. NAT-Control-Remove AVP
The NAT-Control-Remove AVP (AVP code TBD) is of type Grouped, and it
is used to deactivate or remove NAT bindings.
AVP format:
NAT-Control-Remove ::= < AVP Header: TBD >
* [ NAT-Control-Definition ]
[ NAT-Control-Binding-Rule ]
* [ AVP ]
8.7.4. NAT-Control-Definition AVP
The NAT-Control-Definition AVP (AVP code TBD) is of type Grouped, and
it describes a binding.
The NAT-Control-Definition AVP uniquely identifies the binding
between DNCA Agent and DNCA Manager.
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If both the NAT-Internal-Address and NAT-External-Address AVP(s) are
supplied, it is a pre-defined binding.
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 address are specified then the binding reserves the
addresses for all transport protocols.
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, NAT-
Internal-Address refers to the address of the subscriber device that
needs to be translated. If Direction AVP is "IN", NAT-Internal-
Address is the destination address that has to be translated.
AVP format:
NAT-Control-Definition ::= < AVP Header: TBD >
{ NAT-Internal-Address }
[ Protocol ]
[ Direction ]
[ NAT-External-Address ]
[ Session-Id ]
* [ AVP ]
8.7.5. NAT-Internal-Address AVP
The NAT-Internal-Address AVP (AVP code TBD) 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.
AVP format:
NAT-Internal-Address ::= < AVP Header: TBD >
[ Framed-IP-Address ]
[ Framed-IPv6-Prefix ]
[ Port]
* [ AVP ]
8.7.6. NAT-External-Address AVP
The NAT-External-Address AVP (AVP code TBD) is of type Grouped, and
it describes the external IP address and port for a binding. IP-
Address-Mask AVP can only be specified when Framed-IP-Address AVP is
present. External IP address specified in this attribute can be
reused for multiple subscribers by specifying the same address in the
respective NAT-External-Address AVPs.
AVP format:
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NAT-External-Address ::= < AVP Header: TBD >
[ Framed-IP-Address ]
[ IP-Address-Mask ]
[ Port ]
* [ AVP ]
8.7.7. Max-NAT-Bindings
The Max-NAT-Bindings AVP (AVP code TBD) is of type Unsigned32. It
indicates the maximum number of NAT bindings allowed.
8.7.8. NAT-Control-Binding-Rule AVP
The NAT-Control-Binding-Rule AVP (AVP code TBD) is of type
OctetString. It defines a name for a policy template that will be
predefined at NAT. 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,
address pool for external address allocation of NAT binding, and
maximum allowed NAT bindings. Such policy template can be reused by
specifying same NAT-Control-Binding-Rule AVP in corresponding NAT-
Control-Install AVPs of multiple subscribers.
8.7.9. Duplicate-Session-Id AVP
The Duplicate-Session-Id AVP (AVP Code TBD) is of type UTF8String.
It is used to report error and contains the Session-Id of an existing
session.
9. Accounting Commands
DNCA reuses session based accounting as defined in Diameter Base
Protocol[RFC3588] to report the bindings per endpoint. This
reporting is achieved by sending Diameter Accounting Requests (ACR)
[Start, Interim and Stop] from DNCA Agent to DNCA Manager.
DNCA Agent sends an ACR Start on receiving an 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 DNCA Manager, or when it creates or tears down bindings. An ACR
Stop is sent by DNCA Agent on receiving STR.
The function of correlating the multiple bindings used by an endpoint
at any given time is relegated to the post processor.
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DNCA Agent may trigger an interim accounting record when maximum
number of bindings, if received in NCR, is reached.
9.1. NAT Control Accounting Messages
The ACR and ACA messages are reused as defined in Diameter Base
Protocol [RFC3588] for exchanging endpoint NAT binding details
between DNCA Agent and DNCA Manager. DNCA Application ID is used in
the accounting commands. ACR contains one or more optional NAT-
Control-Record AVP to report the bindings. DNCA Agent indicates the
number of allocated NAT bindings to DNCA Manager using the Current-
NAT-Bindings AVP. This number needs to match the number of bindings
identified as active within the NAT-Control-Record AVP.
9.2. NAT Control Accounting AVPs
In addition to AVPs for ACR specified in [RFC3588], DNCA Agent must
add the NAT-Control-Record AVP.
9.2.1. NAT-Control-Record
The NAT-Control-Record AVP (AVP code TBD) 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.
NAT-Control-Record ::= < AVP Header: TBD >
{ NAT-Control-Definition }
{ NAT-Control-Binding-Status }
[ Event-Timestamp ]
9.2.2. NAT-Control-Binding-Status
The NAT-Control-Binding-Status AVP (AVP code TBD) is of type
enumerated. It indicates the status of the binding - created,
removed, or active.
The following values are defined:
Created (1)
NAT binding is created.
Active (2)
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NAT binding is active.
Removed (3)
NAT binding was removed.
9.2.3. Current-NAT-Bindings
The Current-NAT-Bindings AVP (AVP code TBD) is of type Unsigned32.
It indicates number of NAT bindings active on NAT device.
10. AVP Occurrence Table
The following sections presents the AVPs defined in this document and
specifies the Diameter messages in which, they MAY be present. Note:
AVPs that can only be present within a Grouped AVP are not
represented in this table.
The table uses the following symbols:
0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the
message. It is considered an error if there is more
than one instance of the AVP.
1 One instance of the AVP MUST be present in the message.
1+ At least one instance of the AVP MUST be present in the
message.
10.1. DNCA AVP Table for NAT Control Initial and Update Requests
The following table lists DNCA specific AVPs that have to be present
in NCR and NCA with NC-Request-Type set to INITIAL_REQUEST or
UPDATE_REQUEST.
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+-------------------+
| 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 |
+-------------------------------------------------------+
10.2. DNCA AVP Table for Session Query request
The following table lists DNCA specific AVPs that have to be present
in NCR and NCA with NC-Request-Type set to QUERY_REQUEST.
+-------------------+
| 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+ |
|Current-NAT-Bindings 0 1 |
|Duplicate-Session-Id 0 0 |
+-------------------------------------------------------+
10.3. DNCA AVP Table for Accounting Message
The following table lists DNCA specific AVPs, which may or may not be
present in ACR and ACA messages.
+-------------------+
| Command Code |
+-----------------------------------+-------------------+
| Attribute Name ACR ACA |
+-------------------------------------------------------+
|NAT-Control-Record 0+ 0 |
|Current-NAT-Bindings 1 0 |
+-------------------------------------------------------+
11. IANA Considerations
This section contains the namespaces that have either been created in
this specification or had their values assigned to existing
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namespaces managed by IANA.
11.1. Command Codes
IANA is requested to allocate command code values for the following.
Registry:
+------------+-----------------------------------+------------------+
| Code Value | Name | Reference |
+------------+-----------------------------------+------------------+
| to be | NAT-Control-Request (NCR), | Section 6.1, |
| assigned | NAT-Control-Answer (NCA) | Section 6.2 |
+------------+-----------------------------------+------------------+
Table 1: Command codes
11.2. AVP Codes
IANA is requested to allocate AVP codes for the following AVPs that
are defined in this document.
Registry:
+----------------+----------------------------+---------------+
| Code Value | Name | Reference |
+----------------+----------------------------+---------------+
| to be assigned | NC-Request-Type | Section 8.7.1 |
| to be assigned | NAT-Control-Install | Section 8.7.2 |
| to be assigned | NAT-Control-Remove | Section 8.7.3 |
| to be assigned | NAT-Control-Definition | Section 8.7.4 |
| to be assigned | NAT-Internal-Address | Section 8.7.5 |
| to be assigned | NAT-External-Address | Section 8.7.6 |
| to be assigned | Max-NAT-Bindings | Section 8.7.7 |
| to be assigned | NAT-Control-Binding-Rule | Section 8.7.8 |
| to be assigned | Duplicate-Session-Id | Section 8.7.9 |
| to be assigned | NAT-Control-Record | Section 9.2.1 |
| to be assigned | NAT-Control-Binding-Status | Section 9.2.2 |
| to be assigned | Current-NAT-Bindings | Section 9.2.3 |
+----------------+----------------------------+---------------+
Table 2: AVP codes
11.3. AVP Values
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11.3.1. Result-Code AVP Values
Section 8.2 defines several new values for the Result-Code AVP for
transient and permanent failures. IANA is requested to allocate the
corresponding values from the ranges for transient (4xxx) and
permantent (5xxx) failures.
+-----------+---------------------------------------+---------------+
| Code | Name | Reference |
| Value | | |
+-----------+---------------------------------------+---------------+
| to be | RESOURCE_FAILURE | Section 8.2.2 |
| assigned | | |
| (4xxx) | | |
| to be | UNKNOWN_BINDING_RULE_NAME | Section 8.2.3 |
| assigned | | |
| (5xxx) | | |
| to be | BINDING_FAILURE | Section 8.2.3 |
| assigned | | |
| (5xxx) | | |
| to be | MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT | Section 8.2.3 |
| assigned | | |
| (5xxx) | | |
| to be | SESSION_EXISTS | Section 8.2.3 |
| assigned | | |
| (5xxx) | | |
| to be | INSUFFICIENT_CLASSIFIERS | Section 8.2.3 |
| assigned | | |
| (5xxx) | | |
+-----------+---------------------------------------+---------------+
Table 3: Result Code AVP Values
11.4. Application IDs
IANA is requested to allocate the following application ID using the
next value from the 7-16777215 range.
Registry:
+----------------+----------------------------------+-----------+
| ID Value | Name | Reference |
+----------------+----------------------------------+-----------+
| to be assigned | Diameter NAT Control Application | Section 4 |
+----------------+----------------------------------+-----------+
Table 4: Diameter Application ID values
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12. Security Considerations
Similar to the impact of Diameter QoS application (see [RFC5866]) on
authorization of QoS reservations, this document describes procedures
for authorizing NAT related attributes and parameters by an entity,
which is non-local to the device performing NAT. The security
considerations for the Diameter QoS application (see [RFC5866]
section 11) apply in a similar way to DNCA. To secure the
information exchange between the authorizing entity (DNCA Manager)
and the NAT device (DNCA Agent) requires bilateral authentication of
the involved parties, authorization of the involved parties to
perform the required procedures and functions, and procedures to
ensure integrity and confidentiality of the information exchange MAY
be performed. DNCA makes use of the capabilities offered by Diameter
and the underlying transport protocols to deliver these requirements
(see Section 5.1 ).
It is assumed that DNCA Agent and DNCA Manager are in the same domain
and have a mutual trust set up. Authorization between DNCA Agent and
DNCA Manager is beyond the scope of this document.
13. Acknowledgements
The authors would like to thank Jouni Korhonen, Avi Lior, Chris Metz,
Pallavi Mishra, Lionel Morand, Hannes Tschofenig, Shashank Vikram,
Greg Weber, and Glen Zorn for their input on this document.
14. Change History (to be removed prior to publication as an RFC)
Changes from -00 to -01
a. new values for Result-Code AVP used - instead of Experimental-
Result AVP
b. added support for transport specific binding (UDP/TCP)
c. added support for twice-NAT
d. clarified the use of the two different types of query-requests
Changes from -01 to -02
a. Reference to pull mode removed, session initiation event
clarified in section 4.1
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b. added Redirect-* AVPs in NCA command
c. Removed reference to Called-Station-Id AVP in NCR command
d. Editorial changes
e. added support for bindings providing AFT (NAT64)
Changes from -02 to -03
a. Editorial changes
Changes from -03 to -04
a. Editorial changes suggested in WG Lastcall review
b. Removed NCR Request type terminate and replaced with STR
c. All references to Auth-Session-State are removed and a new
section to describe FSM for Manager and Agent has been added
d. Clarified reuse of External address and address pools among
multiple subscribers
Changes from -04 to -05
a. Removed references to Large Scale NAT as per review comments
Changes from -05 to -06
a. Editorial changes
Changes from -06 to -07
a. Added a note in section 4.3 stating the state of pre-existing
bindings on update failure
b. Security considerations are made consistent between sections 5.1
and 12
c. Editorial changes
15. References
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15.1. Normative References
[ETSIES283034]
ETSI, "Telecommunications and Internet Converged Services
and Protocols for Advanced Networks (TISPAN),Network
Attachment Sub-System (NASS),e4 interface based on the
Diameter protocol.", September 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
"Diameter Network Access Server Application", RFC 4005,
August 2005.
[RFC4675] Congdon, P., Sanchez, M., and B. Aboba, "RADIUS Attributes
for Virtual LAN and Priority Support", RFC 4675,
September 2006.
[RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M.,
and A. Lior, "Traffic Classification and Quality of
Service (QoS) Attributes for Diameter", RFC 5777,
February 2010.
15.2. Informative References
[RFC5866] Sun, D., McCann, P., Tschofenig, H., Tsou, T., Doria, A.,
and G. Zorn, "Diameter Quality-of-Service Application",
RFC 5866, May 2010.
Authors' Addresses
Frank Brockners
Cisco
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
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Shwetha Bhandari
Cisco
Cessna Business Park, Sarjapura Marathalli Outer Ring Road
Bangalore, KARNATAKA 560 087
India
Email: shwethab@cisco.com
Vaneeta Singh
18, Cambridge Road
Bangalore 560008
India
Email: vaneeta.singh@gmail.com
Victor Fajardo
Telcordia Technologies
1 Telcordia Drive #1S-222
Piscataway, NJ 08854
USA
Email: vf0213@gmail.com
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