Internet Engineering Task Force F. Brockners
Internet-Draft S. Bhandari
Intended status: Standards Track Cisco
Expires: January 11, 2012 V. Singh
V. Fajardo
Telcordia Technologies
July 10, 2011
Diameter Network Address and Port Translation Control Application
draft-ietf-dime-nat-control-09
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 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.
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 January 11, 2012.
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
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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 . . . . . . . . 9
3.3. Deployment Scenarios For DNCA . . . . . . . . . . . . . . 10
4. DNCA Session Establishment and Management . . . . . . . . . . 12
4.1. Session Establishment . . . . . . . . . . . . . . . . . . 12
4.2. Session Re-Authorization . . . . . . . . . . . . . . . . . 14
4.3. Session and Binding Query . . . . . . . . . . . . . . . . 17
4.4. Session Termination . . . . . . . . . . . . . . . . . . . 18
4.5. Session Abort . . . . . . . . . . . . . . . . . . . . . . 19
4.6. Failure cases of the DNCA Diameter peers . . . . . . . . . 20
5. Use Of The Diameter Base Protocol . . . . . . . . . . . . . . 21
5.1. Securing Diameter Messages . . . . . . . . . . . . . . . . 21
5.2. Accounting Functionality . . . . . . . . . . . . . . . . . 22
5.3. Use Of Sessions . . . . . . . . . . . . . . . . . . . . . 22
5.4. Routing Considerations . . . . . . . . . . . . . . . . . . 22
5.5. Advertising Application Support . . . . . . . . . . . . . 22
6. DNCA Commands . . . . . . . . . . . . . . . . . . . . . . . . 22
6.1. NAT-Control Request (NCR) Command . . . . . . . . . . . . 22
6.2. NAT-Control Answer (NCA) Command . . . . . . . . . . . . . 23
7. NAT Control Application Session State Machine . . . . . . . . 24
8. DNCA AVPs . . . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1. Reused Base Protocol AVPs . . . . . . . . . . . . . . . . 27
8.2. Additional Result-Code AVP Values . . . . . . . . . . . . 28
8.2.1. Success . . . . . . . . . . . . . . . . . . . . . . . 28
8.2.2. Transient Failures . . . . . . . . . . . . . . . . . . 28
8.2.3. Permanent Failures . . . . . . . . . . . . . . . . . . 29
8.3. Reused NASREQ Diameter Application AVPs . . . . . . . . . 30
8.4. Reused AVPs from RFC 4675 . . . . . . . . . . . . . . . . 30
8.5. Reused AVPs from Diameter QoS Application . . . . . . . . 31
8.6. Reused AVPs from ETSI ES 283 034, e4 Diameter
Application . . . . . . . . . . . . . . . . . . . . . . . 31
8.7. DNCA Defined AVPs . . . . . . . . . . . . . . . . . . . . 32
8.7.1. NC-Request-Type AVP . . . . . . . . . . . . . . . . . 32
8.7.2. NAT-Control-Install AVP . . . . . . . . . . . . . . . 33
8.7.3. NAT-Control-Remove AVP . . . . . . . . . . . . . . . . 33
8.7.4. NAT-Control-Definition AVP . . . . . . . . . . . . . . 33
8.7.5. NAT-Internal-Address AVP . . . . . . . . . . . . . . . 34
8.7.6. NAT-External-Address AVP . . . . . . . . . . . . . . . 34
8.7.7. Max-NAT-Bindings . . . . . . . . . . . . . . . . . . . 35
8.7.8. NAT-Control-Binding-Rule AVP . . . . . . . . . . . . . 35
8.7.9. Duplicate-Session-Id AVP . . . . . . . . . . . . . . . 35
9. Accounting Commands . . . . . . . . . . . . . . . . . . . . . 35
9.1. NAT Control Accounting Messages . . . . . . . . . . . . . 36
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9.2. NAT Control Accounting AVPs . . . . . . . . . . . . . . . 36
9.2.1. NAT-Control-Record . . . . . . . . . . . . . . . . . . 36
9.2.2. NAT-Control-Binding-Status . . . . . . . . . . . . . . 36
9.2.3. Current-NAT-Bindings . . . . . . . . . . . . . . . . . 37
10. AVP Occurrence Table . . . . . . . . . . . . . . . . . . . . . 37
10.1. DNCA AVP Table for NAT Control Initial and Update
Requests . . . . . . . . . . . . . . . . . . . . . . . . . 37
10.2. DNCA AVP Table for Session Query request . . . . . . . . . 38
10.3. DNCA AVP Table for Accounting Message . . . . . . . . . . 38
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38
11.1. Application Identifier . . . . . . . . . . . . . . . . . . 39
11.2. Command Codes . . . . . . . . . . . . . . . . . . . . . . 39
11.3. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 39
11.4. Result-Code AVP Values . . . . . . . . . . . . . . . . . . 39
11.5. NC-Request-Type AVP . . . . . . . . . . . . . . . . . . . 39
11.6. NAT-Control-Binding-Status AVP . . . . . . . . . . . . . . 39
12. Security Considerations . . . . . . . . . . . . . . . . . . . 40
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 41
14. Change History (to be removed prior to publication as an
RFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
15. Normative References . . . . . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44
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1. Introduction
Internet service providers have started to deploy Network Address
Translators (NATs) and Network Address and Port Translators (NAPTs)
in their networks to deal with the depletion of available public IPv4
addresses. This document defines a Diameter application allowing
providers to control the behavior of these 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 end point or user. The main motivation for
restricting the number of bindings on a per end point basis is to
protect the service of the service provider against denial of
service attacks. If multiple end points share a single public IP
address, these end points can share fate. If one end point 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 end points sharing
the same public IP address. The efficiency of a NAPT deployment
depends on the maximum number of bindings an end point could use.
Given that the typical number of bindings an end point uses
depends on the type of end point (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 end points, it is desirable to actively manage
the maximum number of bindings.
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. 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
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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 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.
4. Generates reports and accounting records: Reports established
bindings for a particular user. The collected information is
used by accounting systems for statistical purposes.
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
(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.
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
occurence 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:
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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
NAT-device: Network Address Translator or Network Address and Port
Translator: An entity performing NAT or NAPT
NAT-controller: Entity controlling the behavior of a NAT-device
NAS: Network Access Server
NCR: NAT Control Request
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.
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+---------+
| |
| 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
impacted. This includes cases like:
o Provisioning static NAT bindings for particular endpoints
o Using different public IP address pools for different set of
endpoints (for example, residential or business customers)
o Reporting allocated bindings on a per endpoint basis
o Integrate control of the NAT-device into the already existing per
endpoint management infrastructure of the service provider
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+---------+
| |
| AAA |
| |
+---------+
|
|
|
|
+--------+ +---------+ +--------+ +----------+
| IPv4/ | | | | | | IPv4 |
| IPv6 |----| NAS |----| NAT- |----| Internet |
| Host | | | | device | | |
+--------+ +---------+ +--------+ +----------+
<-------- 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 two DNCA Diameter peers. One DNCA Diameter peer
resides within the NAT-device, the other DNCA Diameter peer resides
within the NAT-Controller. 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.
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
DNCA can be deployed in different ways. Two common deployment
scenarios are outlined in Figure 3 ("integrated deployment") and
Figure 4 ("autonomous deployment"). The two 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.
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 NAT-device. With this
information, the NAS can provide a single accounting record for the
endpoint. A system correlating the accounting information received
from NAS and NAT-device would not be needed.
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.
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+---------+
| |
| AAA |
| |
+---------+
|
|
|
+--------+ +---------+ +--------+ +----------+
| IPv4/ | | (C) | | | | IPv4 |
| IPv6 |----| NAS |----| NAT- |----| Internet |
| Host | | | | device | | |
+--------+ +---------+ +--------+ +----------+
<-------- 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. 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.
+---------+
| (C) |
| AAA |---------
| | |
+---------+ |
| |
| |
| |
+--------+ +---------+ +---------+ +----------+
| IPv4/ | | | | | | IPv4 |
| IPv6 |----| NAS |----| NAT- |----| Internet |
| Host | | | | device | | |
+--------+ +---------+ +---------+ +----------+
<-------- 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. DNCA runs between a Diameter peer residing in a NAT-
controller and a Diameter peer residing in a NAT-device. 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 set up
include local configuration, receipt of a packet from a formerly
unknown IP-address, etc.
4.1. Session Establishment
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.
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. Figure 5 shows the initial protocol interaction
between the two DNCA Diameter peers.
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 which may be included,
comprises:
o A list of NAT bindings, which should be pre-allocated for the
session; for example, in case a user requires a fixed external IP-
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address/port pair for one of his applications.
o The maximum number of NAT-bindings allowed for an endpoint.
o A description of the external IP-address pool(s) to be used for
the session.
o A reference to a predefined binding rule on the NAT-device, which
is applied to the session. Such a predefined binding rule 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.
In certain cases, the NAT-device may not be able to perform the tasks
requested within the NCR. These include the following:
o 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, DNCA Diameter peer and endpoint identifier match
an already existing session, the DNCA Diameter peer within the
NAT-device returns NCA with Result-Code set to SESSION_EXISTS, and
provides the Session-Id of the existing session in the Duplicate-
Session-Id AVP.
o 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 returns a 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.
o If the NCR contains a binding rule not defined on the NAT-device,
the DNCA Diameter peer within the NAT-device returns NCA with
Result-Code AVP set to UNKNOWN_BINDING_RULE.
o In case the NAT-device is unable to establish all of the bindings
requested in the NCR, the DNCA Diameter peer will return a NCA
with Result-Code set to BINDING_FAILURE. A DNCA Diameter peer
within a 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 fails.
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o If a NAT-device does not have sufficient resources to process a
request, the DNCA Diameter peer returns a 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.
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
Trigger |
| |
| NCR |
|------------------------------------------>|
| (INITIAL_REQUEST, endpoint classifier, |
| session id, NAT control config data) |
| |
| |
| |
| |
| If Able to comply
| with Request then
| Create session state
| |
| |
| NCA |
|<------------------------------------------|
| (result code) |
| |
| |
Figure 5: Initial NAT control request and session establishment
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 a NCA with Result-Code set to DIAMETER_SUCCESS.
4.2. Session Re-Authorization
Session re-authorization is performed if the NAT-controller desires
to change the behavior of the NAT-device for an existing session.
Session re-authorization could be used, for example, to change the
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number of allowed bindings for a particular session, or establish or
remove a pre-defined binding.
The DNCA Diameter peer within the NAT-controller generates a NCR
message to DNCA Diameter peer within 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. Figure 6 shows the
protocol interaction between the two DNCA Diameter peers.
In certain cases, the NAT-device may not be able to perform the tasks
requested within the NCR. These include the following:
o If DNCA Diameter peer within a NAT-device 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,
a NCA with Result-Code AVP set to UNKNOWN_BINDING_RULE is
returned.
o If the NAT-device cannot establish the requested binding because
the maximum number of allowed bindings has been reached for the
endpoint classifier, a NCA with Result-Code AVP set to
MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT by the DNCA Diameter peer.
o If the NAT-device 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 endpoint, a NCA with Result-Code set to
BINDING_FAILURE is returned. As already noted, the DNCA Diameter
peer in a NAT-device treats a 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.
o If the NAT-device does not have sufficient resources to process a
request, a NCA with Result-Code set to RESOURCE_FAILURE is
returned.
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
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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 the NAT-
device, the binding rule overrides any previously defined rule 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 the NAT-device) and the values in Max-NAT-Binding and
NAT-Control-Definition AVPs contradict those specified in the pre-
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 in case the tasks requested within the NCR cannot be
completed.
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
Change of session |
attributes |
| |
| NCR |
|------------------------------------------>|
| (UPDATE_REQUEST session id, |
| NAT control config data) |
| |
| |
| If able to comply
| with the request:
| Update session state
| |
| |
| NCA |
|<------------------------------------------|
| (result code) |
| |
| |
Figure 6: NAT control request for session update
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4.3. Session and Binding Query
Session query can 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.
A DNCA Diameter peer within the NAT-controller starts a session query
by sending a NCR message with NC-Request-Type AVP set to
QUERY_REQUEST. Figure 7 shows the protocol interaction between the
DNCA Diameter peers.
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 IP-address.
1. Request a list of currently allocated NAT bindings for a
particular session: On receiving a NCR, the NAT-device looks up
the session information for the session ID contained in the NCR,
and reports all currently active NAT-bindings for the session
using a 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 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 the DNCA Diameter
peer within the NAT-controller 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. The
DNCA Diameter peer within the NAT-device 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 was 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.
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NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| |
DNCA Session Established |
| |
| NCR |
|------------------------------------------>|
| (QUERY_REQUEST) |
| |
| |
| |
| Look up corresponding session
| and associated NAT-bindings
| |
| NCA |
|<------------------------------------------|
| (Result-Code) |
| |
| |
Figure 7: Session query
4.4. Session Termination
Similar to session initiation, session tear down is always 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.
In response, the DNCA Diameter peer within the NAT-device sends an
accounting stop record reporting all bindings and notifies its DNCA
Diameter peer 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
the two DNCA Diameter peers.
If a DNCA Diameter peer within a NAT-device receives a STR and fails
to find a matching session, the DNCA Diameter peer returns a STA with
Result-Code set to DIAMETER_UNKNOWN_SESSION_ID.
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NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
Trigger |
| |
| STR |
|------------------------------------------->|
| (session id) |
| |
| |
| Remove NAT-bindings
| of session
| |
| |
| Send accounting stop |
|<-------------------------------------------|
| reporting all session bindings |
| |
| Terminate session /
| Remove session state
| |
| |
| |
| STA |
|<-------------------------------------------|
| (Result-Code) |
| |
Figure 8: Terminate NAT control session
4.5. Session Abort
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
acknowledges successful session abort using a Abort Session Answer
(ASA) message with Result-Code set to DIAMETER_SUCCESS. Figure 9
shows the protocol interaction between the DNCA Diameter peers. The
DNCA Diameter peers will start a session termination procedure as
described in Section 4.4 following an ASA with Result-Code set to
DIAMETER_SUCCESS.
If the DNCA Diameter peer within a NAT-controller receives an ASR but
fails to find a matching session, it returns 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 is
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returned.
NAT-controller (DNCA Diameter peer) NAT-device (DNCA Diameter peer)
| |
| |
| Trigger
| |
| ASR |
|<-------------------------------------------|
| (session id) |
| |
| |
| ASA |
|------------------------------------------->|
| (Result-Code) |
| |
| |
| On successful ASA |
|<------Session Termination Procedure------->|
Figure 9: Abort NAT control session
4.6. Failure cases of the DNCA Diameter peers
This document does not specify the behavior in case NAT-device and
NAT-controller, or their respective DNCA Diameter peers are out of
sync. This could happen for example if one of the entities restarts,
in case of a (temporary) loss of network connectivity etc. The
peering entities MUST have built-in redundancy support to recover
state in case of failure.
Example failure cases include the following:
o NAT-controller and the DNCA Diameter peer within the NAT-
controller lose state (e.g. due to a restart). In this case,
* the DNCA Diameter peer within the NAT-device may receive a 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 returns a
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.
* 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
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DIAMETER_UNKNOWN_SESSION_ID in response. On receiving the
response, the DNCA Diameter peer clears the session and removes
the associated session state.
o 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 returns NCA with Result-Code set
to DIAMETER_UNKNOWN_SESSION_ID.
o The DNCA Diameter peer within the NAT-controller is unreachable,
for example detected by Diameter watchdog, or down and accounting
requests from the DNCA Diameter peer fail to get a response. The
mechanism to ensure that a DNCA Diameter peer within the NAT-
controller no longer has associated state for a session which was
cleared or removed by the DNCA Diameter peer within the NAT-device
is beyond the scope of this document.
o The DNCA Diameter peer within the NAT-device 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 could for example choose to stop
offering connectivity service.
5. Use Of The Diameter Base Protocol
The Diameter Base Protocol defined by [RFC3588] applies with the
clarifications listed in the present specification.
5.1. Securing Diameter Messages
For secure transport of Diameter messages recommendations in
[RFC3588] apply.
DNCA Diameter peers MAY verify their identity during the Capabilities
Exchange Request procedure.
A DNCA Diameter peer within the NAT-device MAY verify that a DNCA
Diameter peer that issues a NCR command is allowed to do so based on:
o The identity of the DNCA Diameter peer
o The type of NCR Command
o The content of the NCR Command
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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. 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. 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
[RFC3588] if it is unable to maintain sessions due to resource
limitation.
5.4. Routing Considerations
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.
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-
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 the DNCA Diameter peer within the NAT-controller to the DNCA
Diameter peer within the NAT-device in order to install NAT-bindings.
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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.
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 ]
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 the DNCA Diameter peer within the NAT-device in response
to NAT-Control-Request command.
Message format:
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<NC-Answer> ::= < Diameter Header: TBD, PXY >
[ Session-Id ]
{ Origin-Host }
{ Origin-Realm }
{ Result-Code }
[ 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 ]
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 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
[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 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 NCA.
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
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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 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.
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 Sent STR Discon
received
but peer 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
NCA received.
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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
user/device
The following state machine is observed by a DNCA Diameter peer
within a NAT-device.
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DNCA Diameter peer within a NAT-device
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 10: 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)
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.
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)
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-Rule AVP,
that refers to a predefined policy template in the NAT-device,
is unknown.
BINDING_FAILURE (TBD)
DNCA indicates that the requested binding(s) could not be
installed. For example: Requested ports are already in use.
MAXIMUM_BINDINGS_REACHED_FOR_ENDPOINT (TBD)
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.
SESSION_EXISTS (TBD)
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.
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INSUFFICIENT_CLASSIFIERS (TBD)
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.
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 11: Reused NASREQ Diameter application AVPs
8.4. Reused AVPs 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 12: Reused attributes from RFC 4675
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8.5. Reused AVPs from Diameter QoS Application
The following AVPs are reused from the Traffic Classification and
Quality of Service (QoS) Attributes for Diameter [RFC5777].
+-------------------+
| 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 13: Reused QoS-attributes
8.6. Reused AVPs 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 14: 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 8.7.1 Enumerated | M | P | Y |
|NAT-Control-Install TBD 8.7.2 Grouped | M | P | Y |
|NAT-Control-Remove TBD 8.7.3 Grouped | M | P | Y |
|NAT-Control-Definition TBD 8.7.4 Grouped | M | P | Y |
|NAT-Internal-Address TBD 8.7.5 Grouped | M | P | Y |
|NAT-External-Address TBD 8.7.6 Grouped | M | P | Y |
|Max-NAT-Bindings TBD 8.7.7 Unsigned32 | M | P | Y |
|NAT-Control- TBD 8.7.8 OctetString| M | P | Y |
| Binding-Rule | | | |
|Duplicate- TBD 8.7.9 UTF8String | M | P | Y |
| Session-ID | | | |
|NAT-Control-Record TBD 9.2.1 Grouped | M | P | Y |
|NAT-Control- TBD 9.2.2 Enumerated | M | P | Y |
| Binding-Status | | | |
|Current-NAT-Bindings TBD 9.2.3 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. |
+-------------------------------------------------------------------+
Figure 15: 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 to initiate a Diameter NAT control
session between the DNCA Diameter peers.
UPDATE_REQUEST (2)
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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 (3)
Query Request is used to query a NAT-device 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 the maximum number of NAT bindings to be
allowed for a subscriber and the NAT-Control-Binding-Rule that
references a predefined policy 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.
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 the DNCA Diameter peers.
If both the NAT-Internal-Address and NAT-External-Address AVP(s) are
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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 IP-address are specified then the binding reserves the
IP-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, 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.
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 the Framed-IP-Address AVP
is present. 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.
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 for a particular
endpoint.
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 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-
Rule AVP in the corresponding NAT-Control-Install AVPs of multiple
endpoints.
8.7.9. Duplicate-Session-Id AVP
The Duplicate-Session-Id AVP (AVP Code TBD) is of type UTF8String.
It is used to report errors and contains the Session-Id of an
existing session.
9. Accounting Commands
The DNCA reuses session based accounting as defined in the 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 the DNCA Diameter peer within the NAT-
device to its associated DNCA Diameter peer within the NAT-
controller.
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-
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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.
The function of correlating the multiple bindings used by an endpoint
at any given time is relegated to the post processor.
The DNCA Diameter peer within the NAT-device 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 the DNCA Diameter peers. DNCA Application ID is used in the
accounting commands. ACR contains one or more optional NAT-Control-
Record AVP to report the bindings. The NAT-device indicates the
number of allocated NAT bindings to 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.
9.2. NAT Control Accounting AVPs
In addition to AVPs for ACR specified in [RFC3588], the DNCA Diameter
peer within the NAT-device 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:
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Created (1)
NAT binding is created.
Active (2)
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 the values assigned to existing namespaces
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managed by IANA.
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.
11.1. Application Identifier
This specification assigns the value <TBD>, 'Diameter NAT Control
Application', to the Application Identifier namespace defined in
[RFC3588]. See Section 4 for more information.
11.2. Command Codes
This specification uses the value <TBD> from the Command code
namespace defined in [RFC3588] for the NAT-Control-Request (NCR),
NAT-Control-Answer (NCA) commands. See Section 6.1 and Section 6.2
for more information on these commands.
11.3. AVP Codes
This specification assigns the values <TBD> from the AVP code
namespace defined in [RFC3588]. See Figure 15for the assignment of
the namespace in this specification.
11.4. Result-Code AVP Values
This specification assigns the values <TBD> (4xxx, 5xxx, 5xxx, 5xxx,
5xxx,5xxx) from the Result-Code AVP value namespace defined in
[RFC3588]. See Section 8.2 for the assignment of the namespace in
this specification.
11.5. NC-Request-Type AVP
As defined in Section 8.7.1, 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 [RFC5226].
11.6. NAT-Control-Binding-Status AVP
As defined in Section 8.7.1, 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 [RFC5226].
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12. Security Considerations
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.
Security between NAT-controller and NAT-device has a number of
components: authentication, authorization, integrity, and
confidentiality.
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 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, templates on the NAT-device specifying pre-defined binding
rules 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.
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.
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.
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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.
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 Section 5.1 ). If the DNCA communication traverses
untrusted networks, it is assumed that messages between DNCA Diameter
peers are secured using either IPsec or TLS. Please refer to
[RFC3588], section 13 for details. DNCA Diameter peers MAY perform
bilateral authentication, authorization as well as procedures to
ensure integrity and confidentiality of the information exchange.
It is assumed that the DNCA Diameter peers are typically in the same
domain and have a mutual trust set up. This document does not
specify a mechanisms for authorization between the DNCA Diameter
peers. It is assumed that the DNCA Diameter peers are 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.
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 end points 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 end point. In addition one could setup 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 protections on
DNCA and its Diameter protocol exchanges don't prevent such abuses of
NAT-control. 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.
13. Acknowledgements
The authors would like to thank Wesley Eddy, Miguel A. Garcia, Jouni
Korhonen, Matt Lepinski, Avi Lior, Chris Metz, Pallavi Mishra, Lionel
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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
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 last call 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
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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
Changes from -07 to -08
a. Added section 4.6 to describe session abort
b. Editorial changes
c. Nomenclature change: From DNCA Agent/Manager to DNCA Diameter
peers identifying the location where they reside (NAT-controller
or NAT-device)
d. IANA consideration Section format changes
e. Updated security section (included considerations directly,
rather than referring to Diameter QoS similarities).
Changes from -08 to -09
a. expanded on the need for an SP controlling the maximum number of
bindings of an end point (see introduction section)
b. 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
c. editorial changes
15. Normative References
[ETSIES283034]
ETSI, "Telecommunications and Internet Converged Services
and Protocols for Advanced Networks (TISPAN),Network
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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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[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.
Authors' Addresses
Frank Brockners
Cisco
Hansaallee 249, 3rd Floor
DUESSELDORF, NORDRHEIN-WESTFALEN 40549
Germany
Email: fbrockne@cisco.com
Shwetha Bhandari
Cisco
Cessna Business Park, Sarjapura Marathalli Outer Ring Road
Bangalore, KARNATAKA 560 087
India
Email: shwethab@cisco.com
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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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