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SIPPING D. Petrie
Internet-Draft SIPez LLC.
Intended status: Standards Track S. Channabasappa, Ed.
Expires: April 1, 2010 CableLabs
September 28, 2009
A Framework for Session Initiation Protocol User Agent Profile Delivery
draft-ietf-sipping-config-framework-16
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Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Abstract
This document specifies a framework to enable configuration of
Session Initiation Protocol (SIP) User Agents in SIP deployments.
The framework provides a means to deliver profile data that User
Agents need to be functional, automatically and with minimal or no
User and Administrative intervention. The framework describes how
SIP User Agents can discover sources, request profiles and receive
notifications related to profile modifications. As part of this
framework, a new SIP event package is defined for notification of
profile changes. The framework provides minimal data retrieval
options to ensure interoperability. The framework does not include
specification of the profile data within its scope.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Reference Model . . . . . . . . . . . . . . . . . . . . . 7
3.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Profile Types . . . . . . . . . . . . . . . . . . . . . . 10
3.4. Profile delivery stages . . . . . . . . . . . . . . . . . 11
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Simple Deployment Scenario . . . . . . . . . . . . . . . . 12
4.2. Devices supporting multiple users from different
Service Providers . . . . . . . . . . . . . . . . . . . . 13
5. Profile Delivery Framework . . . . . . . . . . . . . . . . . . 15
5.1. Profile delivery stages . . . . . . . . . . . . . . . . . 15
5.1.1. Profile Enrollment . . . . . . . . . . . . . . . . . . 16
5.1.2. Content Retrieval . . . . . . . . . . . . . . . . . . 18
5.1.3. Change Notification . . . . . . . . . . . . . . . . . 18
5.1.4. Enrollment Data and Caching . . . . . . . . . . . . . 19
5.2. Securing Profile Delivery . . . . . . . . . . . . . . . . 22
5.2.1. Securing Profile Enrollment . . . . . . . . . . . . . 23
5.2.2. Securing Content Retrieval . . . . . . . . . . . . . . 24
5.2.3. Securing Change Notification . . . . . . . . . . . . . 25
5.3. Additional Considerations . . . . . . . . . . . . . . . . 25
5.3.1. Bootstrapping Identities and Credentials . . . . . . . 25
5.3.2. Profile Enrollment Request Attempt . . . . . . . . . . 27
5.3.3. Device Types . . . . . . . . . . . . . . . . . . . . . 31
5.3.4. Profile Data . . . . . . . . . . . . . . . . . . . . . 31
5.3.5. Profile Data Frameworks . . . . . . . . . . . . . . . 32
5.3.6. Additional Profile Types . . . . . . . . . . . . . . . 33
5.3.7. Deployment considerations . . . . . . . . . . . . . . 33
5.4. Support for NATs . . . . . . . . . . . . . . . . . . . . . 34
6. Event Package Definition . . . . . . . . . . . . . . . . . . . 34
6.1. Event Package Name . . . . . . . . . . . . . . . . . . . . 34
6.2. Event Package Parameters . . . . . . . . . . . . . . . . . 34
6.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 37
6.4. Subscription Duration . . . . . . . . . . . . . . . . . . 38
6.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 38
6.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 38
6.7. Notifier Generation of NOTIFY Requests . . . . . . . . . . 39
6.8. Subscriber Processing of NOTIFY Requests . . . . . . . . . 39
6.9. Handling of Forked Requests . . . . . . . . . . . . . . . 40
6.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 40
6.11. State Agents . . . . . . . . . . . . . . . . . . . . . . . 40
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7.1. Example 1: Device requesting profile . . . . . . . . . . . 40
7.2. Example 2: Device obtaining change notification . . . . . 43
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47
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8.1. SIP Event Package . . . . . . . . . . . . . . . . . . . . 47
8.2. Registry of SIP configuration profile types . . . . . . . 47
9. Security Considerations . . . . . . . . . . . . . . . . . . . 48
9.1. Local-network profile . . . . . . . . . . . . . . . . . . 49
9.2. Device profile . . . . . . . . . . . . . . . . . . . . . . 50
9.3. User profile . . . . . . . . . . . . . . . . . . . . . . . 52
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 52
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53
11.1. Normative References . . . . . . . . . . . . . . . . . . . 53
11.2. Informative References . . . . . . . . . . . . . . . . . . 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 55
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1. Introduction
SIP User Agents require configuration data to function properly.
Examples include local network, device and user specific information.
A configuration data set specific to an entity is termed a profile.
For example, device profile contains the configuration data related
to a device. The process of providing devices with one or more
profiles is termed profile delivery. Ideally, this profile delivery
process should be automatic and require minimal or no user
intervention.
Many deployments of SIP User Agents require dynamic configuration and
cannot rely on pre-configuration. This framework provides a standard
means of providing dynamic configuration which simplifies deployments
containing SIP User Agents from multiple vendors. This framework
also addresses change notifications when profiles change. However,
the framework does not define the content or format of the profile,
leaving that to future standardization activities.
This document is organized as follows. Section 3 provides a high-
level overview of the abstract components, profiles, and the profile
delivery stages. Section 4 provides some motivating use cases.
Section 5 provides details of the framework operation and
requirements. Section 6 provides a concise event package definition.
Section 7 follows with illustrative examples of the framework in use.
2. Terminology
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 RFC 2119 [RFC2119].
This document also reuses the SIP terminology defined in [RFC3261]
and [RFC3265], and specifies the usage of the following terms.
Device: software or hardware entity containing one or more SIP user
agents. It may also contain entities such as a DHCP client.
Device Provider: the entity responsible for managing a given device.
Local Network Provider: the entity that controls the local network
to which a given device is connected.
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SIP Service Provider: the entity providing SIP services to users.
This can refer to private enterprises or public entities.
Profile: configuration data set specific to an entity (e.g., user,
device, local network or other).
Profile Type: a particular category of Profile data (e.g., User,
Device, Local Network or other).
Profile Delivery Server (PDS): the source of a Profile, it is the
logical collection of the Profile Notification Component (PNC) and
the Profile Content Component(PCC).
Profile Notification Component (PNC): the logical component of a
Profile Delivery Server that is responsible for enrolling devices
and providing profile notifications.
Profile Content Component (PCC): the logical component of a Profile
Delivery Server that is responsible for storing, providing access
to, and accepting profile content.
Profile Delivery Stages: the processes that lead a device to obtain
profile data, and any subsequent changes, are collectively called
profile delivery stages.
3. Overview
This section provides an overview of the configuration framework. It
presents the reference model, the motivation, the profile delivery
stages and a mapping of the concepts to specific use cases. It is
meant to serve as a reference section for the document, rather than
providing a specific logical flow of material, and it may be
necessary to revisit these sections for a complete appreciation of
the framework.
The SIP UA Profile Delivery Framework uses a combination of SIP event
messages (SUBSCRIBE and NOTIFY; [RFC3265]) and traditional file
retrieval protocols, such as HTTP [RFC2616], to discover, monitor,
and retrieve configuration profiles. The framework defines three
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types of profiles (local-network, device, and user) in order to
separate aspects of the configuration which may be independently
managed by different administrative domains. The initial SUBSCRIBE
message for each profile allows the UA to describe itself (both its
implementation and the identity requesting the profile), while
requesting access to a profile by type, without prior knowledge of
the profile name or location. Discovery mechanisms are specified to
help the UA form the subscription URI (the Request URI for the SIP
SUBSCRIBE). The SIP UAS handling these subscriptions is the Profile
Delivery Server (PDS). When the PDS accepts a subscription, it sends
a NOTIFY to the device. The initial NOTIFY from the PDS for each
profile may contain profile data or a reference to the location of
the profile, to be retrieved using HTTP or similar file retrieval
protocols. By maintaining a subscription to each profile, the UA
will receive additional NOTIFY messages if the profile is later
changed. These may contain a new profile, a reference to a new
profile, or a description of profile changes, depending on the
Content-Type [RFC3261] in use by the subscription. The framework
describes the mechanisms for obtaining three different profile types,
but does not describe the data model they utilize (the data model is
out of scope for this specification).
3.1. Reference Model
The design of the framework was the result of a careful analysis to
identify the configuration needs of a wide range of SIP deployments.
As such, the reference model provides for a great deal of
flexibility, while breaking down the interactions to their basic
forms, which can be reused in many different scenarios.
The reference model for the framework defines the interactions
between the Profile Delivery Server(PDS) and the device. The device
needs the profile data to function effectively in the network. The
PDS is responsible for responding to device requests and providing
the profile data. The reference model is illustrated in Figure 1.
+-------------------------+
+--------+ | Profile Delivery Server |
| Device |<==========================>| +---+ +---+ |
+--------+ | |PNC| |PCC| |
| +---+ +---+ |
+-------------------------+
PNC = Profile Notification Component
PCC = Profile Content Component
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Figure 1: Framework Reference Model
The PDS is subdivided into two logical components:
o Profile Notification Component (PNC), responsible for enrolling
devices for profiles and providing profile change notifications;
o Profile Content Component (PCC), responsible for storing,
providing access to, and accepting modifications related to
profile content.
3.2. Motivation
The motivation for the framework can be demonstrated by applying the
reference model presented in Section 3.1 to two scenarios that are
representative of the two ends of a spectrum of potential SIP
deployments.
In the simplest deployment scenario, a device connects through a
network that is controlled by a single provider who provides the
local-network, manages the devices, and offers services to the users.
The provider propagates profile data to the device that contains all
the necessary information to obtain services in the network
(including information related to the local-network and the users).
This is illustrated in Figure 2. An example is a simple enterprise
network that supports SIP-based devices.
--------------
/ Local-network, \
| Device & Service |
\ Provider /
----------------
|
|
--------
| Device |
--------
|
|
----
|User|
----
Figure 2: Simple Deployment Model
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In more complex deployments, devices connect via a local network that
is not controlled by the SIP Service Provider, such as devices that
connect via available public WiFi hot spots. In such cases, local
network providers may wish to provide local network information such
as bandwidth constraints to the devices.
Devices may also be controlled by device providers that are
independent of the SIP service provider who provides user services,
such as kiosks that allow users to access services from remote
locations. In such cases the profile data may have to be obtained
from different profile sources: local network provider, device
provider and SIP service provider. This is indicated in Figure 3 .
--------
/ SIP \
| Service | -> Provides 'user' profile
| Provider | data (e.g., services
\ / configuration)
-------- --------
| / \
| | Device | -> Provides 'device' profile
| | Provider | data (e.g., device specifics)
| \ /
| ---------
| /
| / -------
| / / Local \
| / | Network |
| | | Provider | -> Provides 'local-network' profile
| | \ / data (e.g., bandwidth)
| | -------
| | /
| | /
| | |
===================
( Local Network )
===================
|
|
--------
| Device | -> Needs the 'local-network'
-------- and 'device' profile
/ \
/ \
------ ------
|User A| |User B| -> Users need 'user' profiles
------ ------
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Figure 3: Complex Deployment Model
In either case, Providers need to deliver to the device, profile data
that is required to participate in their network. Examples of
profile data include the list of codecs that can be used and the SIP
proxies to connect to for services. Pre-configuration of such
information is one option if the device is always served by the same
set of Providers. In all other cases, the profile delivery needs to
be automated and consistent across Providers. Given the presence of
a number of large deployments where pre-configuration is neither
desired nor optimal, there is a need for a common configuration
framework such as the one described in this document.
Further, the former deployment model can be accomplished by the
device obtaining profile data from a single provider. However, the
latter deployment model requires the device to obtain profile data
from different providers. To address either deployment, or any
variation in between, one needs to allow for profile delivery via
one, or more, Providers. The framework accomplishes this by
specifying multiple profile types and a set of profile delivery
stages to obtain them. These are introduced in the sub-sections to
follow.
3.3. Profile Types
The framework handles the presence of potentially different Providers
by allowing for multiple profile types. Clients request each profile
separately, and obtain them from the same, or different, Providers.
A deployment can also choose to pre-configure the device to request
only a subset of the specified profile types. The framework
specifies three basic profile types, as follows:
Local Network Profile: contains configuration data related to the
local network to which a device is directly connected, provided by
the Local Network Provider.
Device Profile: contains configuration data related to a specific
device, provided by the Device Provider.
User Profile: contains configuration data related to a specific
User, as required to reflect that user's preferences and the
particular services subscribed to. It is provided by the SIP
Service Provider.
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Additional profile types may also be specified.
PDSs and devices will implement all the three profile types. A
device that has not been configured otherwise will try to obtain all
the three profile types, in the order specified by this framework. A
device being bootstrapped SHOULD request the device profile type (see
Section 5.3.1 for more information). The device can be configured
with a different behavior via profile data previously obtained by the
device, or by using other means such as pre-configuration or manual
configuration. The data models associated with each profile type are
out of scope for this document. Follow-on standardization activities
are expected to specify such data models.
3.4. Profile delivery stages
The framework specified in this document requires a device to
explicitly request profiles. It also requires one or more PDSs which
provide the profile data. The processes that lead a device to obtain
profile data, and any subsequent changes, can be explained in three
stages, termed the profile delivery stages.
Profile Enrollment: the process by which a device requests, and if
successful, enrolls with a PDS capable of providing a profile. A
successful enrollment is indicated by a notification containing
the profile information (contents or content indirection
information). Depending on the request, this could also result in
a subscription to notification of profile changes.
Profile Content Retrieval: the process by which a device retrieves
profile contents, if the profile enrollment resulted in content
indirection information.
Profile Change Notification: the process by which a device is
notified of any changes to an enrolled profile. This may provide
the device with modified profile data or content indirection
information.
4. Use Cases
This section provides a small, non-comprehensive set of
representative use cases to further illustrate how this Framework can
be utilized in SIP deployments. The first use case is simplistic in
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nature, whereas the second is relatively complex. The use cases
illustrate the effectiveness of the framework in either scenario.
For Security Considerations please refer to Section 5 and Section 9.
4.1. Simple Deployment Scenario
Description: Consider a deployment scenario (e.g., a small private
enterprise) where a participating device implements this framework
and is configured, using previously obtained profile data, to request
only the device profile. Assume that the device operates in the same
network as the PDS (i.e., there is no NAT) and it obtains its IP
configuration using DHCP. Typical communication between the device
and the PDS will traverse one or more SIP proxies, but is not
required, and is omitted in this illustration.
Figure 4 illustrates the sequence of events that include device
startup and a successful profile enrollment for the device profile
that results in device profile data. It then illustrates how a
change in the profile data is delivered via Profile Change
Notification.
+----------------------+
+--------+ | Provider's Network |
| Device | | |
| | | |
+--------+ | DHCP PDS |
+----------------------+
| | |
(A) |<============== DHCP =============>| |
| |
| |
| |
(B) |<=========== Profile Enrollment ============>|
| | Profile data
| | is modified
| |
(C) |<============ Profile Change ================|
| Notification |
| |
| |
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Figure 4: Use Case 1
The following is an explanation of the interactions in Figure 4.
(A) Upon initialization, the device obtains IP configuration
parameters such as IP address using DHCP.
(B) The device requests profile enrollment for the device profile.
Successful enrollment provides it with a notification containing
the device profile data.
(C) Due to a modification of the device profile, a profile change
notification is sent across to the device, along with the
modified profile.
4.2. Devices supporting multiple users from different Service Providers
Description: Consider a single device that allows multiple users to
obtain services from different SIP Service Providers, e.g., a kiosk
at an airport.
The following assumptions apply:
o Provider A is the Device and Local Network Provider for the
device, and the SIP Service Provider for user A; Provider B is
the SIP Service Provider for user B.
o Profile enrollment always results in content indirection
information requiring profile content retrieval.
o Communication between the device and the PDSs is facilitated via
one or more SIP proxies (only one is shown in the illustration).
Figure 5 illustrates the use case and highlights the communications
relevant to the framework specified in this document.
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User User
A B +----------------------+ +----------------------+
+--------+ | Provider | | Provider |
| Device | | A | | B |
| | | | | |
+--------+ | DHCP PROXY PDS | | PROXY PDS |
+----------------------+ +----------------------+
| | | | | |
(A) |<====DHCP====>| | | | |
| | | | |
| | | | |
| Profile Enrollment | | | |
(B) |<local-network profile>|<====>| | |
|
| <<Profile content retrieval>>
|
|
| Profile Enrollment | | | |
(C) |<== device profile ==> |<====>| | |
|
| <<Profile content retrieval>>
|
.
.
.
[[User A obtains services]]
| Profile Enrollment | | | |
(D) |<= user profile (A) => |<====>| | |
| | | | |
|
| <<Profile content retrieval>>
.
.
.
.
[[User B obtains services]]
|
| Profile Enrollment | |
(E) |<=========== user profile (B) ==========>|<=========>|
| | |
| <<Profile content retrieval>>
|
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Figure 5: Use Case 2
The following is an explanation of the interactions in Figure 5.
(A) Upon initialization, the device obtains IP configuration
parameters using DHCP. This also provides the local domain
information to help with local-network profile enrollment.
(B) The device requests profile enrollment for the local network
profile. It receives an enrollment notification containing
content indirection information from Provider A's PDS. The
device retrieves the profile (this contains useful information
such as firewall port restrictions and available bandwidth).
(C) The device then requests profile enrollment for the device
profile. It receives an enrollment notification resulting in
device profile content retrieval. The device initializes the
user interface for services.
(D) User A with a pre-existing service relationship with Provider A
attempts communication via the user Interface. The device uses
the user supplied information (including any credential
information) and requests profile enrollment for user A's
profile. Successful enrollment and profile content retrieval
results in services for user A.
(E) At a different point in time, user B with a service relationship
with Provider B attempts communication via the user Interface.
It enrolls and retrieves user B's profile and this results in
services for user B.
The discovery mechanisms for profile enrollment described by the
framework, or the profile data themselves, can result in outbound
proxies that support devices behind NATs, using procedures specified
in [I-D.ietf-sip-outbound].
5. Profile Delivery Framework
This section specifies the profile delivery framework. It provides
the requirements for the three profile delivery stages introduced in
Section 3.4 and presents the associated security requirements. It
also presents considerations such as back-off and retry mechanisms.
5.1. Profile delivery stages
The three profile delivery stages - enrollment, content retrieval and
change notification - apply separately to each profile type specified
for use with this framework. The following sub-sections provide the
requirements associated with each stage.
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5.1.1. Profile Enrollment
Profile enrollment is the process by means of which a device
requests, and receives, profile data. Each profile type specified in
this document requires an independent enrollment request. However, a
particular PDS can support enrollment for one or more profile types.
Profile enrollment consists of the following operations, in the
specified order.
Enrollment request transmission
Profile enrollment is initiated when the device transmits a SIP
SUBSCRIBE request [RFC3265] for the 'ua-profile' event package,
specified in Section 6. The profile being requested is indicated
using the 'profile-type' parameter. The device MUST transmit the
SIP SUBSCRIBE message via configured outbound proxies for the
destination domain, or in accordance with RFC 3263 [RFC3263].
The device needs certain data to create an enrollment request,
form a Request URI, and authenticate to the network. This
includes the profile provider's domain name, identities and
credentials. Such data can be "configured" during device
manufacturing, by the user, or via profile data enrollment (see
Section 5.3.1). The data can also be "discovered" using the
procedures specified by this framework. The "discovered" data can
be retained across device resets (but not across factory resets)
and such data is referred to as "cached". Thus, data can be
configured, discovered or cached. The following requirements
apply.
* If the device is configured with a specific domain name (for
the local network provider or device provider), it MUST NOT
attempt "discovery" of the domain name. This is the case when
the device is pre-configured (e.g., via a user interface) to be
managed by specific entities.
* The device MUST only use data associated with the provider's
domain in an enrollment request. As an example, when the
device is requesting a local-network profile in the domain
'example.net', it cannot present a user AoR associated with the
local domain 'example.com'.
* The device SHOULD adhere to the following order of data usage:
configured, cached and discovered. An exception is when the
device is explicitly configured to use a different order.
Upon failure to obtain the profile using any methods specified in
this framework, the device MAY provide a user interface to allow
for user intervention. This can result in temporary, one-time
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data to bootstrap the device. Such temporary data is not
considered to be "configured" and SHOULD NOT not be cached across
resets. The configuration obtained using such data MAY provide
the configuration data required for the device to continue
functioning normally.
Devices attempting enrollment MUST comply with the SIP-specific
event notification specified in [RFC3265], the event package
requirements specified in Section 6.2, and the security
requirements specified in Section 5.2.
Enrollment request admittance
A PDS or a SIP proxy will receive a transmitted enrollment
request. If a SIP infrastructure element receives the request, it
will relay it to the authoritative proxy for the domain indicated
in the Request-URI (the same way it would handle any other
SUBSCRIBE message). The authoritative proxy is required to
examine the request (e.g., event package) and transmit it to a PDS
capable of addressing the profile enrollment request.
A PDS receiving the enrollment request SHOULD respond to the
request, or proxy it to a PDS that can respond. An exception to
responding or proxying the request is when a policy prevents
response (e.g., recognition of a DoS attack, an invalid device,
etc.). The PDS then verifies the identity presented in the
request and performs any necessary authentication. Once
authentication is successful, the PDS MUST either admit or reject
the enrollment request, based on applicable authorization
policies. A PDS admitting the enrollment request indicates it via
a 2xx-class response, as specified in [RFC3265].
Refer to Section 6.6 and Section 5.2 for more information on
subscription request handling and security requirements,
respectively.
Enrollment request acceptance
A PDS that admits the enrollment request verifies applicable
policies, identifies the requested profile data and prepares a SIP
NOTIFY message to the device. Such a notification can either
contain the profile data or contain content indirection
information that results in the device performing profile content
retrieval. The PDS then transmits the prepared SIP notification.
When the device successfully receives and accepts the SIP
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notification, profile enrollment is complete.
When it receives the SIP NOTIFY message, indicating successful
profile enrollment, the device SHOULD make the new profile
effective within the specified time frame, as described in
Section 6.2. The exception is when the profile data is delivered
via content indirection, and the device cannot obtain the profile
data within the specified time frame.
Once profile enrollment is successful, the PDS MUST consider the
device enrolled for the specific profile, for the duration of the
subscription.
5.1.2. Content Retrieval
A successful profile enrollment leads to an initial SIP notification,
and may result in subsequent change notifications. Each of these
notifications can either contain profile data, or content indirection
information. If it contains content indirection information, the
device is required to retrieve the profile data using the specified
content retrieval protocols. This process is termed profile content
retrieval. For information regarding the use of the SIP NOTIFY
message body please refer to Section 6.5.
Devices and PDSs implementing this framework MUST implement two
content retrieval protocols: HTTP and HTTPS as specified in [RFC2616]
and [RFC2818], respectively. Future enhancements or usage of this
framework may specify additional or alternative content retrieval
protocols. For security requirements and considerations please refer
to Section 5.2.
5.1.3. Change Notification
Profile data can change over time. Changes can be initiated by
various entities (e.g., via the device, back-office components and
end-user web interfaces) and for various reasons (e.g., change in
user preferences and modifications to services). Profiles may also
be shared by multiple devices simultaneously. When a profile is
changed the PDS MUST inform all the devices currently enrolled for
the specific profile. This process of informing a device of any
changes to the profile that it is currently enrolled for is termed
change notification.
The PDS provides change notification using a SIP notification (SIP
NOTIFY message as specified in [RFC3265]). The SIP notification may
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provide the changes, a revised profile or content indirection which
contains a pointer to the revised data. When a device successfully
receives a profile change notification for an enrolled profile, it
MUST act upon the changes prior to the expiration of the
'effective-by' parameter.
For NOTIFY content please refer to Section 6.5.
5.1.4. Enrollment Data and Caching
The requirements for the contents of the SIP SUBSCRIBE used to
request profile enrollment are described in this section. The data
required can be configured, cached or discovered - depending on the
profile type. If the data is not configured, the device MUST use
relevant cached data or proceed with data discovery. This section
describes the requirements for creating a SIP SUBSCRIBE for
enrollment, the caching requirements and how data can be discovered.
5.1.4.1. Local-Network Profile
To create a Subscription URI to request the local-network profile a
device needs the local network domain name, the device identifier and
optionally a user AoR with associated credentials (if one is
configured). Since the device can be potentially initialized in a
different local-network each time, it SHOULD NOT cache the local
network domain, the SIP subscription URI or the local-network profile
data across resets. An exception to this is when the device can
confirm that it is reinitialized in the same network (using means
outside the scope of this document). Thus, in most cases, the device
needs to discover the local network domain name. The device
discovers this by establishing IP connectivity in the local network
(such as via DHCP or pre-configured IP information). Once
established, the device MUST attempt to use the local network domain
obtained via pre-configuration, if available. If it is not pre-
configured, it MUST employ dynamic discovery using DHCPv4 ([RFC2132],
Domain Name option) or DHCPv6 ([RFC4704]). Once the local network
domain is obtained, the device creates the SIP SUBSCRIBE for
enrollment as described below.
o The device MUST NOT populate the user part of the Request URI.
The device MUST set the host portion of the Request URI to the
dot-separated concatenation of "_sipuaconfig" and the local
network domain (see example below).
o If the device has been configured with a user AoR for the local
network domain (verified as explained in Section 5.2) it MUST use
it to populate the "From" field, unless configured not to (due to
privacy concerns, for example). Otherwise, the device MUST set
the "From" field to a value of "anonymous@anonymous.invalid".
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o The device MUST include the +sip.instance parameter within the
'Contact' header, as specified in [I-D.ietf-sip-outbound]. The
device MUST ensure that the value of this parameter is the same as
that included in any subsequent profile enrollment request.
For example, if the device requested and received the local domain
name via DHCP to be: airport.example.net, then the local-network
Profile SUBSCRIBE Request URI would look like:
sip:_sipuaconfig.airport.example.net
The local-network profile SUBSCRIBE Request URI does not have a user
part so that the URI is distinct between the "local" and "device"
URIs when the domain is the same for the two. This provides a means
of routing to the appropriate PDS in domains where there are distinct
servers.
The From field is populated with the user AoR, if available. This
allows the local network provider to propagate user-specific profile
data, if available. The "+sip.instance" parameter within the
"Contact" header is set to the device identifier or specifically, the
SIP UA instance. Even though every device may get the same (or
similar) local-network Profile, the uniqueness of the "+sip.instance"
parameter provides an important capability. Having unique instance
ID fields allows the management of the local network to track devices
present in the network and consequently also manage resources such as
bandwidth allocation.
5.1.4.2. Device Profile Type
Once associated with a device, the device provider is not expected to
change frequently. Thus, the device is allowed to, and SHOULD cache
the Subscription URI for the device profile upon successful
enrollment. Exceptions include cases where the device identifier has
changed (e.g., new network card), device provider information has
changed (e.g., user initiated change) or the device cannot obtain its
profile using the Subscription URI. Thus, when available, the device
MUST use a cached Subscription URI. If no cached URI is available
then it needs to create a Subscription URI. To create a Subscription
URI, the device needs a device identity and the device provider's
domain name. Unless already configured, the device needs to discover
the necessary information and form the subscription URI. In such
cases, the following requirements apply for creating a Subscription
URI for requesting the device profile:
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o The device MUST populate the user part of the Request URI with the
device identifier. The device MUST set the host portion of the
Request URI to the domain name of the device provider. The device
identifier format is explained in detail later in this section.
o The device MUST set the "From" field to a value of anonymous@
<device provider's domain>.
o The device MUST include the +sip.instance parameter within the
'Contact' header, as specified in [I-D.ietf-sip-outbound]. The
device MUST use the same value as the one presented while
requesting the local-network profile.
Note that the discovered AoR for the Request URI can be overridden by
a special, provisioned, AoR that is unique to the device. In such
cases, the provisioned AoR is used to form the Request URI and to
populate the From field.
If the device is not configured with an AoR, and needs a domain name
to populate the Request URI and the From field, it can either use a
configured domain name, if available, or discover it. The options to
discover are described below. The device MUST use the results of
each successful discovery process for one enrollment attempt, in the
order specified below.
o Option 1: Devices that support DHCP MUST attempt to obtain the
domain name of the outbound proxy during the DHCP process, using
the DHCP option for SIP servers defined in [RFC3361] or [RFC3319]
(for IPv4 and IPv6 respectively).
o Option 2: Devices that support DHCP MUST attempt to obtain the
local IP network domain during the DHCP process (refer to
[RFC2132] and [RFC4704] ).
o Option 3: Devices MUST use the local network domain name
(configured or discovered to retrieve the local-network profile),
prefixing it with the label "_sipuaconfig".
If the device needs to create a subscription URI and needs to use its
device identifier, it MUST use the UUID-based URN representation as
specified in [RFC4122]. The following requirements apply:
o When the device has a non-alterable MAC address it SHOULD use
version 1 UUID representation with the timestamp and clock
sequence bits set to a value of '0'. This will allow for easy
recognition, and uniqueness of MAC address based UUIDs. An
exception is the case where the device supports independent device
configuration for more than one SIP UA. An example would be
multiple SIP UAs on the same platform.
o If the device cannot use a non-alterable device identifier, it
SHOULD use an alternative non-alterable device identifier. For
example, the International Mobile Equipment Identity (IMEI) for
mobile devices.
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o If the device cannot use a non-alterable MAC Address, it MUST be
use the same approach as defining a user agent Instance ID in
[I-D.ietf-sip-outbound].
o Note: when the URN is used as the user part of the Request URI, it
MUST be URL escaped since the colon (":") is not a legal character
in the user part of an addr-spec ([RFC4122]), and must be escaped.
For example, the instance ID:
urn:uuid:f81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com
would be escaped to look as follows in a URI:
sip:urn%3auuid%3af81d4fae-7ced-11d0-a765-00a0c91e6bf6@
example.com
The ABNF for the UUID representation is provided in [RFC4122]
5.1.4.3. User Profile Type
To create a Subscription URI to request the user profile on behalf of
a user, the device needs to know the user's AoR. This can be
statically or dynamically configured on the device (e.g., user input,
or propagated as part of the device profile). Similar to device
profiles, the content and propagation of user profiles may differ,
based on deployment scenarios (i.e., users belonging to the same
domain may - or may not - be provided the same profile). To create a
subscription URI, the following rules apply:
o The device MUST set the Request URI to the user AoR.
o The device MUST populate the "From" field with the user AoR.
An authoritative SIP proxy for a SIP provider's network that receives
a profile enrollment request for the user profile type will route
based on the Event Header field values, thus allowing a subscription
to the user's AoR to be routed to the appropriate PDS.
5.2. Securing Profile Delivery
Profile data can contain sensitive information that needs to be
secured, such as identities and credentials. Security involves
authentication, message integrity and privacy. Authentication is the
process by which you verify that an entity is who it claims to be,
such as a user AoR presented during profile enrollment. Message
integrity provides the assurance that the message contents
transmitted between two entities, such as between the PDS and the
device, has not been modified during transit. Privacy ensures that
the message contents have not been subjected to monitoring by
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unwanted elements during transit. Authentication and message
integrity are required to ensure that the profile contents were
received by a valid entity, from a valid source, and without any
modifications during transit. For profiles that contain sensitive
data, privacy is also required.
For an overview of potential security threats, refer to Section 9.
For information on how the device can be configured with identities
and credentials, refer to Section 5.3.1. The following subsections
provide the security requirements associated with each profile
delivery stage, and applies to each of profile types specified by
this framework.
5.2.1. Securing Profile Enrollment
Profile enrollment may result in sensitive profile data. In such
cases, the PDS MUST authenticate the device, except during the
bootstrapping scenario when the device does not have existing
credentials (see Section 5.3.1 for more information on
bootstrapping). Additionally, the device MUST authenticate the PDS
to ensure that it is obtaining sensitive profile data from a valid
PDS, except in the bootstrapping scenario.
To authenticate a device that has been configured with identities and
credentials as specified in Section 5.3.1 and support profiles
containing sensitive profile data (refer to Section 5.3.4), devices
and PDSs MUST support Digest Authentication as specified in
[RFC3261]. Future enhancements may provide other authentication
methods such as authentication using X.509 certificates. For the
device to authenticate the PDS, the device MUST mutually authenticate
with the PDS during digest authentication (device challenges the PDS,
which responds with the Authorization header). Transmission of
sensitive profile data also requires message integrity. This can be
accomplished by configuring the device with, or by ensuring that the
discovery process during profile enrollment provides, a SIPS URI
resulting in TLS establishment ([RFC5246]). TLS also prevents
offline dictionary attacks when digest authentication is used. Thus,
in the absence of TLS, the device MUST NOT respond to any
authentication challenges. It is to be noted that the digest
credentials used for obtaining profile data via this framework may,
or may not, be the same as that used for SIP registration (see
Section 5.3.1).
When the PDS challenges a profile enrollment request, and it fails,
the PDS MAY refuse enrollment or provide profile data without the
user-specific information (e.g., to bootstrap a device as indicated
in Section 5.3.1). If the device challenges, but fails to
authenticate the PDS, it MUST reject the initial notification and
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retry the profile enrollment process. If the device is configured
with, or discovers, a SIPS URI but TLS establishment fails because
the next-hop SIP entity does not support TLS, the device SHOULD
attempt other resolved next-hop SIP entities. When the device
establishes TLS with the next-hop entity, the device MUST use the
procedures specified in [RFC2818], Section 3.1, for authentication,
unless it does not have any configured information (e.g., CA
certificate) to perform authentication (like prior to bootstrapping).
The 'Server Identity' for authentication is always the domain of the
next-hop SIP entity. If the device attempts validation, and it
fails, it MUST reject the initial notification and retry profile
enrollment. In the absence of a SIPS URI for the device and a
mechanism for mutual authentication, the PDS MUST NOT present any
sensitive profile data in the initial notification, except when the
device is being bootstrapped. It MAY still use content indirection
to transmit sensitive profile data.
When a device is being provided with bootstrapping profile data
within the notification, and it contains sensitive information, the
SIP Identity header SHOULD be used as specified in [RFC4474]. This
helps with devices that MAY be pre-configured with certificates to
validate bootstrapping sources (e.g., list of allowed domain
certificates, or a list of root CA certificates using PKI). When the
SIP Identity header is used, the PDS MUST set the host portion of the
AoR in the 'From' header to the Provider's domain (the user portion
is a entity-specific identifier). If the device is capable of
validating the SIP Identity, and it fails, it MUST reject
bootstrapping profile data.
5.2.2. Securing Content Retrieval
Initial or change notifications following a successful enrollment can
provide a device with the requested profile data, or use content
indirection to direct it to a PCC that can provide the profile data.
This document specifies HTTP and HTTPS as content retrieval
protocols.
If the profile is provided via content indirection and contains
sensitive profile data then the PDS MUST use a HTTPS URI for content
indirection. PCCs and devices MUST NOT use HTTP for sensitive
profile data, except for bootstrapping a device via the device
profile. A device MUST authenticate the PCC as specified in
[RFC2818], Section 3.1. A device that is being provided with profile
data that contains sensitive data MUST be authenticated using digest
authentication as specified in [RFC2617], with the exception of a
device that is being bootstrapped for the first time via the device
profile. The resulting TLS channel also provides message integrity
and privacy.
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5.2.3. Securing Change Notification
If the device requested enrollment via a SIP subscription with a non-
zero 'Expires' parameter, it can also result in change notifications
for the duration of the subscription. For change notifications
containing sensitive profile data, this framework RECOMMENDS the use
of the SIP Identity header as specified in [RFC4474]. When the SIP
Identity header is used, the PDS MUST set the host portion of the AoR
in the 'From' header to the Provider's domain (the user portion is a
entity-specific identifier). This provides header and body integrity
as well. However, for sensitive profile data requiring privacy, if
the contact URI to which the NOTIFY request is to be sent is not
SIPS, the PDS MUST use content indirection. Additionally, the PDS
MUST also use content indirection for notifications containing
sensitive profile data, when the profile enrollment was not
authenticated.
5.3. Additional Considerations
This section provides additional considerations such as details on
how a device obtains identities and credentials, backoff and retry
methods, guidelines on profile data and additional profile types.
5.3.1. Bootstrapping Identities and Credentials
When requesting a profile the device can provide an identity (i.e., a
user AoR), and contain associated credentials for authentication. To
do so, the device needs to obtain this information via bootstrapping.
This can be accomplished in one of the following ways:
Pre-configuration
The device may be pre-configured with identities and associated
credentials, such as a user AoR and digest password.
Out-of-band methods
A device or Provider may provide hardware- or software-based
credentials such as SIM cards or Universal Serial Bus (USB)
drives.
End-user interface
The end-user may be provided with the necessary identities and
credentials. The end-user can then configure the device (using a
user interface), or present when required (e.g., IM login screen).
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Using this framework
When a device is initialized, even if it has no pre-configured
information, it can request the local-network and device profiles.
For purposes of bootstrapping, this framework recommends that the
device profile provide one of the following to bootstrap the
device:
* Profile data that allows the end-user to communicate with the
device provider or SIP service provider using non-SIP methods.
For example, the profile data can direct the end-user to a web
portal to obtain a subscription. Upon obtaining a successful
subscription, the end-user or the device can be provided with
the necessary identities and credentials.
* Content indirection information to a PCC that can provide
identities and credentials. As an example, consider a device
that has a X.509 certificate that can be authenticated by the
PCC. In such a case, the PCC can use HTTPS to provide
identities and associated credentials.
* Profile data containing identities and credentials that can be
used to bootstrap the device (see Section 5.3.4 for profile
data recommendations). This can be used in cases where the
device is initialized for the first time, or after a factory
reset. This can be considered only in cases where the device
is initialized in the Provider's network, for obvious security
reasons.
Additionally, AoRs are typically known by PDSs that serve the domain
indicated by the AoR. Thus, devices can only present the configured
AoRs in the respective domains. An exception is the use of federated
identities. This allows a device to use a user's AoR in multiple
domains. Further even within the same domain, the device's domain
proxy and the PDS may be in two different realms, and as such may be
associated with different credentials for digest authentication. In
such cases, multiple credentials may be configured, and associated
with the realms in which they are to be used. This framework
specifies only digest authentication for profile enrollment and the
device is not expected to contain any other credentials. For profile
retrieval using content indirection, the device will need to support
additional credentials such as X.509 certificates (for TLS). Future
enhancements can specify additional credential types for profile
enrollment and retrieval.
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5.3.2. Profile Enrollment Request Attempt
A state diagram representing a device requesting any specific profile
defined by this framework is shown in Figure 6.
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+------------+
| Initialize |
+-----+------+
|
|
V
+-------------+
| Prepare |
+--------->| Enrollment |<------------------+
| | Request | |
| +------+------+ |
+------+------+ | |
| Failure | Enroll. Req. prepared |
+-->| Handling & | /Send Req |
| | Delay | | |
| +-------------+ V |
| ^ ^ +-------------+ |
| | | | Await | |
| | +--------+ Enrollment | |
| | Timeout, | acceptance | |
| | non-2xx/- +------+------+ |
| | | |
| Timeout 200 OK/- Enrollment
| /Terminate | Timeout/-
| Enrollment V |
| | +--------------+ |
| | | Enrollment | |
| +------------+ accepted | |
Retries Exceeded |(await NOTIFY)| |
/Retry Enrollment +---+------+---+ |
| | | |
| | | |
| NOTIFY w. Content Ind| | NOTIFY w. Profile |
| /Retrieve Profile | | /Accept Profile |
| +------------+ +------------+ |
| | | |
| V V |
| +------------+ +------------+ |
+-----+ Retrieving | Retrieved | Enrollment +---+
,->| Profile +--/Apply Profile-->| Successful |
/ | | |(monitoring)|<--.
Timeout +--+---------+ +--+----+----+ :
/Retry ; ^ | : ;
`------' | NOTIFY w. Cont.Ind | `-------'
+---/Retrieve Profile-----+ NOTIFY w. Profile
/Apply Profile
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Figure 6: Device State Diagram
As a reminder:
o The timeout for SIP messages is specified by [RFC3261]. In the
cases where this is not specified such as the timeout to wait for
the initial notification during profile enrollment, it is left to
device implementations or future protocol enhancements.
o The timeout for profile retrieval using content indirection will
be as specified by profile retrieval protocols employed. If none
exists, it is left to device implementations.
In addition, since profile enrollment is a process unique to this
framework, the device MUST follow the enrollment attempt along with
exponential backoff and retry mechanisms as indicated in Figure 7.
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Function for Profile Enrollment ()
Init Function: Iteration i=0
Loop 1: Attempt
Loop 2: For each SIP Subscription URI
Loop 3: For each next-hop SIP entity
- Prepare & transmit Enrollment Request
- Await Enrollment Acceptance and initial NOTIFY
+ If the profile enrollment is successful
= Exit this function()
+ If profile enrollment fails due to an explicit
failure or a timeout as specified in RFC3261
= Continue with the next-hop SIP entity (Loop 3)
End Loop: Loop 3
End Loop: Loop 2
(Note: If you are here, profile enrollment did not succeed)
+ Is any valid cached profile data available?
= If yes, use it and continue with Loop 1
+ If the enrollment request is for a non-mandatory profile
= Start profile enrollment for the next profile,
if applicable
- Delay for 2^i*(64*T1); -- this is exponential backoff
- increment i;
- If i>8, reset i=8;
End loop: Loop 1
End Function()
Figure 7: Profile Enrollment Attempt (pseudo-code)
The pseudo-code above (Figure 7) allows for cached profiles to be
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used. However, any cached Local Network profile MUST NOT be used
unless the device can ensure that it is in the same local network
which provided the cached data. This framework does not provide any
procedures for local network recognition. Any cached device and user
profiles MUST only be used in domains that they are associated with.
For example, a cached device profile is used only when the associated
domain matches the current device provider's domain. If a PDS wants
to invalidate a profile it may do so by transmitting a NOTIFY with an
'empty profile', i.e., profile instance without any included data (if
supported by the profile data model; not to be confused with an empty
NOTIFY), or via an explicit profile data element that invalidates the
data. A device receiving such a NOTIFY MUST discard the applicable
profile (i.e., it cannot even store it in the cache). Additionally,
if a factory reset is available and performed on a device, it MUST
reset the device to its initial state prior to any configuration.
Specifically, the device MUST set the device back to the state when
it was originally distributed.
The order of profile enrollment is important. For the profiles
specified in this framework, the device must enroll in the following
default order: local-network, device and user. The pseudo-code
presented earlier (Figure 7) differentiates between 'mandatory' and
'non-mandatory' profiles. This distinction is left to profile data
definitions.
It is to be noted that this framework does not allow the devices to
inform the PDSs of profile retrieval errors such as invalid data.
Follow-on standardization activities are expected to address this
feature.
5.3.3. Device Types
The examples in this framework tend to associate devices with
entities that are accessible to end-users. However, this is not
necessarily the only type of device that can utilize the specified
Framework. Devices can be entities such as SIP Phones or soft
clients, with or without user interfaces (that allow for device
Configuration), entities in the network that do not directly
communicate with any users (e.g., gateways, media servers, etc) or
network infrastructure elements e.g., SIP servers).
5.3.4. Profile Data
This framework does not specify the contents for any profile type.
Follow-on standardization activities are expected to address profile
contents. However, the framework provides the following requirements
and recommendations for profile data definitions:
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o The device profile type SHOULD specify parameters to configure the
identities and credentials for use in scenarios such as
bootstrapping (see Section 5.3.1) and run-time modifications to
identities and credentials. This framework recommends the device
profile to provide the identities and credentials due to a couple
of reasons. The local-network profile may not always be
available, and even if present, may not be controlled by the
device provider who controls device configuration to provide
services. Further, the device may not have any users configured
prior to being bootstrapped, resulting in an absence of user
profile requests. However, this framework does not prevent other
profile types from providing identities and credentials to meet
deployment needs. For example, the user profile can contain
identities and credentials for communicating with specific
applications.
o Each profile MUST clearly identify if it may contain any sensitive
data. Such profiles MUST also identify the data elements that are
considered sensitive, i.e., data that cannot be compromised. As
an example, a device profile definition may identify itself as
containing sensitive data and indicate data such as device
credentials to be sensitive.
o When the device receives multiple profiles, the contents of each
profile type SHOULD only contain data relevant to the entity it
represents. As an example, consider a device that obtains all the
defined profiles. Information pertaining to the local network is
contained in the 'local-network' profile and not the 'user'
profile. This does not preclude relevant data about a different
entity from being included in a profile type, e.g., the 'device'
profile type may contain information about the users allowed to
access services via the device. A profile may also contain
starting information to obtain subsequent Profiles.
o Data overlap SHOULD be avoided across profile types, unless
necessary. If data overlap is present, prioritization of the data
is left to data definitions. As an example, the device profile
may contain the list of codecs to be used by the device and the
user Profile (for a user on the device) may contain the codecs
preferred by the user. Thus, the same data (usable codecs) is
present in two profiles. However, the data definitions may
indicate that to function effectively, any codec chosen for
communication needs to be present in both the profiles.
5.3.5. Profile Data Frameworks
The framework specified in this document does not address profile
data representation, storage or retrieval protocols. It assumes that
the PDS has a PCC based on existing or other Profile Data Frameworks.
While this framework does not impose specific constraints on any such
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framework, it does allow for the propagation of profile content to
the PDS (specifically the PCC) from a network element or the device.
Thus, Profile Data or Retrieval frameworks used in conjunction with
this framework MAY consider techniques for propagating incremental,
atomic changes to the PDS. One means for propagating changes to a
PDS is defined in XCAP ([RFC4825]).
5.3.6. Additional Profile Types
This document specifies three profile types: local-network, device
and user. However, there may be use cases for additional profile
types. e.g., profile types for application specific profile data or
to provide enterprise-specific policies. Definition of such
additional profile types is not prohibited, but considered out of
scope for this document. Such profile definitions MUST specify the
order of retrieval with respect to all the other profiles such as the
local-network, device and user profile types defined in this
document.
5.3.7. Deployment considerations
The framework defined in this document was designed to address
various deployment considerations, some of which are highlighted
below.
Provider relationships:
o The local network provider and the SIP service provider can often
be different entities, with no administrative or business
relationship with each other.
o There may be multiple SIP service providers involved, one for each
service that a user subscribes to (telephony service, instant
messaging, etc.); this Framework does not specify explicit
behavior in such a scenario, but it does not prohibit its usage
either.
o Each user accessing services via the same device may subscribe to
different sets of services, from different Service Providers.
User-device relationship:
o The relationship between devices and users can be many-to-many
(e.g., a particular device may allow for many users to obtain
subscription services through it, and individual users may have
access to multiple devices).
o Each user may have different preferences for use of services, and
presentation of those services in the device user interface.
o Each user may have different personal information applicable to
use of the device, either as related to particular services, or
independent of them.
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5.4. Support for NATs
PDSs that support devices behind NATs, and devices that can be behind
NATs can use procedures specified in [I-D.ietf-sip-outbound]. The
Outbound proxies can be configured or discovered. Clients that
support such behavior MUST include the 'outbound' option-tag in a
Supported header field value, and add the "ob" parameter as specified
in [I-D.ietf-sip-outbound] within the SIP SUBSCRIBE for profile
enrollment.
6. Event Package Definition
The framework specified in this document proposes and specifies a new
SIP Event Package as allowed by [RFC3265]. The purpose is to allow
for devices to subscribe to specific profile types with PDSs and for
the PDSs to notify the devices with the profile data or content
indirection information.
The requirements specified in [RFC3265] apply to this package. The
following sub-sections specify the Event Package description and the
associated requirements. The framework requirements are defined in
Section 5.
6.1. Event Package Name
The name of this package is "ua-profile". This value appears in the
Event header field present in SUBSCRIBE and NOTIFY requests for this
package as defined in [RFC3265].
6.2. Event Package Parameters
This package defines the following new parameters for the event
header:
"profile-type", "vendor", "model", "version", and "effective-by"
The following rules apply:
o All the new parameters, with the exception of the "effective-by"
parameter MUST only be used in SUBSCRIBE requests and ignored if
they appear in NOTIFY requests.
o The "effective-by" parameter is for use in NOTIFY requests only
and MUST be ignored if it appears in SUBSCRIBE requests.
The semantics of these new parameters are specified in the following
sub-sections.
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6.2.1. profile-type
The "profile-type" parameter is used to indicate the token name of
the profile type the user agent wishes to obtain and to be notified
of subsequent changes. This document defines three logical types of
profiles and their token names. They are as follows:
local-network: specifying the "local-network" type profile indicates
the desire for profile data, and potentially, profile change
notifications specific to the local network.
device: specifying the "device" type profile(s) indicates the desire
for the profile data, and potentially, profile change notification
that is specific to the device or user agent.
user: Specifying "user" type profile indicates the desire for the
profile data, and potentially, profile change notification
specific to the user.
The profile type is identified in the Event header parameter:
"profile-type". A separate SUBSCRIBE dialog is used for each profile
type. Thus, the subscription dialog on which a NOTIFY arrives
implies which profile's data is contained in, or referred to, by the
NOTIFY message body. The Accept header of the SUBSCRIBE request MUST
include the MIME types for all profile content types for which the
subscribing user agent wishes to retrieve profiles, or receive change
notifications.
In the following syntax definition using ABNF, EQUAL and token are
defined in [RFC3261]. It is to be noted that additional profile
types may be defined in subsequent documents.
Profile-type = "profile-type" EQUAL profile-value
profile-value = profile-types / token
profile-types = "device" / "user" / "local-network"
The "device", "user" or "local-network" token in the profile-type
parameter may represent a class or set of profile properties.
Follow-on standards defining specific profile contents may find it
desirable to define additional tokens for the profile-type parameter.
Also, additional content types may be defined along with the profile
formats that can be used in the Accept header of the SUBSCRIBE to
filter or indicate what data sets of the profile are desired.
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6.2.2. vendor, model and version
The "vendor", "model" and "version" parameter values are tokens
specified by the implementer of the user agent. These parameters
MUST be provided in the SUBSCRIBE request for all profile types. The
implementer SHOULD use their DNS domain name (e.g., example.com) as
the value of the "vendor" parameter so that it is known to be unique.
These parameters are useful to the PDS to affect the profiles
provided. In some scenarios it is desirable to provide different
profiles based upon these parameters. e.g., feature property X in a
profile may work differently on two versions of the same user agent.
This gives the PDS the ability to compensate for or take advantage of
the differences. In the following ABNF defining the syntax, EQUAL
and quoted-string are defined in [RFC3261].
Vendor = "vendor" EQUAL quoted-string
Model = "model" EQUAL quoted-string
Version = "version" EQUAL quoted-string
6.2.3. effective-by parameter
The "effective-by" parameter in the Event header of the NOTIFY
request specifies the maximum number of seconds before the user agent
must attempt to make the new profile effective. The "effective-by"
parameter MAY be provided in the NOTIFY request for any of the
profile types. A value of 0 (zero) indicates that the subscribing
user agent must attempt to make the profiles effective immediately
(despite possible service interruptions). This gives the PDS the
power to control when the profile is effective. This may be
important to resolve an emergency problem or disable a user agent
immediately. If it is absent, the device SHOULD attempt to make the
profile data effective at the earliest possible opportunity that does
not disrupt any services being offered. The "effective-by" parameter
is ignored in all messages other than the NOTIFY request. In the
following ABNF, EQUAL and DIGIT are defined in [RFC3261].
Effective-By = "effective-by" EQUAL 1*DIGIT
6.2.4. Summary of event parameters
The following are example Event headers which may occur in SUBSCRIBE
requests. These examples are not intended to be complete SUBSCRIBE
requests.
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Event: ua-profile;profile-type=device;
vendor="vendor.example.com";model="Z100";version="1.2.3"
Event: ua-profile;profile-type=user;
vendor="premier.example.com";model="trs8000";version="5.5"
The following are example Event headers which may occur in NOTIFY
requests. These example headers are not intended to be complete
SUBSCRIBE requests.
Event: ua-profile;effective-by=0
Event: ua-profile;effective-by=3600
The following table shows the use of Event header parameters in
SUBSCRIBE requests for the three profile types:
profile-type || device | user | local-network
=============================================
vendor || m | m | m
model || m | m | m
version || m | m | m
effective-by || | |
m - mandatory
s - SHOULD be provided
o - optional
Non-specified means that the parameter has no meaning and should be
ignored.
The following table shows the use of Event header parameters in
NOTIFY requests for the three profile types:
profile-type || device | user | local-network
=============================================
vendor || | |
model || | |
version || | |
effective-by || o | o | o
6.3. SUBSCRIBE Bodies
This package defines no use of the SUBSCRIBE request body. If
present, it SHOULD be ignored. Exceptions include future
enhancements to the framework which may specify a use for the
SUBSCRIBE request body.
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6.4. Subscription Duration
The duration of a subscription is specific to SIP deployments and no
specific recommendation is made by this Event Package. If absent, a
value of 86400 seconds (24 hours; 1 day) is RECOMMENDED since the
presence (or absence) of a device subscription is not time critical
to the regular functioning of the PDS.
It is to be noted that a one-time fetch of a profile, without ongoing
subscription, can be accomplished by setting the 'Expires' parameter
to a value of Zero, as specified in [RFC3265].
6.5. NOTIFY Bodies
The framework specifying the Event Package allows for the NOTIFY body
to contain the profile data, or a pointer to the profile data using
content indirection. For profile data delivered via content
indirection, i.e., a pointer to a PCC, then the Content-ID MIME
header, as described in [RFC4483] MUST be used for each Profile
document URI. At a minimum, the "http:" [RFC2616] and "https:"
[RFC2818] URI schemes MUST be supported; other URI schemes MAY be
supported based on the Profile Data Frameworks (examples include FTP
[RFC0959], LDAP [RFC4510] and XCAP [RFC4825] ).
A non-empty NOTIFY body MUST include a MIME type specified in the
'Accept' header of the SUBSCRIBE. Further, if the Accept header of
the SUBSCRIBE included the MIME type message/external-body
(indicating support for content indirection) then the PDS MAY use
content indirection in the NOTIFY body for providing the profiles.
6.6. Notifier Processing of SUBSCRIBE Requests
A successful SUBSCRIBE request results in a NOTIFY with either
profile contents or a pointer to it (via Content Indirection). The
SUBSCRIBE SHOULD be either authenticated, or transmitted over an
integrity protected SIP communications channel. Exceptions include
cases where the identity of the Subscriber is unknown and the
Notifier is configured to accept such requests.
The Notifier MAY also authenticate SUBSCRIBE messages even if the
NOTIFY is expected to only contain a pointer to profile data.
Securing data sent via Content Indirection is covered in Section 9.
If the profile type indicated in the "profile-type" Event header
parameter is unavailable or the Notifier is configured not to provide
it, the Notifier SHOULD return a 404 response to the SUBSCRIBE
request. If the specific user or device is unknown, the Notifier MAY
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accept the subscription, or else it may reject the subscription (with
a 403 response).
6.7. Notifier Generation of NOTIFY Requests
As specified in [RFC3265], the Notifier MUST always send a NOTIFY
request upon accepting a subscription. If the device or user is
unknown and the Notifier chooses to accept the subscription, the
Notifier MAY either respond with profile data (e.g., default profile
data) or provide no profile information (i.e., empty NOTIFY).
If the identity indicated in the SUBSCRIBE request (From header) is a
known identity and the requested profile information is available
(i.e. as specified in the profile-type parameter of the Event
header), the Notifier SHOULD send a NOTIFY with profile data.
Profile data MAY be sent as profile contents or via Content
Indirection (if the content indirection MIME type was included in the
Accept header). The Notifier MUST NOT use any scheme that was not
indicated in the "schemes" Contact header field.
The Notifier MAY specify when the new profiles must be made effective
by the Subscriber by specifying a maximum time in seconds (zero or
more) in the "effective-by" event header parameter.
If the SUBSCRIBE was received over an integrity protected SIP
communications channel, the Notifier SHOULD send the NOTIFY over the
same channel.
6.8. Subscriber Processing of NOTIFY Requests
A Subscriber to this event package MUST adhere to the NOTIFY request
processing behavior specified in [RFC3265]. If the Notifier
indicated an effective time (using the "effective-by" Event Header
parameter), the Subscriber SHOULD attempt to make the profiles
effective within the specified time. Exceptions include deployments
that prohibit such behavior in certain cases (e.g., emergency
sessions are in progress). When profile data cannot be applied
within the recommended time frame and this affects device behavior,
any actions to be taken SHOULD be defined by the profile data
definitions. By default, the Subscriber is RECOMMENDED to make the
profiles effective as soon as possible.
When accepting content indirection, the Subscriber MUST always
support "http:" or "https:" and be prepared to accept NOTIFY messages
with those URI schemes. If the Subscriber wishes to support
alternative URI schemes they MUST each be indicated in the "schemes"
Contact header field parameter as defined in [RFC4483]. The
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Subscriber MUST also be prepared to receive a NOTIFY request with no
body. The subscriber MUST NOT reject the NOTIFY request with no
body. The subscription dialog MUST NOT be terminated by a empty
NOTIFY, i.e., with no body.
6.9. Handling of Forked Requests
This Event package allows the creation of only one dialog as a result
of an initial SUBSCRIBE request as described in section 4.4.9 of
[RFC3265]. It does not support the creation of multiple
subscriptions using forked SUBSCRIBE requests.
6.10. Rate of Notifications
The rate of notifications for the profiles in this framework is
deployment specific, but expected to be infrequent. Hence, the Event
Package specification does not specify a throttling or minimum period
between NOTIFY requests
6.11. State Agents
State agents are not applicable to this Event Package.
7. Examples
This section provides examples along with sample SIP message bodies
relevant to this framework. Both the examples are derived from the
use case illustrated in Section 4.1, specifically the request for the
device profile. The examples are informative only.
7.1. Example 1: Device requesting profile
This example illustrates the detailed message flows between the
device and the SIP Service Provider's network for requesting and
retrieving the profile (the flow uses the device profile as an
example).
The following are assumed for this example:
o Device is assumed to have established local network connectivity;
NAT and Firewall considerations are assumed to have been addressed
by the SIP Service Provider.
o Examples are snapshots only and do not illustrate all the
interactions between the device and the Service Provider's network
(and none between the entities in the SIP Service Provider's
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network).
o All SIP communication with the SIP Service Provider happens via a
SIP Proxy.
o HTTP over TLS is assumed to be the Content Retrieval method used
(any suitable alternative can be used as well).
The flow diagram and an explanation of the messages follow.
+----------------------+
+--------+ | SIP Service Provider |
| Device | | |
|(SIP UA)| | SIP PDS HTTP |
+--------+ | PROXY Server |
| |
+----------------------+
| | | |
| | | |
| SUBSCRIBE | | |
(SReq)|--------device profile--------->| | |
| |------>| |
| |200 OK | |
| 200 OK |<------| |
(SRes)|<-------------------------------| | |
| | | |
| | NOTIFY| |
| NOTIFY (Content Indirection)|<------| |
(NTFY)|<-------------------------------| | |
| 200 OK | | |
(NRes)|------------------------------->|200 OK | |
| |------>| |
| |
| |
| |
|<<<<<<<<<<<<< TLS establishment >>>>>>>>>>>>>|
| |
| HTTP Request |
(XReq)|---------------------------------------------->|
| |
| HTTP Response |
(XRes)|<----------------------------------------------|
| |
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(SReq)
the device transmits a request for the 'device' profile using the
SIP SUBSCRIBE utilizing the Event Package specified in this
framework.
* Note: Some of the header fields (e.g., SUBSCRIBE, Event, via)
are continued on a separate line due to format constraints of
this document.
SUBSCRIBE sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@example.com SIP/2.0
Event: ua-profile;profile-type=device;vendor="vendor.example.net";
model="Z100";version="1.2.3"
From: anonymous@example.com;tag=1234
To: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
Call-ID: 3573853342923422@192.0.2.44
CSeq: 2131 SUBSCRIBE
Contact: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@192.168.1.44
;+sip.instance="<urn:uuid:00000000-0000-0000-0000-123456789AB0>"
;schemes="http,https"
Via: SIP/2.0/TCP 192.0.2.41;
branch=z9hG4bK6d6d35b6e2a203104d97211a3d18f57a
Accept: message/external-body, application/x-z100-device-profile
Content-Length: 0
(SRes)
the SUBSCRIBE request is received by a SIP Proxy in the Service
Provider's network which transmits it to the PDS. The PDS accepts
the response and responds with a 200 OK
* Note: The device and the SIP proxy may have established a
secure communications channel (e.g., TLS).
(NTFY)
subsequently, the PDS transmits a SIP NOTIFY message indicating
the profile location
* Note: Some of the fields (e.g., content-type) are continued on
a separate line due to format constraints of this document.
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NOTIFY sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@192.168.1.44 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
;tag=abca
To: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
;tag=1234
Call-ID: 3573853342923422@192.0.2.44
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d0
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://example.com/z100-000000000000.html";
size=9999;
hash=10AB568E91245681AC1B
Content-Type: application/x-z100-device-profile
Content-ID: <39EHF78SA@example.com>
.
.
.
(NRes)
Device accepts the NOTIFY message and responds with a 200 OK
(XReq)
once the necessary secure communications channel is established,
the device sends an HTTP request to the HTTP server indicated in
the NOTIFY
(XRes)
the HTTP server responds to the request via a HTTP response
containing the profile contents
7.2. Example 2: Device obtaining change notification
The following example illustrates the case where a user (X) is
simultaneously accessing services via two different devices (e.g.,
Multimedia entities on a PC and PDA) and has access to a user
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interface that allows for changes to the user profile.
The following are assumed for this example:
o The devices (A & B) obtain the necessary profiles from the same
SIP Service Provider.
o The SIP Service Provider also provides a user interface that
allows the user to change preferences that impact the user
profile.
The flow diagram and an explanation of the messages follow.
o Note: The example only shows retrieval of user X's profile, but it
may request and retrieve other profiles (e.g., local-network,
Device).
----- -----
|User |_________| UI* | * = User Interface
| X | | |
----- -----
/ \
/ \
/ \ +----------------------+
+--------+ +--------+ | SIP Service Provider |
| Device | | Device | | |
| A | | B | | SIP PDS HTTP |
+--------+ +--------+ | PROXY Server |
+----------------------+
| | | |
| | | |
(A-EX)|<=Enrolls for User X's profile=>|<=====>| |
| | | |
| |
(A-RX)|<===Retrieves User X's profile================>|
| |
| | | | |
| | Enrolls for | | |
| (B-EX)|<== User X's ==>|<=====>| |
| | profile | | |
| | | | |
| | |
| (B-RX)|<= Retrieves User X's profile=>|
| |
| | |
| (HPut)|---------------------->|
| | |
| (HRes)|<----------------------|
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| |
| | | |
| | NOTIFY| |
| NOTIFY |<------| |
(A-NT)|<-------------------------------| | |
| 200 OK | | |
(A-RS)|------------------------------->|200 OK | |
| |------>| |
| |
| | | NOTIFY| |
| | NOTIFY |<------| |
| (B-NT)|<---------------| | |
| | 200 OK | | |
| (B-RS)|--------------->|200 OK | |
| | |------>| |
| |
| |
(A-RX)|<===Retrieves User X's profile================>|
| |
| | |
| | |
| (B-RX)|<= Retrieves User X's profile=>|
| | |
(A-EX) Device A discovers, enrolls and obtains notification related
to user X's profile.
(A-RX) Device A retrieves user X's profile.
(B-EX) Device B discovers, enrolls and obtains notification related
to user X's profile.
(B-RX) Device B retrieves user X's profile.
(HPut) Changes affected by the user via the user interface are
uploaded to the HTTP Server.
* Note: The UI itself can act as a device and subscribe to user
X's profile. This is not the case in the example shown.
(HRes) Changes are accepted by the HTTP server.
(A-NT) PDS transmits a NOTIFY message to device A indicating the
changed profile. A sample message is shown below:
Note: Some of the fields (e.g., Via) are continued on a
separate line due to format constraints of this document.
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NOTIFY sip:userX@192.0.2.44 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:userX@sip.example.net;tag=abcd
To: sip:userX@sip.example.net.net;tag=1234
Call-ID: 3573853342923422@192.0.2.44
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d1
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://www.example.com/user-x-profile.html";
size=9999;
hash=123456789AAABBBCCCDD
.
.
.
(A-RS) Device A accepts the NOTIFY and sends a 200 OK
(B-NT) PDS transmits a NOTIFY message to device B indicating the
changed profile. A sample message is shown below:
Note: Some of the fields (e.g., Via) are continued on a
separate line due to format constraints of this document.
NOTIFY sip:userX@192.0.2.43 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:userX@sip.example.net;tag=abce
To: sip:userX@sip.example.net.net;tag=1234
Call-ID: 3573853342923422@192.0.2.43
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d2
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://www.example.com/user-x-profile.html";
size=9999;
hash=123456789AAABBBCCCDD
.
.
.
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(B-RS) Device B accepts the NOTIFY and sends a 200 OK
(A-RX) Device A retrieves the updated profile pertaining to user X
(B-RX) Device B retrieves the updated profile pertaining to user X
8. IANA Considerations
There are two IANA considerations associated with this document, SIP
Event Package and SIP configuration profile types. These are
outlined in the following sub-sections.
8.1. SIP Event Package
This specification registers a new event package as defined in
[RFC3265]. The following information required for this registration:
Package Name: ua-profile
Package or Template-Package: This is a package
Published Document: RFC XXXX (Note to RFC Editor: Please fill in
XXXX with the RFC number of this specification)
Persons to Contact: Daniel Petrie dan.ietf AT SIPez DOT com,
sumanth@cablelabs.com
New event header parameters: profile-type, vendor, model, version,
effective-by (the profile-type parameter has predefined values.
The new event header parameters do not)
The following table illustrates the additions to the IANA SIP Header
Field Parameters and Parameter Values: (Note to RFC Editor: Please
fill in XXXX with the RFC number of this specification)
Predefined
Header Field Parameter Name Values Reference
---------------------------- --------------- --------- ---------
Event profile-type Yes [RFCXXXX]
Event vendor No [RFCXXXX]
Event model No [RFCXXXX]
Event version No [RFCXXXX]
Event effective-by No [RFCXXXX]
8.2. Registry of SIP configuration profile types
This document requests IANA to register new SIP configuration profile
types at http://www.iana.org/assignments/sip-parameters under "SIP
Configuration Profile Types".
SIP configuration profile types allocations fall under the category
"Specification Required", as explained in "Guidelines for Writing an
IANA Considerations Section in RFCs" ([RFC5226]).
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Registrations with the IANA MUST include a the profile type, and a
published document which describes its purpose and usage.
As this document specifies three SIP configuration profile types, the
initial IANA registration will contain the information shown in the
table below. It also demonstrates the type of information maintained
by the IANA.
Profile Type Reference
-------------- ---------
local-network [RFCXXXX]
device [RFCXXXX]
user [RFCXXXX]
CONTACT:
-------
sumanth@cablelabs.com
Daniel Petrie dan.ietf AT SIPez DOT com
Note to RFC editor: Please replace RFCXXXX with the RFC number
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9. Security Considerations
The framework specified in this documents specifies profile delivery
stages, an event package and three profile types to enable profile
delivery. The profile delivery stages are: enrollment, content
retrieval, and change notification. The event package helps with
enrollment and change notifications. Each profile type allows for
profile retrieval from a PDS belonging to a specific provider.
Enrollment allows a device to request, and if successful, enroll with
a PDS to obtain profile data. To transmit the request the device
relies on configured, cached or discovered data. Such data includes
provider domain names, identities, and credentials. The device
either uses configured outbound proxies or discovers the next-hop
entity using [RFC3263] that can result in a SIP proxy or the PDS. It
then transmits the request. A SIP Proxy receving the request uses
the Request-URI and event header contents to route it to a PDS (via
other SIP proxies, if required).
When a PDS receives the enrollment request, it can either challenge
any contained identity or admit the enrollment. Authorization rules
then decide if the enrollment gets accepted. If accepted, the PDS
sends an initial notification that contains either the profile data,
or content indirection information. The profile data can contain
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generic profile data (common across multiple devices) or information
specific to an entity (such as the device or a user). If specific to
an entity, it may contain sensitive information such as credentials.
Compromise of sensitive data can lead to threats such as
impersonation attacks (establishing rogue sessions), theft of service
(if services are obtainable), and zombie attacks. It is important
for the device to ensure the authenticity of the PNC and the PCC
since impersonation of the SIP service provider can lead to Denial of
Service and Man-in-the-Middle attacks.
Profile content retrieval allows a device to retrieve profile data
via content indirection from a PCC. This communication is
accomplished using one of many profile delivery protocols or
frameworks, such as HTTP or HTTPS as specified in this document.
However, since the profile data returned is subject to the same
considerations as that sent via profile notification, similar threats
exist. For example, denial of service attacks (rogue devices bombard
the PCC with requests for a specific profile) and attempts to modify
erroneous data onto the PCC (since the location and format may be
known). Thus, for the delivery of any sensitive profile data,
authentication of the entity requesting profile data is required. It
is also important for the requesting entity to authenticate the
profile source via content indirection, and ensure that the sensitive
profile data is protected via message integrity. For sensitive data
that should not be subject to snooping, privacy is also required.
The following sub-sections highlight the security considerations that
are specific to each profile type.
9.1. Local-network profile
A local network may or may not (e.g., home router) support local-
network profiles as specified in this framework. Even if supported,
the PDS may only be configured with a generic local-network profile
that is provided to every device that requests the local-network
profile. Such a PDS may not implement any authentication
requirements or TLS.
Alternatively, certain deployments may require the entities - device
and the PDS - to authenticate each other prior to successful profile
enrollment. Such networks may pre-configure user identities to the
devices and allow user-specific local-network profiles. In such
networks the PDS will support digest, and the devices are configured
with user identities and credentials as specified in Section 5.3.1.
If sensitive profile data is being transmitted, the user identity is
a SIPS URI that results in TLS with the next-hop (which is
authenticated), and digest authentication is used by the PDS and the
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device.
This framework supports both use cases and any variations in-between.
However, devices obtaining local-network profiles from an
unauthenticated PDS are cautioned against potential Man-in-the-Middle
or PDS impersonation attacks. This framework requires that a device
reject sensitive data, such as credentials, from unauthenticated
local-network sources. It also prohibits devices from responding to
authentication challenges in the absence TLS on all hops as a result
of using a SIPS URI. Responding to unauthenticated challenges allows
for dictionary attacks that can reveal weak passwords. The only
exception to accepting such sensitive data without authentication of
the PDS is in the case of bootstrapping (see Section 5.3.1). In the
case of bootstrapping, the methods employed need to be aware of
potential security threats such as impersonation.
The use of SIP Identity is useful for the device to validate
notifications in the absence of a secure channel such as TLS when a
SIPS URI is used. In such cases the device can validate the SIP
Identity header to verify the source of the profile notification, and
the source of the profile data when content indirection is not used.
However, the presence of the header does not guarantee the validity
of the data. It verifies the source and confirms data integrity, but
the data obtained from an undesired source may still be invalid,
e.g., invalid outbound proxy information, resulting in Denial of
Service. Thus, devices requesting the local-network profile from
unknown networks need to be prepared to discard information that
prevent retrieval of other, required, profiles.
9.2. Device profile
Device profiles deal with device-specific configuration. They may be
provided to unknown devices that are attempting to obtaining profiles
for purposes such as trials, self-subscription (not to be confused
with [RFC3265]) and emergency services ([I-D.ietf-ecrit-phonebcp]).
This framework allows for the device profile to be used for
bootstrapping a device. Such bootstrapping profile data may contain
enough information to connect to a Provider. For example, it may
enable the device to communicate with a device provider, allowing for
trial or self-subscription services via visual or audio interfaces
(e.g., interactive voice response), or customer service
representatives. The profile data may also allow the device a choice
of device providers and allow the end-user to choose one. The
profile data may also contain identities and credentials (temporary
or long-term) that can be used to obtain further profile data from
the network. This framework recommends the use of the SIP Identity
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header by the PDS. However, to be able to validate the SIP Identity
header, the device needs to be pre-configured with the knowledge of
allowable domains or certificates for validation (e.g., using PKI).
If not, the device can still guarantee header and body integrity if
the profile data contains the domain certificate (but the data can
still be invalid or malicious). In such cases, devices supporting
user interfaces may obtain confirmation from the user trying to
bootstrap the device (confirming header and body integrity).
However, when the SIP Identity header is not present, or the device
is not capable of validating it, the bootstrapping data is
unauthenticated and obtained without any integrity protection. Such
bootstrapping data, however, may contain only temporary credentials
(SIPS URI and digest credentials) that can be used to reconnect to
the network to ensure message integrity and privacy prior to
obtaining long-term credentials. It is to be noted that such devices
are at the mercy of the network they request the device profile from.
If they are initialized in a rogue network, or get hijacked by a
rogue PDS, the end-user may be left without desired device operation
or, worse, unwanted operation. To mitigate such factors the device
provider may communicate temporary credentials (e.g., passwords that
can be entered via an interface) or permanent credentials (e.g., a
USB device) to the end-user for connectivity. If such methods are
used, those credentials MUST be quickly replaced by large-entropy
credentials, to minimize the impact of dictionary attacks. Future
enhancements to this framework may specify device capabilities that
allow for authentication without any provider specific configuration
(e.g., X.509 certificates using PKI can allow for authentication by
any provider with access to the CA certificate). Alternatively, the
device may be pre-configured with with credentials for use with
content indirection mechanisms. In such circumstances a PDS can use
secure content indirection mechanism, such as HTTPS, to provide the
bootstrapping data.
Once a device is associated with a device provider the device profile
is vital to device operation. This is because the device profile can
contain important operational information such as users that are to
be allowed access (white-list or black-list), user credentials (if
required) and other sensitive information. Thus, it is necessary to
ensure that any device profile containing sensitive information is
obtained via an authenticated source, with integrity protection, and
delivered to an authenticated device. For sensitive information such
as credentials, privacy is also required. The framework requires
that devices obtain sensitive information only from authenticated
entities except while it is being bootstrapped. In cases where
privacy needs to be mandated for notifications, the device provider
can configure the device with a SIPS URI, to be used as the
subscription URI, during profile enrollment. The framework also
requires a PDS presenting sensitive profile data to use digest
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authentication. This ensures that the data is delivered to an
authenticated entity. Authentication of profile retrieval via
content indirection for sensitive profiles is via HTTPS utilizing
HTTP digest.
9.3. User profile
Devices can only request user profiles for users that are known by a
SIP service provider. PDSs are required to reject user profile
enrollment requests for any users that are unknown in the network.
For known user AoRs that are allowed to retrieve profiles, the
security considerations are similar to that of the device profile
(except for bootstrapping).
10. Acknowledgements
The author appreciates all those who contributed and commented on the
many iterations of this document. Detailed comments were provided by
the following individuals: Jonathan Rosenberg from Cisco, Henning
Schulzrinne from Columbia University, Cullen Jennings from Cisco,
Rohan Mahy from Plantronics, Rich Schaaf from Pingtel, Volker Hilt
from Bell Labs, Adam Roach of Estacado Systems, Hisham Khartabil from
Telio, Henry Sinnreich from MCI, Martin Dolly from AT&T Labs, John
Elwell from Siemens, Elliot Eichen and Robert Liao from Verizon, Dale
Worley from Pingtel, Francois Audet from Nortel, Roni Even from
Polycom, Jason Fischl from Counterpath, Josh Littlefield from Cisco,
Nhut Nguyen from Samsung.
The final revisions of this document were a product of design team
discussions. The editor wishes to extend special appreciation to the
following design team members for their numerous reviews and specific
contributions to various sections: Josh Littlefield from Cisco
(Overview, Section 6), Peter Blatherwick from Mitel (Section 6),
Cullen Jennings (Security), Sam Ganesan (Section 6) and Mary Barnes
(layout, Section 6).
The following design team members are thanked for numerous reviews
and general contributions: Martin Dolly from AT&T Labs, Jason Fischl
from Counterpath, Alvin Jiang of Engin and Francois Audet from
Nortel.
The following SIPPING WG members are thanked for numerous reviews,
comments and recommendations: John Elwell from Siemens, Donald Lukacs
from Telcordia, Roni Even from Polycom, David Robbins from Verizon,
Shida Schubert from NTT Advanced Technology Corporation, and Eugene
Nechamkin from Broadcom. The editor would also like to extend a
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special thanks to the comments and recommendations provided by the
SIPPING WG, specifically Keith Drage from Lucent (restructuring
proposal) and John Elwell from Siemens (numerous reviews and
recommendations).
Additionally, appreciation is also due to Peter Koch for expert DNS
advice.
And finally, sincere appreciation is extended to the chairs (Mary
Barnes from Nortel and Gonzalo Camarillo from Ericsson) and the Area
Directors (Cullen Jennings from Cisco and Jon Peterson from Neustar)
for facilitating discussions, reviews and contributions.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263,
June 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3319] Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
Protocol (DHCPv6) Options for Session Initiation Protocol
(SIP) Servers", RFC 3319, July 2003.
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[RFC3361] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCP-for-IPv4) Option for Session Initiation Protocol
(SIP) Servers", RFC 3361, August 2002.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC4483] Burger, E., "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", RFC 4483,
May 2006.
[RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
Option", RFC 4704, October 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
11.2. Informative References
[I-D.ietf-ecrit-phonebcp]
Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in support of Emergency Calling",
draft-ietf-ecrit-phonebcp-13 (work in progress),
July 2009.
[I-D.ietf-sip-outbound]
Jennings, C., "Managing Client Initiated Connections in
the Session Initiation Protocol (SIP)",
draft-ietf-sip-outbound-20 (work in progress), June 2009.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): Technical Specification Road Map", RFC 4510,
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Internet-Draft SIP Configuration Framework September 2009
June 2006.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
Authors' Addresses
Daniel Petrie
SIPez LLC.
34 Robbins Rd
Arlington, MA 02476
USA
Email: dan.ietf AT SIPez DOT com
URI: http://www.SIPez.com/
Sumanth Channabasappa (Editor)
CableLabs
858 Coal Creek Circle
Louisville, Co 80027
USA
Email: sumanth@cablelabs.com
URI: http://www.cablelabs.com/
Petrie & Channabasappa, Ed. Expires April 1, 2010 [Page 55]
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