SIPPING D. Petrie
Internet-Draft SIPez LLC.
Intended status: Standards Track S. Channabasappa, Ed.
Expires: April 27, 2008 CableLabs
October 25, 2007
A Framework for Session Initiation Protocol User Agent Profile Delivery
draft-ietf-sipping-config-framework-13
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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
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Reference Model . . . . . . . . . . . . . . . . . . . . . 6
3.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Profile Types . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Profile delivery stages . . . . . . . . . . . . . . . . . 10
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Simple Deployment Scenario . . . . . . . . . . . . . . . . 11
4.2. Devices supporting multiple users from different
Service Providers . . . . . . . . . . . . . . . . . . . . 12
5. Profile Delivery Framework . . . . . . . . . . . . . . . . . . 14
5.1. Profile delivery stages . . . . . . . . . . . . . . . . . 14
5.1.1. Profile Enrollment . . . . . . . . . . . . . . . . . . 14
5.1.2. Content Retrieval . . . . . . . . . . . . . . . . . . 17
5.1.3. Change Notification . . . . . . . . . . . . . . . . . 17
5.1.4. Enrollment Data and Caching . . . . . . . . . . . . . 18
5.2. Securing Profile Delivery . . . . . . . . . . . . . . . . 21
5.2.1. Securing Profile Enrollment . . . . . . . . . . . . . 21
5.2.2. Securing Content Retrieval . . . . . . . . . . . . . . 23
5.2.3. Securing Change Notification . . . . . . . . . . . . . 24
5.3. Additional Considerations . . . . . . . . . . . . . . . . 24
5.3.1. Identities and Credentials . . . . . . . . . . . . . . 24
5.3.2. Profile Enrollment Request Attempt . . . . . . . . . . 26
5.3.3. Device Types . . . . . . . . . . . . . . . . . . . . . 30
5.3.4. Profile Data . . . . . . . . . . . . . . . . . . . . . 30
5.3.5. Profile Data Frameworks . . . . . . . . . . . . . . . 31
5.3.6. Additional Profile Types . . . . . . . . . . . . . . . 31
5.3.7. Deployment considerations . . . . . . . . . . . . . . 32
5.4. Usage of Outbound . . . . . . . . . . . . . . . . . . . . 32
6. Event Package Definition . . . . . . . . . . . . . . . . . . . 33
6.1. Event Package Name . . . . . . . . . . . . . . . . . . . . 33
6.2. Event Package Parameters . . . . . . . . . . . . . . . . . 33
6.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 36
6.4. Subscription Duration . . . . . . . . . . . . . . . . . . 36
6.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 37
6.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 37
6.7. Notifier Generation of NOTIFY Requests . . . . . . . . . . 37
6.8. Subscriber Processing of NOTIFY Requests . . . . . . . . . 38
6.9. Handling of Forked Requests . . . . . . . . . . . . . . . 38
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6.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 39
6.11. State Agents . . . . . . . . . . . . . . . . . . . . . . . 39
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.1. Example 1: Device requesting profile . . . . . . . . . . . 39
7.2. Example 2: Device obtaining change notification . . . . . 42
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46
8.1. SIP Event Package . . . . . . . . . . . . . . . . . . . . 46
8.2. Registry of SIP configuration profile types . . . . . . . 46
9. Security Considerations . . . . . . . . . . . . . . . . . . . 47
9.1. Local-network profile . . . . . . . . . . . . . . . . . . 49
9.2. Device profile . . . . . . . . . . . . . . . . . . . . . . 50
9.3. User profile . . . . . . . . . . . . . . . . . . . . . . . 51
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 52
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53
11.1. Normative References . . . . . . . . . . . . . . . . . . . 53
11.2. Informative References . . . . . . . . . . . . . . . . . . 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54
Intellectual Property and Copyright Statements . . . . . . . . . . 56
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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 hotspots. 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
and obtain them from the same, or different, Providers. Additional
profile types may also be specified. 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.
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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.
PDSs and devices will implement all the three profile types. Unless
configured otherwise, a device will try to obtain all the three
profile types. A retrieval order is specified by the framework. The
data models associated with each profile type is 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
nature, whereas the second is relatively complex. The use cases
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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 single entity enables the local network, manages
deployed devices and provides SIP services. The devices only attach
to the local network, and are pre-configured with a single user.
The following assumptions apply:
o The device profile data contains all the information necessary
for the device to participate in the local network and obtain
services.
o The device is pre-configured to only request the device profile.
o The enrollment notification contains the profile data (profile
content retrieval is not required).
o There are no proxies in the network.
Figure 4 illustrates this use case and highlights the communications
relevant to the framework specified in this document.
+----------------------+
+--------+ | Local Network, Device|
| Device | |& SIP Service Provider|
| | | |
+--------+ | 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 using DHCP.
(B) The device performs Profile Enrollment for the device profile;
the device profile data is contained in the enrollment
notification.
(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 (e.g., Kiosk at an airport)
that allows multiple users to obtain services from a list of pre-
configured SIP Service Providers.
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 by
SIP proxies.
Figure 4 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.
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 to any profile type specified for use
with this framework. The following sub-sections provide the
requirements associated with each stage.
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.
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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 retrieval (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 UI) 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
data to bootstrap the device. Such temporary data is not
considered to be "configured" and is not expected to 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
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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 is
when a policy prevents a 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 MAY
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
notification, profile enrollment is complete.
When it receives the SIP NOTIFY message, indicating successful
profile enrollment, the device MUST make the new profile effective
within the specified timeframe, as described in Section 6.2.
Once profile enrollment is successful, the PDS MUST consider the
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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
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.
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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".
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:
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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. An exception is a user who changes device
providers, but retains the device. 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:
o The device MUST use the device identifier and the device
provider's domain name to form the Request URI.
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
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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,
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
hostname 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 MAC Address, it SHOULD
use an alternative non-alterable device identifier. For example,
the International Manufacturer's Equipment Identifier (IMEI) for
mobile devices.
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 As a note, when the URN is used as the user part of the Request
URI, it MUST be URL escaped
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:
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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.
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
unwanted elements, during transit. At a minimum, 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 required to ensure that the data is not snooped by
unwanted elements.
For an overview of potential security threats, refer to Section 9.The
requirements to address the concerns are required for all stages of
profile delivery, and are presented in the following subsections.
5.2.1. Securing Profile Enrollment
During profile enrollment, the device needs to authenticate two
entities. The next-hop entity, i.e., a proxy or a PDS, to which the
device transmits the profile enrollment request, and the initial
notification from the PDS. On the Provider's side, a PDS that
recognizes an identity, such as the user AoR, that will result in
sensitive (or even non-generic) data included in the initial or
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change notifications, will need to authenticate the device claiming
such identities.
Authentication of the next-hop entity by the device is accomplished
by using the procedures specified in [RFC2818], Section 3.1, over an
establish TLS connection ([RFC4346]). The 'Server Identity' in this
case is always the domain of the next-hop SIP entity. A device
presenting a SIPS URI as a user AoR MUST establish TLS with the next-
hop SIP entity to which it sends the enrollment request. In all
other cases, the device SHOULD still attempt establishment of TLS
with the next-hop SIP entity. An exception is when it is explicitly
configured not to. If it attempts to establish TLS and it fails
because the next-hop SIP entity does not support TLS, the device
SHOULD attempt other resolved next-hop SIP entities prior to
attempting enrollment without TLS. If the device attempts to
establish a TLS session and fails to verify the next-hop entity
(e.g., the domain name could not be verified) the device MUST NOT
continue with the current enrollment request, and must retry with
other resolved next-hop SIP entities. If the device is attempting to
establish TLS, and exhausts the entire list of next-hop entities,
then:
o if the device has a user interface, and unless configured not to,
the device SHOULD prompt the user if it can continue without TLS;
o if the device has no user interface, and unless configured not to,
the device MUST retry enrollment without TLS and without
presenting any configured user AoR (note: this means that user
profiles cannot be retrieved).
In the absence of a Server Identity authenticated TLS session with
the next-hop SIP entity:
o the device MUST NOT respond to any authentication challenges;
o the device MUST ignore any notifications containing sensitive
profile data.
Once enrolled, the device obtains the initial notification. This is
authenticated using two methods. If this initial notification was
transmitted on the mutually authenticated TLS session established for
enrollment requests, then it is considered authenticated. If not,
the device MUST verify the presence of a SIP Identity header from the
PDS and validate that it belongs to the Provider's domain. If the
SIP Identity header is absent or the device cannot validate it, the
device MUST reject any sensitive profile data. If the SIP Identity
header is present, and the device cannot validate it, then it MUST
reject the profile data and retry enrollment. To allow for this
authentication, the PDS SHOULD include the SIP Identity header as
specified in [RFC4474]. Exceptions are PDSs that do not serve
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sensitive profiles, or those in deployments where communication with
the PDS in the absence of a mutually authenticated TLS is disallowed.
When the SIP Identify header is used, the PDS MUST set the host
portion of the AoR in the 'From' header to the Provider's domain.
Note that both Server Identity authentication ([RFC2818]) and SIP
Identity ([RFC4474] require X.509 certificates. Additionally, the
use of TLS and mutual authentication also provides message integrity
and privacy between the device and the next-hop entity. When the
next-hop entity is a proxy, the Provider will need ensure mutual
authentication and integrity between intermediary components such as
proxies and PDSs. This is mandatory when a SIPS URI is presented by
the device.
Authentication of the identity requesting the profile is accomplished
by the PDS by using the Digest Authentication mechanism, over TLS.
Thus, devices and PDSs MUST implement Digest Authentication specified
in [RFC3261], and TLS as specified in [RFC4346]. If the device
presents a user AoR, it should be recognized by the network. If not
(e.g., discovered or device identities) it may not be known by the
PDS (and hence, may not be associated with credentials). If known by
the PDS and the notification will result in data specific to the user
AoR, the PDS MUST challenge the request using Digest authentication
specified in [RFC3261]. If the device successfully responds to the
challenge, it is provided the initial notification, which contains
the profile data within, or via content indirection. If user
authentication fails the PDS MAY refuse enrollment, or provide
profile data without the user-specific information. As a note, if
the PDS attempts authentication in the absence of an authenticated
TLS session between the device and the next-hop entity, it will be
ignored by the device. A PDS that does not perform authentication
MUST use content indirection to a PCC that supports authentication,
integrity protection and privacy for conveying sensitive 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. A device MUST authenticate the PCC as specified in
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[RFC2818], Section 3.1. A device that is being provided with profile
data that contains sensitive data MUST be authenticated using Digest
as specified in [RFC2617], with the exception of a device that is
being bootstrapped for the first time. The resulting mutually
authenticated TLS channel also provides message integrity.
5.2.3. Securing Change Notification
A successful profile enrollment results in an initial 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.
If the device established TLS with the next-hop entity then any such
notifications SHOULD be sent over the same TLS session by the PDS.
If the TLS session exists, the device MUST ignore any notifications
sent outside the TLS session. If no such TLS session exists, the
device MUST NOT accept any sensitive profile data without verifying
the presence of, and validating, a SIP Identity header.
A PDS that does not support TLS MUST use content indirection to a PCC
that supports authentication and integrity protection for conveying
sensitive profile data.
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. Identities and Credentials
When requesting a profile the device can provide an identity such as
a user AoR. To do so, the device needs to be configured. This can
be accomplished in one of many 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 USB drives.
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End-user interface
The end-user may be provided with user AoRs and credentials. The
end-user can then configure the device (using a user interface),
or present when required (e.g., IM login screen).
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.
In such a case the device profile can provide three kinds of
information:
* Profile data that allows the end-user to communicate with the
device or SIP service provider. The provider can then use any
applicable method (e.g., web portal) to provide the user AoR.
* Profile data that redirects the device to an entity, such as
the PCC, that can provide identity data. 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 the user AoR.
* Profile data containing user identity to be used. This can be
used in cases where the device is initialized for the first
time, or after a factory reset, in the device provider's
network.
If a device presents a user AoR in the enrollment request, the PDS
can challenge it. To respond to such authentication challenges, the
device needs to have associated credentials. Thus, any of the
configuration methods indicated above need to provide the user
credentials along with any AoRs.
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.
The configured user AoR and associated credentials can be used in
applicable domains for any of the profile types specified by this
framework. In the absence of the user AoR, the device is not
expected to contain any other credentials. Future enhancements can
specify additional identities and credentials.
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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]
o The timeout for profile retrieval using content indirection will
be as specified by profile retrieval protocols employed
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 ()
Iteration i=0
Loop: Attempt
Loop: For each SIP Subscription URI
Loop: 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 this function()
End Loop: Next-hop SIP entity contact
End Loop: SIP Subscription URI formation
(Note: If you are here, profile enrollment did not succeed)
+ Is any valid cached profile data available?
= If yes, use it and continue with this function()
+ If the enrollment request is for a non-mandatory profile
= then spawn the next profile and continue with this
function()
- Delay for 2^i*(64*T1); -- this is exponential backoff
- increment i;
- If i>8, reset i=8;
End loop: Attempt
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' (not to be confused with an empty NOTIFY). 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 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:
o The device profile type SHOULD specify parameters to configure the
identities and credentials. These parameters may be optional or
mandatory and will be used for dynamically configuring devices
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that initialize in a network without any pre-configuration.
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
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
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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.
5.4. Usage of Outbound
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.
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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.
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:
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local-network: specifying the "local-network" type profile indicates
the desire for profile data specific to the local network.
device: specifying the "device" type profile(s) indicates the desire
for the profile data and 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 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.
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
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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. 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.
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
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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. The exception being future
enhancements to the framework which may specify a use for the
SUBSCRIBE request body.
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].
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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:" and "https:" URI schemes
MUST be supported; other URI schemes MAY be supported based on the
Profile Data Frameworks (examples include FTP [RFC0959], HTTP
[RFC2616], HTTPS [RFC2818], 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
either accept or reject the subscription.
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. no body or content
indirection).
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If the URI in the SUBSCRIBE request 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 timeframe 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. The Subscriber wishes to support alternative
URI schemes it MUST be indicated in the "schemes" Contact header
field parameter as defined in [RFC4483]. The 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 NOTIFY 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.
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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 a
snapshot of Section 4.1, specifically the request for the device
profile. The examples are purely informative and in case of
conflicts with the framework or protocols used for illustration, the
latter should be deemed normative.
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
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.
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+----------------------+
+--------+ | 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)|<----------------------------------------------|
| |
(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.
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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: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@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
@example.com
;+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
@192.0.2.44 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=1231
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 (UI) 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 (UI) 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 (UI) 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=1235
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" ([RFC2434]).
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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
assigned to this document.
9. Security Considerations
The framework specified in this document enables profile data
delivery to devices. It specifies profile delivery stages, an event
package and several profile types.
There are three stages: Enrollment, Content Retrieval, and Change
Notification.
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+------+ +-----+
| | | |
|Device| | PNC |
| | | |
+------+ +-----+
| |
| Profile Enrollment |
|---------------------->|
| |
| Initial Notification |
|<----------------------|
| |
+------+ +-----+
| | | |
|Device| | PNC |
| | | |
+------+ +-----+
| |
| Profile Enrollment |
|---------------------->|
| |
| Change Notification |
|<----------------------|
| |
+------+ +-----+
| | | |
|Device| | PCC |
| | | |
+------+ +-----+
| |
| Profile Request | (When content
|---------------------->| indirection
| | is used)
| Profile Response |
|<----------------------|
| |
PNC = Profile Notification Component
PCC = Profile Content Component
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Figure 23: Profile Delivery Stages
Enrollment allows a device to request a profile. 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
discoveries the next-hop entity using [RFC3263] that can result in a
SIP proxy or the PDS. It then transmits the request, after
establishing a TLS session if required. If obtained via a SIP proxy,
the Request-URI is used to route it to a PDS (via an authoritative
SIP proxy, if required).
When a PDS receives the enrollment request, it can either challenge
the presented identity (if any) or admit the enrollment.
Authorization then decides if the enrollment is accepted. If
accepted, the PDS sends an initial notification that contains either
the profile data, or content indirection information. The profile
data can contain information specific to an entity (such as the
device or a user) and may contain sensitive information (such as
credentials). Compromise of such data can lead to threats such as
impersonation attacks (establishing rogue sessions), theft of service
(if services are obtainable), and zombie attacks. Even if the
profile data is provided using content indirection, PCC information
within the notification can lead to threats such as 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). It is also important for the
device to ensure the authenticity of the PNC since impersonation of
the SIP service provider can lead to Denial of Service, Man-in-the-
Middle attacks, etc.
Profile content retrieval allows a device to retrieve profile data
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, the same threats exist.
Profile-specific considerations follow.
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 capable of accessing the network.
Such a PDS may not implement any authentication requirements or TLS.
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Alternatively, certain deployments may require the entities - device
and the PDS - to mutually authenticate prior to 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 contain X.509 certificates and support TLS, and the devices are
pre-configured with user identities, credentials and implement TLS.
This framework supports both use cases and variations in-between.
However, devices obtaining local-network profiles from an
unauthenticated PDS are cautioned against potential MiM or PDS
impersonation attacks. This framework requires that a device reject
sensitive data, such as credentials, from unauthenticated local-
network sources (exceptions are noted). It also prohibits devices
from responding to authentication challenges from unauthenticated
PDSs. Responding to unauthenticated challenges allows for dictionary
attacks that can reveal weak passwords.
If deployments prefer devices to obtain profiles only from pre-
configured domains (e.g., partner networks), they MAY require such
devices to establish TLS prior to obtaining the local-network
profile.
The use of SIP Identity is useful in cases when TLS is not used but
the device still obtains a profile (e.g., the local-network profile).
In such cases the device provider, or the user, can use the SIP
Identity header to verify the source of the local-network profile.
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., it can be invalid or contain malicious content).
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 of trials and self-subscription to SIP services (not to
be confused with [RFC3265]), emergency services
([I-D.ietf-ecrit-phonebcp]), or to devices that are known by the PDS.
Devices that are not aware of any device providers (i.e., no cached
or configured information) will have to discover a PDS in the network
they connect to. In such a case the discovered information may lead
them to a PDS that provides enough profile data to enable device
operation. This configuration can also provide a user AoR that can
be used in the local-network and credentials (temporary or long-term)
that will be used for future communication with the network. This
may enable the device to communicate with a device provider who
allows for self-subscription (e.g., web interface, interactive voice
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response or customer service representative). It may also allow the
device a choice of device providers and allow the end-user to choose
one. It is to be noted that such devices are at the mercy of the
network they connect to initially. 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 (PINs 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 the large-entropy credentials
MUST be used, or quickly replaced with such, to minimize the impact
of dictionary attacks. Future enhancements to this framework may
specify device capabilities that allow for mutual authentication
without pre-configuration (e.g., X.509 certificates using PKI).
Once a device is associated with a device provider (either
dynamically or via pre-configuration using a user interface or prior
to distribution), 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 also necessary to ensure that the device
profile is not obtained via an unauthenticated source or tampered
during transit. Thus the framework requires that devices supporting
any sensitive device profiles establish next-hop authenticated TLS
connections prior to device enrollment. However, given the
importance of the device profile it also allows for profile requests
in cases where the PDS does not implement TLS. It also allows the
PDSs to perform authentication without requiring TLS. However, this
leaves the communication open to MiM attacks and SHOULD be avoided.
Additionally any credential used SHOULD be of sufficiently large-
entropy to prevent dictionary attacks. Devices SHOULD use the
'cnonce' parameter ([RFC2617]) to thwart "offline" dictionary
attacks.
9.3. User profile
Devices can only request user profiles for users that are known by a
SIP service provider. Thus, PDSs are prohibited from accepting user
profile enrollment requests for users that are unknown in the
network. If the user AoR is a SIPS URI then the device is required
to establish a next-hop authenticated TLS session. This framework
requires this for profiles with sensitive data. If it is a SIP URI,
then the device is still recommended to attempt TLS establishment to
ensure protection against rogue PDSs. Further, the PDS will
authenticate requests prior to accepting profile enrollment requests
that can result in sensitive data. A mutually authenticated TLS
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channel provides message integrity and privacy.
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
special thanks to the comments and recommendations provided by the
SIPPING WG, specifically Keith Drage from Lucent (restructuring
proposal).
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.
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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.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[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.
[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.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
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[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.
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-02 (work in progress),
September 2007.
[I-D.ietf-sip-outbound]
Jennings, C. and R. Mahy, "Managing Client Initiated
Connections in the Session Initiation Protocol (SIP)",
draft-ietf-sip-outbound-10 (work in progress), July 2007.
[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,
June 2006.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
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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/
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Full Copyright Statement
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Petrie & Channabasappa, Ed. Expires April 27, 2008 [Page 56]
