RFC 6080
A Framework for Session Initiation Protocol User Agent Profile Delivery
Pages: 54
Proposed Standard
Proposed Standard
Part 2 of 3 – Pages 14 to 33
5. Profile Delivery Framework
This section specifies the profile delivery framework. It provides the requirements for the three profile delivery stages introduced in Section 3.4 and presents the associated security requirements. It also presents considerations such as back-off and retry mechanisms.5.1. Profile Delivery Stages
The three profile delivery stages -- enrollment, content retrieval, and change notification -- apply separately to each profile type specified for use with this framework. The following subsections 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. PDSs and devices MUST implement all of the three profile types. A device that has not been configured otherwise SHOULD try to obtain all the three profile types, in the order specified by this framework. The exceptions are bootstrapping when it SHOULD request the device profile type (see Section 5.3.1) or when it has been explicitly configured with a different order via mechanisms such as previously retrieved profile data or pre-configuration or manual configuration. 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 and device or user identities and credentials. Such data can be "configured" during device manufacturing, by the user, or via profile data enrollment (see Section 5.3.1). The data can also be "discovered" using the procedures specified by this framework. The "discovered" data can be retained across device resets (but not across factory resets) and such data is referred to as "cached". Thus, data can be configured, discovered, or cached. The following requirements apply. * If the device is configured with a specific domain name (for the local network provider or device provider), it MUST NOT attempt "discovery" of the domain name. This is the case when the device is pre-configured (e.g., via a user interface) to be managed by specific entities.
* The device MUST only use data associated with the provider's
domain in an enrollment request. As an example, when the
device is requesting a local-network profile in the domain
'example.net', it cannot present a user Address of Record (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 SHOULD NOT be cached across
resets. The configuration obtained using such data MAY provide
the configuration data required for the device to continue
functioning normally.
Devices attempting enrollment MUST comply with the SIP-specific
event notification specified in [RFC3265], the event package
requirements specified in Section 6.2, and the security
requirements specified in Section 5.2.
Enrollment request admittance
A PDS or a SIP proxy will receive a transmitted enrollment
request. If a SIP infrastructure element receives the request, it
will relay it to the authoritative proxy for the domain indicated
in the Request-URI (the same way it would handle any other
SUBSCRIBE message). The authoritative proxy is required to
examine the request (e.g., event package) and transmit it to a PDS
capable of addressing the profile enrollment request.
A PDS receiving the enrollment request SHOULD respond to the
request, or proxy it to a PDS that can respond. An exception to
responding or proxying the request is when a policy prevents
response (e.g., recognition of a denial-of-service (DoS) attack,
an invalid device, etc.). The PDS then verifies the identity
presented in the request and performs any necessary
authentication. Once authentication is successful, the PDS MUST
either admit or reject the enrollment request, based on applicable
authorization policies. A PDS admitting the enrollment request
indicates it via a 2xx-class response, as specified in [RFC3265].
Refer to Sections 6.6 and 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 SHOULD make the new profile
effective within the specified time frame, as described in
Section 6.2. The exception is when the profile data is delivered
via content indirection, and the device cannot obtain the profile
data within the specified time frame.
Once profile enrollment is successful, the PDS MUST consider the
device enrolled for the specific profile, for the duration of the
subscription.
5.1.2. Content Retrieval
A successful profile enrollment leads to an initial SIP notification,
and may result in subsequent change notifications. Each of these
notifications can either contain profile data or content indirection
information. If it contains content indirection information, the
device is required to retrieve the profile data using the specified
content retrieval protocols. This process is termed "profile content
retrieval". For information regarding the use of the SIP NOTIFY
message body, please refer to Section 6.5.
Devices and PDSs implementing this framework MUST implement two
content retrieval protocols: HTTP and HTTPS, as specified in
[RFC2616] and [RFC2818], respectively. Future enhancements or usage
of this framework may specify additional or alternative content
retrieval protocols. For security requirements and considerations,
please refer to Section 5.2.
5.1.3. Change Notification
Profile data can change over time. Changes can be initiated by
various entities (e.g., via the device, back-office components, and
end-user web interfaces) and for various reasons (e.g., change in
user preferences and modifications to services). Profiles may also
be shared by multiple devices simultaneously. When a profile is
changed, the PDS MUST inform all the devices currently enrolled for
the specific profile. This process of informing a device of any changes to the profile that it is currently enrolled for is termed change notification. The PDS provides change notification using a SIP notification (the 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 6.5.5.1.4. 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) the device
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 [RFC5626]. The device MUST ensure
that the value of this parameter is the same as that included in
any subsequent profile enrollment request.
For example, if the device requested and received the local domain
name via DHCP to be: airport.example.net, then the local-network
profile SUBSCRIBE Request-URI would look like:
sip:_sipuaconfig.airport.example.net
The local-network profile SUBSCRIBE Request-URI does not have a user
part so that the URI is distinct between the "local" and "device"
URIs when the domain is the same for the two. This provides a means
of routing to the appropriate PDS in domains where there are distinct
servers.
The From field is populated with the user AoR, if available. This
allows the local network provider to propagate user-specific profile
data, if available. The "+sip.instance" parameter within the Contact
header is set to the device identifier or specifically, the SIP UA
instance. Even though every device may get the same (or similar)
local-network profile, the uniqueness of the "+sip.instance"
parameter provides an important capability. Having unique instance
ID fields allows the management of the local network to track devices
present in the network and consequently also manage resources such as
bandwidth allocation.
5.1.4.2. Device Profile Type
Once associated with a device, the device provider is not expected to
change frequently. Thus, the device is allowed to, and SHOULD, cache
the Subscription URI for the device profile upon successful
enrollment. Exceptions include cases where the device identifier has
changed (e.g., new network card), device provider information has
changed (e.g., user initiated change), or the device cannot obtain
its profile using the Subscription URI. Thus, when available, the
device MUST use a cached Subscription URI. If no cached URI is
available then it needs to create a Subscription URI. To create a
Subscription URI, the device needs a device identity and the device
provider's domain name. Unless already configured, the device needs
to discover the necessary information and form the Subscription URI.
In such cases, the following requirements apply for creating a
Subscription URI for requesting the device profile:
o The device MUST populate the user part of the Request-URI with the
device identifier. The device MUST set the host portion of the
Request-URI to the domain name of the device provider. The device
identifier format is explained in detail later in this section.
o The device MUST set the From field to a value of anonymous@<device
provider's domain>.
o The device MUST include the "+sip.instance" parameter within the
Contact header, as specified in [RFC5626]. The device MUST use
the same value as the one presented while requesting the local-
network profile.
Note that the discovered AoR for the Request-URI can be overridden by
a special, provisioned, AoR that is unique to the device. In such
cases, the provisioned AoR is used to form the Request-URI and to
populate the From field.
If the device is not configured with an AoR, and needs a domain name
to populate the Request-URI and the From field, it can either use a
configured domain name, if available, or discover it. The options to
discover are described below. The device MUST use the results of
each successful discovery process for one enrollment attempt, in the
order specified below.
o Option 1: Devices that support DHCP MUST attempt to obtain the
domain name of the outbound proxy during the DHCP process, using
the DHCP option for SIP servers defined in [RFC3361] or [RFC3319]
(for IPv4 and IPv6, respectively).
o Option 2: Devices that support DHCP MUST attempt to obtain the
local IP network domain during the DHCP process (refer to
[RFC2132] and [RFC4704]).
o Option 3: Devices MUST use the local network domain name
(configured or discovered to retrieve the local-network profile),
prefixing it with the label "_sipuaconfig".
If the device needs to create a Subscription URI and needs to use its device identifier, it MUST use the UUID-based (Universally Unique Identifier) URN representation as specified in [RFC4122]. The following requirements apply: o When the device has a non-alterable Media Access Control (MAC) address, it SHOULD use the version 1 UUID representation with the timestamp and clock sequence bits set to a value of '0'. This will allow for easy recognition, and uniqueness of MAC-address- based UUIDs. An exception is the case where the device supports independent device configuration for more than one SIP UA. An example would be multiple SIP UAs on the same platform. o If the device cannot use a non-alterable device identifier, it SHOULD use an alternative non-alterable device identifier. For example, the International Mobile Equipment Identity (IMEI) for mobile devices. o If the device cannot use a non-alterable MAC address, it MUST use the same approach as defining a user agent instance ID in [RFC5626]. o Note: when the URN is used as the user part of the Request-URI, it MUST be URL escaped since the colon (":") is not a legal character in the user part of an addr-spec ([RFC4122]), and must be escaped. For example, the instance ID: urn:uuid:f81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com would be escaped to look as follows in a URI: sip:urn%3auuid%3af81d4fae-7ced-11d0-a765-00a0c91e6bf6@ example.com The ABNF ([RFC5234]) for the UUID representation is provided in [RFC4122].5.1.4.3. User Profile Type
To create a Subscription URI to request the user profile on behalf of a user, the device needs to know the user's AoR. This can be statically or dynamically configured on the device (e.g., user input, or propagated as part of the device profile). Similar to device profiles, the content and propagation of user profiles may differ, based on deployment scenarios (i.e., users belonging to the same domain may -- or may not -- be provided the same profile). To create a Subscription URI, the following rules apply:
o The device MUST set the Request-URI to the user AoR. o The device MUST populate the From field with the user AoR. An authoritative SIP proxy for a SIP provider's network that receives a profile enrollment request for the user profile type will route based on the Event Header field values, thus allowing a subscription to the user's AoR to be routed to the appropriate PDS.5.2. Securing Profile Delivery
Profile data can contain sensitive information that needs to be secured, such as identities and credentials. Security involves authentication, data integrity and data confidentiality. 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. Authentication and data 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, data confidentiality is also required. For an overview of potential security threats, refer to Section 9. For information on how the device can be configured with identities and credentials, refer to Section 5.3.1. The following subsections provide the security requirements associated with each profile delivery stage, and applies to each of profile types specified by this framework.5.2.1. Securing Profile Enrollment
Profile enrollment may result in sensitive profile data. In such cases, the PDS MUST authenticate the device, except during the bootstrapping scenario when the device does not have existing credentials (see Section 5.3.1 for more information on bootstrapping). Additionally, the device MUST authenticate the PDS to ensure that it is obtaining sensitive profile data from a valid PDS. To authenticate a device that has been configured with identities and credentials, as specified in Section 5.3.1, and support profiles containing sensitive profile data (refer to Section 5.3.3), devices and PDSs MUST support digest authentication (over Transport Layer Security (TLS)) as specified in [RFC3261]. Future enhancements may
provide other authentication methods such as authentication using X.509 certificates. For the device to authenticate the PDS, the device MUST mutually authenticate with the PDS during digest authentication (device challenges the PDS, which responds with the Authorization header). Transmission of sensitive profile data also requires data integrity. This can be accomplished by configuring the device with, or by ensuring that the discovery process during profile enrollment provides, a Session Initiation Protocol Secure (SIPS) URI resulting in TLS establishment ([RFC5246]). TLS also prevents offline dictionary attacks when digest authentication is used. Thus, in the absence of TLS, the device MUST NOT respond to any authentication challenges. It is to be noted that the digest credentials used for obtaining profile data via this framework may, or may not, be the same as those used for SIP registration (see Section 5.3.1). In addition, while [RFC3261] considers MD5 to be a reasonable choice to compute the hash, and this may have been true when [RFC3261] was published, implementers are recommended to use stronger alternatives such as SHA-256. Refer to [FIPS-180-3] and [RFC4634] for more information about SHA-256. When the PDS challenges a profile enrollment request, and it fails, the PDS MAY refuse enrollment or provide profile data without the user-specific information (e.g., to bootstrap a device as indicated in Section 5.3.1). If the device challenges, but fails to authenticate the PDS, it MUST reject the initial notification and retry the profile enrollment process. If the device is configured with, or discovers, a SIPS URI but TLS establishment fails because the next-hop SIP entity does not support TLS, the device SHOULD attempt other resolved next-hop SIP entities. When the device establishes TLS with the next-hop entity, the device MUST use the procedures specified in [RFC2818], Section 3.1, for authentication, unless it does not have any configured information (e.g., certification authority (CA) certificate) to perform authentication (like prior to bootstrapping). The 'Server Identity' for authentication is always the domain of the next-hop SIP entity. If the device attempts validation, and it fails, it MUST reject the initial notification and retry profile enrollment. In the absence of a SIPS URI for the device and a mechanism for mutual authentication, the PDS MUST NOT present any sensitive profile data in the initial notification, except when the device is being bootstrapped. It MAY still use content indirection to transmit sensitive profile data. When a device is being provided with bootstrapping profile data within the notification, and it contains sensitive information, the SIP Identity header SHOULD be used, as specified in [RFC4474]. This helps with devices that MAY be pre-configured with certificates to validate bootstrapping sources (e.g., list of allowed domain certificates, or a list of root CA certificates using Public Key
Infrastructure (PKI)). When the SIP Identity header is used, the PDS MUST set the host portion of the AoR in the From header to the Provider's domain (the user portion is a entity-specific identifier). If the device is capable of validating the SIP Identity, and it fails, it MUST reject bootstrapping profile data.5.2.2. Securing Content Retrieval
Initial or change notifications following a successful enrollment can provide a device with the requested profile data or use content indirection to direct it to a PCC that can provide the profile data. This document specifies HTTP and HTTPS as content retrieval protocols. If the profile is provided via content indirection and contains sensitive profile data, then the PDS MUST use a HTTPS URI for content indirection. PCCs and devices MUST NOT use HTTP for sensitive profile data, except for bootstrapping a device via the device profile. A device MUST authenticate the PCC as specified in [RFC2818], Section 3.1. A device that is being provided with profile data that contains sensitive data MUST be authenticated using digest authentication as specified in [RFC2617], with the exception of a device that is being bootstrapped for the first time via the device profile. The resulting TLS channel also provides data integrity and data confidentiality.5.2.3. Securing Change Notification
If the device requested enrollment via a SIP subscription with a non- zero 'Expires' parameter, it can also result in change notifications for the duration of the subscription. For change notifications containing sensitive profile data, this framework RECOMMENDS the use of the SIP Identity header as specified in [RFC4474]. When the SIP Identity header is used, the PDS MUST set the host portion of the AoR in the From header to the Provider's domain (the user portion is a entity-specific identifier). This provides header and body integrity as well. However, for sensitive profile data requiring data confidentiality , if the contact URI to which the NOTIFY request is to be sent is not SIPS, the PDS MUST use content indirection. Additionally, the PDS MUST also use content indirection for notifications containing sensitive profile data, when the profile enrollment was not authenticated.5.3. Additional Considerations
This section provides additional considerations, such as details on how a device obtains identities and credentials, back-off and retry methods, guidelines on profile data, and additional profile types.
5.3.1. Bootstrapping Identities and Credentials
When requesting a profile, the profile delivery server will likely require the device to provide an identity (i.e., a user AoR) and associated credentials for authentication. During this process (e.g., digest authentication), the PDS is also required to present its knowledge of the credentials to ensure mutual authentication (see Section 5.2.1). For mutual authentication with the PDS, the device needs to be provided with the necessary identities and credentials (e.g., username/password, certificates). This is done via bootstrapping. For a discussion around the security considerations related to bootstrapping, please see Section 9.2. Bootstrapping a device with the required identities and credentials can be accomplished in one of the following ways: Pre-configuration The device may be pre-configured with identities and associated credentials, such as a user AoR and digest password. Out-of-band methods A device or Provider may provide hardware- or software-based credentials such as Subscriber Identity Module (SIM) cards or Universal Serial Bus (USB) drives. End-user interface The end-user may be provided with the necessary identities and credentials. The end-user can then configure the device (using a user interface), or present when required (e.g., IM login screen). Using this framework When a device is initialized, even if it has no pre-configured information, it can request the local-network and device profiles. For purposes of bootstrapping, this framework recommends that the device profile provide one of the following to bootstrap the device: * Profile data that allows the end-user to communicate with the device provider or SIP service provider using non-SIP methods. For example, the profile data can direct the end-user to a web portal to obtain a subscription. Upon obtaining a successful subscription, the end-user or the device can be provided with the necessary identities and credentials.
* Content indirection information to a PCC that can provide
identities and credentials. As an example, consider a device
that has an X.509 certificate that can be authenticated by the
PCC. In such a case, the PCC can use HTTPS to provide
identities and associated credentials.
* Profile data containing identities and credentials that can be
used to bootstrap the device (see Section 5.3.3 for profile
data recommendations). This can be used in cases where the
device is initialized for the first time, or after a factory
reset. This can be considered only in cases where the device
is initialized in the Provider's network, for obvious security
reasons.
For interoperability purposes, this framework requires PDSs and
devices to support the last option (above), which is to use this
framework. Specifically, the option of providing identities and
credentials via the profile data MUST be supported.
Additionally, AoRs are typically known by PDSs that serve the domain
indicated by the AoR. Thus, devices can only present the configured
AoRs in the respective domains. An exception is the use of federated
identities. This allows a device to use a user's AoR in multiple
domains. Further even within the same domain, the device's domain
proxy and the PDS may be in two different realms, and as such may be
associated with different credentials for digest authentication. In
such cases, multiple credentials may be configured, and associated
with the realms in which they are to be used. This framework
specifies only digest authentication for profile enrollment and the
device is not expected to contain any other credentials. For profile
retrieval using content indirection, the device will need to support
additional credentials such as X.509 certificates (for TLS). Future
enhancements can specify additional credential types for profile
enrollment and retrieval.
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.
+------------+ | 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 Figure 6: Device State Diagram
As a reminder: o The timeout for SIP messages is specified by [RFC3261]. In the cases where this is not specified such as the timeout to wait for the initial notification during profile enrollment, it is left to device implementations or future protocol enhancements. o The timeout for profile retrieval using content indirection will be as specified by profile retrieval protocols employed. If none exists, it is left to device implementations. In addition, since profile enrollment is a process unique to this framework, the device MUST follow the enrollment attempt along with exponential back-off and retry mechanisms as indicated in Figure 7.
Function for Profile Enrollment () Init Function: Iteration i=0 Loop 1: Attempt Loop 2: For each SIP Subscription URI Loop 3: For each next-hop SIP entity - Prepare and transmit Enrollment Request - Await Enrollment Acceptance and initial NOTIFY + If the profile enrollment is successful = Exit this function() + If profile enrollment fails due to an explicit failure or a timeout as specified in [RFC3261] = Continue with the next-hop SIP entity (Loop 3) End Loop: Loop 3 End Loop: Loop 2 (Note: If you are here, profile enrollment did not succeed) + Is any valid cached profile data available? = If yes, use it and continue with Loop 1 + If the enrollment request is for a non-mandatory profile = Start profile enrollment for the next profile, if applicable - Delay for 2^i*(64*T1); -- this is exponential back-off - increment i; - If i>8, reset i=8; End loop: Loop 1 End Function() Figure 7: Profile Enrollment Attempt (Pseudo-Code)
The pseudo-code above (Figure 7) allows for cached profiles to be used. However, any cached local-network profile MUST NOT be used unless the device can ensure that it is in the same local network that 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 with which they are associated. For example, a cached device profile is used only when the associated domain matches the current device provider's domain. If a PDS wants to invalidate a profile it may do so by transmitting a NOTIFY with an 'empty profile', i.e., profile instance without any included data (if supported by the profile data model; not to be confused with an empty NOTIFY), or via an explicit profile data element that invalidates the data. A device receiving such a NOTIFY MUST discard the applicable profile (i.e., it cannot even store it in the cache). Additionally, if a factory reset is available and performed on a device, it MUST reset the device to its initial state prior to any configuration. Specifically, the device MUST set the device back to the state when it was originally distributed. The order of profile enrollment is important. For the profiles specified in this framework, the device MUST enroll in the following default order: local network, device, and user. The pseudo-code presented earlier (Figure 7) differentiates between 'mandatory' and 'non-mandatory' profiles. This distinction is left to profile data definitions. It is to be noted that this framework does not allow the devices to inform the PDSs of profile retrieval errors such as invalid data. Follow-on standardization activities are expected to address this feature.5.3.3. 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 for use in scenarios such as bootstrapping (see Section 5.3.1) and run-time modifications to identities and credentials. This framework recommends the device profile provide the identities and credentials due to a couple of reasons. The local-network profile may not always be available, and even if present, may not be controlled by the device provider who controls device configuration to provide services. Further, the device may not have any users configured prior to being bootstrapped, resulting in an absence of user profile requests.
However, this framework does not prevent other profile types from
providing identities and credentials to meet deployment needs.
For example, the user profile can contain identities and
credentials for communicating with specific applications.
o Each profile MUST clearly identify if it may contain any sensitive
data. Such profiles MUST also identify the data elements that are
considered sensitive, i.e., data that cannot be disclosed to
unauthorized parties. 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.
5.3.4. 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). Thus, Profile Data Frameworks 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 XML
Configuration Access Protocol (XCAP) ([RFC4825]).
5.3.5. Additional Profile Types
This document specifies three profile types: local-network, device, and user. However, there may be use cases for additional profile types. e.g., profile types for application specific profile data or to provide enterprise-specific policies. Definition of such additional profile types is not prohibited, but considered out of scope for this document. Such profile definitions MUST specify the order of retrieval with respect to all the other profiles such as the local-network, device, and user profile types defined in this document.5.3.6. 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 to which a user subscribes (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. Support for NATs
PDSs that support devices behind NATs, and devices that can be behind NATs can use procedures specified in [RFC5626]. 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 [RFC5626], within the SIP SUBSCRIBE for profile enrollment.
(page 33 continued on part 3)