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RFC 6080

 
 
 

A Framework for Session Initiation Protocol User Agent Profile Delivery

Part 2 of 3, p. 14 to 33
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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.

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5.1.1.  Profile Enrollment

   Profile enrollment is the process by means of which a device
   requests, and receives, profile data.  Each profile type specified in
   this document requires an independent enrollment request.  However, a
   particular PDS can support enrollment for one or more profile types.

   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.

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      *  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.

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   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

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   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.

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   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

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   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".

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   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:

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   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

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   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

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   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.

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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.

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      *  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.

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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

                      Figure 6: Device State Diagram

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   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.

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     Function for Profile Enrollment ()

        Init Function: Iteration i=0

        Loop 1: Attempt

             Loop 2: For each SIP Subscription URI

                  Loop 3: For each next-hop SIP entity

                     - Prepare 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)

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   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.

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      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]).

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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.

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5.4.  Support for NATs

   PDSs that support devices behind NATs, and devices that can be behind
   NATs can use procedures specified in [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)

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