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This document specifies a framework to enable configuration of Session Initiation Protocol (SIP) User Agents in SIP deployments. The framework provides a means to deliver profile data that User Agents need to be functional, automatically and with minimal or no User and Administrative intervention. The framework describes how SIP User Agents can discover sources, request profiles and receive notifications related to profile modifications. As part of this framework, a new SIP event package is defined for notification of profile changes. The framework provides minimal data retrieval options to ensure interoperability. The framework does not include specification of the profile data within its scope.
1.
Introduction
2.
Terminology
3.
Overview
3.1.
Reference Model
3.2.
Motivation
3.3.
Profile Types
3.4.
Profile delivery stages
4.
Use Cases
4.1.
Simple Deployment Scenario
4.2.
Devices supporting multiple users from different Service Providers
5.
Profile Delivery Framework
5.1.
Profile delivery stages
5.1.1.
Profile Enrollment
5.1.2.
Content Retrieval
5.1.3.
Change Notification
5.1.4.
Enrollment Data and Caching
5.2.
Securing Profile Delivery
5.2.1.
Securing Profile Enrollment
5.2.2.
Securing Content Retrieval
5.2.3.
Securing Change Notification
5.3.
Additional Considerations
5.3.1.
Identities and Credentials
5.3.2.
Profile Enrollment Request Attempt
5.3.3.
Device Types
5.3.4.
Profile Data
5.3.5.
Profile Data Frameworks
5.3.6.
Additional Profile Types
5.3.7.
Deployment considerations
5.4.
Usage of Outbound
6.
Event Package Definition
6.1.
Event Package Name
6.2.
Event Package Parameters
6.3.
SUBSCRIBE Bodies
6.4.
Subscription Duration
6.5.
NOTIFY Bodies
6.6.
Notifier Processing of SUBSCRIBE Requests
6.7.
Notifier Generation of NOTIFY Requests
6.8.
Subscriber Processing of NOTIFY Requests
6.9.
Handling of Forked Requests
6.10.
Rate of Notifications
6.11.
State Agents
7.
Examples
7.1.
Example 1: Device requesting profile
7.2.
Example 2: Device obtaining change notification
8.
IANA Considerations
8.1.
SIP Event Package
8.2.
Registry of SIP configuration profile types
9.
Security Considerations
9.1.
Local-network profile
9.2.
Device profile
9.3.
User profile
10.
Acknowledgements
11.
References
11.1.
Normative References
11.2.
Informative References
§
Authors' Addresses
§
Intellectual Property and Copyright Statements
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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.
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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 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [RFC2119].
This document also reuses the SIP terminology defined in [RFC3261] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.) and [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.), 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.
- 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.
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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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.)) and traditional file retrieval protocols, such as HTTP [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.), to discover, monitor, and retrieve configuration profiles. The framework defines three 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] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.) 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).
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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 (Framework Reference Model).
+-------------------------+
+--------+ | Profile Delivery Server |
| Device |<==========================>| +---+ +---+ |
+--------+ | |PNC| |PCC| |
| +---+ +---+ |
+-------------------------+
PNC = Profile Notification Component
PCC = Profile Content Component
| Figure 1: Framework Reference Model |
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The motivation for the framework can be demonstrated by applying the reference model presented in Section 3.1 (Reference Model) 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 (Simple Deployment Model). An example is a simple enterprise network that supports SIP-based devices.
--------------
/ Local-network, \
| Device & Service |
\ Provider /
----------------
|
|
--------
| Device |
--------
|
|
----
|User|
----
| Figure 2: Simple Deployment Model |
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 (Complex Deployment Model) .
--------
/ 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
------ ------
| 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.
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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.
- 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.
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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.
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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 illustrate the effectiveness of the framework in either scenario.
For Security Considerations please refer to Section 5 (Profile Delivery Framework) and Section 9 (Security Considerations).
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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:
Figure 4 (Use Case 1) 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 |
| |
| |
| Figure 4: Use Case 1 |
- (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.
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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:
Figure 4 (Use Case 1) illustrates the use case and highlights the communications relevant to the framework specified in this document.
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>>
|
| Figure 5: Use Case 2 |
- (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.
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This section specifies the profile delivery framework. It provides the requirements for the three profile delivery stages introduced in Section 3.4 (Profile delivery stages) and presents the associated security requirements. It also presents considerations such as back-off and retry mechanisms.
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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.
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Profile enrollment is the process by means of which a device requests, and receives, profile data. Each profile type specified in this document requires an independent enrollment request. However, a particular PDS can support enrollment for one or more profile types.
Profile enrollment consists of the following operations, in the specified order.
- Enrollment request transmission
Profile enrollment is initiated when the device transmits a SIP SUBSCRIBE request [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.) for the 'ua-profile' event package, specified in Section 6 (Event Package Definition). 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] (Rosenberg, J. and H. Schulzrinne, “Session Initiation Protocol (SIP): Locating SIP Servers,” June 2002.).
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 (Identities and Credentials)). 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 event notification specified in [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.), the event package requirements specified in Section 6.2 (Event Package Parameters), and the security requirements specified in Section 5.2 (Securing Profile Delivery).
- 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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.).
Refer to Section 6.6 (Notifier Processing of SUBSCRIBE Requests) and Section 5.2 (Securing Profile Delivery) 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 (Event Package Parameters).
Once profile enrollment is successful, the PDS MUST consider the device enrolled for the specific profile, for the duration of the subscription.
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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 (NOTIFY Bodies).
Devices and PDSs implementing this framework MUST implement two content retrieval protocols: HTTP and HTTPS as specified in [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.) and [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.), 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 (Securing Profile Delivery).
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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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.)). 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 (NOTIFY Bodies).
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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.
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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] (Alexander, S. and R. Droms, “DHCP Options and BOOTP Vendor Extensions,” March 1997.), Domain Name option) or DHCPv6 ([RFC4704] (Volz, B., “The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option,” October 2006.)). Once the local network domain is obtained, the device creates the SIP SUBSCRIBE for enrollment as described below.
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.
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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:
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, 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.
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] (Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace,” July 2005.). The following requirements apply:
- The colon (":") is not a legal character in the user part of an addr-spec ([RFC4122] (Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace,” July 2005.)), and must be escaped.
For example, the instance ID: urn:uuid:f81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com
would be escaped to look as follows in a URI:
sip:urn%3auuid%3af81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com
The ABNF for the UUID representation is provided in [RFC4122] (Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace,” July 2005.)
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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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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 (Security Considerations).The requirements to address the concerns are required for all stages of profile delivery, and are presented in the following subsections.
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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 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] (Rescorla, E., “HTTP Over TLS,” May 2000.), Section 3.1, over an establish TLS connection ([RFC4346] (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.1,” April 2006.)). 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:
In the absence of a Server Identity authenticated TLS session with the next-hop SIP entity:
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] (Peterson, J. and C. Jennings, “Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP),” August 2006.). Exceptions are PDSs that do not serve 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] (Rescorla, E., “HTTP Over TLS,” May 2000.)) and SIP Identity ([RFC4474] (Peterson, J. and C. Jennings, “Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP),” August 2006.) 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] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.), and TLS as specified in [RFC4346] (Dierks, T. and E. Rescorla, “The Transport Layer Security (TLS) Protocol Version 1.1,” April 2006.). 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] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.). 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.
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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 [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.), 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] (Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, “HTTP Authentication: Basic and Digest Access Authentication,” June 1999.), with the exception of a device that is being bootstrapped for the first time. The resulting mutually authenticated TLS channel also provides message integrity.
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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.
| TOC |
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.
| TOC |
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.
- 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.
| TOC |
A state diagram representing a device requesting any specific profile defined by this framework is shown in Figure 6 (Device State Diagram).
+------------+
| 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 |
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 (Profile Enrollment Attempt (pseudo-code)).
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) |
| TOC |
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).
| TOC |
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:
| TOC |
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] (Rosenberg, J., “The Extensible Markup Language (XML) Configuration Access Protocol (XCAP),” May 2007.)).
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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.
| TOC |
The framework defined in this document was designed to address various deployment considerations, some of which are highlighted below.
Provider relationships:
User-device relationship:
| TOC |
PDSs that support devices behind NATs, and devices that can be behind NATs can use procedures specified in [I‑D.ietf‑sip‑outbound] (Jennings, C., “Managing Client Initiated Connections in the Session Initiation Protocol (SIP),” June 2009.). 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] (Jennings, C., “Managing Client Initiated Connections in the Session Initiation Protocol (SIP),” June 2009.) within the SIP SUBSCRIBE for profile enrollment.
| TOC |
The framework specified in this document proposes and specifies a new SIP Event Package as allowed by [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.). 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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.) 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 (Profile Delivery Framework).
| TOC |
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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.).
| TOC |
This package defines the following new parameters for the event header:
- "profile-type", "vendor", "model", "version", and "effective-by"
The following rules apply:
The semantics of these new parameters are specified in the following sub-sections.
| TOC |
The "profile-type" parameter is used to indicate the token name of the profile type the user agent wishes to obtain and to be notified of subsequent changes. This document defines three logical types of profiles and their token names. They are as follows:
- local-network:
- specifying the "local-network" type profile indicates the desire for profile data 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] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.). 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.
| TOC |
The "vendor", "model" and "version" parameter values are tokens specified by the implementer of the user agent. These parameters MUST be provided in the SUBSCRIBE request for all profile types. The implementer SHOULD use their DNS domain name (e.g., example.com) as the value of the "vendor" parameter so that it is known to be unique. These parameters are useful to the PDS to affect the profiles provided. In some scenarios it is desirable to provide different profiles based upon these parameters. e.g., feature property X in a profile may work differently on two versions of the same user agent. This gives the PDS the ability to compensate for or take advantage of the differences. In the following ABNF defining the syntax, EQUAL and quoted-string are defined in [RFC3261] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.).
Vendor = "vendor" EQUAL quoted-string Model = "model" EQUAL quoted-string Version = "version" EQUAL quoted-string
| TOC |
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] (Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, “SIP: Session Initiation Protocol,” June 2002.).
Effective-By = "effective-by" EQUAL 1*DIGIT
| TOC |
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
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
| TOC |
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.
| TOC |
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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.).
| TOC |
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] (Burger, E., “A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages,” May 2006.) 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] (Postel, J. and J. Reynolds, “File Transfer Protocol,” October 1985.), HTTP [RFC2616] (Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1,” June 1999.), HTTPS [RFC2818] (Rescorla, E., “HTTP Over TLS,” May 2000.), LDAP [RFC4510] (Zeilenga, K., “Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map,” June 2006.) and XCAP [RFC4825] (Rosenberg, J., “The Extensible Markup Language (XML) Configuration Access Protocol (XCAP),” May 2007.) ).
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.
| TOC |
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 (Security Considerations).
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.
| TOC |
As specified in [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.), 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).
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.
| TOC |
A Subscriber to this event package MUST adhere to the NOTIFY request processing behavior specified in [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.). 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] (Burger, E., “A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages,” May 2006.). 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.
| TOC |
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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.). It does not support the creation of multiple subscriptions using forked SUBSCRIBE requests.
| TOC |
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
| TOC |
State agents are not applicable to this Event Package.
| TOC |
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 (Simple Deployment Scenario), 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.
| TOC |
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:
The flow diagram and an explanation of the messages follow.
+----------------------+
+--------+ | SIP Service Provider |
| Device | | |
|(SIP UA)| | SIP PDS HTTP |
+--------+ | PROXY Server |
| |
+----------------------+
| | | |
| | | |
| SUBSCRIBE | | |
(SReq)|--------device profile--------->| | |
| |------>| |
| |200 OK | |
| 200 OK |<------| |
(SRes)|<-------------------------------| | |
| | | |
| | NOTIFY| |
| NOTIFY (Content Indirection)|<------| |
(NTFY)|<-------------------------------| | |
| 200 OK | | |
(NRes)|------------------------------->|200 OK | |
| |------>| |
| |
| |
| |
|<<<<<<<<<<<<< TLS establishment >>>>>>>>>>>>>|
| |
| HTTP Request |
(XReq)|---------------------------------------------->|
| |
| HTTP Response |
(XRes)|<----------------------------------------------|
| |
- (SReq)
the device transmits a request for the 'device' profile using the SIP SUBSCRIBE utilizing the Event Package specified in this framework.
- Note: Some of the header fields (e.g., SUBSCRIBE, Event, via) are continued on a separate line due to format constraints of this document.
SUBSCRIBE sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB @example.com SIP/2.0 Event: ua-profile;profile-type=device;vendor="vendor.example.net"; model="Z100";version="1.2.3"; From: 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.
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
| TOC |
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 Interface (UI) that allows for changes to the user profile.
The following are assumed for this example:
The flow diagram and an explanation of the messages follow.
----- -----
|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)|<----------------------|
| |
| | | |
| | 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.
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 . . .
- (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
| TOC |
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.
| TOC |
This specification registers a new event package as defined in [RFC3265] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.). 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]
| TOC |
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] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” October 1998.)).
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.
| TOC |
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.
+------+ +-----+
| | | |
|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
| Figure 8: Profile Delivery Stages |
| TOC |
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.
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).
| TOC |
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] (Roach, A., “Session Initiation Protocol (SIP)-Specific Event Notification,” June 2002.)), emergency services ([I‑D.ietf‑ecrit‑phonebcp] (Rosen, B. and J. Polk, “Best Current Practice for Communications Services in support of Emergency Calling,” September 2007.)), 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 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] (Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, “HTTP Authentication: Basic and Digest Access Authentication,” June 1999.)) to thwart "offline" dictionary attacks.
| TOC |
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 channel provides message integrity and privacy.
| TOC |
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.
| TOC |
| TOC |
| TOC |
| [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 (TXT). |
| [I-D.ietf-sip-outbound] | Jennings, C., “Managing Client Initiated Connections in the Session Initiation Protocol (SIP),” draft-ietf-sip-outbound-20 (work in progress), June 2009 (TXT). |
| [RFC0959] | Postel, J. and J. Reynolds, “File Transfer Protocol,” STD 9, RFC 959, October 1985 (TXT). |
| [RFC2132] | Alexander, S. and R. Droms, “DHCP Options and BOOTP Vendor Extensions,” RFC 2132, March 1997 (TXT, HTML, XML). |
| [RFC4510] | Zeilenga, K., “Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map,” RFC 4510, June 2006 (TXT). |
| [RFC4825] | Rosenberg, J., “The Extensible Markup Language (XML) Configuration Access Protocol (XCAP),” RFC 4825, May 2007 (TXT). |
| TOC |
| 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/ |
| TOC |
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