Updated contact information.
-Updated example JIDs to example.org
+Updated example JIDs to example.org
@@ -479,12 +479,12 @@
@@ -493,16 +493,16 @@
Depending on the reason for rejecting the request, different XMPP errors can be returned, according to the description in the following table. The table also
@@ -597,76 +597,76 @@
The above example defines a language module called Watchamacallit. In this language module it defines four strings, with IDs 1-4. A system might store these as follows,
@@ -1410,257 +1410,257 @@
Updated contact information. Updated example JIDs to example.org Element renamed from Friend to friend when recommending friendships. clearCache IQ stanzas now of type set instead of get. Corrected schema with regards to tokens. The getToken command now takes a base-64 encoded X.509 certificate (public part) instead of arbitrary string IDs. An additional challenge/response step has been added to make sure the sender of a certificate has access to the private part of the certificate. Named links to all sections in the document. Added reference to XEP-0347, for how things can find provisioning servers. Added method of finding provisioning server, if server hosted as a server component. Updated examples to reflect a provisioning server hosted as a server component, harmonizing with XEP-0347. Added a section about token challenges and token propagation. Added a security note regarding token challenges. Updated id-attributes in examples. Corrected downloadPrivileges example. Made several corrections of the language. Expanded the introduction. Changes "Sensor Networks" to "Internet of Things". Fixed links to documents with new numbers. Changed namespace urn:xmpp:sn to urn:xmpp:iot Initial published version approved by the XMPP Council. Added control use cases. Grouped use cases. Added altitude credentials. Added resource information of original called to their corresponding JIDs. Changed the return type of a rejected message. Made images inline. Converted the glossary into a definition list. Added information about how to read sensors from large subsystems. Added friend recommendation message. Added client/device/service tokens. Added use cases for service access rights and corresponding user privileges. First draft.
- This specification describes an architecture for efficient provisioning of services, access rights and user privileges in for the Internet of Things, where
- communication between Things is done using the XMPP protocol.
-
- Note has to be taken, that this XEP, and other Internet of Things-related XEP's, are designed for implementation in small devices, many of which have very limited
- amount of memory (both RAM and ROM) or resources (processing power). Therefore, simplicity is of utmost importance. Furthermore, Internet of Things networks can
- become huge, easily containing millions or billions of devices in peer-to-peer networks.
+ Updated contact information. Updated example JIDs to example.org Element renamed from Friend to friend when recommending friendships. clearCache IQ stanzas now of type set instead of get. Corrected schema with regards to tokens. The getToken command now takes a base-64 encoded X.509 certificate (public part) instead of arbitrary string IDs. An additional challenge/response step has been added to make sure the sender of a certificate has access to the private part of the certificate. Named links to all sections in the document. Added reference to XEP-0347, for how things can find provisioning servers. Added method of finding provisioning server, if server hosted as a server component. Updated examples to reflect a provisioning server hosted as a server component, harmonizing with XEP-0347. Added a section about token challenges and token propagation. Added a security note regarding token challenges. Updated id-attributes in examples. Corrected downloadPrivileges example. Made several corrections of the language. Expanded the introduction. Changes "Sensor Networks" to "Internet of Things". Fixed links to documents with new numbers. Changed namespace urn:xmpp:sn to urn:xmpp:iot Initial published version approved by the XMPP Council. Added control use cases. Grouped use cases. Added altitude credentials. Added resource information of original called to their corresponding JIDs. Changed the return type of a rejected message. Made images inline. Converted the glossary into a definition list. Added information about how to read sensors from large subsystems. Added friend recommendation message. Added client/device/service tokens. Added use cases for service access rights and corresponding user privileges. First draft.
+ This specification describes an architecture for efficient provisioning of services, access rights and user privileges in for the Internet of Things, where
+ communication between Things is done using the XMPP protocol.
+
+ Note has to be taken, that this XEP, and other Internet of Things-related XEP's, are designed for implementation in small devices, many of which have very limited
+ amount of memory (both RAM and ROM) or resources (processing power). Therefore, simplicity is of utmost importance. Furthermore, Internet of Things networks can
+ become huge, easily containing millions or billions of devices in peer-to-peer networks.
+
+ An added complexity in the provisioning case is that Things (small sensors for example) often have very limited user interface options. Therefore, this document
+ explains how provisioning can be done efficiently using a trusted third party with more power and options when it comes to user interface design and storage.
+
+ This document defines the following important operations to allow for efficient provisioning of services in the Internet of Things, based on XMPP:
+
+ This XEP relies on &xep0323; and &xep0325; for sensor data readout and control interfaces. It relies on &xep0326; for bridging protocols and interfaing entities with multiple devices
+ behind them. It also ties into &xep0347; for automatic discovery of provisioning servers by things.
+
+ Internet of Things contain many different architectures and use cases. For this reason, the IoT standards have been divided into multiple XEPs according to the following table:
+ The following table lists common terms and corresponding descriptions.
+ The most basic use case in sensor networks is to read out sensor data from a sensor. However, since protecting end-user integrity and system security is vital, access
+ rights and user privileges have to be imposed on the network.
+
+ To store access rights in all sensors might be very impractical. Not only does it consume memory, it's difficult to maintain track of the current system status, make sure
+ all devices have the latest configuration, distribute changes to the configuration, etc.
+
+ Furthermore, most sensors and small devices have very limited possibility to provide a rich user interface. Perhaps all it can do is to provide a small LED and a button,
+ useful perhaps for installing the sensor in the network, but not much more.
+
+ As an added complexity, the sensor network operator might not even have access to the XMPP Servers used, and provisioning needs to lie outside of the XMPP Server domains.
+
+ To solve this problem in an efficient manner, an architecture using distributed trusted third parties is proposed. Such third parties would:
+
+ A provisioning server can be accessed either through a JID published by the provisioning server, or through a subdomain address, if hosted as a server component.
+ This section will show how to delegate original trust to a Provisioning Server, in the case the server uses a JID to communicate with things.
- An added complexity in the provisioning case is that Things (small sensors for example) often have very limited user interface options. Therefore, this document
- explains how provisioning can be done efficiently using a trusted third party with more power and options when it comes to user interface design and storage.
-
- This document defines the following important operations to allow for efficient provisioning of services in the Internet of Things, based on XMPP:
-
- This XEP relies on &xep0323; and &xep0325; for sensor data readout and control interfaces. It relies on &xep0326; for bridging protocols and interfaing entities with multiple devices
- behind them. It also ties into &xep0347; for automatic discovery of provisioning servers by things.
-
- Internet of Things contain many different architectures and use cases. For this reason, the IoT standards have been divided into multiple XEPs according to the following table:
- The following table lists common terms and corresponding descriptions.
- The most basic use case in sensor networks is to read out sensor data from a sensor. However, since protecting end-user integrity and system security is vital, access
- rights and user privileges have to be imposed on the network.
-
- To store access rights in all sensors might be very impractical. Not only does it consume memory, it's difficult to maintain track of the current system status, make sure
- all devices have the latest configuration, distribute changes to the configuration, etc.
-
- Furthermore, most sensors and small devices have very limited possibility to provide a rich user interface. Perhaps all it can do is to provide a small LED and a button,
- useful perhaps for installing the sensor in the network, but not much more.
-
- As an added complexity, the sensor network operator might not even have access to the XMPP Servers used, and provisioning needs to lie outside of the XMPP Server domains.
-
- To solve this problem in an efficient manner, an architecture using distributed trusted third parties is proposed. Such third parties would:
+ Trust is delegated to a provisioning server by a device, simply by befriending the provisioning server and asking it questions and complying with
+ its answers. As an illustrative example, following is a short description of how such a trust relationship can be created in a scenario where the sensor only
+ has a single LED and a single button.
- A provisioning server can be accessed either through a JID published by the provisioning server, or through a subdomain address, if hosted as a server component.
- This section will show how to delegate original trust to a Provisioning Server, in the case the server uses a JID to communicate with things.
-
- Trust is delegated to a provisioning server by a device, simply by befriending the provisioning server and asking it questions and complying with
- its answers. As an illustrative example, following is a short description of how such a trust relationship can be created in a scenario where the sensor only
- has a single LED and a single button.
-
- The following diagram shows the general case:
-
-
- The successful case can also be illustrated in a sequence diagram, as follows:
-
-
- Note: In many cases, an address to a provisioning server might be preprogrammed during production of the
- device. In these cases, parts of the above procedure may not be necessary. All the client needs to do, if the provisioning server is not available
- in the roster of the device, is to send a subscription request to the provisioning server, to alert the server of the existence of the device,
- and possibly request a device token.
-
- Note 2: A certificate token has an undefined lifetime. It can be reused across sessions.
-
- The following use cases will assume such a trust relationship has been created between the corresponding device and the provisioning server.
-
- A provisioning server can also be hosted as a server component, and in these cases be addressed by using the component address, or sub-domain address of the component.
- In this case, the client searches through the components hosted by the server to see if one of them is a Provisioning Server. There are no friendship requests and
- presence subscriptions necessary, when communicating with a Provisioning Server hosted as a server component.
-
- To search for a Provisioning Server hosted as a component on an XMPP Server, you first request a list of available components, as follows:
-
+ The following diagram shows the general case:
+
+
+ The successful case can also be illustrated in a sequence diagram, as follows:
+
+
+ Note: In many cases, an address to a provisioning server might be preprogrammed during production of the
+ device. In these cases, parts of the above procedure may not be necessary. All the client needs to do, if the provisioning server is not available
+ in the roster of the device, is to send a subscription request to the provisioning server, to alert the server of the existence of the device,
+ and possibly request a device token.
+
+ Note 2: A certificate token has an undefined lifetime. It can be reused across sessions.
+
+ The following use cases will assume such a trust relationship has been created between the corresponding device and the provisioning server.
+
+ A provisioning server can also be hosted as a server component, and in these cases be addressed by using the component address, or sub-domain address of the component.
+ In this case, the client searches through the components hosted by the server to see if one of them is a Provisioning Server. There are no friendship requests and
+ presence subscriptions necessary, when communicating with a Provisioning Server hosted as a server component.
+
+ To search for a Provisioning Server hosted as a component on an XMPP Server, you first request a list of available components, as follows:
+
- If components (items) are supported, a request for available components is made:
-
- The client then loops through all components (items) and checks what features they support, until a Provisioning Server is found:
-
- The provisioning server contains a set of rules defining what operation can take place and by whom, by participants in the network. Rules can be applied based on JIDs used,
- content affected, and also through device, service and user identities based on X.509 Certificates. In order for a service (for instance) to identify itself in the network, it
- uses an X.509 certificate. It sends the public part of this certificate to the provisioning server, and receives a token back in the form of a simple string. This token can then
- be used in requests and propagated through the network.
-
- To validate that the sender is allowed to use the certificate using its token, it encrypts a challenge using the public part of the certificate and sends it to the sender of the
- token, who in turn decrypts it using the private part of the certificate and returns it to the server. The provisioning server can also use the public part of the certificate to
- perform validation checks on the certificate itself. If the certificate becomes invalid, the provisioning server can invalidate any corresponding rules in the network. If the sender
- of a token cannot respond to a token challenge, the provisioning server can also refuse to allow the operation.
-
- In case of multiple units being part of an operation, a token can be propagated in the network. For example, a service can read data from U1, who reads data from U2. The service
- provides a token to U1, who propagates this token in the request to U2. When U2 asks the provisioning server if the operation should be allowed or not, the server knows what entity
- originated the request. If the provisioning server wants to challenge U2, concerning the token, U2 propagates the challenge to U1, who propagates it to the service, who can resolve
- the challenge, returns the response back to U1 who returns the response to U2 who in turn returns it to the provisioning server.
-
-
- The following example shows how a device or service can request a token from the provisioning server, by providing the base-64 encoded public part of an X.509 certificate.
- This step is optional, but can be used as a method to identify the device (or service), apart from the JID it is using. This might be useful if you want to assign a particular
- device or service privileges in the provisioning server, regardless of the JID it uses to perform the action.
-
- The getToken element contains the base-64 encoded public version of the certificate that is used to identify the device or service. The server
- responds with a challenge in a getTokenChallenge response. This challenge is also a base-64 encoded binary block of data, which corresponds to a random
- sequence of bytes that is then encrypted using the public certificate. Now, the device, or service, decrypts this challenge using the private part of the certificate, and
- returns the base-64 encoded decrypted version of the challenge back to the provisioning server using the getTokenChallengeResponse element. The provisioning
- server checks the response to the original random sequence of bytes. If equal, the provisioning server responds with a getTokenResponse result, containing
- the token (a string this time) that can be used when reference to the identity defined by the certificate has to be made. The provisioning server must not return tokens that
- contain white space characters.
-
- If the response to the challenge is wrong, the server returns a bad-request error result, as is shown below.
-
- If the sequence number identifying the challenge is not found on the server, the server returns a item-not-found error result, as is shown below.
-
- The server must retain the challenge in memory for at least one minute before assuming the challenge will go unresponded.
-
- For reasons the provisioning server determines, it can challenge the use of a token in any of the requests made to it. This is done by sending a
- iq get stanza with a tokenChallenge to the party sending the token. This element contains both the token being challenged, and a binary
- challenge. This challenge is made up of a random block of data that is encrypted using the public certificate referred to by the token.
-
- The receiver of the challenge, if it has access to the private certificate referenced, decrypts the challenge, and returns the decrypted binary block of data
- to the caller (i.e. the Provisioning Server in this case). If the decrypted block of data corresponds to the original random block of data encrypted, the sender
- of the token is considered to be allowed to use the token.
-
- If the received of the challenge does not have access to the private certificate referenced, but used the token in a propagated request made to it, it can propagate the
- request to the original sender of the token. When the response is returned, it returns the response in turn to the sender of the challenge.
-
- A challenge/response sequence can look as follows:
-
- Note: It is important that a unit only responds to a tokenChallenge request from a JID to which the corresponding token
- has been sent. If a token challenge is received from a JID to which the token has not been sent the last minute, the following error message must be returned:
-
- The isFriendResponse element returned by the provisioning server contains an attribute secondaryTrustAllowed that is by default
- set to false. If the provisioning server has no problem with allowing multiple trust to be delegated by devices in the network, it can choose to set this
- attribute to true in the response. If true, the device knows it has the right to add its own friends, or to add secondary trust relationships.
-
- The following diagram continues with the example given above, of how a sensor with a limited user interface, can allow to manually add new friends, including new
- trust relationships using a single LED and a button.
-
-
- When multiple trust is used, the entity (client, user, service, etc.) has one token from each provisioning server. However, when sending a token to a third party,
- the sender does not know what provisioning server(s) the third party uses to check access rights and user privileges. Therefore, the client must send all tokens, separated
- by a space.
-
- When a provisioning server receives a request containing multiple tokens, the most forgiving response must be returned.
-
- Note: When a provisioning server wants to challenge multiple tokens, separate token challenges are sent, one for each token being challenged.
-
- The following diagram displays how a friendship request from an external party can be handled, delegating the responsibility to a trusted third party:
-
-
- The communication between the XMPP Device and the Provisioning Server could be as follows:
-
- Note: The provisioning server implicitly understands which two JIDs that are to be checked: The first one is the sender of the message, the second one
- is the JID available in the jid attribute in the request.
-
- Note 2: Any resource information in the JID must be ignored by the provisioning server.
-
- The following diagram displays a friendship request from an external party being rejected as a result of the trusted third party negating the friendship:
-
-
- The communication between the XMPP Device and the Provisioning Server could be as follows:
-
- If the provisioning server decides that two friends in the network should no longer be friends and communicate with each other, it simply sends a message to
- at least one of the friends as follows:
-
-
- The provisioning server should only send such messages to clients that have previously asked the provisioning server if friendship requests should be accepted or not.
-
- Note: The device should only honor such messages, if the sender is the trusted third party. Such messages received from other entities not trusted should
- be silently ignored.
-
- The provisioning server can, apart from accepting new friendships and rejecting old friendships, also recommend new friendships. In this case, the provisioning server
- simply sends a message to one or both of the soon to be friends, as follows:
-
-
- Note that the receptor can still ask the provisioning server if it can form a friendship with the suggested friend, using the isFriend command.
-
- An important use case for provisioning in sensor networks is who gets to read out sensor data from which sensors. This use case details how communication with a
- provisioning server can help the device determine if a client has sufficient access rights to read the values of the device.
-
-
- Note: This use case is an extension of the use case 'Read-out rejected' in the XEP-0323
- Internet of Things - Sensor Data.
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- In case the device handles multiple nodes that can be read, the provisioning server has the possibility to grant read-out, but to limit the nodes that can be read out.
- The provisioning server does this by returning the list of nodes that can be read.
-
-
- Note: This use case is an extension of the use case 'Read-out of multiple devices' in the XEP-0323
- Internet of Things - Sensor Data.
-
- Note 2: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
- to be read. If no nodes in the request are allowed to be read, the provisioning server must respond with a result='false', so the device can reject the read-out request.
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- Note that the provisioning server responds with a canReadResponse element, similar to the canRead element in the request, except
- only the nodes allowed to be read are read. The device must only permit read-out of nodes listed in the response from the provisioning server. Other nodes available
- in the request should be ignored.
-
- In case the provisioning server wants to limit the fields a device can send to a client, the provisioning server has the possibility to grant read-out, but
- list a set of fields the device is allowed to send to the corresponding client.
-
-
- Note: If the server responds, but without specifying a list of field names, the device can assume that all fields available in the original request are allowed
- to be sent. If no fields in the request are allowed to be sent, the provisioning server must respond with a result='false', so the device can reject the read-out request.
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- Note that the provisioning server responds with a canReadResponse element, similar to the canRead element in the request, except only
- the fields allowed to be sent are listed. The client must only send fields having field names in this list.
-
- Also note, that the provisioning server can return a list of both allowed nodes and allowed field names in the response. In this case, the device must only send allowed fields
- from allowed nodes, and ignore all other fields and/or nodes.
-
- An important use case for provisioning in sensor networks is who gets to control devices, and what they can control. This use case details how communication with a
- provisioning server can help the device determine if a client has sufficient access rights to perform control actions on the device.
-
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- In case the device handles multiple nodes that can be read, the provisioning server has the possibility to grant control access, but to limit the nodes that can be controlled.
- The provisioning server does this by returning the list of nodes that can be controlled.
-
-
- Note: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
- to be controlled. If no nodes in the request are allowed to be controlled, the provisioning server must respond with a result='false', so the device can reject the read-out request.
- The same is true for parameters: If the provisioning server does not specify parameters in the response, the caller can assume all parameters are allowed.
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- Note that the provisioning server responds with a canControlResponse element, similar to the canControl element in the request, except
- only the nodes allowed to be controlled are included. The device must only permit control of nodes listed in the response from the provisioning server. Other nodes available
- in the request should be ignored.
-
- Also note, that the restricted set of nodes and/or parameters returned from the provisioning server must be returned to the original caller, so it can
- act on the information that only a partial control action was allowed and taken.
-
- In case the provisioning server wants to limit the control parameters a client can control in a device, the provisioning server has the possibility to grant
- control access, but list a set of parameters the client is allowed to control in the corresponding device.
-
-
- Note: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
- to be controlled. If no nodes in the request are allowed to be controlled, the provisioning server must respond with a result='false', so the device can reject the read-out request.
- The same is true for parameters: If the provisioning server does not specify parameters in the response, the caller can assume all parameters are allowed.
-
- The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
-
- Note that the provisioning server responds with a canControlResponse element, similar to the canControl element in the request, except only
- the parameters allowed to be sent are listed. The device must only control parameters included in this list.
-
- Also note, that the provisioning server can return a list of both allowed nodes and allowed parameter names in the response back to the client, so it can
- act on the information that only a partial control action was allowed and taken.
-
- When the provisioning server updates access rights and user privileges in the system, it will send a clearCache command to corresponding devices.
- If a device was offline during the change, the provisioning server must send the clearCache message when the device comes online again. To acknowledge
- the receipt of the command, the client responds with a clearCacheResponse element. This response message does not contain any information on what was
- done by the client. It simply acknowledges the receipt of the command, to make sure the provisioning server does not resend the clear cache command again.
-
- Note: The clearCache command does not include information on what has been changed, so the device needs to clear the entire cache. This
- to avoid complexities in making sure updates made to the provisioning rules works in all cases, and to minimize complexity in the implementation of the protocol on the sensor side.
- It is also not deemed to decrease network performance, since changing provisioning rules for a device is an exceptional event and therefore does not affect performance during
- normal operation.
-
- A service requesting provisioning assistance, needs to retrieve a service token from the provisioning server, by providing a base-64 encoded X.509 certificate.
- The following example shows how this can be done.
-
- Provisioning in sensor networks also requires control of user access to different services in the network. This use case shows how service access rights are controlled using
- a trusted provisioning server.
-
-
- First, the user connects to the service in some way. This can be done using XMPP, HTTP, HTTPS or some other means. The service need to extract some form of identifying
- credentials from the user, and provide that to the provisioning server. The provisioning server determines if the client has access rights to the service based on these
- credentials, and also provides the service with a userToken that the service can use in further communication with the provisioning server regarding
- the user and its privileges.
-
- The following table lists some different types of credentials that the service can extract from the client:
-
- The provisioning server receives these credentials, and decides if the user should have access to the service or not, based on rules configured in the provisioning service.
- If the user is granted access, a userToken is generated and returned to the service.
-
- Now, the service can determine if this access grant is sufficient or not. It can require the user to login into the service first. If so, the service should provide the provisioning
- server with the user name used during login, when logged in.
-
- When a user has been given access to a service, and properly been identified, the service can ask the provisioning service for detailed user privileges to control
- different aspects of the service. This can be done using the hasPrivilege command. Here, the service sends its serviceToken and
- the userToken earlier received when being granted access to the service. Furthermore a privilegeId has to be provided.
-
- A Privilege ID is a string composed of one or a sequence of parts, delimited by period characters. The Privilege IDs form a tree of privileges,
- using an invisible, but common, root privilege.
-
- The following table suggests some examples of Privilege IDs, with suggestive descriptions. (Only used as an example.)
-
- Note: Note that privilege IDs are local to the service. Different services are allowed to use similar or same Privilege IDs, in different contexts and
- with different meanings. The provisioning server must separate Privilege IDs from different services.
-
- The client must always provide full Privilege IDs to the provisioning server. The provisioning server however, can grant partial privilege IDs, pointing to parent
- privilege nodes to a user or a role object, granting a user a specific role. If granting a parent privilege ID to a user or role, this is interpreted as
- giving the corresponding user or role the privileges of the entire sub-tree defined by the parent privilege ID.
-
- If additional control over privileges is desired, negative privileges can be assigned to the user or role. Granted or explicitly rejected privileges are specified in a
- sequential list of full or partial privilege IDs. This list is then processed sequentially to determine if a privilege is granted or not.
-
- Example: Consider the privileges above. Give a user or its corresponding role the following privileges in a sequential list:
-
- This would give the user rights to select and insert data, but not to delete data from the Energy database.
-
- Note: Care should be taken when constructing Privilege IDs, so they do not include variable data that potentially can create an infinite amount of
- privilege IDs. For example: Do not include user names, sensor IDs, etc., in privilege IDs, as the number of such entities cannot be estimated or is scalable beforehand.
-
- The following diagram shows an example of how a service asks permission from a provisioning server before an action is taken:
-
-
- To improve performance, services can download the entire set of user privileges, and perform privilege checks internally. The following diagram displays
- how the above two use cases could be handled in such a case:
-
-
- Note: When downloading privileges using this command, a sequential list of full or partial privilege IDs will be returned together with the
- corresponding include or exclude flags. The above mentioned algorithm of determining user privileges must be implemented by the service, if this method is
- to be used.
-
- Note: If the user or service has not been correctly identified, logged in, etc., the resulting list must only include privileges
- that default users that are not logged in can have. This list can be empty.
-
- If an entity is a Provisioning Server and supports the protocol specified herein, it MUST advertise that fact by returning a feature of "urn:xmpp:iot:provisioning"
- in response to &xep0030; information requests.
-
+ The client then loops through all components (items) and checks what features they support, until a Provisioning Server is found:
+
- In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined
- in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
+ The provisioning server contains a set of rules defining what operation can take place and by whom, by participants in the network. Rules can be applied based on JIDs used,
+ content affected, and also through device, service and user identities based on X.509 Certificates. In order for a service (for instance) to identify itself in the network, it
+ uses an X.509 certificate. It sends the public part of this certificate to the provisioning server, and receives a token back in the form of a simple string. This token can then
+ be used in requests and propagated through the network.
- A client must treat the connection between a Provisioning Server differently if it is hosted as a client, having a JID, or if it is hosted as a Jabber Server Component.
- If it is hosted as a server component, there's no need for the thing to become friends with the Provisioning Server. Messages and requests can be made directly to the
- server component without having to add it to the roster or request presence subscriptions. If the Provisioning Server is hosted as a client, having a JID (@ in the address),
- the Provisioning Server must be added to the roster of the client before the client can communicate with the Provisioning Server.
-
- To minimize network traffic, and optimize response time, devices should cache access rights and user privileges provided by the provisioning server. If memory is limited,
- items in the cache should be ordered by last access, and items with the oldest last access timestamp should be removed first. A safety valve can optionally be implemented as well,
- removing unused cache items after a certain age, even if memory is available.
-
- The device can assume that access rights and user privileges on the provisioning server do not change over time, unless the provisioning server says so.
-
- The provisioning server on the other hand, must keep track of when a device is online and offline, and clear the cache of the device if changes are made that affects the device.
- If the device was offline when those changes occurred, the provisioning server must send the clear cache command as soon as the device comes online again.
-
- When creating a new trust relationship, the device should always clear its cache, if it contains information from before.
-
- To minimize stress of the provisioning server during synchronous sensor start up, for instance after a power failure, all clients should aim to persist its cache if possible. Clients
- not persisting its cache may produce too much stress on the provisioning server on start-up, practically removing it from the network.
-
- When working with multiple provisioning servers, there are some things that should be considered:
-
- One important design consideration when implementing a provisioning server is how to handle new services, users and privileges. One option might be to automatically
- ignore anything not recognized. Another option might be to dynamically add new services, user names and privileges to internal data sources, making it easier to manage
- new types of services dynamically. However, adding such items automatically might also make such data sources grow beyond control.
-
- All examples in this document have been simplified examples where a few devices containing a few fields have been read. However, in many cases large subsystems with
- very many sensors containing many fields have to be read, as is documented in Internet of Things - Concentrators
- Internet of Things - Concentrators. In such cases, a node may have to be specified using two or perhaps
- even three ID's: a sourceId identifying the data source controlling the device, a possible cacheType narrowing down the search to
- a specific kind of node, and the common nodeId. For more information about this, see
- Internet of Things - Concentrators.
-
- Note: For cases where the nodeId is sufficient to uniquely identify the node, it is sufficient to provide this attribute in the request.
- If there is ambiguity in the request, the receptor must treat the request as a request with a set of nodes, all with the corresponding nodeId as requested.
-
- A small note regarding the use of different tokens. A service can get a Service Token, a device a Device Token and a user
- a User Token. When delegating these tokens to third parties, a service sends its Service Token. But, if the service does this
- within the context of a user action, the service sends both its Service Token and the users User Token. The same with a device.
- If a device delegates its token to a third party, it sends its Device Token. But if the device performs the action in the context of a user action,
- the device sends both its Device Token as well as its User Token.
-
- Delegating trust to a third party may create a weak link in the overall security of a sensor network. Therefore, it's vitally important that the following be adhered to:
-
- When receiving token challenges from somebody, make sure you've sent the corresponding token to the corresponding party less than a minute before receiving the token
- challenge. If not, the token challenge might represent a malicious attempt by somebody else to use the token to gain privileges in the network otherwise not enjoyed.
- This document requires no interaction with &IANA;.
- The protocol schema needs to be added to the list of XMPP protocol schemas.
-
+ To validate that the sender is allowed to use the certificate using its token, it encrypts a challenge using the public part of the certificate and sends it to the sender of the
+ token, who in turn decrypts it using the private part of the certificate and returns it to the server. The provisioning server can also use the public part of the certificate to
+ perform validation checks on the certificate itself. If the certificate becomes invalid, the provisioning server can invalidate any corresponding rules in the network. If the sender
+ of a token cannot respond to a token challenge, the provisioning server can also refuse to allow the operation.
+
+ In case of multiple units being part of an operation, a token can be propagated in the network. For example, a service can read data from U1, who reads data from U2. The service
+ provides a token to U1, who propagates this token in the request to U2. When U2 asks the provisioning server if the operation should be allowed or not, the server knows what entity
+ originated the request. If the provisioning server wants to challenge U2, concerning the token, U2 propagates the challenge to U1, who propagates it to the service, who can resolve
+ the challenge, returns the response back to U1 who returns the response to U2 who in turn returns it to the provisioning server.
+
+
+ The following example shows how a device or service can request a token from the provisioning server, by providing the base-64 encoded public part of an X.509 certificate.
+ This step is optional, but can be used as a method to identify the device (or service), apart from the JID it is using. This might be useful if you want to assign a particular
+ device or service privileges in the provisioning server, regardless of the JID it uses to perform the action.
+
+ The getToken element contains the base-64 encoded public version of the certificate that is used to identify the device or service. The server
+ responds with a challenge in a getTokenChallenge response. This challenge is also a base-64 encoded binary block of data, which corresponds to a random
+ sequence of bytes that is then encrypted using the public certificate. Now, the device, or service, decrypts this challenge using the private part of the certificate, and
+ returns the base-64 encoded decrypted version of the challenge back to the provisioning server using the getTokenChallengeResponse element. The provisioning
+ server checks the response to the original random sequence of bytes. If equal, the provisioning server responds with a getTokenResponse result, containing
+ the token (a string this time) that can be used when reference to the identity defined by the certificate has to be made. The provisioning server must not return tokens that
+ contain white space characters.
+
+ If the response to the challenge is wrong, the server returns a bad-request error result, as is shown below.
+
+ If the sequence number identifying the challenge is not found on the server, the server returns a item-not-found error result, as is shown below.
+
+ The server must retain the challenge in memory for at least one minute before assuming the challenge will go unresponded.
+
+ For reasons the provisioning server determines, it can challenge the use of a token in any of the requests made to it. This is done by sending a
+ iq get stanza with a tokenChallenge to the party sending the token. This element contains both the token being challenged, and a binary
+ challenge. This challenge is made up of a random block of data that is encrypted using the public certificate referred to by the token.
+
+ The receiver of the challenge, if it has access to the private certificate referenced, decrypts the challenge, and returns the decrypted binary block of data
+ to the caller (i.e. the Provisioning Server in this case). If the decrypted block of data corresponds to the original random block of data encrypted, the sender
+ of the token is considered to be allowed to use the token.
+
+ If the received of the challenge does not have access to the private certificate referenced, but used the token in a propagated request made to it, it can propagate the
+ request to the original sender of the token. When the response is returned, it returns the response in turn to the sender of the challenge.
+
+ A challenge/response sequence can look as follows:
+
+ Note: It is important that a unit only responds to a tokenChallenge request from a JID to which the corresponding token
+ has been sent. If a token challenge is received from a JID to which the token has not been sent the last minute, the following error message must be returned:
+
+ The isFriendResponse element returned by the provisioning server contains an attribute secondaryTrustAllowed that is by default
+ set to false. If the provisioning server has no problem with allowing multiple trust to be delegated by devices in the network, it can choose to set this
+ attribute to true in the response. If true, the device knows it has the right to add its own friends, or to add secondary trust relationships.
+
+ The following diagram continues with the example given above, of how a sensor with a limited user interface, can allow to manually add new friends, including new
+ trust relationships using a single LED and a button.
+
+
+ When multiple trust is used, the entity (client, user, service, etc.) has one token from each provisioning server. However, when sending a token to a third party,
+ the sender does not know what provisioning server(s) the third party uses to check access rights and user privileges. Therefore, the client must send all tokens, separated
+ by a space.
+
+ When a provisioning server receives a request containing multiple tokens, the most forgiving response must be returned.
+
+ Note: When a provisioning server wants to challenge multiple tokens, separate token challenges are sent, one for each token being challenged.
+
+ The following diagram displays how a friendship request from an external party can be handled, delegating the responsibility to a trusted third party:
+
+
+ The communication between the XMPP Device and the Provisioning Server could be as follows:
+
+ Note: The provisioning server implicitly understands which two JIDs that are to be checked: The first one is the sender of the message, the second one
+ is the JID available in the jid attribute in the request.
+
+ Note 2: Any resource information in the JID must be ignored by the provisioning server.
+
+ The following diagram displays a friendship request from an external party being rejected as a result of the trusted third party negating the friendship:
+
+
+ The communication between the XMPP Device and the Provisioning Server could be as follows:
+
+ If the provisioning server decides that two friends in the network should no longer be friends and communicate with each other, it simply sends a message to
+ at least one of the friends as follows:
+
+
+ The provisioning server should only send such messages to clients that have previously asked the provisioning server if friendship requests should be accepted or not.
+
+ Note: The device should only honor such messages, if the sender is the trusted third party. Such messages received from other entities not trusted should
+ be silently ignored.
+
+ The provisioning server can, apart from accepting new friendships and rejecting old friendships, also recommend new friendships. In this case, the provisioning server
+ simply sends a message to one or both of the soon to be friends, as follows:
+
+
+ Note that the receptor can still ask the provisioning server if it can form a friendship with the suggested friend, using the isFriend command.
+
+ An important use case for provisioning in sensor networks is who gets to read out sensor data from which sensors. This use case details how communication with a
+ provisioning server can help the device determine if a client has sufficient access rights to read the values of the device.
+
+
+ Note: This use case is an extension of the use case 'Read-out rejected' in the XEP-0323
+ Internet of Things - Sensor Data.
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ In case the device handles multiple nodes that can be read, the provisioning server has the possibility to grant read-out, but to limit the nodes that can be read out.
+ The provisioning server does this by returning the list of nodes that can be read.
+
+
+ Note: This use case is an extension of the use case 'Read-out of multiple devices' in the XEP-0323
+ Internet of Things - Sensor Data.
+
+ Note 2: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
+ to be read. If no nodes in the request are allowed to be read, the provisioning server must respond with a result='false', so the device can reject the read-out request.
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ Note that the provisioning server responds with a canReadResponse element, similar to the canRead element in the request, except
+ only the nodes allowed to be read are read. The device must only permit read-out of nodes listed in the response from the provisioning server. Other nodes available
+ in the request should be ignored.
+
+ In case the provisioning server wants to limit the fields a device can send to a client, the provisioning server has the possibility to grant read-out, but
+ list a set of fields the device is allowed to send to the corresponding client.
+
+
+ Note: If the server responds, but without specifying a list of field names, the device can assume that all fields available in the original request are allowed
+ to be sent. If no fields in the request are allowed to be sent, the provisioning server must respond with a result='false', so the device can reject the read-out request.
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ Note that the provisioning server responds with a canReadResponse element, similar to the canRead element in the request, except only
+ the fields allowed to be sent are listed. The client must only send fields having field names in this list.
+
+ Also note, that the provisioning server can return a list of both allowed nodes and allowed field names in the response. In this case, the device must only send allowed fields
+ from allowed nodes, and ignore all other fields and/or nodes.
+
+ An important use case for provisioning in sensor networks is who gets to control devices, and what they can control. This use case details how communication with a
+ provisioning server can help the device determine if a client has sufficient access rights to perform control actions on the device.
+
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ In case the device handles multiple nodes that can be read, the provisioning server has the possibility to grant control access, but to limit the nodes that can be controlled.
+ The provisioning server does this by returning the list of nodes that can be controlled.
+
+
+ Note: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
+ to be controlled. If no nodes in the request are allowed to be controlled, the provisioning server must respond with a result='false', so the device can reject the read-out request.
+ The same is true for parameters: If the provisioning server does not specify parameters in the response, the caller can assume all parameters are allowed.
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ Note that the provisioning server responds with a canControlResponse element, similar to the canControl element in the request, except
+ only the nodes allowed to be controlled are included. The device must only permit control of nodes listed in the response from the provisioning server. Other nodes available
+ in the request should be ignored.
+
+ Also note, that the restricted set of nodes and/or parameters returned from the provisioning server must be returned to the original caller, so it can
+ act on the information that only a partial control action was allowed and taken.
+
+ In case the provisioning server wants to limit the control parameters a client can control in a device, the provisioning server has the possibility to grant
+ control access, but list a set of parameters the client is allowed to control in the corresponding device.
+
+
+ Note: If the server responds, but without specifying a list of nodes, the device can assume that all nodes available in the original request are allowed
+ to be controlled. If no nodes in the request are allowed to be controlled, the provisioning server must respond with a result='false', so the device can reject the read-out request.
+ The same is true for parameters: If the provisioning server does not specify parameters in the response, the caller can assume all parameters are allowed.
+
+ The following example shows the communication first between the client and the device, then between the device and the provisioning server, and last between the device and the client:
+
+ Note that the provisioning server responds with a canControlResponse element, similar to the canControl element in the request, except only
+ the parameters allowed to be sent are listed. The device must only control parameters included in this list.
+
+ Also note, that the provisioning server can return a list of both allowed nodes and allowed parameter names in the response back to the client, so it can
+ act on the information that only a partial control action was allowed and taken.
+
+ When the provisioning server updates access rights and user privileges in the system, it will send a clearCache command to corresponding devices.
+ If a device was offline during the change, the provisioning server must send the clearCache message when the device comes online again. To acknowledge
+ the receipt of the command, the client responds with a clearCacheResponse element. This response message does not contain any information on what was
+ done by the client. It simply acknowledges the receipt of the command, to make sure the provisioning server does not resend the clear cache command again.
+
+ Note: The clearCache command does not include information on what has been changed, so the device needs to clear the entire cache. This
+ to avoid complexities in making sure updates made to the provisioning rules works in all cases, and to minimize complexity in the implementation of the protocol on the sensor side.
+ It is also not deemed to decrease network performance, since changing provisioning rules for a device is an exceptional event and therefore does not affect performance during
+ normal operation.
+
+ A service requesting provisioning assistance, needs to retrieve a service token from the provisioning server, by providing a base-64 encoded X.509 certificate.
+ The following example shows how this can be done.
+
+ Provisioning in sensor networks also requires control of user access to different services in the network. This use case shows how service access rights are controlled using
+ a trusted provisioning server.
+
+
+ First, the user connects to the service in some way. This can be done using XMPP, HTTP, HTTPS or some other means. The service need to extract some form of identifying
+ credentials from the user, and provide that to the provisioning server. The provisioning server determines if the client has access rights to the service based on these
+ credentials, and also provides the service with a userToken that the service can use in further communication with the provisioning server regarding
+ the user and its privileges.
+
+ The following table lists some different types of credentials that the service can extract from the client:
+
+ The provisioning server receives these credentials, and decides if the user should have access to the service or not, based on rules configured in the provisioning service.
+ If the user is granted access, a userToken is generated and returned to the service.
+
+ Now, the service can determine if this access grant is sufficient or not. It can require the user to login into the service first. If so, the service should provide the provisioning
+ server with the user name used during login, when logged in.
+
+ When a user has been given access to a service, and properly been identified, the service can ask the provisioning service for detailed user privileges to control
+ different aspects of the service. This can be done using the hasPrivilege command. Here, the service sends its serviceToken and
+ the userToken earlier received when being granted access to the service. Furthermore a privilegeId has to be provided.
+
+ A Privilege ID is a string composed of one or a sequence of parts, delimited by period characters. The Privilege IDs form a tree of privileges,
+ using an invisible, but common, root privilege.
+
+ The following table suggests some examples of Privilege IDs, with suggestive descriptions. (Only used as an example.)
+
+ Note: Note that privilege IDs are local to the service. Different services are allowed to use similar or same Privilege IDs, in different contexts and
+ with different meanings. The provisioning server must separate Privilege IDs from different services.
+
+ The client must always provide full Privilege IDs to the provisioning server. The provisioning server however, can grant partial privilege IDs, pointing to parent
+ privilege nodes to a user or a role object, granting a user a specific role. If granting a parent privilege ID to a user or role, this is interpreted as
+ giving the corresponding user or role the privileges of the entire sub-tree defined by the parent privilege ID.
+
+ If additional control over privileges is desired, negative privileges can be assigned to the user or role. Granted or explicitly rejected privileges are specified in a
+ sequential list of full or partial privilege IDs. This list is then processed sequentially to determine if a privilege is granted or not.
+
+ Example: Consider the privileges above. Give a user or its corresponding role the following privileges in a sequential list:
+
+ This would give the user rights to select and insert data, but not to delete data from the Energy database.
+
+ Note: Care should be taken when constructing Privilege IDs, so they do not include variable data that potentially can create an infinite amount of
+ privilege IDs. For example: Do not include user names, sensor IDs, etc., in privilege IDs, as the number of such entities cannot be estimated or is scalable beforehand.
+
+ The following diagram shows an example of how a service asks permission from a provisioning server before an action is taken:
+
+
+ To improve performance, services can download the entire set of user privileges, and perform privilege checks internally. The following diagram displays
+ how the above two use cases could be handled in such a case:
+
+
+ Note: When downloading privileges using this command, a sequential list of full or partial privilege IDs will be returned together with the
+ corresponding include or exclude flags. The above mentioned algorithm of determining user privileges must be implemented by the service, if this method is
+ to be used.
+
+ Note: If the user or service has not been correctly identified, logged in, etc., the resulting list must only include privileges
+ that default users that are not logged in can have. This list can be empty.
+
+ If an entity is a Provisioning Server and supports the protocol specified herein, it MUST advertise that fact by returning a feature of "urn:xmpp:iot:provisioning"
+ in response to &xep0030; information requests.
+
+ In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined
+ in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
+
+ A client must treat the connection between a Provisioning Server differently if it is hosted as a client, having a JID, or if it is hosted as a Jabber Server Component.
+ If it is hosted as a server component, there's no need for the thing to become friends with the Provisioning Server. Messages and requests can be made directly to the
+ server component without having to add it to the roster or request presence subscriptions. If the Provisioning Server is hosted as a client, having a JID (@ in the address),
+ the Provisioning Server must be added to the roster of the client before the client can communicate with the Provisioning Server.
+
+ To minimize network traffic, and optimize response time, devices should cache access rights and user privileges provided by the provisioning server. If memory is limited,
+ items in the cache should be ordered by last access, and items with the oldest last access timestamp should be removed first. A safety valve can optionally be implemented as well,
+ removing unused cache items after a certain age, even if memory is available.
+
+ The device can assume that access rights and user privileges on the provisioning server do not change over time, unless the provisioning server says so.
+
+ The provisioning server on the other hand, must keep track of when a device is online and offline, and clear the cache of the device if changes are made that affects the device.
+ If the device was offline when those changes occurred, the provisioning server must send the clear cache command as soon as the device comes online again.
+
+ When creating a new trust relationship, the device should always clear its cache, if it contains information from before.
+
+ To minimize stress of the provisioning server during synchronous sensor start up, for instance after a power failure, all clients should aim to persist its cache if possible. Clients
+ not persisting its cache may produce too much stress on the provisioning server on start-up, practically removing it from the network.
+
+ When working with multiple provisioning servers, there are some things that should be considered:
+
+ One important design consideration when implementing a provisioning server is how to handle new services, users and privileges. One option might be to automatically
+ ignore anything not recognized. Another option might be to dynamically add new services, user names and privileges to internal data sources, making it easier to manage
+ new types of services dynamically. However, adding such items automatically might also make such data sources grow beyond control.
+
+ All examples in this document have been simplified examples where a few devices containing a few fields have been read. However, in many cases large subsystems with
+ very many sensors containing many fields have to be read, as is documented in Internet of Things - Concentrators
+ Internet of Things - Concentrators. In such cases, a node may have to be specified using two or perhaps
+ even three ID's: a sourceId identifying the data source controlling the device, a possible cacheType narrowing down the search to
+ a specific kind of node, and the common nodeId. For more information about this, see
+ Internet of Things - Concentrators.
+
+ Note: For cases where the nodeId is sufficient to uniquely identify the node, it is sufficient to provide this attribute in the request.
+ If there is ambiguity in the request, the receptor must treat the request as a request with a set of nodes, all with the corresponding nodeId as requested.
+
+ A small note regarding the use of different tokens. A service can get a Service Token, a device a Device Token and a user
+ a User Token. When delegating these tokens to third parties, a service sends its Service Token. But, if the service does this
+ within the context of a user action, the service sends both its Service Token and the users User Token. The same with a device.
+ If a device delegates its token to a third party, it sends its Device Token. But if the device performs the action in the context of a user action,
+ the device sends both its Device Token as well as its User Token.
+
+ Delegating trust to a third party may create a weak link in the overall security of a sensor network. Therefore, it's vitally important that the following be adhered to:
+
+ When receiving token challenges from somebody, make sure you've sent the corresponding token to the corresponding party less than a minute before receiving the token
+ challenge. If not, the token challenge might represent a malicious attempt by somebody else to use the token to gain privileges in the network otherwise not enjoyed.
+ This document requires no interaction with &IANA;.
+ The protocol schema needs to be added to the list of XMPP protocol schemas.
+
- For more information, please see the following resources:
-
- The Sensor Network section of the XMPP Wiki contains further information about the
- use of the sensor network XEPs, links to implementations, discussions, etc.
-
- The XEP's and related projects are also available on github, thanks to Joachim Lindborg.
-
- A presentation giving an overview of all extensions related to Internet of Things can be found here:
- http://prezi.com/esosntqhewhs/iot-xmpp/.
- Thanks to Joachim Lindborg, Karin Forsell, Tina Beckman and Teemu Väisänen for all valuable feedback.
+ For more information, please see the following resources:
+
+ The Sensor Network section of the XMPP Wiki contains further information about the
+ use of the sensor network XEPs, links to implementations, discussions, etc.
+
+ The XEP's and related projects are also available on github, thanks to Joachim Lindborg.
+
+ A presentation giving an overview of all extensions related to Internet of Things can be found here:
+ http://prezi.com/esosntqhewhs/iot-xmpp/.
+ Thanks to Joachim Lindborg, Karin Forsell, Tina Beckman and Teemu Väisänen for all valuable feedback.
+
+
+
+
+
+ XEP
+ Description
+
+
+ xep-0000-IoT-BatteryPoweredSensors
+ Defines how to handle the peculiars related to battery powered devices, and other devices intermittently available on the network.
+
+
+ xep-0000-IoT-Events
+ Defines how Things send events, how event subscription, hysteresis levels, etc., are configured.
+
+
+ xep-0000-IoT-Interoperability
+ Defines guidelines for how to achieve interoperability in Internet of Things, publishing interoperability interfaces for different types of devices.
+
+
+ xep-0000-IoT-Multicast
+ Defines how sensor data can be multicast in efficient ways.
+
+
+ xep-0000-IoT-PubSub
+ Defines how efficient publication of sensor data can be made in Internet of Things.
+
+
+ xep-0000-IoT-Chat
+ Defines how human-to-machine interfaces should be constructed using chat messages to be user friendly, automatable and consistent with other IoT extensions and possible underlying architecture.
+
+
+ XEP-0322
+
+ Defines how to EXI can be used in XMPP to achieve efficient compression of data. Albeit not an Internet of Things specific XEP, this XEP should be considered
+ in all Internet of Things implementations where memory and packet size is an issue.
+
+
+
+ XEP-0323
+
+ Provides the underlying architecture, basic operations and data structures for sensor data communication over XMPP networks.
+ It includes a hardware abstraction model, removing any technical detail implemented in underlying technologies. This XEP is used by all other
+ Internet of Things XEPs.
+
+
+
+ XEP-0324
+ This specification. Defines how provisioning, the management of access privileges, etc., can be efficiently and easily implemented.
+
+
+ XEP-0325
+ Defines how to control actuators and other devices in Internet of Things.
+
+
+ XEP-0326
+ Defines how to handle architectures containing concentrators or servers handling multiple Things.
+
+
+ XEP-0331
+ Defines extensions for how color parameters can be handled, based on &xep0004;
+
+
+ XEP-0336
+ Defines extensions for how dynamic forms can be created, based on &xep0004;, &xep0122;, &xep0137; and &xep0141;.
+
+
+ XEP-0347
+ Defines the peculiars of sensor discovery in sensor networks. Apart from discovering sensors by JID, it also defines how to discover sensors based on location, etc.
+
+
+
+
+
-
-
-
-
-
- XEP
- Description
-
-
- xep-0000-IoT-BatteryPoweredSensors
- Defines how to handle the peculiars related to battery powered devices, and other devices intermittently available on the network.
-
-
- xep-0000-IoT-Events
- Defines how Things send events, how event subscription, hysteresis levels, etc., are configured.
-
-
- xep-0000-IoT-Interoperability
- Defines guidelines for how to achieve interoperability in Internet of Things, publishing interoperability interfaces for different types of devices.
-
-
- xep-0000-IoT-Multicast
- Defines how sensor data can be multicast in efficient ways.
-
-
- xep-0000-IoT-PubSub
- Defines how efficient publication of sensor data can be made in Internet of Things.
-
-
- xep-0000-IoT-Chat
- Defines how human-to-machine interfaces should be constructed using chat messages to be user friendly, automatable and consistent with other IoT extensions and possible underlying architecture.
-
-
- XEP-0322
-
- Defines how to EXI can be used in XMPP to achieve efficient compression of data. Albeit not an Internet of Things specific XEP, this XEP should be considered
- in all Internet of Things implementations where memory and packet size is an issue.
-
-
-
- XEP-0323
-
- Provides the underlying architecture, basic operations and data structures for sensor data communication over XMPP networks.
- It includes a hardware abstraction model, removing any technical detail implemented in underlying technologies. This XEP is used by all other
- Internet of Things XEPs.
-
-
-
- XEP-0324
- This specification. Defines how provisioning, the management of access privileges, etc., can be efficiently and easily implemented.
-
-
- XEP-0325
- Defines how to control actuators and other devices in Internet of Things.
-
-
- XEP-0326
- Defines how to handle architectures containing concentrators or servers handling multiple Things.
-
-
- XEP-0331
- Defines extensions for how color parameters can be handled, based on &xep0004;
-
-
- XEP-0336
- Defines extensions for how dynamic forms can be created, based on &xep0004;, &xep0122;, &xep0137; and &xep0141;.
-
-
- XEP-0347
- Defines the peculiars of sensor discovery in sensor networks. Apart from discovering sensors by JID, it also defines how to discover sensors based on location, etc.
-
-
-
-
-
-
- 
- 
-
+
+ 
- 
- 
- 
- 
- 
- 
- 
-
- 
-
- 
-
-
-
- 
-
-
-
-
- Type
- Protocols
- Description
-
-
- JID
- XMPP
- Allows provisioning to be done on the JID the user has.
-
-
- IP Address
- HTTP, HTTPS
- Allows provisioning to be done on IP address or IP-ranges for instance.
-
-
- Host Name
- HTTP, HTTPS with DNS
- If the service has access to the client host name, for instance in an intra network, this can be used for provisioning.
-
-
- X.509 Certificate
- HTTPS
- If the client provides a client certificate, such a certificate can be used to provide provisioning.
-
-
- X.509 Certificate Thumbprint
- HTTPS
-
- The client can also choose to validate the certificate itself and only send the certificate thumbprint to the provisioning server. Even though this
- provides somewhat lesser security than providing the entire certificate, it might be an option to distribute certificate validation checks across the network
- to lower the work load on the provisioning server.
-
-
-
- User Name
- HTTP, HTTPS, XMPP
-
- If authenticated HTTP(S) access is implemented, the service can provide the user name as credentials. XMPP based clients can use
- information in the roster to provide user name information to the provisioning server.
-
-
-
- Geolocation
- HTML5 over HTTP(S), XMPP
-
- If the geographic location (longitude, latitude and possibly altitude) of the user client is known, it can be used. HTML 5 provides mechanism whereby the location
- of the client can be fetched. &xep0080; provides a mechanism whereby client location can be obtained over XMPP.
-
-
-
- SSO Token
- Intranet
- If a single sign on token is available, such a token could be provided as credentials.
-
-
- Protocol
- Any
- Connection protocol used to connect to the service.
-
-
-
-
- Privilege ID
- Description
-
-
- Databases.Energy.Select
- Gives the user the rights to select data from the Energy database.
-
-
- Databases.Energy.Insert
- Gives the user the rights to insert data into the Energy database.
-
-
- Databases.Energy.Delete
- Gives the user the rights to delete data from the Energy database.
-
-
- 
- 
-
-
-
-
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Type
+ Protocols
+ Description
+
+
+ JID
+ XMPP
+ Allows provisioning to be done on the JID the user has.
+
+
+ IP Address
+ HTTP, HTTPS
+ Allows provisioning to be done on IP address or IP-ranges for instance.
+
+
+ Host Name
+ HTTP, HTTPS with DNS
+ If the service has access to the client host name, for instance in an intra network, this can be used for provisioning.
+
+
+ X.509 Certificate
+ HTTPS
+ If the client provides a client certificate, such a certificate can be used to provide provisioning.
+
+
+ X.509 Certificate Thumbprint
+ HTTPS
+
+ The client can also choose to validate the certificate itself and only send the certificate thumbprint to the provisioning server. Even though this
+ provides somewhat lesser security than providing the entire certificate, it might be an option to distribute certificate validation checks across the network
+ to lower the work load on the provisioning server.
+
+
+
+ User Name
+ HTTP, HTTPS, XMPP
+
+ If authenticated HTTP(S) access is implemented, the service can provide the user name as credentials. XMPP based clients can use
+ information in the roster to provide user name information to the provisioning server.
+
+
+
+ Geolocation
+ HTML5 over HTTP(S), XMPP
+
+ If the geographic location (longitude, latitude and possibly altitude) of the user client is known, it can be used. HTML 5 provides mechanism whereby the location
+ of the client can be fetched. &xep0080; provides a mechanism whereby client location can be obtained over XMPP.
+
+
+
+ SSO Token
+ Intranet
+ If a single sign on token is available, such a token could be provided as credentials.
+
+
+ Protocol
+ Any
+ Connection protocol used to connect to the service.
+
+
+
+
+ Privilege ID
+ Description
+
+
+ Databases.Energy.Select
+ Gives the user the rights to select data from the Energy database.
+
+
+ Databases.Energy.Insert
+ Gives the user the rights to insert data into the Energy database.
+
+
+ Databases.Energy.Delete
+ Gives the user the rights to delete data from the Energy database.
+
+
+
+
+
+
+
+
+
+
-
-
-
+
+
+ Actuators are devices in sensor networks that can be controlled through the network and act with the outside world. In sensor networks and Internet of Things applications, + actuators make it possible to automate real-world processes. This document defines a mechanism whereby actuators can be controlled in XMPP-based sensor networks, making it + possible to integrate sensors and actuators of different brands, makes and models into larger Internet of Things applications. +
++ Note has to be taken, that these XEP's are designed for implementation in sensors, many of which have very limited amount of memory (both RAM and ROM) or resources (processing power). + Therefore, simplicity is of utmost importance. Furthermore, sensor networks can become huge, easily with millions of devices in peer-to-peer networks. +
++ Sensor networks contains many different architectures and use cases. For this reason, the sensor network standards have been divided into multiple XEPs according to the following table: +
+| XEP | +Description | +
|---|---|
| xep-0000-IoT-BatteryPoweredSensors | +Defines how to handle the peculiars related to battery powered devices, and other devices intermittently available on the network. | +
| xep-0000-IoT-Discovery | +Defines the peculiars of sensor discovery in sensor networks. Apart from discovering sensors by JID, it also defines how to discover sensors based on location, etc. | +
| xep-0000-IoT-Events | +Defines how sensors send events, how event subscription, hysteresis levels, etc., are configured. | +
| xep-0000-IoT-Interoperability | +Defines guidelines for how to achieve interoperability in sensor networks, publishing interoperability interfaces for different types of devices. | +
| xep-0000-IoT-Multicast | +Defines how sensor data can be multicast in efficient ways. | +
| xep-0000-IoT-PubSub | +Defines how efficient publication of sensor data can be made in sensor networks. | +
| xep-0000-IoT-Chat | +Defines how human-to-machine interfaces should be constructed using chat messages to be user friendly, automatable and consistent with other IoT extensions and possible underlying architecture. | +
| XEP-0322 | ++ Defines how to EXI can be used in XMPP to achieve efficient compression of data. Albeit not a sensor network specific XEP, this XEP should be considered + in all sensor network implementations where memory and packet size is an issue. + | +
| XEP-0323 | ++ Provides the underlying architecture, basic operations and data structures for sensor data communication over XMPP networks. + It includes a hardware abstraction model, removing any technical detail implemented in underlying technologies. This XEP is used by all other sensor network XEPs. + | +
| XEP-0324 | +Defines how provisioning, the management of access privileges, etc., can be efficiently and easily implemented. | +
| XEP-0325 | +This specification. Defines how to control actuators and other devices in Internet of Things. | +
| XEP-0326 | +Defines how to handle architectures containing concentrators or servers handling multiple sensors. | +
| XEP-0331 | +Defines extensions for how color parameters can be handled, based on &xep0004; | +
| XEP-0336 | +Defines extensions for how dynamic forms can be created, based on &xep0004;, &xep0122;, &xep0137; and &xep0141;. | +
The following table lists common terms and corresponding descriptions.
+-
+
- Actuator +
- Device containing at least one configurable property or output that can and should be controlled by some other entity or device. +
- Computed Value +
- A value that is computed instead of measured. +
- Concentrator +
- Device managing a set of devices which it publishes on the XMPP network. +
- Field +
- + One item of sensor data. Contains information about: Node, Field Name, Value, Precision, Unit, Value Type, Status, Timestamp, Localization information, etc. + Fields should be unique within the triple (Node ID, Field Name, Timestamp). + +
- Field Name +
- Name of a field of sensor data. Examples: Energy, Volume, Flow, Power, etc. +
- Field Type +
- What type of value the field represents. Examples: Momentary Value, Status Value, Identification Value, Calculated Value, Peak Value, Historical Value, etc. +
- Historical Value +
- A value stored in memory from a previous timestamp. +
- Identification Value +
- A value that can be used for identification. (Serial numbers, meter IDs, locations, names, etc.) +
- Localization information +
- Optional information for a field, allowing the sensor to control how the information should be presented to human viewers. +
- Meter +
- A device possible containing multiple sensors, used in metering applications. Examples: Electricity meter, Water Meter, Heat Meter, Cooling Meter, etc. +
- Momentary Value +
- A momentary value represents a value measured at the time of the read-out. +
- Node +
- + Graphs contain nodes and edges between nodes. In Internet of Things, sensors, actuators, meters, devices, gatewats, etc., are often depicted as nodes whereas links between sensors (friendships) + are depicted as edges. In abstract terms, it's easier to talk about a Node, rather than list different possible node types (sensors, actuators, meters, devices, gateways, etc.). + Each Node has a Node ID. + +
- Node ID +
- + An ID uniquely identifying a node within its corresponding context. If a globally unique ID is desired, an architecture should be used using a universally accepted + ID scheme. + +
- Parameter +
- + Readable and/or writable property on a node/device. The XEP-0326 &xep0326; deals with reading and writing parameters + on nodes/devices. Fields are not parameters, and parameters are not fields. + +
- Peak Value +
- A maximum or minimum value during a given period. +
- Precision +
- + In physics, precision determines the number of digits of precision. In sensor networks however, this definition is not easily applicable. Instead, precision + determines, for example, the number of decimals of precision, or power of precision. Example: 123.200 MWh contains 3 decimals of precision. All entities parsing and + delivering field information in sensor networks should always retain the number of decimals in a message. + +
- Sensor +
- + Device measuring at least one digital value (0 or 1) or analog value (value with precision and physical unit). Examples: Temperature sensor, pressure sensor, etc. + Sensor values are reported as fields during read-out. Each sensor has a unique Node ID. + +
- SN +
- Sensor Network. A network consisting, but not limited to sensors, where transport and use of sensor data is of primary concern. A sensor network may contain actuators, network applications, monitors, services, etc. +
- Status Value +
- A value displaying status information about something. +
- Timestamp +
- Timestamp of value, when the value was sampled or recorded. +
- Token +
- + A client, device or user can get a token from a provisioning server. These tokens can be included in requests to other entities in the network, so these entities can validate + access rights with the provisioning server. + +
- Unit +
- Physical unit of value. Example: MWh, l/s, etc. +
- Value +
- A field value. +
- Value Status +
- Status of field value. Contains important status information for Quality of Service purposes. Examples: Ok, Error, Warning, Time Shifted, Missing, Signed, etc. +
- Value Type +
- Can be numeric, string, boolean, Date & Time, Time Span or Enumeration. +
- WSN +
- Wireless Sensor Network, a sensor network including wireless devices. +
- XMPP Client +
- Application connected to an XMPP network, having a JID. Note that sensors, as well as applications requesting sensor data can be XMPP clients. +
+ Control in sensor networks is about setting output values. To make the implementation simple, it is assumed that control of a device can be made using a single message. + If only a simple set operation is requested, a <message> stanza can be sent. If an acknowledgement (ACK) of the operation (or Not-acknowledgement NACK) of the operation + is desired, an <iq> stanza can be used instead. +
++ To set control parameters in a device, the set command is sent to the device. The set command allows for two different ways of setting control parameters: +
+-
+
- Using strongly typed parameters. This way performs best in EXI compression and automation. +
- Using a weakly typed data form. This might be better for manually setting control parameters, since it allows the device to give the user a better user interface explaining + available control parameters. +
+ What type of control parameters there are available in different types of devices is described in
+
+ If the device is a concentrator, as defined in Internet of Things - Concentrators, + an handles multiple nodes behind it, which node(s) to control is defined using node elements. If not a concentrator, + the use of node elements is not necessary, and control commands are sent directly to the device itself. +
+- Actuators are devices in sensor networks that can be controlled through the network and act with the outside world. In sensor networks and Internet of Things applications, - actuators make it possible to automate real-world processes. This document defines a mechanism whereby actuators can be controlled in XMPP-based sensor networks, making it - possible to integrate sensors and actuators of different brands, makes and models into larger Internet of Things applications. + Following is an example of a control command sent using a message stanza: +
++ Note that any response is supressed when sending a message stanza, regardless if the desired control command could be executed or not. The following example shows how the same + control command could be issued using an IQ stanza instead: +
++ Following is an example of a control command sent using an iq stanza: +
++ Note: An empty setResponse element means that the control command was executed as provided in the request. Sometimes, the device + can restrict the command to a subset of nodes and/or parameters. In such cases, the setResponse element will contain what nodes and/or parameters + were finally used to perform the command. For examples of this, see &xep0324;.
- Note has to be taken, that these XEP's are designed for implementation in sensors, many of which have very limited amount of memory (both RAM and ROM) or resources (processing power). - Therefore, simplicity is of utmost importance. Furthermore, sensor networks can become huge, easily with millions of devices in peer-to-peer networks. + In the following use cases, often a message stanza will be used to illustrate the point. However, the same operation could equally well be used using an iq stanza instead. +
++ By using an IQ stanza, the caller can receive an acknowledgement of the reception of the command, or error information if the command could not be processed. + Following is an example of a control command sent using an iq stanza, where the receiver reports an error back to the caller: +
++ Here, the paramError element is used in the IQ Error response, to provide error information related to a specific control parameter. +
++ The following sub-sections illustrate how to set parameters of different types in a device. +
++ Setting single boolean-valued control parameters is a common use case, for instance when controlling digital outputs. The following example shows how a boolean value + can be set in a device. +
++ Setting single integer-valued control parameters is a common use case, for instance when controlling analog outputs. The following example shows how a 32-bit integer value + can be set in a device. +
++ Setting single integer-valued control parameters is a common use case, for instance when controlling analog outputs. Even though 32-bit integers may cover most control needs, + it might in some cases be limiting. Therefore, a 64-bit control parameters can be created. The following example shows how a 64-bit integer value + can be set in a device. +
++ Setting single string-valued control parameters is a common use case, for instance when controlling text displays. The following example shows how a string value + can be set in a device. +
++ Setting single double-valued control parameters can be an alternative form of controlling analog outputs for instance. The following example shows how a double value + can be set in a device. +
++ Setting date-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. + The following example shows how a date value can be set in a device. +
++ Setting time-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. + The following example shows how a time value can be set in a device. +
++ Setting date & time-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. + The following example shows how a date & time value can be set in a device. +
++ Setting duration-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. + The following example shows how a duration value can be set in a device. +
++ Setting single color values in a device can occur in instances where color or lighting is important. Sometimes color is set using enumerations (string-valued + or integer-valued parameters), and sometimes as a color property. The following example shows how a color value can be set in a device. +
++ Often, setting a single control parameter is not sufficient for a control action. In these cases, setting multiple control parameters at once is necessary. + The set command makes this easy however, since it allows for any number of control parameters to be set at once, as the following example shows: +
++ Sometimes the order of control parameters are important in the device, and sometimes the parameters form part of a whole. It depends on the context of the device. + In the above example, the order is important. When the OutputPercent control parameter is set, it will start to fade in or out to the desired setting (10%), using the + fade time set previously. If the FadeTimeMilliseconds control parameter would have been set after the OutputPercent parameter, the fading would have been started using + the previous setting, which might be unknown.
- Sensor networks contains many different architectures and use cases. For this reason, the sensor network standards have been divided into multiple XEPs according to the following table: + The order of control parameters to use depends on the device. The Control Form lists available control parameters of the device in the + order they are expected to be sent to the device. The XEP xep-0000-IoT-Interoperability details what control parameters + must be available for different interfaces, and if the order of control parameters is important.
-| XEP | -Description | -
|---|---|
| xep-0000-IoT-BatteryPoweredSensors | -Defines how to handle the peculiars related to battery powered devices, and other devices intermittently available on the network. | -
| xep-0000-IoT-Discovery | -Defines the peculiars of sensor discovery in sensor networks. Apart from discovering sensors by JID, it also defines how to discover sensors based on location, etc. | -
| xep-0000-IoT-Events | -Defines how sensors send events, how event subscription, hysteresis levels, etc., are configured. | -
| xep-0000-IoT-Interoperability | -Defines guidelines for how to achieve interoperability in sensor networks, publishing interoperability interfaces for different types of devices. | -
| xep-0000-IoT-Multicast | -Defines how sensor data can be multicast in efficient ways. | -
| xep-0000-IoT-PubSub | -Defines how efficient publication of sensor data can be made in sensor networks. | -
| xep-0000-IoT-Chat | -Defines how human-to-machine interfaces should be constructed using chat messages to be user friendly, automatable and consistent with other IoT extensions and possible underlying architecture. | -
| XEP-0322 | -- Defines how to EXI can be used in XMPP to achieve efficient compression of data. Albeit not a sensor network specific XEP, this XEP should be considered - in all sensor network implementations where memory and packet size is an issue. - | -
| XEP-0323 | -- Provides the underlying architecture, basic operations and data structures for sensor data communication over XMPP networks. - It includes a hardware abstraction model, removing any technical detail implemented in underlying technologies. This XEP is used by all other sensor network XEPs. - | -
| XEP-0324 | -Defines how provisioning, the management of access privileges, etc., can be efficiently and easily implemented. | -
| XEP-0325 | -This specification. Defines how to control actuators and other devices in Internet of Things. | -
| XEP-0326 | -Defines how to handle architectures containing concentrators or servers handling multiple sensors. | -
| XEP-0331 | -Defines extensions for how color parameters can be handled, based on &xep0004; | -
| XEP-0336 | -Defines extensions for how dynamic forms can be created, based on &xep0004;, &xep0122;, &xep0137; and &xep0141;. | -
The following table lists common terms and corresponding descriptions.
--
-
- Actuator -
- Device containing at least one configurable property or output that can and should be controlled by some other entity or device. -
- Computed Value -
- A value that is computed instead of measured. -
- Concentrator -
- Device managing a set of devices which it publishes on the XMPP network. -
- Field -
- - One item of sensor data. Contains information about: Node, Field Name, Value, Precision, Unit, Value Type, Status, Timestamp, Localization information, etc. - Fields should be unique within the triple (Node ID, Field Name, Timestamp). - -
- Field Name -
- Name of a field of sensor data. Examples: Energy, Volume, Flow, Power, etc. -
- Field Type -
- What type of value the field represents. Examples: Momentary Value, Status Value, Identification Value, Calculated Value, Peak Value, Historical Value, etc. -
- Historical Value -
- A value stored in memory from a previous timestamp. -
- Identification Value -
- A value that can be used for identification. (Serial numbers, meter IDs, locations, names, etc.) -
- Localization information -
- Optional information for a field, allowing the sensor to control how the information should be presented to human viewers. -
- Meter -
- A device possible containing multiple sensors, used in metering applications. Examples: Electricity meter, Water Meter, Heat Meter, Cooling Meter, etc. -
- Momentary Value -
- A momentary value represents a value measured at the time of the read-out. -
- Node -
- - Graphs contain nodes and edges between nodes. In Internet of Things, sensors, actuators, meters, devices, gatewats, etc., are often depicted as nodes whereas links between sensors (friendships) - are depicted as edges. In abstract terms, it's easier to talk about a Node, rather than list different possible node types (sensors, actuators, meters, devices, gateways, etc.). - Each Node has a Node ID. - -
- Node ID -
- - An ID uniquely identifying a node within its corresponding context. If a globally unique ID is desired, an architecture should be used using a universally accepted - ID scheme. - -
- Parameter -
- - Readable and/or writable property on a node/device. The XEP-0326 &xep0326; deals with reading and writing parameters - on nodes/devices. Fields are not parameters, and parameters are not fields. - -
- Peak Value -
- A maximum or minimum value during a given period. -
- Precision -
- - In physics, precision determines the number of digits of precision. In sensor networks however, this definition is not easily applicable. Instead, precision - determines, for example, the number of decimals of precision, or power of precision. Example: 123.200 MWh contains 3 decimals of precision. All entities parsing and - delivering field information in sensor networks should always retain the number of decimals in a message. - -
- Sensor -
- - Device measuring at least one digital value (0 or 1) or analog value (value with precision and physical unit). Examples: Temperature sensor, pressure sensor, etc. - Sensor values are reported as fields during read-out. Each sensor has a unique Node ID. - -
- SN -
- Sensor Network. A network consisting, but not limited to sensors, where transport and use of sensor data is of primary concern. A sensor network may contain actuators, network applications, monitors, services, etc. -
- Status Value -
- A value displaying status information about something. -
- Timestamp -
- Timestamp of value, when the value was sampled or recorded. -
- Token -
- - A client, device or user can get a token from a provisioning server. These tokens can be included in requests to other entities in the network, so these entities can validate - access rights with the provisioning server. - -
- Unit -
- Physical unit of value. Example: MWh, l/s, etc. -
- Value -
- A field value. -
- Value Status -
- Status of field value. Contains important status information for Quality of Service purposes. Examples: Ok, Error, Warning, Time Shifted, Missing, Signed, etc. -
- Value Type -
- Can be numeric, string, boolean, Date & Time, Time Span or Enumeration. -
- WSN -
- Wireless Sensor Network, a sensor network including wireless devices. -
- XMPP Client -
- Application connected to an XMPP network, having a JID. Note that sensors, as well as applications requesting sensor data can be XMPP clients. -
- Control in sensor networks is about setting output values. To make the implementation simple, it is assumed that control of a device can be made using a single message. - If only a simple set operation is requested, a <message> stanza can be sent. If an acknowledgement (ACK) of the operation (or Not-acknowledgement NACK) of the operation - is desired, an <iq> stanza can be used instead. + A client can get a control form containing available control parameters of the device. This is done using the getForm command, + as is shown in the following example:
-- To set control parameters in a device, the set command is sent to the device. The set command allows for two different ways of setting control parameters: -
--
-
- Using strongly typed parameters. This way performs best in EXI compression and automation. -
- Using a weakly typed data form. This might be better for manually setting control parameters, since it allows the device to give the user a better user interface explaining - available control parameters. -
- What type of control parameters there are available in different types of devices is described in
-
- If the device is a concentrator, as defined in Internet of Things - Concentrators, - an handles multiple nodes behind it, which node(s) to control is defined using node elements. If not a concentrator, - the use of node elements is not necessary, and control commands are sent directly to the device itself. -
-- Following is an example of a control command sent using a message stanza: -
-- Note that any response is supressed when sending a message stanza, regardless if the desired control command could be executed or not. The following example shows how the same - control command could be issued using an IQ stanza instead: -
-- Following is an example of a control command sent using an iq stanza: -
-- Note: An empty setResponse element means that the control command was executed as provided in the request. Sometimes, the device - can restrict the command to a subset of nodes and/or parameters. In such cases, the setResponse element will contain what nodes and/or parameters - were finally used to perform the command. For examples of this, see &xep0324;. -
-- In the following use cases, often a message stanza will be used to illustrate the point. However, the same operation could equally well be used using an iq stanza instead. -
-- By using an IQ stanza, the caller can receive an acknowledgement of the reception of the command, or error information if the command could not be processed. - Following is an example of a control command sent using an iq stanza, where the receiver reports an error back to the caller: -
-- Here, the paramError element is used in the IQ Error response, to provide error information related to a specific control parameter. -
-- The following sub-sections illustrate how to set parameters of different types in a device. -
-- Setting single boolean-valued control parameters is a common use case, for instance when controlling digital outputs. The following example shows how a boolean value - can be set in a device. -
-- Setting single integer-valued control parameters is a common use case, for instance when controlling analog outputs. The following example shows how a 32-bit integer value - can be set in a device. -
-- Setting single integer-valued control parameters is a common use case, for instance when controlling analog outputs. Even though 32-bit integers may cover most control needs, - it might in some cases be limiting. Therefore, a 64-bit control parameters can be created. The following example shows how a 64-bit integer value - can be set in a device. -
-- Setting single string-valued control parameters is a common use case, for instance when controlling text displays. The following example shows how a string value - can be set in a device. -
-- Setting single double-valued control parameters can be an alternative form of controlling analog outputs for instance. The following example shows how a double value - can be set in a device. -
-- Setting date-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. - The following example shows how a date value can be set in a device. -
-- Setting time-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. - The following example shows how a time value can be set in a device. -
-- Setting date & time-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. - The following example shows how a date & time value can be set in a device. -
-- Setting duration-valued control parameters might be necessary when timing is an issue. Often it forms part of a larger context. - The following example shows how a duration value can be set in a device. -
-- Setting single color values in a device can occur in instances where color or lighting is important. Sometimes color is set using enumerations (string-valued - or integer-valued parameters), and sometimes as a color property. The following example shows how a color value can be set in a device. -
-- Often, setting a single control parameter is not sufficient for a control action. In these cases, setting multiple control parameters at once is necessary. - The set command makes this easy however, since it allows for any number of control parameters to be set at once, as the following example shows: -
-- Sometimes the order of control parameters are important in the device, and sometimes the parameters form part of a whole. It depends on the context of the device. - In the above example, the order is important. When the OutputPercent control parameter is set, it will start to fade in or out to the desired setting (10%), using the - fade time set previously. If the FadeTimeMilliseconds control parameter would have been set after the OutputPercent parameter, the fading would have been started using - the previous setting, which might be unknown. -
-- The order of control parameters to use depends on the device. The Control Form lists available control parameters of the device in the - order they are expected to be sent to the device. The XEP xep-0000-IoT-Interoperability details what control parameters - must be available for different interfaces, and if the order of control parameters is important. -
-- A client can get a control form containing available control parameters of the device. This is done using the getForm command, - as is shown in the following example: -
-
- IMPORTANT: The device MUST mark all control parameters in the form as notSame, as defined in
-
- All parameters in the form MUST also have validation rules defined according to XEP-0122, - specifically validation data types and ranges where appropriate. This to give type information to the client, which the client later can use to send - typed control commands directly, without the need to get and send data forms to the device to control it. -
-- Also, the device SHOULD group control parameters that should be written together using pages and sections, as described in - XEP-0141. Parameters - MUST also be ordered in a way so that when set in that order using the typed commands, the corresponding control actions can be successfully executed. -
-- Note: There's a difference between node parameters, as described in XEP-0326 - Internet of Things - Concentrators, - and control parameters as described in this document. For more information about this, please see - Difference between node parameters and node control parameters. -
-- A device can reject a control form request. It does this returning an error iq stanza, as is shown in the following example: -
-- Control actions can be requested by submitting a full or partial control form back to the device. Control parameters not edited MUST not be included - in the form, and the device in turn MUST ONLY invoke control actions corresponding to the parameters returned in the form. -
-- The following example shows how control actions can be requested submitting a control parameters form to the device: -
-- In this example, the FadeTimeMilliseconds and OutputPercent control parameters are sent, while the MainSwitch control parameter is left as is. Fading is therefore - parformed only if the dimmer is switched on. -
-- A device can reject a control form submission. It does this returning an error iq stanza. If there are errors in the form, details are listed - using paramError elements in the response, as is shown in the following example: -
-- Controlling devices behind a concentrator can be done by specifying what device(s) to control using node elements within the - command elements sent to the concentrator. The following sub-sections show examples of how this is done. -
-- To send a control message to a specific node behind a concentrator, the node element can be used to identify the node, - as is shown in the following example: -
-- The client can send the same control command to multiple nodes behind a concentrator by simply adding more node elements in the request, - as is shown in the following example: -
-- By using an IQ stanza, the caller can receive an acknowledgement of the reception of the command, or error information if the command could not be processed. - When sending a control command to multiple nodes at a time the device must validate all parameters against all nodes before taking any control action. If - validation fails, an error message is returned and no control action is taken. The following example shows an example of an erroneous control message made to - multiple nodes on a device: -
-- A client can get a control form containing available control parameters common between a set of nodes controlled by the concentrator. This is done - adding a sequence of node elements to a getForm command sent to the concentrator, as is shown in the following example: -
-- Note that only parameters that are common between the nodes defined in the request must be returned. However, all parameters must have the - notSame flag set, regardless of current output status. -
-- A device can reject a control form request. It does this returning an error iq stanza. The following example shows the device rejecting - a control form request, because it does not support the handling of common parameters between multiple nodes: -
-- You set a control form to multiple nodes controlled by a - concentrator by adding node elements to the - set command sent to the concentrator, as is - shown in the following example: -
-- A device can reject a control form submission. It does this returning an error iq stanza. The following example shows the device rejecting a - control form submission because one of the control parameters, even though it exists on all nodes, is not of the same type on all nodes. -
-If an entity supports the protocol specified herein, it MUST advertise that fact by returning a feature of "urn:xmpp:iot:control" in response to &xep0030; information requests.
-
+ IMPORTANT: The device MUST mark all control parameters in the form as notSame, as defined in
+
+ All parameters in the form MUST also have validation rules defined according to XEP-0122, + specifically validation data types and ranges where appropriate. This to give type information to the client, which the client later can use to send + typed control commands directly, without the need to get and send data forms to the device to control it. +
++ Also, the device SHOULD group control parameters that should be written together using pages and sections, as described in + XEP-0141. Parameters + MUST also be ordered in a way so that when set in that order using the typed commands, the corresponding control actions can be successfully executed. +
++ Note: There's a difference between node parameters, as described in XEP-0326 + Internet of Things - Concentrators, + and control parameters as described in this document. For more information about this, please see + Difference between node parameters and node control parameters. +
+ ++ A device can reject a control form request. It does this returning an error iq stanza, as is shown in the following example: +
++ Control actions can be requested by submitting a full or partial control form back to the device. Control parameters not edited MUST not be included + in the form, and the device in turn MUST ONLY invoke control actions corresponding to the parameters returned in the form. +
++ The following example shows how control actions can be requested submitting a control parameters form to the device: +
++ In this example, the FadeTimeMilliseconds and OutputPercent control parameters are sent, while the MainSwitch control parameter is left as is. Fading is therefore + parformed only if the dimmer is switched on. +
++ A device can reject a control form submission. It does this returning an error iq stanza. If there are errors in the form, details are listed + using paramError elements in the response, as is shown in the following example: +
++ Controlling devices behind a concentrator can be done by specifying what device(s) to control using node elements within the + command elements sent to the concentrator. The following sub-sections show examples of how this is done. +
++ To send a control message to a specific node behind a concentrator, the node element can be used to identify the node, + as is shown in the following example: +
++ The client can send the same control command to multiple nodes behind a concentrator by simply adding more node elements in the request, + as is shown in the following example: +
++ By using an IQ stanza, the caller can receive an acknowledgement of the reception of the command, or error information if the command could not be processed. + When sending a control command to multiple nodes at a time the device must validate all parameters against all nodes before taking any control action. If + validation fails, an error message is returned and no control action is taken. The following example shows an example of an erroneous control message made to + multiple nodes on a device: +
++ A client can get a control form containing available control parameters common between a set of nodes controlled by the concentrator. This is done + adding a sequence of node elements to a getForm command sent to the concentrator, as is shown in the following example: +
++ Note that only parameters that are common between the nodes defined in the request must be returned. However, all parameters must have the + notSame flag set, regardless of current output status. +
++ A device can reject a control form request. It does this returning an error iq stanza. The following example shows the device rejecting + a control form request, because it does not support the handling of common parameters between multiple nodes: +
++ You set a control form to multiple nodes controlled by a + concentrator by adding node elements to the + set command sent to the concentrator, as is + shown in the following example: +
++ A device can reject a control form submission. It does this returning an error iq stanza. The following example shows the device rejecting a + control form submission because one of the control parameters, even though it exists on all nodes, is not of the same type on all nodes. +
+If an entity supports the protocol specified herein, it MUST advertise that fact by returning a feature of "urn:xmpp:iot:control" in response to &xep0030; information requests.
+- In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined - in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead. -
-- Depending on the reason for rejecting a control request, different XMPP errors can be returned, according to the description in the following table. The table also - lists recommended error type for each error. Error stanzas may also include paramError child elements to provide additional textual error information that - corresponds to a particular control parameter provided in the request. Any custom error message not related to control parameters is returned in a text - element. -
-| Error Type | -Error Element | -Namespace | -Description | -
|---|---|---|---|
| cancel | -forbidden | -urn:ietf:params:xml:ns:xmpp-stanzas | -If the caller lacks privileges to perform the action. | -
| cancel | -item-not-found | -urn:ietf:params:xml:ns:xmpp-stanzas | -If an item, parameter or data source could not be found. | -
| modify | -bad-request | -urn:ietf:params:xml:ns:xmpp-stanzas | -If the request was malformed. Examples can include trying to set a parameter to a value outside the allowed range. | -
| cancel | -feature-not-implemented | -urn:ietf:params:xml:ns:xmpp-stanzas | -If an action has not been implemented in the device. | -
| wait | -conflict | -urn:ietf:params:xml:ns:xmpp-stanzas | -If an item was locked by another user or process and could not be accessed. The operation can be retried at a later point in time. | -
- The simplest way to read the current control states of a device, is to request the control form of the device. The control form should contain the current - values for all avilable control parameters. However, since current states might not be available at the time of the request, the states might be delivered - asynchronously, using messages defined in &xep0336;. -
-- Using this method has the advantage that a small actuator device does not need to implement other XEPs to support readout of current control states. If the device - contains all current states readily accessible, there's no need of asynchronous updates making readout simple and straightforward. -
-- A second option is to use &xep0323; to deliver current control states. Since this XEP contains mechanisms allowing for asynchronous readout of control parameter - states. This makes readout of such parameters simpler. However, there's a need to map values between the two XEPs. -
-- If a client wants to know the current status of control parameters using this method, it performs a readout of Momentary and Status values - from the device, and from the returned set of values take the current control parameter value according to the following rules, ordered by priority: -
--
-
-
-
- If there's a field marked as momentary value, with an unlocalized field name equal to the unlocalized control parameter name and having a compatible - field value type (see table below) and a status field without the missing flag set, the value of the field should be considered the current value of - the control parameter. -
-
- -
-
- If there's a field marked as status value, with an unlocalized field name equal to the unlocalized control parameter name and having a compatible - field value type (see table below) and a status field without the missing flag set, the value of the field should be considered the current value of - the control parameter. -
-
- -
-
- To simplify mapping, a writable attribute can be used to inform the client if a field name corresponds to a control parameter or not. If the - attribute is available, it tells the client if it corresponds to a control parameter or not. If not available, no such deduction can be made. -
-
-
- Even though getting the the control form could provide the client with a quicker and easier way of retrieving control parameter values, the form is not - guaranteed to contain correct current values, as described above. -
-- The following table shows how corresponding field values should be converted to the corresponding control parameter value based on field type (x-axis) and - control parameter type (y-axis). An empty cell means conversion has no meaning and types are not compatible. -
-| 325 \ 323 | -boolean | -date | -dateTime | -duration | -enum | -int | -long | -numeric | -string | -time | -
|---|---|---|---|---|---|---|---|---|---|---|
| boolean | -x | -- | - | - | - | !=0 | -!=0 | -!=0 | -- | - |
| color | -- | - | - | - | - | - | - | - | RRGGBB or RRGGBBAA | -- |
| date | -- | x | -Date part | -- | - | - | - | - | (1) | -- |
| dateTime | -- | x | -x | -- | - | - | - | - | (2) | -- |
| double | -Z2 | -- | - | - | - | x | -x | -x | -(3) | -- |
| duration | -- | - | - | x | -- | - | - | - | (4) | -x | -
| int | -Z2 | -- | - | - | Ordinal | -x | -Thunk | -Thunk | -(5) | -- |
| long | -Z2 | -- | - | - | Ordinal | -x | -x | -Thunk | -(5) | -- |
| string | -xs:boolean | -xs:date | -xs:dateTime | -xs:duration | -x | -xs:int | -xs:long | -(6) | -x | -xs:time | -
| time | -- | - | Time part | -(7) | -- | - | - | - | (8) | -x | -
- The following table lists notes with details on how to do conversion, if in doubt. -
-| Note | -Description | -
|---|---|
| (1) | -- The client should try to convert the string to a date value, first according to the format specified by the XML data type xs:date, and if not possible - by RFC 822. - | -
| (2) | -- The client should try to convert the string to a date & time value, first according to the format specified by the XML data type xs:dateTime, and if not possible - by RFC 822. - | -
| (3) | -- The client should try to convert the string to a double-precision floating-point value, first according to the format specified by the XML data type xs:double, - and if not possible using system-local string to floating-point conversion using local decimal and throusand separator settings. - | -
| (4) | -- The client should try to convert the string to a duration value, first according to the format specified by the XML data type xs:duration, - and if not possible using the XML data type xs:time. - | -
| (5) | -The client should try to convert the string to an integer value according to the corresponding XML data type formats xs:int and xs:long. | -
| (6) | -- The numeric field value consists of three parts: Numeric value, number of decimals and optional unit. If no unit is provided, only the numeric value should - be converted to a string (compatible with the XML data type xs:double), using exactly the number of decimals provided in the field. If a unit is provided - (non-empty string) it must not be appended to the value, if the value is to be used for control output. For presentation purposes however, a space could be - appended to the number and the unit appended after the space. - | -
| (7) | -- A duration field value contains a xs:duration value. The xs:duration has a larger domain than xs:time, and contains all xs:time values, but xs:time does - not contain all possible xs:duration values. So, conversion of an xs:duration value to an xs:time value should be performed only if a duration lies - between 00:00:00 and 23:59:59. - | -
| (8) | -- The client should try to convert the string to a time value according to the format specified by the XML data type xs:time. - | -
| x | -Use the canonical conversion method. | -
| Z2 | -true = 1, false = 0. | -
| !=0 | -Nonzero = true, Zero = false. | -
| RRGGBB | -A string of six hexadecimal characters, the first two the red component of the color, the next two the green component and the last two the blue component. | -
| RRGGBBAA | -A string of eight hexadecimal characters, the first two the red component of the color, the next two the green component, the following two the blue component and the last two the alpha channel. | -
| Date part | -Only the date part of the xs:dateTime value should be used. | -
| Time part | -Only the time part of the xs:dateTime value should be used. | -
| Ordinal | -Each enumeration value may in the implementation correspond to an ordinal number. | -
| Thunk | -The value is thunked down to lower precision in the canonical way. | -
| xs:boolean | -Conversion to a string should follow the rules specified for the XML datatype xs:boolean. | -
| xs:dateTime | -Conversion to a string should follow the rules specified for the XML datatype xs:dateTime. | -
| xs:duration | -Conversion to a string should follow the rules specified for the XML datatype xs:duration. | -
- Note: the namespace prefix xs is here supposed to be linked with the XML Schema namespace - http://www.w3.org/2001/XMLSchema. -
-- When representing control parameters as momentary field values, it is important to note the similarities and differences between XEP-0323 (Sensor Data) and XEP-0325 (this document): -
-- The enum field value data type is not available in XEP-0325 (this document). Instead enumeration valued parameters are represented as string control - parameters, while the control form explicitly lists available options for the parameter. Options are not available in XEP-0323, since it would not be practical to list all options - every time the corresponding parameter was read out. Instead, the enum element contains a data type attribute, that can be used to identify the type of the enumeration. -
-- The numeric field value data type is not available in XEP-0325 (this document). The reason is that a controller is not assumed to understand unit conversion. Any - floating-point valued control parameters are represented by double control parameters, which lack a unit attribute. They are assumed to have the same unit as - the corresponding numeric field value. On the other hand, floating point valued control parameters without units, are reported using the numeric - field element, but leaving the unit blank. -
-- Control pameters of type color have no corresponding field value data type. The color value must be represented in another way, and is implementation specific. - Possibilities include representing the color as a string, using a specific pattern (for instance RRGGBBAA), or report it using multiple fields, one for each component for instance. -
-- The boolean, date, dateTime, duration, int, long, string - and time field value data types correspond to control parameters having the same types and same element names. -
-- A node defined in a concentrator, as defined by Internet of Things - Concentrators, supporting control has - two sets of parameters that are different: First a set of node parameters and then a set of control parameters. -
-- Node parameters are defined by the node type in the concentrator, as described in Internet of Things - Concentrators, - and they are typically used by the concentrator to define the node and how to communicate or interact with the underlying device. The important part here is to know - that the node parameters are maintained by the concentrator, not the underlying device. -
-- Control parameters however, are parameters that reside on the underlying device. When set, they change the actual state or behaviour of the underlying device. - The connection to the device however, controlled by the concentrator, remains unchanged by such a control parameter update. -
-- Many control actions available in a device can be controlled using only one control parameter. If a device only publishes such control parameters, the order - of control parameters is not that important. -
-- However, there are many control actions that require the client to set multiple control parameters at the same time, for the device to have a complete understanding - what the client wants to do. -
-- XEP-0141 defines a way to group parameters in a data form by including the concept of pages and sections. - Even though these pages and sections are used for layout purposes, it should be used by devices to mark parameters that should be used together to perform control actions. -
-- The following set of rules should be adhered to, by devices as well as clients, to minimize confusion and resulting errors: -
--
-
-
-
- Control parameters should be listed in control forms in the order the device expects the client to write them back. -
-
- -
-
- Clients should set control parameters in the order they are listed in the corresponding control forms. -
-
- -
-
- Control actions that require multiple control parameters should report these together, grouped by pages or sections within pages, - to make clear that the parameters belong together. -
-
- -
-
- For control actions requiring multiple control parameters, devices should strive to publish default values for all parameters involved. - These default values should then be used by the device if a client happens to write only a subset of the control parameters required for - a control action. The default value could be the current state of the parameter. -
-
-
- Note however, that one cannot always make the assumption that parameters on the same page or same section in a control form belong to the same control action. - For instance, a PLC with 16 digital outputs might publish a control form containing a single page with 16 check boxes on (boolean parameters), that can be - controlled individually. -
-- To solve the problem of grouping parameters together, so a client can know which parameters belong together, a new element is defined that can be used in - data forms: parameterGroup. It is optional, but can be added to control parameters in forms, as a way to tell the client that parameters - having the same parameterGroup belong together and should be written together. -
-- Note: If used, the server must not include a parameter in more than one parameter group at a time. The form may contain multiple group, but each - parameter must only have at most one parameterGroup element. -
-- The following example illustrates the use of the parameterGroup element to group parameters together. -
-- The above example informs the client that the two parameters HorizontalAngle and ElevationAngle should be written together to control a control action - (named direction). -
-- For more information about common control actions and their parameters, see xep-0000-IoT-Interoperability.html, - which defines a set of interoperable interfaces and their abilities. -
-- Nodes behind a concentrator, as defined in Internet of Things - Concentrators, have an additional means of - publishing control interfaces: Node Commands. -
-- However, there are many differences between Node Commands and Control Parameters, as shown in the following list: -
--
-
-
-
- Node Commands are defined by the node type in the concentrator, and not by the device itself. -
-
- -
-
- Node Commands may do many different things, not only performing control actions. -
-
- -
-
- Parametrized Node Commands require the client to always get a parameter data form, and write back values. There's no way to send simple - control messages using Node Commands. -
-
- -
-
- Node Commands can be partitioned, grouped and sorted separately. -
-
- -
-
- Each Parametrized Node Command has a separate parameter form, which makes grouping of parameters normal. -
-
- -
-
- Node Commands are only available for nodes controlled by a concentrator. -
-
-
- If implementing a device with many complex control actions (like an advanced PLC), consideration should be made to divide the device into logical groups and - implement the concentrators interface as well. Then the more complex control actions could be implemented as Node Commands instead of control actions - as defined in this document, and implementing the simpler more intuitive control actions as described in this document. -
-- If control interaction is performed in a context of delegated trust, as defined in the Sensor Network Provisioning XEP-0324 &xep0324;, - tokens should always be included in all calls. This to allow devices to check privileges with provisioning servers. -
-- The set and getForm commands support the following token attributes: -
--
-
- - serviceToken - -
- - deviceToken - -
- - userToken - -
- For more information about provisioning, see Internet of Things - Provisioning. -
-- Most examples in this document have been simplified examples where a few devices containing a few control parameters have been used. However, in many cases large subsystems with - very many actuators containing many different control actions have to be controlled, as is documented in - Internet of Things - Concentrators. - In such cases, a node may have to be specified using two or perhaps even three ID's: a sourceId identifying the data source controlling the device, a possible - cacheType narrowing down the search to a specific kind of node, and the common nodeId. For more information about this, see - Internet of Things - Concentrators. -
-- Note: For cases where the nodeId is sufficient to uniquely identify the node, it is sufficient to provide this attribute in the request. - If there is ambiguity in the request, the receptor must treat the request as a request with a set of nodes, all with the corresponding nodeId as requested. -
-- All timestamps and dateTime values use the XML data type xs:dateTime to specify values. These values include a date, an optional time and an optional time zone. -
-- Note: If time zone is not available, it is supposed to be undefined. The client reading the sensor that reports fields without time zone information - should assume the sensor has the same time zone as the client, if not explicitly configured otherwise on the client side. -
-- If devices report time zone, this information should be propagated throughout the system. Otherwise, comparing timestamps from different time zones will be impossible. -
-- Control commands sent using IQ stanzas instead of messages, should consider using the xml:lang attribute to specify the desired language - used (if possible) when returning information back to the caller, like error messages, localized control forms, etc. -
-+ In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined + in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead. +
++ Depending on the reason for rejecting a control request, different XMPP errors can be returned, according to the description in the following table. The table also + lists recommended error type for each error. Error stanzas may also include paramError child elements to provide additional textual error information that + corresponds to a particular control parameter provided in the request. Any custom error message not related to control parameters is returned in a text + element. +
+| Error Type | +Error Element | +Namespace | +Description | +
|---|---|---|---|
| cancel | +forbidden | +urn:ietf:params:xml:ns:xmpp-stanzas | +If the caller lacks privileges to perform the action. | +
| cancel | +item-not-found | +urn:ietf:params:xml:ns:xmpp-stanzas | +If an item, parameter or data source could not be found. | +
| modify | +bad-request | +urn:ietf:params:xml:ns:xmpp-stanzas | +If the request was malformed. Examples can include trying to set a parameter to a value outside the allowed range. | +
| cancel | +feature-not-implemented | +urn:ietf:params:xml:ns:xmpp-stanzas | +If an action has not been implemented in the device. | +
| wait | +conflict | +urn:ietf:params:xml:ns:xmpp-stanzas | +If an item was locked by another user or process and could not be accessed. The operation can be retried at a later point in time. | +
- Controlling devices in a large sensor network is a hackers wet dream. Therefore, consideration of how network security is implemented should not be underestimated. - The following sections provide some general items that should be considered. + The simplest way to read the current control states of a device, is to request the control form of the device. The control form should contain the current + values for all avilable control parameters. However, since current states might not be available at the time of the request, the states might be delivered + asynchronously, using messages defined in &xep0336;.
-+ Using this method has the advantage that a small actuator device does not need to implement other XEPs to support readout of current control states. If the device + contains all current states readily accessible, there's no need of asynchronous updates making readout simple and straightforward. +
++ A second option is to use &xep0323; to deliver current control states. Since this XEP contains mechanisms allowing for asynchronous readout of control parameter + states. This makes readout of such parameters simpler. However, there's a need to map values between the two XEPs. +
++ If a client wants to know the current status of control parameters using this method, it performs a readout of Momentary and Status values + from the device, and from the returned set of values take the current control parameter value according to the following rules, ordered by priority: +
+-
+
-
- Consider to always use an encrypted connection with any XMPP Server used in the network. Also, make sure the server is properly authenticated and any server - certificate properly validated. + If there's a field marked as momentary value, with an unlocalized field name equal to the unlocalized control parameter name and having a compatible + field value type (see table below) and a status field without the missing flag set, the value of the field should be considered the current value of + the control parameter.
+
+ -
- Control commands should only be accepted by trusted parties. A minimum is to make sure only authenticated and validated clients (friends) can perform control actions - on the device. + If there's a field marked as status value, with an unlocalized field name equal to the unlocalized control parameter name and having a compatible + field value type (see table below) and a status field without the missing flag set, the value of the field should be considered the current value of + the control parameter.
-
- Consider using provisioning servers to allow for detailed control of who can do what in a sensor network. Implementing proper provisioning support decreases - the risk for adverse effects, not only from intentional hacking, but also from unintentional errors. + To simplify mapping, a writable attribute can be used to inform the client if a field name corresponds to a control parameter or not. If the + attribute is available, it tells the client if it corresponds to a control parameter or not. If not available, no such deduction can be made.
-- If using delegated trust, make sure the provisioning servers are properly authenticated and validated before trusting them. -
-- More information about provisioning can be found in Internet of Things - Provisioning. -
-This document requires no interaction with &IANA;.
-- The protocol schema needs to be added to the list of XMPP protocol schemas. -
-
-
+
+
+ Even though getting the the control form could provide the client with a quicker and easier way of retrieving control parameter values, the form is not
+ guaranteed to contain correct current values, as described above.
+
+
+ The following table shows how corresponding field values should be converted to the corresponding control parameter value based on field type (x-axis) and
+ control parameter type (y-axis). An empty cell means conversion has no meaning and types are not compatible.
+
+
+
+ 325 \ 323
+ boolean
+ date
+ dateTime
+ duration
+ enum
+ int
+ long
+ numeric
+ string
+ time
+
+
+ boolean
+ x
+
+
+
+
+ !=0
+ !=0
+ !=0
+
+
+
+
+ color
+
+
+
+
+
+
+
+
+ RRGGBB or RRGGBBAA
+
+
+
+ date
+
+ x
+ Date part
+
+
+
+
+
+ (1)
+
+
+
+ dateTime
+
+ x
+ x
+
+
+
+
+
+ (2)
+
+
+
+ double
+ Z2
+
+
+
+
+ x
+ x
+ x
+ (3)
+
+
+
+ duration
+
+
+
+ x
+
+
+
+
+ (4)
+ x
+
+
+ int
+ Z2
+
+
+
+ Ordinal
+ x
+ Thunk
+ Thunk
+ (5)
+
+
+
+ long
+ Z2
+
+
+
+ Ordinal
+ x
+ x
+ Thunk
+ (5)
+
+
+
+ string
+ xs:boolean
+ xs:date
+ xs:dateTime
+ xs:duration
+ x
+ xs:int
+ xs:long
+ (6)
+ x
+ xs:time
+
+
+ time
+
+
+ Time part
+ (7)
+
+
+
+
+ (8)
+ x
+
+
+
+ The following table lists notes with details on how to do conversion, if in doubt.
+
+
+
+ Note
+ Description
+
+
+ (1)
+
+ The client should try to convert the string to a date value, first according to the format specified by the XML data type xs:date, and if not possible
+ by RFC 822.
+
+
+
+ (2)
+
+ The client should try to convert the string to a date & time value, first according to the format specified by the XML data type xs:dateTime, and if not possible
+ by RFC 822.
+
+
+
+ (3)
+
+ The client should try to convert the string to a double-precision floating-point value, first according to the format specified by the XML data type xs:double,
+ and if not possible using system-local string to floating-point conversion using local decimal and throusand separator settings.
+
+
+
+ (4)
+
+ The client should try to convert the string to a duration value, first according to the format specified by the XML data type xs:duration,
+ and if not possible using the XML data type xs:time.
+
+
+
+ (5)
+ The client should try to convert the string to an integer value according to the corresponding XML data type formats xs:int and xs:long.
+
+
+ (6)
+
+ The numeric field value consists of three parts: Numeric value, number of decimals and optional unit. If no unit is provided, only the numeric value should
+ be converted to a string (compatible with the XML data type xs:double), using exactly the number of decimals provided in the field. If a unit is provided
+ (non-empty string) it must not be appended to the value, if the value is to be used for control output. For presentation purposes however, a space could be
+ appended to the number and the unit appended after the space.
+
+
+
+ (7)
+
+ A duration field value contains a xs:duration value. The xs:duration has a larger domain than xs:time, and contains all xs:time values, but xs:time does
+ not contain all possible xs:duration values. So, conversion of an xs:duration value to an xs:time value should be performed only if a duration lies
+ between 00:00:00 and 23:59:59.
+
+
+
+ (8)
+
+ The client should try to convert the string to a time value according to the format specified by the XML data type xs:time.
+
+
+
+ x
+ Use the canonical conversion method.
+
+
+ Z2
+ true = 1, false = 0.
+
+
+ !=0
+ Nonzero = true, Zero = false.
+
+
+ RRGGBB
+ A string of six hexadecimal characters, the first two the red component of the color, the next two the green component and the last two the blue component.
+
+
+ RRGGBBAA
+ A string of eight hexadecimal characters, the first two the red component of the color, the next two the green component, the following two the blue component and the last two the alpha channel.
+
+
+ Date part
+ Only the date part of the xs:dateTime value should be used.
+
+
+ Time part
+ Only the time part of the xs:dateTime value should be used.
+
+
+ Ordinal
+ Each enumeration value may in the implementation correspond to an ordinal number.
+
+
+ Thunk
+ The value is thunked down to lower precision in the canonical way.
+
+
+ xs:boolean
+ Conversion to a string should follow the rules specified for the XML datatype xs:boolean.
+
+
+ xs:dateTime
+ Conversion to a string should follow the rules specified for the XML datatype xs:dateTime.
+
+
+ xs:duration
+ Conversion to a string should follow the rules specified for the XML datatype xs:duration.
+
+
+
+ Note: the namespace prefix xs is here supposed to be linked with the XML Schema namespace
+ http://www.w3.org/2001/XMLSchema.
+
+
+
+
+ When representing control parameters as momentary field values, it is important to note the similarities and differences between XEP-0323 (Sensor Data) and XEP-0325 (this document):
+
+
+ The enum field value data type is not available in XEP-0325 (this document). Instead enumeration valued parameters are represented as string control
+ parameters, while the control form explicitly lists available options for the parameter. Options are not available in XEP-0323, since it would not be practical to list all options
+ every time the corresponding parameter was read out. Instead, the enum element contains a data type attribute, that can be used to identify the type of the enumeration.
+
+
+ The numeric field value data type is not available in XEP-0325 (this document). The reason is that a controller is not assumed to understand unit conversion. Any
+ floating-point valued control parameters are represented by double control parameters, which lack a unit attribute. They are assumed to have the same unit as
+ the corresponding numeric field value. On the other hand, floating point valued control parameters without units, are reported using the numeric
+ field element, but leaving the unit blank.
+
+
+ Control pameters of type color have no corresponding field value data type. The color value must be represented in another way, and is implementation specific.
+ Possibilities include representing the color as a string, using a specific pattern (for instance RRGGBBAA), or report it using multiple fields, one for each component for instance.
+
+
+ The boolean, date, dateTime, duration, int, long, string
+ and time field value data types correspond to control parameters having the same types and same element names.
+
+
+
+
+
+ A node defined in a concentrator, as defined by Internet of Things - Concentrators, supporting control has
+ two sets of parameters that are different: First a set of node parameters and then a set of control parameters.
+
+
+ Node parameters are defined by the node type in the concentrator, as described in Internet of Things - Concentrators,
+ and they are typically used by the concentrator to define the node and how to communicate or interact with the underlying device. The important part here is to know
+ that the node parameters are maintained by the concentrator, not the underlying device.
+
+
+ Control parameters however, are parameters that reside on the underlying device. When set, they change the actual state or behaviour of the underlying device.
+ The connection to the device however, controlled by the concentrator, remains unchanged by such a control parameter update.
+
+
+
+
+ Many control actions available in a device can be controlled using only one control parameter. If a device only publishes such control parameters, the order
+ of control parameters is not that important.
+
+
+ However, there are many control actions that require the client to set multiple control parameters at the same time, for the device to have a complete understanding
+ what the client wants to do.
+
+
+ XEP-0141 defines a way to group parameters in a data form by including the concept of pages and sections.
+ Even though these pages and sections are used for layout purposes, it should be used by devices to mark parameters that should be used together to perform control actions.
+
+
+ The following set of rules should be adhered to, by devices as well as clients, to minimize confusion and resulting errors:
+
+
+ -
+
+ Control parameters should be listed in control forms in the order the device expects the client to write them back.
+
+
+ -
+
+ Clients should set control parameters in the order they are listed in the corresponding control forms.
+
+
+ -
+
+ Control actions that require multiple control parameters should report these together, grouped by pages or sections within pages,
+ to make clear that the parameters belong together.
+
+
+ -
+
+ For control actions requiring multiple control parameters, devices should strive to publish default values for all parameters involved.
+ These default values should then be used by the device if a client happens to write only a subset of the control parameters required for
+ a control action. The default value could be the current state of the parameter.
+
+
+
+
+ Note however, that one cannot always make the assumption that parameters on the same page or same section in a control form belong to the same control action.
+ For instance, a PLC with 16 digital outputs might publish a control form containing a single page with 16 check boxes on (boolean parameters), that can be
+ controlled individually.
+
+
+ To solve the problem of grouping parameters together, so a client can know which parameters belong together, a new element is defined that can be used in
+ data forms: parameterGroup. It is optional, but can be added to control parameters in forms, as a way to tell the client that parameters
+ having the same parameterGroup belong together and should be written together.
+
+
+ Note: If used, the server must not include a parameter in more than one parameter group at a time. The form may contain multiple group, but each
+ parameter must only have at most one parameterGroup element.
+
+
+ The following example illustrates the use of the parameterGroup element to group parameters together.
+
+
+
+
+
+ Spotlight
+
+
+
+
+
+ 325ED0F3-9A9A-45A4-9634-4E0D41C5EA06
+
+
+ If the spotlight is turned on or off.
+ true
+
+
+ Horizontal angle of the spotlight.
+ 0
+
+
+
+
+ Elevation angle of the spotlight.
+ 0
+
+
+
+
+ ]]>
+
+
+ The above example informs the client that the two parameters HorizontalAngle and ElevationAngle should be written together to control a control action
+ (named direction).
+
+
+ For more information about common control actions and their parameters, see xep-0000-IoT-Interoperability.html,
+ which defines a set of interoperable interfaces and their abilities.
+
+
+
+
+ Nodes behind a concentrator, as defined in Internet of Things - Concentrators, have an additional means of
+ publishing control interfaces: Node Commands.
+
+
+ However, there are many differences between Node Commands and Control Parameters, as shown in the following list:
+
+
+ -
+
+ Node Commands are defined by the node type in the concentrator, and not by the device itself.
+
+
+ -
+
+ Node Commands may do many different things, not only performing control actions.
+
+
+ -
+
+ Parametrized Node Commands require the client to always get a parameter data form, and write back values. There's no way to send simple
+ control messages using Node Commands.
+
+
+ -
+
+ Node Commands can be partitioned, grouped and sorted separately.
+
+
+ -
+
+ Each Parametrized Node Command has a separate parameter form, which makes grouping of parameters normal.
+
+
+ -
+
+ Node Commands are only available for nodes controlled by a concentrator.
+
+
+
+
+ If implementing a device with many complex control actions (like an advanced PLC), consideration should be made to divide the device into logical groups and
+ implement the concentrators interface as well. Then the more complex control actions could be implemented as Node Commands instead of control actions
+ as defined in this document, and implementing the simpler more intuitive control actions as described in this document.
+
+
+
+
+ If control interaction is performed in a context of delegated trust, as defined in the Sensor Network Provisioning XEP-0324 &xep0324;,
+ tokens should always be included in all calls. This to allow devices to check privileges with provisioning servers.
+
+
+ The set and getForm commands support the following token attributes:
+
+
+ -
+ serviceToken
+
+ -
+ deviceToken
+
+ -
+ userToken
+
+
+
+ For more information about provisioning, see Internet of Things - Provisioning.
+
+
+
+
+ Most examples in this document have been simplified examples where a few devices containing a few control parameters have been used. However, in many cases large subsystems with
+ very many actuators containing many different control actions have to be controlled, as is documented in
+ Internet of Things - Concentrators.
+ In such cases, a node may have to be specified using two or perhaps even three ID's: a sourceId identifying the data source controlling the device, a possible
+ cacheType narrowing down the search to a specific kind of node, and the common nodeId. For more information about this, see
+ Internet of Things - Concentrators.
+
+
+ Note: For cases where the nodeId is sufficient to uniquely identify the node, it is sufficient to provide this attribute in the request.
+ If there is ambiguity in the request, the receptor must treat the request as a request with a set of nodes, all with the corresponding nodeId as requested.
+
+
+ + All timestamps and dateTime values use the XML data type xs:dateTime to specify values. These values include a date, an optional time and an optional time zone. +
++ Note: If time zone is not available, it is supposed to be undefined. The client reading the sensor that reports fields without time zone information + should assume the sensor has the same time zone as the client, if not explicitly configured otherwise on the client side. +
++ If devices report time zone, this information should be propagated throughout the system. Otherwise, comparing timestamps from different time zones will be impossible. +
++ Control commands sent using IQ stanzas instead of messages, should consider using the xml:lang attribute to specify the desired language + used (if possible) when returning information back to the caller, like error messages, localized control forms, etc. +
++ Controlling devices in a large sensor network is a hackers wet dream. Therefore, consideration of how network security is implemented should not be underestimated. + The following sections provide some general items that should be considered. +
++ Consider to always use an encrypted connection with any XMPP Server used in the network. Also, make sure the server is properly authenticated and any server + certificate properly validated. +
++ Control commands should only be accepted by trusted parties. A minimum is to make sure only authenticated and validated clients (friends) can perform control actions + on the device. +
++ Consider using provisioning servers to allow for detailed control of who can do what in a sensor network. Implementing proper provisioning support decreases + the risk for adverse effects, not only from intentional hacking, but also from unintentional errors. +
++ If using delegated trust, make sure the provisioning servers are properly authenticated and validated before trusting them. +
++ More information about provisioning can be found in Internet of Things - Provisioning. +
+This document requires no interaction with &IANA;.
++ The protocol schema needs to be added to the list of XMPP protocol schemas. +
+
+
+ xmlns:xs='http://www.w3.org/2001/XMLSchema'
+ targetNamespace='urn:xmpp:iot:control'
+ xmlns='urn:xmpp:iot:control'
+ xmlns:sn='urn:xmpp:iot:sensordata'
+ xmlns:xd="jabber:x:data"
+ xmlns:xdv="http://jabber.org/protocol/xdata-validate"
+ xmlns:xdl="http://jabber.org/protocol/xdata-layout"
+ elementFormDefault='qualified'>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
+
+
+
+
+
-
-
-
-
-
+
+
+
+
+
+
-
-
-
-
-
+
+
+
+
-
-
-
-
-
-
+
+
-
-
-
-
-
-
+
+
-
-
-
-
-
-
+
+
-
-
-
-
-
-
+
+
+
+
+
+
-
-
-
-
-
-
+
+
+
+
+
+
-
-
-
-
-
-
+
+
+
+
+
+
-
-
-
-
-
-
+
+
+
+
+
+
-
-
-
-
-
-
+
+
+
+
+
+
-
-
+
+
+
+
+
+
-
-
-
-
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
]]>
-
- - For more information, please see the following resources: -
--
-
-
-
- The Sensor Network section of the XMPP Wiki contains further information about the - use of the sensor network XEPs, links to implementations, discussions, etc. -
-
- -
-
- The XEP's and related projects are also available on github, thanks to Joachim Lindborg. -
-
- -
-
- A presentation giving an overview of all extensions related to Internet of Things can be found here: - http://prezi.com/esosntqhewhs/iot-xmpp/. -
-
-
Thanks to Joachim Lindborg and Tina Beckman for all valuable feedback.
-+ For more information, please see the following resources: +
+-
+
-
+
+ The Sensor Network section of the XMPP Wiki contains further information about the + use of the sensor network XEPs, links to implementations, discussions, etc. +
+
+ -
+
+ The XEP's and related projects are also available on github, thanks to Joachim Lindborg. +
+
+ -
+
+ A presentation giving an overview of all extensions related to Internet of Things can be found here: + http://prezi.com/esosntqhewhs/iot-xmpp/. +
+
+
Thanks to Joachim Lindborg and Tina Beckman for all valuable feedback.
+