4 Presence Architecture

23.1413GPPArchitecture and functional descriptionPresence serviceRelease 15TS

4.1 Overview

The Presence Service provides the ability for the home network to manage presence information of a user’s device, service or service media even whilst roaming. A user’s presence information may be obtained through input from the user, information supplied by network entities or information supplied by elements external to the home network. Consumers of presence information, watchers, may be internal or external to the home network.

4.2 Reference Architecture Model

The generic reference architectural model for providing presence service is depicted in Figure 4.2-1 below. The details of the elements in the figure (e.g. agents, proxies) are provided in clause 5.

The mapping of the Presence Service functional elements and reference points to the functional elements and reference points in the 3GPP Network Architecture TS 23.002 [18] (and additionally IMS) is defined in clauses 4.3 and clause 5.

Figure 4.2-1: Reference architecture to support a presence service

4.3 Reference points

4.3.1 Reference point Presence User Agent – Presence Server (Peu)

This reference point shall allow the Presence User Agent to manage subscription authorization policies.

IPv6 shall be supported for all functionalities required from a Presence User Agent that supports the Peu reference point. An IPv6 capable 3GPP UE shall use IPv6 when accessing Peu. However, early IMS implementations and deployments may use IPv4;if IPv4 is used, the guidelines and recommendations in TR 23.981 [21] should be followed.

This reference point uses capabilities defined for the Ut reference point as defined in TS 23.002 [18].

4.3.2 Reference point Presence Network Agent – Presence Server (Pen)

This reference point shall allow a presentity’s presence information to be supplied to the Presence Server. The transport on this reference point shall not impose any limitations to the size of the presence information.

Pen shall provide mechanisms for the Network Agent to manage subscription authorisation policies.

Pen shall provide mechanisms for the Network Agent to supply or update only a certain subset of the presentity’s presence information to the Presence Server.

Pen shall provide mechanisms for activating or deactivating the reporting of Presence Information for a given presentity from the network entities within the PLMN.

The Pen interface is an intra-operator interface. In order to provide the all the functionalities required on this reference point, a combination of multiple protocols may be used. In general the protocols used at the Pen reference point are not standardised. However, for 3GPP2 systems this reference point is defined in X.S0027-004 [x]. At least, this interface shall support the transport of presence information under the PIDF format as specified in IETF RFC 3863 [3].

4.3.3 Reference point Presence External Agent – Presence Server (Pex)

This reference point shall allow a presentity’s presence information to be supplied to the Presence Server. The transport on this reference point shall not impose any limitations on the size of the presence information.

Pex shall provide mechanisms for the Presence External Agent to supply or update only a certain subset of the presentity’s presence information to the Presence Server.

In order to provide all the functionalities required on this reference point, a combination of multiple protocols may be used. Presence information obtained from an external network by the Presence External Agent is transferred across the Pex reference point to the Presence Server. This interface shall support the transport of presence information under the PIDF format as specified in IETF RFC 3863 [3].

4.3.4 Reference point Watcher applications – Presentity Presence Proxy (Pw)

This reference point shall allow a Watcher application to request and obtain presence information. This interface shall support the transport of presence information under the PIDF format as specified in IETF RFC 3863 [3].

The transport shall not impose any limitations to the size of the presence information.

In order to provide all the functionalities required on this interface, a combination of multiple protocols may be used.

This reference point shall support both presence monitoring and fetching modes. In the fetching mode, it shall be possible for the watcher to once request all or only a subset of a presentity’s presence information (e.g. one or more tuples). The subset of the presence information is defined by the filter that is carried in the presence information subscription.

In the monitoring mode, it shall be possible for the watcher to request monitoring of all or a subset of a presentity’s presence information (i.e. one or more tuples) . Watcher shall be able to explicitly indicate the capability to process partial updates. The subset of the presence information is defined by the filter that is carried in the presence information subscription. It shall be possible for the watcher to request the presence server to filter out information when the watcher is equal to the publishing Presence User Agent.

It shall be possible for the notifications containing the presentity’s presence information to contain only information as defined by filters. It shall be possible for the notifications containing the presentity’s presence information to contain only the modified tuples, i.e. only those tuples which have changed since the last notification.

This reference point may allow a Watcher application to use presence lists in presence information subscriptions, and the Watcher Presence Proxy to interface to a server that provides the functionality of Presence List Server.

IPv6 shall be supported for all functionalities required from a Watcher application that supports the Pw reference point. An IPv6 capable 3GPP UE shall use IPv6 when accessing Pw. However, early IMS implementations and deployments may use IPv4; if IPv4 is used, the guidelines and recommendations in TR 23.981 [21] should be followed.

4.3.5 Reference point HSS/HLR – Presence Network Agent (Ph)

This reference point shall allow the Presence Network Agent to query HSS/HLR about the state and status of a subscriber (associated with a presentity) from the serving network (for 3GPP this is the CS domain or GPRS) and IMS perspective.

This reference point permits the Presence Network Agent to activate and deactivate the reporting of mobility management events from the serving network (for 3GPP this is the CS domain or GPRS) and/or the IMS-specific reports from the S-CSCF.

This reference point uses capabilities defined for the Sh reference point as defined in TS 23.002 [18] as well as the MAP interface.

4.3.6 Reference point S-CSCF – Presence Network Agent (Pi)

The S-CSCF may provide IMS-specific presence information (e.g. about IMS registration state). This reference point shall use mechanisms defined for the ISC reference point as defined in TS 23.002 [18].

4.3.7 Reference point Presentity Presence Proxy – HSS (Px)

The Px interface is an intra-operator interface. This interface shall assist locating the Presence Server of the presentity. This interface is implemented using the mechanisms defined for the Cx and Dx reference points as defined in TS 23.002 [18].

4.3.8 Reference point Presence Network Agent – GMLC (Pl)

This reference point shall be used by the Presence Network Agent to retrieve location information related to a subscriber (associated with the presentity). This reference point is the interface to GMLC and it is an instance of the Le reference point (defined in TS 23.271 [14] and TS 23.002 [18]). In the case of Presence the LCS client (defined in TS 23.271 [14]) is the Presence Network Agent and so the protocol implementing Pl needs to be defined. Though normally a stage 3 responsibility in this case the protocol to be used is defined here since it is a reference to an existing protocol. Thus, Pl shall conform to OMA’s LIF-MLP specification [20].

For 3GPP2 systems, the interface for this reference point is to the 3GPP2 Position Server and is not supported in the current release of the specification.

4.3.9 Reference point Presence Network Agent – SGSN (Pg)

This reference point shall allow the SGSN to report mobility management related events (such as attach/not reachable for paging/detach/routing area update) to the Presence Network Agent.

This reference point may allow the SGSN to report Mobility States (such as Detached, Idle and Connected) and Session States (such as PDP context active and inactive).

This reference point is implemented using the existing mechanisms of CAMEL phase 4, 3GPP Release 5.

For 3GPP2 systems, this reference point is not supported.

4.3.10 Reference point Presence Network Agent –MSC Server/VLR (Pc)

This reference point shall allow the MSC Server/VLR to report the mobility management related events to the Network Agent (such as attach/detach/location area update) and may allow the MSC Server/VLR to report call related events (such as call setup with the bearer information and call release).

This reference point may allow the MSC Server/ VLR to report Mobility States (such as Detached, Idle and Connected) and Call States (such as Busy with Bearer information and Idle).

This reference point is implemented using the existing mechanisms of CAMEL phase 4, 3GPP Release 5.

For 3GPP2 systems, the interface to this reference point is defined in 3GPP2 X.S0004 [23].

4.3.11 Reference point Presence Network Agent – GGSN (Pk)

This reference point shall allow the GGSN to report presence relevant events to the Presence Network Agent (such as PDP context activation/de-activation). This reference point is implemented using the mechanisms of the RADIUS interface for reporting of access requests on Gi reference point as defined in TS 29.061 [13].

For 3GPP2 systems, this reference point is not supported.

4.3.12 Reference point Presence Network Agent – 3GPP AAA Server (Pr)

This reference point shall allow the 3GPP AAA Server to report IP-connectivity related events to the Presence Network Agent (such as WLAN UE attaching/detaching and tunnel establishment/removal). The Pr reference point shall be as much as possible based on mechanisms of existing interfaces.

For 3GPP2 systems, the interface for this reference point is to the AAA server and is defined in X.S0027-004 [22].

4.3.13 Reference point Presence Network Agent – PDG (Pp)

This reference point shall allow the PDG to report presence relevant events to the Presence Network Agent (such as tunnel establishment/removal, allocation of the remote IP address for the WLAN UE). This reference point is based on reusing of the Wi reference point.

For 3GPP2 systems, this reference point is not supported.

4.3.14 Reference point Presence User Agent – Presentity Presence Proxy (Pep)

This reference point shall allow a presentity’s presence information to be supplied to the Presence Server. The transport on this reference point shall not impose any limitations on the size of the presence information. This interface shall support the transport of presence information under the PIDF format as specified in IETF RFC 3863 [3].

Pep shall provide mechanisms for the Presence User Agent to obtain information on watcher subscriptions to the presentity’s presence information.

Pep shall provide mechanisms for the Presence User Agent to supply or update only a certain subset of the presentity’s presence information to the Presence Server. It shall also be possible for the Presence User Agent to supply the complete presence document over Pep.

Pep shall support SIP-based communications for publishing presence information.

IPv6 shall be supported for all functionalities required from a Presence User Agent that supports the Pep reference point. An IPv6 capable 3GPP UE shall use IPv6 when accessing Pep. However, early IMS implementations and deployments may use IPv4; if IPv4 is used, the guidelines and recommendations in TR 23.981 [21] should be followed.

4.3.15 Reference point Presentity Presence Proxy – Presence Server (Pwp)

The Pwp interface is an intra-operator interface. This reference point shall allow all the functionalities provided by the Pw and Pep reference points.

4.3.16 Reference point Watcher Applications – Presence List Server (Pet)

This reference point shall allow a Watcher application to manage presence list information in the Presence List Server.

This reference point uses capabilities defined for the Ut reference point as defined in TS 23.228 [9].

4.4 Support of OSA Presence Service Capability Server in the Presence Architecture

An OSA API may be provided to allow external application to access presence service features, details of which are found in TS 23.198 [15].

The OSA Presence SCS may act like a presentity or a watcher. The application may then register as a presentity and/or watcher, to supply presence information, to request presence information, to be notified of subsequent changes, to request watcher information, and to manage subscription authorisation policies.