WO2013060356A1

WO2013060356A1 - Method and apparatus relating to policy control in a telecommunications network

Info

Publication number: WO2013060356A1
Application number: PCT/EP2011/068605
Authority: WO
Inventors: Susana Fernandez Alonso; Fabian Castro Castro; Irene Martin Cabello; Emiliano Merino Vazquez
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2011-10-25
Filing date: 2011-10-25
Publication date: 2013-05-02

Abstract

A method is provided for use in a telecommunications network. A first message is received (S1 ) at an application function (10). The first message relates to a request for a service involving the establishment of a data flow between a first terminal and a second terminal. The application function (10) is associated with the first terminal for the service. A second message is sent (S3) from the application function (10) to a policy control function (20). The policy control function (20) is associated with the first terminal for the service. The policy control function (20) is assigned to determine at least one policy to be applied to the data flow. The second message comprises first information relating to at least one characteristic of the service that is common with respect to the first and second devices. The second message also comprises second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; these can be regarded as being equivalent. The second message is received (S4) at the policy control function (20). The second message comprises the first and second information. At least one policy is determined (S5) at the policy control function (20) based on the first and second information received in the second message. A third message is sent (S6) from the policy control function (20) to a gateway node. The gateway node is associated with the first terminal for the service. The gateway node is assigned to enforce at least one policy to the data flow. The third message comprises the at least one determined policy.

Description

Method and Apparatus relating to Policy Control in a Telecommunications Network

Technical field

The present invention relates to policy control in a telecommunications network. Background Modern telecommunications networks provide services to their users based on data packet communications. One or more packet data flows are established between the parties involved in a communication, with the flows conveying data packets which themselves containing signaling or user information exchanged between the parties. One example is a 3GPP communications network comprising an Internet Protocol (IP) Multimedia Subsystem (IMS) as disclosed by the 3GPP Specification TS 23.228 v1 1 .1 .0, which provides a Multimedia Telephony service (MMTel).

Figure 1 of the accompanying drawings illustrates schematically a telecommunications network architecture including a General Packet Radio Service (GPRS) access network and an IP Multimedia Subsystem (IMS). The IP Multimedia Subsystem (IMS) is the technology defined by the Third Generation Partnership Project (3GPP) to provide IP multimedia services over telecommunication networks, including mobile (wireless) or fixed (wired) access. IP multimedia services can provide a dynamic combination of voice, video, messaging, data, etc. within the same session. The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals. The Session Description Protocol (SDP), carried by SIP signals, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to-user protocol, the IMS allows operators and service providers to control user access to services and to charge users accordingly.

As shown in Figure 1 , managing of communications of user terminals (user equipment, UE; not shown in the figure) that connect to the network of Figure 1 can be considered as held at three layers (or planes). The lowest layer (illustrated in the figure as Connectivity Layer 1 ), is also referred to as the bearer or user plane, and provides the connectivity means through which signals are directed to/from UEs accessing the network. The entities within the connectivity layer 1 that connect a UE to a further network providing application services (e.g. allowing an IMS subscriber to access from his UE to IMS services provided by IMS network 3b) form a network that is referred to as an IP-Connectivity Access Network, IP-CAN. A GPRS network is an example of a IP-CAN network and, apart of the radio access nodes, includes various GPRS Support Nodes (GSNs), such as Gateway GPRS Support Nodes (GGSN) and Serving GPRS Support Nodes (SGSN). A GGSN (e.g. GGSN 2a) cooperates with one or more SGSNs, and acts as an interface between the GPRS backbone network and other networks (such as an IMS network). A middle layer (illustrated in the figure as Control Layer 4) implements control functions relating to the signals held by the IP-CAN network. For example, in case of an IP-CAN network comprising GPRS, part of these functions can be implemented by SGSNs and GGSNs of said IP-CAN network, and relate to the processing of signals received from, or addressing to, a UE that connects through the IP-CAN network (e.g. bearer establishment, bearer termination, etc). At the top of a UE's communication there can be further servers managing high-layer aspects of said communication (illustrated in the figure by an Application Layer 6 comprising one or more Application Servers 7).

In the illustrated example, the IMS subsystem 3 includes a core network 3a and a service network 3b. The IMS core network 3a includes nodes that send/receive signals to/from nodes in the IP-CAN network (e.g. via the GGSN 2a). In particular, the IMS 3 comprises network nodes (known as Call Session Control Functions, CSCFs, which operate as SIP proxies, and which are arranged to communicate with nodes of an IP- CAN network that perform connectivity and control functions (e.g. with a GGSN, 2a).

The 3GPP architecture defines three types of CSCFs: the Proxy CSCF (P-CSCF) which is the first point of contact within the IMS for a SIP terminal; the Serving CSCF (S-CSCF) which provides services to the user that the user is subscribed to; and the Interrogating CSCF (l-CSCF) whose role is to identify the correct S-CSCF and to forward to that S-CSCF a request received from a SIP terminal via a P-CSCF. Application Servers (AS) 7 can be provided for implementing some of IMS service functionality. For example, an AS 7 can receive and process signaling related to a UE (i.e. as received from an IP-CAN network to which said UE attaches) so as to control higher layer aspects of a service (e.g. divert an incoming call to a voice mail service, or forward it to a certain terminal, etc). Ensuring the appropriate Quality of Service (QoS) in data packet based communications has been previously considered. For example, the 3GPP Specification 3GPP TS 23.203 v1 1 .2.0 discloses a "Policy and Charging Control" (PCC) architecture, which provides solutions in a telecommunications network for (first) determining the rules governing QoS aspects of a data packet based communication between a user terminal (UE) and any other party, and (then) for the enforcement of the QoS rules. Among other functional nodes, it discloses the functionality of: the Policy and Charging Rules Function (PCRF), Policy and Charging Enforcement Function (PCEF) and Bearer Binding and Event Reporting Function (BBERF), which interact among them (through the so-called "Gx" and "Gxx" interfaces) so as to apply policy and charging rules to the data bearer(s) set up for a user terminal (UE). In short, a PCRF is a PCC rules decision node, whilst a PCEF or a BBERF are functional entities implemented in gateway nodes routing media of the related bearer(s) and enforcing said PCC rules; e.g. a GGSN or a Packet Data Network Gateway (PDN-GW, also referred herein as PGW) can implement PCEF functions.

Figure 2 of the accompanying drawings is taken from 3GPP specification TS 23.203. Figure 2 shows an overall PCC logical architecture, in the case of non-roaming UEs when SPR is used, and is derived from Figure 5.1 -1 of 3GPP TS 23.203. The reader is also referred to: Figure 5.1 -2 of 3GPP TS 23.203, which shows an overall PCC logical architecture (non-roaming) when UDR is used; Figure 5.1 -3 of 3GPP TS 23.203, which shows an overall PCC architecture (roaming with home routed access) when SPR is used; and Figure 5.1 -4 of 3GPP TS 23.203, which shows an overall PCC architecture for roaming with PCEF in a visited network (local breakout) when SPR is used. 3GPP TS 23.203 specifies the PCC functionality for Evolved 3GPP Packet Switched domain, including both 3GPP accesses and non-3GPP accesses. The AF and PCRF functional elements in Figure 2 have been marked with hatching not present in Figure 5.1 -1 of 3GPP TS 23.203, and the significance of this will be explained below.

In telecommunication systems that employ dynamic Policy and Charging Control (PCC), such as 3GPP-based systems like the EPS and 2G/3G-GPRS or non-3GPP based systems like HRPD and WiMax, the PCEF interacts with the Online Charing System (OCS) over an interface known as the Gy interface. The PCEF also interacts with the PCRF over an interface known as the Gx interface. The BBERF performs so- called bearer management in the Access Network, and carries out event reporting to the PCRF over an interface known as the Gxx interface. The BBERF interacts with the PCEF via an interface known as the S5/S8 interface that is based on the Proxy Mobile IP (PMIP) protocol.

Since the PCRF is a functional element that encompasses policy control decision and flow based charging control functionalities, it provides network control regarding the service data flow detection, gating, QoS and flow based charging (except credit management), towards the PCEF. The PCRF receives session and media related information from the AF and informs AF of traffic plane events.

The PCRF provisions PCC Rules to the PCEF via the Gx reference point and may also provision QoS Rules to the BBERF via the Gxx reference point (for deployments based on PMIP/DSMIP protocol in the core network). The PCRF informs the PCEF through the use of PCC rules on the treatment of each service data flow that is under PCC control, in accordance with the PCRF policy decision(s).

The PCEF encompasses service data flow detection (based on the filters definitions included in the PCC rules), as well as online and offline charging interactions (not described here) and policy enforcement. Since the PCEF is the one handling the bearers, it is where the QoS is enforced for the bearer according to the QoS information coming from the PCRF.

The Application Function (AF) is an element offering applications in which service is delivered in a different layer (i.e. transport layer) from the one the service has been requested (i.e. signaling layer), the control of IP bearer resources according to what has been negotiated. One example of an AF is the P-CSCF of the IMS. In this respect, TS 23.228 discloses an IP Multimedia Subsystem, IMS, and details of a P- CSCF, which is considered as an example of "Application Function" AF in TS 23.203.

The AF communicates with the PCRF to transfer dynamic session information (i.e. description of the media to be delivered in the transport layer). This communication is performed using the Rx interface. For dynamic services such as MMTel, the PCRF decides policies relating to the quality of the media to be allocated for voice, video, instant messaging, picture sharing, white board, etc., which results, for example, in the establishment of dedicated bearer(s) with guaranteed bit rate (GBR) or non guaranteed bit rate (non GBR), also about packet forwarding treatment in the Radio Access Network (RAN) by means of determining the quality of service (QoS) Class Identifier (QCI). These policies are communicated from the PCRF to one or more gateways implementing enforcing capabilities (e.g. gateways implementing PCEF or BBERF functionalities according to 3GPP PCC terminology) to be enforced therein in relationship with data flows originating and/or terminating in a given communication terminal.

The PCRF also decides at the packet core control plane if the bearer to be established and maintained has priority over other bearers for the same of different users, providing the allocation and retention priority information (ARP), which contains a level of priority (i.e. how important is the bearer compared to other bearers) and a pre-emption capability and vulnerability (i.e. if a bearer with lower priority is allowed to be torn down in favour of a bearer with higher priority).

When an Application Function (e.g. P-CSCF) detects that a user initiates/receives a request (e.g. a voice call), it may interact with the PCRF to provide service information (e.g. MMTel service) and Service Data Flows (SDFs). This leads to the installation of the SDFs and the decided QoS information (ARP/QCI) in the PCEF. The PCEF checks if an existing bearer can be used for the SDFs (that is, a bearer already exists with the same ARP/QCI value) or if a new bearer is to be established. If a new bearer is to be established, the value of the ARP reflects how important is this bearer in relation to other bearers at the packet core network (IP CAN bearers) and RAN network (Radio Access Bearer or RAB).

As a summary of the above, it can be stated that a telecommunications network can, according to the state of the art, comprise: policy control function apparatuses for determining policies for data flows relating to services between end points (such as PCRFs in a PCC compliant architecture), gateways apparatuses for enforcing said policies (such as gateways implementing PCEF or BBERF functionality in a PCC compliant architecture), and application function apparatuses mediating and processing messages related to services between terminals and which can interface with policy control servers for the sake of determining these policies (such as AFs in a PCC compliant architecture, ne example of which is a P-CSCF of the IMS).

A previously-considered end-to-end use case for the establishment of a voice call over IMS is illustrated in Figure 3 of the accompanying drawings as an example of a service established between two terminals.

In the example illustrated by Figure 3 (as well as in the example later illustrated by Figure 6):

- The AF/P-CSCF illustrated on the left is the application function associated with the terminal originating the service (initiator terminal on the left of the figure), and the AF/P- CSCF illustrated on the right is the application function being associated with the terminal terminating the service (recipient terminal on the right of the figure).

- The PCRF illustrated on the left represents a policy control server associated with the terminal on the left, which is assigned to determine at least one policy to be applied to the data flow(s) relating a service involving said terminal in a data session with the telecom network. The PCRF illustrated on the right represents similar functionality with respect to its associated terminal on the right.

- The PCEFs (PDN-GWs) represent, respectively, the gateway nodes that gets associated (e.g. by roaming procedures) with, respectively, the terminal on the left and the terminal on the right for routing their sent/received data flows, and which are respectively assigned to enforce a policy received from the -respective- PCRFs on said flows.

The nodes implementing any of these functionalities (e.g.: AF/P-CSCF, PCRF, PCEF) are usually assigned dynamically by telecommunications network. For example, document 3GPP TS 23.203 discloses in chapter 7.6 selection principles to associate a PCRF to a terminal for a data session, and document 3GPP TS.228 discloses in chapter selection principles to associate a P-CSCF (i.e. an example of AF) to a terminal for a data session. Accordingly, and for the sake of conciseness, the present description mentions associations between a terminal and the functional entities which get selected and finally associated for intervening in a service relating to said terminal. The steps illustrated in Figure 3 are summarised as follows:

Step 1 of Figure 3: User A initiates an originating service. The service is a voice call as indicated in the SDP offer (audio media with offered codecs) included by the terminal. Steps 2 to 3 of Figure 3: The request is sent to user B by the IMS and EPC network.

Steps 4 to 6 of Figure 3: User B is alerted. User A receives a ringing tone.

Steps 7 to 9 of Figure 3: User B answers to accept the service. When the call is answered the terminal indicates in the SDP answer which are the preferred codecs (from those offered by user A) to be used for the audio.

Steps 10 to 15 of Figure 3: Both P-CSCFs originating and terminating establish an AF session for the service by sending an Rx-AAR message. This AAR (AA-Request) message can include an identifier identifying the service being held by the AF (e.g. IMS voice), information about the codecs negotiated by the terminals (e.g. taken from the SDP signaling) and the flow information (to allow IP traffic and media streaming from A- >B and B->A). Steps 16 to 21 of Figure 3: Both PCRF originating and terminating determine the quality of service (QoS) and charging required based on the information received from the P-CSCF and the subscription data for related users. As a result, the Policy and Charging Control (PCC) rule(s) containing the service data flows (SDFs) allowed, the associated QoS and the charging information are sent to PCEF in a Gx-RAR message (RAR is Re-Auth-Request).

The present applicant has identified the following problem with the above-described approach. The required bearers are established in accordance with the PCC rule(s) received. If both users have the same type of subscription, there is no possibility of treating each leg of the call differently by the PCRF, that is, if user A subscribed for a certain QoS or a special charging rate only for originating services, since the PCRF is not aware of the network he belongs to (originating/terminating; i.e. the PCRF does not know whether the user initiated the service or simply received an invitation for a service, in this case, a voice call), this information is required in order to take policy decisions and select different PCC rules. Enforcing a certain QoS for a data flow (i.e. as determined by the corresponding QoS parameters, such as ARP and/or QCI) implies the involved node(s) to commit their processing and communication resources so as to fulfil with it. These resources are, however, limited by the technical capabilities of the node(s). In any case, a higher QoS assigned to a data flow will act to the detriment of another data flow(s) with a lower assigned QoS.

In view of the impact that QoS policy decisions may have with regard to the use of essential resources in a telecommunications network (e.g. the communication and processing resources of nodes that provide a plurality of user terminals with access and connectivity to a telecommunications system), the present applicant has appreciated the desirability of improving the QoS policy decision process so that it is more flexible.

Summary

Considering the importance and the effects in the network of the QoS decided by the PCRF, it is proposed herein to provide the PCRF with more information to take this decision. A particular aim is to provide more accurate service information to the PCRF so that it can be used when evaluating policies to determine, for example, the proper QoS to be applied. Specifically, it is proposed that the AF (e.g. P-CSCF) provides, in addition to the existing service information and in a clear manner, whether it is an originating service request or a terminating service request. This allows adapting QoS policies according to flexible criteria in a PCC architecture, which takes into whether the concerned (i.e. enforceable) data flow(s) was/were originated as a result of a service originated or terminated by the UE, and then deciding the corresponding QoS parameters to be applied by the policy enforcing point (e.g. PCEF) associated to said UE.

Accordingly, a method is disclosed herein for use in a telecommunications network in such a context. A first message is received at an application function. The first message relates to a service involving the establishment of a data flow between a first terminal and a second terminal. The application function is associated with the first terminal for the service. A second message is sent from the application function to a policy control function. The policy control function is associated with the first terminal for the service. The policy control function is assigned to determine at least one policy to be applied to the data flow. The second message comprises first information relating to at least one characteristic of the service that is common with respect to the first and second devices. The second message also comprises second information relating to (or specifying) (a) whether the service is an originating or terminating service with respect to the first terminal, or (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; these can be regarded as being equivalent. The second message is received at the policy control function. The second message comprises the first and second information. At least one policy is determined at the policy control function based on the first and second information received in the second message. A third message is sent from the policy control function to a gateway node. The gateway node is associated with the first terminal for the service. The gateway node is assigned to enforce at least one policy to the data flow. The third message comprises the at least one determined policy.

Operation of the application function in such a scheme is summarised as follows. A first message is received, the first message relating to a service involving the establishment of a data flow between a first terminal and a second terminal. The application function is associated with the first terminal for the service. A second message is sent to a policy control function, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow. The second message comprises first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (or specifying) (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service. Performance of these steps at the application function enables the policy control function to determine at least one policy based on the first and second information and to send the at least one determined policy to a gateway node associated with the first terminal for the service and assigned to enforce at least one policy to the data flow.

Operation of the policy control function in such a scheme is summarised as follows. A second message is received from an application function associated with a first terminal for a service involving the establishment of a data flow between the first terminal and a second terminal. The application function will have previously received a first message relating to the service; for example, a message requesting the service or a message acknowledging the service. The policy control function is associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow. The second message comprises first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (or specifying) (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service. At least one policy is determined based on the first and second information received in the second message. A third message is sent to a gateway node. The gateway node is that associated with the first terminal for the service and assigned to enforce at least one policy to the data flow. The third message comprises the at least one determined policy.

An apparatus is also disclosed herein that is configured to implement the above- described application function. The apparatus comprises means for receiving (or a receiver / unit / portion / processor / circuitry configured or adapted to receive) a first message, the first message relating to a service involving the establishment of a data flow between a first terminal and a second terminal, and the application function being associated with the first terminal for the service. The apparatus comprises means for sending (or a transmitter / unit / portion / processor / circuitry configured or adapted to send) a second message to a policy control function, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (or specifying) (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service. Operation of these means enable the policy control function to determine at least one policy based on the first and second information and to send the at least one determined policy to a gateway node associated with the first terminal for the service and assigned to enforce at least one policy to the data flow.

An apparatus is also disclosed herein that is configured to implement the above- described policy control function. The apparatus comprises means for receiving (or a receiver / unit / portion / processor / circuitry configured or adapted to receive) a second message from an application function associated with a first terminal for a service involving the establishment of a data flow between the first terminal and a second terminal, the application function having previously received a first message relating to the service, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (or specifying) (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service. The apparatus comprises means for determining (or a unit / portion / processor / circuitry configured or adapted to determine) at least one policy based on the first and second information received in the second message. The apparatus comprises means for sending (or a transmitter / unit / portion / processor / circuitry configured or adapted to send) a third message to a gateway node, the gateway node being associated with the first terminal for the service and assigned to enforce at least one policy to the data flow, the third message comprising the at least one determined policy.

The at least one characteristic may comprise an identifier of the service. The at least one characteristic may comprise a media type for the service. The at least one characteristic may comprise codec information for the service.

The second message may be sent in first and second separate parts respectively comprising the first and second information. In other words, the second message may in fact comprise two messages sent separately.

The second terminal may be associated for the service with a different application function, policy control function and gateway node to the first terminal. The application function, policy control function and gateway node associated with the first terminal may be in a first network, while the application function, policy control function and gateway node associated with the second terminal may be in a second network different to the first network. For example, where the first terminal can be considered to be the originator of the service and the second terminal the recipient of the service, the application function, policy control function and gateway node associated with the first terminal can be considered as being in the originating network, while the application function, policy control function and gateway node associated with the second terminal can be considered as being in the terminating network.

The telecommunications network may comprise a 3GPP Policy and Charging Control, PCC, architecture.

The gateway node may be configured to implement a Policy and Charging Enforcement Function, PCEF. The application function may be configured to implement an Application Function, AF. The policy control function may be configured to implement a Policy and Charging Rules Function, PCRF.

The first message may be a SIP Invite message. The second message may be a Diameter AAR message. The third message may be a Diameter RAR message. The third message may be a Diameter CCA message. The second information may be carried in an attribute-value-pair, AVP, separate from any AVP for the first information. The second information may be carried in the same AVP as the first information. The at least one policy may comprise a quality of service (QoS) policy. The at least one policy may comprise a gating policy. The at least one policy may comprise a charging policy.

Either or both of the first and second terminals may be a user terminal, such as a User Equipment or UE, or any other kind of device able to initiate or terminate a service, for example a streaming server.

There is also provided a program for controlling an apparatus to perform a method as described above in relation to the application function or policy control function, or which, when loaded into an apparatus, causes the apparatus to become an apparatus described above in relation to the application function or policy control function. The program may be carried on a carrier medium. The carrier medium may be a storage medium. The carrier medium may be a transmission medium. An apparatus programmed by such a program is also provided. A storage medium containing such a program is also provided.

An embodiment of the present invention offers a technical advantage of addressing the issue mentioned above relating to the prior art. Technical advantages are set out in more detail below.

Brief description of the drawings

Figure 1 , discussed hereinbefore, illustrates schematically the integration of an IP Multimedia Subsystem into a 3G telecommunications system;

Figure 2, also discussed hereinbefore, illustrates an overall PCC logical architecture (non-roaming), and is derived from Figure 5.1 -1 of 3GPP TS 23.203; Figure 3, also discussed hereinbefore, is a signalling or message exchange diagram illustrating a previously-considered end-to-end use case for the establishment of a voice call over IMS; Figure 4 is a schematic flowchart illustrating the steps performed in an embodiment of the present invention by an Application Function and a Policy Control Function;

Figure 5 is a schematic block diagram illustrating parts of an Application Function and a Policy Control Function embodying the present invention; and

Figure 6 is a signalling or message exchange diagram illustrating operation according to a specific embodiment of the present invention, in the context of establishment of a voice call over IMS (corresponding to Figure 3). Detailed description

An embodiment of the present invention will now be described with reference to Figures 4 and 5. Figure 4 is a schematic flowchart illustrating the steps performed by an Application Function 10 and Policy Control Function 20. Figure 5 is a schematic block diagram illustrating parts of the Application Function 10 and a Policy Control Function 20.

The proposed scheme relates to a service which involves the establishment of a data flow between a first terminal and a second terminal, and in particular relates to the determination of at least one policy which is to be applied to the data flow. The Application Function 10 is that associated with the first terminal for the service. The Policy Control Function 20 is that associated with the first terminal for the service and assigned to determine at least one policy (such as quality of service policy, a gating policy, or a charging policy) to be applied to the data flow.

The Application Function 10 comprises a Receiver R1 , a Processor P2, a Transmitter T3, and Memory M10. The Policy Control Function 20 comprises a Receiver R4, a Processor P5, a Transmitter T6, and Memory M20. In step S1 , a first message is received at the Application Function 10 by the Receiver R1 . The first message relates to a service between a first and a second terminal. For example, the first message can relate to an initial request for a service (e.g. a "SIP INVITE" message).

In step S2, the Processor P2 of the Application Function 10 determines from the content of the message first information relating to at least one characteristic of the service that is common with respect to the first and second devices. For example, the at least one characteristic may comprise one or more of an identifier of the service, a media type for the service, and codec information for the service. Step S2 may involve communicating with other nodes or devices to determine some of these characteristics (for example the media types for the service may need to be negotiated between those devices involved in the service). The first information can be considered to relate to at least one characteristic of the service that is common with respect to the first and second devices because the at least one characteristic is the same (common) for the first and second terminals; for example the identifier of the service is the same when viewed from the first device and the second device, as are the media types agreed between those two devices for the service. In particular, the at least one characteristic does not depend on whether the service is an originating or terminating service with respect to the first terminal, or whether the first terminal can be considered as an initiator of the service or a recipient of the service; these can be regarded as being equivalent.

In step S2, the Processor P2 also determines second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or, in other words, (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; these can be regarded as being equivalent. The second information can be considered not to relate to a characteristic of the service that is common with respect to the first and second devices, because it relates to a characteristic of the service that is different for the first and second terminals: from the point of view of one of the terminals the service is an originating service (characteristic: "originating" or "initiator"), while for the other of the terminals it is a terminating service (characteristic: "terminating" or "recipient"). It may be determined, for example, from the message (e.g. the message referred as "first message" in Figure 4) received at the Application Function 10 whether the first terminal, with which the Application Function 10 is associated for the service, is an initiator of the service or a recipient of the service. For example, in case of a MMTel/IMS service, the AF (a P- CSCF in such a case) determines that the terminal sending a "SIP INVITE" message is to be considered the initiator of the service, and that the terminal to which the "SIP INVITE" is addressed is the recipient of the service. Similarly, a P-CSCF (i.e. as an example of AF in case of a MMTel/IMS service) will determine that the terminal sending a corresponding "SIP 200 OK" message is the terminator of the service, whilst the terminal to which said message is addressed is the originator of the service. In step S3, a second message is sent by the Transmitter T3 from the Application Function 10 to the Policy Control Function 20. The second message comprises the first information and the second information determined in step S2. In step S4, the second message, comprising the first and second information, is received at the Policy Control Function 20 by the Receiver R4. It will be appreciated that the first and second information could in another embodiment be sent in separate messages.

In step S5, the Processor P5 of the Policy Control Function 20 determines at least one policy based on the first and second information received in the second message. In step S6, the transmitter T6 sends a third message from the Policy Control Function 20 to a gateway node. The third message comprises the at least one determined policy. The gateway node is associated with the first terminal for the service. The gateway node is assigned to enforce at least one policy to the data flow. On receipt of the third message, with the at least one determined policy, the gateway node is able to enforce the at least one policy to the data flow.

It will be appreciated that operation of one or more of the above-described components could be controlled or provided at least in part by a program operating on the device or apparatus. Such a program could, for example, be stored in Memory M10 of the Application Function 10, and accessed by the Processor P2. The Processor P2 could operate to control the Receiver R1 and Transmitter T3. Likewise, such a program could, for example, be stored in Memory M20 of the Policy Control Function M20, and accessed by the Processor P5. The Processor P5 could operate to control the Receiver R4 and Transmitter T6. The function of several depicted components may in fact be performed by a single component. A single processor or processing unit may be arranged to perform the function of multiple components. Such an operating program can be stored on a computer-readable medium, or could, for example, be embodied in a signal such as a downloadable data signal provided from an Internet website. The appended claims are to be interpreted as covering an operating program by itself, or as a record on a carrier, or as a signal, or in any other form.

Relating an embodiment of the present invention more specifically with the PCC architecture described briefly above and as disclosed in more detail in 3GPP TS 23.203, in such a context an embodiment of the present invention may comprise: (1 ) modifying the "Rx" interface (i.e. the interface between the AF and the PCRF) in respect to novel contents of the messages sent from an Application Function (AF), such as a Proxy Call Session Control Function (P-CSCF), to a PCRF in relationship to data flows concerning an application service where the UE is involved; (2) the PCRF deciding QoS policies for these flows based on the novel information received from the AF; and

(3) transmitting these decided QoS policies from the PCRF to the PCEF for enforcement.

Referring again to Figure 2, the AF and PCRF nodes have been marked with hatching to signify that they are the nodes that would be affected by implementation of an embodiment of the present invention. In particular, an embodiment is envisaged in which an AF (i.e. the AF associated to a UE for a service) specifies in a message sent to a PCRF (i.e. the PCRF assigned to decide QoS policies for said UE in respect to said service) new kind of information indicating in an explicit manner whether the flow or flows concerned by that message relates to an originating or terminating service with respect to the UE. The PCRF decides one or more QoS parameters determining a QoS policy for the service data flows according to the originating/terminating information received from the AF, and sends a message to the PCEF that is associated to the UE for enforcing QoS policies for data flows relating to the UE, which message comprises the decided QoS parameters, so that the corresponding QoS policy is subsequently enforced with respect to data flows relating to the UE and the service according to the QoS parameters received from the PCRF.

As with the previously-considered scheme, the PCRF at reception of a message (e.g. a Diameter AAR message) sent from an AF is usually provided with the following kind of information:

1 ) An identifier (e.g. an AF-Application Identifier AVP) that identifies the service being held by the AF and for which the message is sent to the PCRF. For example, in the case of MMTel service it is fetched from the SIP header P-Asserted-Service (3gpp.icsi.mmtel) included in the SIP request, which indicates IMS Multimedia Telephony Communication Service.

2) Information about the media type (e.g. audio, video, message, data, etc)

3) Information about data flow(s) which is available to the AF (e.g. extracted by the AF from the SDP signaling between terminals), which usually comprise details about codecs. The above information corresponds to the first information described above with reference to Figures 4 and 5. It has also been previously considered to include information in the message sent from the AF to the PCRF about the direction of a flow (e.g. "uplink" or "downlink" with respect to a terminal). For example, the "codec-data" AVP (which is an AVP that can be included within an optional "Media-Component- Description" AVP conveyed in a Diameter AAR message with respect to a flow) can specify, with respect to a codec negotiated via SPD protocol by a terminal for a flow (either, as an "offer", or as an "answer" to an "offer"), whether it is "uplink" or "downlink"; wherein "uplink" indicates that the SDP message conveying information of said codec was received by the AF from the terminal and sent to the network (i.e. towards the counterpart terminal), and wherein "downlink" indicates that the SDP message conveying information of said codec was received by the AF from the network (i.e. as received from the counterpart terminal) and sent to the terminal.

However, from the flow direction information that can be inferred from the content of a AAR message it cannot be ascertained whether the service is to be considered as initiated or as terminated by the related terminal. Firstly, a terminal initiating a MMTel/IMS service is not forced to include an SDP offer (and, thus can wait for the terminating terminal to send the SDP offer); which disassociates the meaning of "uplink" or "downlink" for the codec/s of a data flow from, respectively, initiating or terminating the service. Secondly, for services other than MMTel/IMS, the AF may not include flow information at all, since it is not required to do so. In summary: information about a flow originating from (or terminated by) a terminal in relationship to a service (i.e. if the flow is "uplink" or "downlink" with respect to the terminal) is not always received; but, even if received, this information does not necessarily imply that the terminal was the one initiating (or terminating) the service to which the flow relates.

An embodiment of the present invention proposes to enhance the information sent from the AF to the PCRF, including an explicit indication of whether the request is received in the originating or in the terminating network, that is, whether the user is the initiator or the recipient of the service. This indication corresponds to the second information described above with reference to Figures 4 and 5. An embodiment of the present invention proposes to pass this information to the PCRF with a new parameter/indicator or extending the range of values of an existing parameter. The PCRF may use this information to take the policy decisions, for example, to determine the proper rules or QoS.

Upon reception of the information about the network in which the user is located, the PCRF would check whether the policies to be applied are different depending on whether this is an originating or terminating request.

Figure 6 is a signalling or message exchange diagram illustrating operation according to an embodiment of the present invention in the context of the PCC architecture. Since Figure 6 corresponds generally to Figure 3 discussed hereinbefore, a detailed discussion of the steps shown is not required; instead, emphasis is placed herein on any differences between Figures 6 and 3.

An Originating Network N-A comprises a Terminal 40-A, a PCEF 30-A, PCRF 20-A and AF 10-A. A Terminating Network N-B comprises a Terminal 40-B, a PCEF 30-B, PCRF 20-B and AF 10-B. The correspondence between components of Figure 6 and components or Figures 4 and 5 is clearly indicated in Figure 6; this shows more clearly how the specific application to PCC relates to the more general procedures described above with reference to Figures 4 and 5.

In particular, it should be noted that the technique illustrated in Figures 4 and 5 applies separately to the corresponding nodes in both the Originating Network N-A and the Terminating Network N-B. In the case of considering the correspondence between the Originating Network N-A and Figures 4 and 5, the first terminal as described with reference to Figures 4 and 5 corresponds to the Terminal 40-A, with the second terminal corresponding to the Terminal 40-B. The Application Function 10 as described with reference to Figures 4 and 5 corresponds to the AF (P-CSCF) 10-A. The Policy Control Function 20 as described with reference to Figures 4 and 5 corresponds to the PCRF 20-A. The gateway node as described with reference to Figures 4 and 5 corresponds to the PCEF 30-A.

Similarly, in the case of considering the correspondence between the Terminating Network N-B and Figures 4 and 5, the first terminal as described with reference to Figures 4 and 5 corresponds to the Terminal 40-B, with the second terminal corresponding to the Terminal 40-A. The Application Function 10 as described with reference to Figures 4 and 5 corresponds to the AF (P-CSCF) 10-B. The Policy Control Function 20 as described with reference to Figures 4 and 5 corresponds to the PCRF 20-B. The gateway node as described with reference to Figures 4 and 5 corresponds to the PCEF 30-B.

As shown in Figure 6, both P-CSCFs 10 originating and terminating establish an AF session for the service by sending an Rx-AAR message, but in addition to the current information conveyed (first information), the P-CSCF 10 includes the direction of the request, that is, User A initiates the service and User B receives the service, so that the PCRF 20 can use this indication (second information) in the policy and charging evaluation (e.g. user is not charged when receiving a call, accumulators for IP traffic are only incremented when the service is initiated, a different quality of service is applied if a voice call is received when roaming, etc.). Different ways can be envisaged for conveying the new information in a message sent from the AF 10 to the PCRF 20 through the so called "Rx" interface (i.e. AF-PCRF) for indicating whether the content of the message concerns to an "originating" or to a "terminating" service (i.e. messages 17 or 10 in Figure 6).

In this respect, two such alternatives are proposed herein, both based on the use of the Diameter protocol (IETF RFC 3588) as disclosed by 3GPP TS 29.214 v1 1 .1 .0, wherein the content of the message named "AAR", as disclosed by chapter 5.6.1 in 3GPP TS 29.214, is modified.

The first alternative comprises including a new attribute-value-pair (AVP) in the AAR message for conveying explicitly a value for the new information (i.e. a new AVP whose contents establish whether the content of the AAR message concerns to an "originating" or to a "terminating" service).

The second alternative comprises including in the AAR message the new kind of information added to, or embedded within, the already existing AVP named "Service- Info-Status"; either: as a new value or as a sub-structured value (e.g.: "FINAL SERVICE INFORMATION-Originating/ or/Terminating", or "PRELIMINARY SERVICE INFORM ATION-/Originating/o\ /Terminating"), so that whether the AAR message concerns to an "originating" or to a "terminating" service is expressed independently on if said message relates to a "final -or- preliminary service information". The QoS parameters, which are decided by the PCRF and which are transmitted therefrom to the PCEF (i.e. messages 13 or 20 in Figure 6) via the so called "Gx" interface (i.e. PCRF-PCEF), can be conveyed in a Diameter protocol message "RAR" as disclosed by 3GPP TS 29.212 V1 1 .1 .0 (e.g. see chapter 5.6.4 in said 3GPP document) and, more preferably in the already existing AVP named "QoS-lnformation".

Preferably, the QoS parameters which are decided by the PCRF and which transmitted to the PCEF (e.g. message 13 or 20 in Figure 6) comprise at least one of: "Allocation and Retention Priority" (ARP) parameter, and "QoS Class Identifier" (QCI) parameter. However, it is to be noted that nothing need be changed in the standardized (and well known) content of the messages exchanged between the PCRF and the PCEF (e.g. 13 or 20 in Figure 6). The contribution of an embodiment of the present invention is that the decision made by a PCEF on the contents of such a kind of messages (13 or 20) is based also on the content of the messages received from the AF (e.g. messages 17 or 10 in Figure 6) with regard to whether a message (i.e. message 17 or 10) relates to an "originating" or to a "terminating" service.

In the diagram of Figure 6, the RAR message (message 20 or 13) corresponds to the third message of Figures 4 and 5. In another embodiment, a request message (e.g. a CCR message) is received by the PCRF 20 from the PCEF 30 (e.g. in cases where the bearer establishing mode is initiated by the UE), and the reply to that request from the gateway (e.g. a CCA message) could also then count as the third message of Figures 4 and 5. This (non illustrated) embodiment can take place in a terminal-initiated bearer. Two examples use cases will now be described where an enhancement proposed according to an embodiment of the present invention applies.

The first example use case relates to notification of an incoming call in a low coverage area. For some services, some operators may be interested in applying a different QoS at the originating and terminating side. For example, when the AF for MMTel (P- CSCF) receives a voice call destined to a user, the network does not know at this stage whether or not the user is reachable, which means that the network does not know yet whether or not UE paging is going to succeed. An operator may be interested in offering special paging (e.g. a "powerful" paging) to those users willing to be notified about an incoming call even if they are in a low coverage area (e.g. inside of a building, in a parking lot), so that they can step outside to recover coverage and take the incoming call. However, these users are treated as normal when they initiate calls.

The operator wants the terminating network to perform a "powerful" paging only for those users paying for this terminating service.

Applied to PCRF, it means that for all calling users, when the destination has not been reached yet (service information is preliminary), a dedicated bearer for voice media is required (QCI=1 ) and the priority is subject operator's policy (e.g. ARP=3). On the other hand, for all called users, when the destination has not been reached yet (same condition required) a dedicated bearer for media is also required (QCI=1 ) but only if the called user is subscribed to the service (notification of incoming call when in low coverage areas) the priority is determined by the subscribed service (ARP=1 -> highest priority, instead of ARP=3) so that the Packet Core and RAN are able to translate this ARP value to the "powerful" paging.

The second example use case relates to wake-up services, where a user can activate a service on demand (via Ut interface used for MMTel) so that at a given time the user receives information considered of importance (e.g. wake up video call from a streaming server), or instant messages which are required not to be delayed or lost even if the network is congested. These users, however, do not require (and they are not charged) for this (high) priority when making calls at those periods of time.

An embodiment of the present invention provides at least one of the following advantages:

• It allows a more flexible policy evaluation since the operator can offer a different quality of service, charging, etc. for originating and/or terminating services. · It prevents an incorrect QoS handling in the network by assigning an incorrect prioritization of bearers in detriment of other bearers that can require high priority.

• It prevents giving privileges to users that do not correspond to their subscription

• It allows notifying originating users (via e-mail, SMS or a redirected web page) about required operator information without disturbing or providing incorrect information to terminating users. It will be appreciated by the person of skill in the art that various modifications may be made to the above-described embodiments without departing from the scope of the present invention as defined by the appended claims. For example, although the specific embodiment of Figure 6 is described in the context of a 3GPP PCC architecture, an embodiment of the present invention is also applicable to like policy control architectures in like networks, with nodes or functions corresponding to the AF, PCRF and PCEF which are applicable to the 3GPP PCC architecture.

Claims

1 . A method for use in a telecommunications network, comprising:

receiving a first message at an application function, the first message relating to a service involving the establishment of a data flow between a first terminal and a second terminal, and the application function being associated with the first terminal for the service;

sending a second message from the application function to a policy control function, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; receiving the second message at the policy control function, the second message comprising the first and second information;

determining at least one policy at the policy control function based on the first and second information received in the second message; and

sending a third message from the policy control function to a gateway node, the gateway node being associated with the first terminal for the service and assigned to enforce at least one policy to the data flow, the third message comprising the at least one determined policy.

2. A method for use by an application function in a telecommunications network, comprising:

receiving a first message, the first message relating to a service involving the establishment of a data flow between a first terminal and a second terminal, and the application function being associated with the first terminal for the service; and

sending a second message to a policy control function, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; thereby to enable the policy control function to determine at least one policy based on the first and second information and to send the at least one determined policy to a gateway node associated with the first terminal for the service and assigned to enforce at least one policy to the data flow.

3. A method for use by a policy control function in a telecommunications network, comprising:

receiving a second message from an application function associated with a first terminal for a service involving the establishment of a data flow between the first terminal and a second terminal, the application function having previously received a first message relating to the service, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service;

determining at least one policy based on the first and second information received in the second message; and

sending a third message to a gateway node, the gateway node being associated with the first terminal for the service and assigned to enforce at least one policy to the data flow, the third message comprising the at least one determined policy.

4. An apparatus configured to implement an application function in a

telecommunications network, the apparatus comprising:

means for receiving a first message, the first message relating to a service involving the establishment of a data flow between a first terminal and a second terminal, and the application function being associated with the first terminal for the service;

means for sending a second message to a policy control function, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service; thereby to enable the policy control function to determine at least one policy based on the first and second information and to send the at least one determined policy to a gateway node associated with the first terminal for the service and assigned to enforce at least one policy to the data flow.

5. An apparatus configured to implement a policy control function in a

telecommunications network, the apparatus comprising:

means for receiving a second message from an application function associated with a first terminal for a service involving the establishment of a data flow between the first terminal and a second terminal, the application function having previously received a first message relating to the service, the policy control function being associated with the first terminal for the service and assigned to determine at least one policy to be applied to the data flow, and the second message comprising first information relating to at least one characteristic of the service that is common with respect to the first and second devices, and second information relating to (a) whether the service is an originating or terminating service with respect to the first terminal, or equivalently (b) whether the first terminal is to be considered as an initiator of the service or a recipient of the service;

means for determining at least one policy based on the first and second information received in the second message; and

means for sending a third message to a gateway node, the gateway node being associated with the first terminal for the service and assigned to enforce at least one policy to the data flow, the third message comprising the at least one determined policy.

6. A method or apparatus as claimed in any preceding claim, wherein the at least one characteristic comprises at least one of an identifier of the service, a media type for the service, and codec information for the service.

7. A method or apparatus as claimed in any preceding claim, wherein the second message is sent in first and second separate parts respectively comprising the first and second information.

8. A method or apparatus as claimed in any preceding claim, wherein the second terminal is associated for the service with a different application function, policy control function and gateway node to the first terminal.

9. A method or apparatus as claimed in any preceding claim, wherein the telecommunications network comprises a 3GPP Policy and Charging Control, PCC, architecture.

10. A method or apparatus as claimed in claim 9, wherein: the gateway node is configured to implement a Policy and Charging Enforcement Function, PCEF; and/or the application function is configured to implement an Application Function, AF; and/or the policy control function is configured to implement a Policy and Charging Rules Function, PCRF.

1 1 . A method or apparatus as claimed in any preceding claim, wherein: the first message is a SIP Invite message; and/or the second message is a Diameter AAR message; and/or the third message is either a Diameter RAR message or a Diameter CCA message.

12. A method or apparatus as claimed in any preceding claim, wherein the second information is carried in an attribute-value-pair, AVP, separate from any AVP for the first information; or wherein the second information is carried in the same AVP as the first information.

13. A method or apparatus as claimed in any preceding claim, wherein the at least one policy comprises at least one of: a quality of service policy; a gating policy; and a charging policy.

14. A program for controlling an apparatus to perform a method as claimed in any one of claims 1 , 2, 3, and 6 to 13, optionally being carried on a carrier medium such as a storage medium or a transmission medium.

15. A storage medium containing a program as claimed in claim 14.