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Content for  TS 29.154  Word version:  16.0.0

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1  ScopeWord‑p. 6
This document defines the protocol for Nt reference point. The Nt reference point includes Nt application and Nta application.
The functional requirements and the stage 2 specifications of the Nt application are contained in TS 23.203. The Nt application of Nt reference point lies between Service Capability Exposure Function (SCEF) and Policy and Charging Rules Function (PCRF), it supports the negotiation of background data transfer policy and is documented in the main body of this document.
The functional requirements and the stage 2 specifications of the Nta application are contained in subclause 5.6.4.1a of TS 23.682. The Nta application of Nt reference point lies between SCEF and PCRF, it supports the event monitoring configuration for a group of UEs and the corresponding event reporting. The Nta application is documented in Annex A.
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2  References

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 23.203: "Policy and charging control architecture".
[3]
RFC 3588:  "Diameter Base Protocol".
[4]
RFC 4006:  "Diameter Credit Control Application".
[5]
TS 29.214: "Policy and Charging Control over Rx reference point".
[6]
TS 29.274: "3GPP Evolved Packet System. Evolved GPRS Tunnelling Protocol for EPS (GTPv2)".
[7]
RFC 5719:  "Updated IANA Considerations for Diameter Command Code Allocations ".
[8]
RFC 2234:  "Augmented BNF for syntax specifications ".
[9]
TS 29.213: "Policy and charging control signalling flows and Quality of Service (QoS) parameter mapping".
[10]
RFC 7683:  "Diameter Overload Indication Conveyance".
[11]
TS 29.229: "Cx and Dx interfaces based on Diameter protocol; Protocol details".
[12]
RFC 7944:  "Diameter Routing Message Priority".
[13]
TS 29.215: "Policy and Charging Control (PCC) over S9 reference point; Stage 3".
[14]
RFC 8583:  "Diameter Load Information Conveyance".
[15]
RFC 6733:  "Diameter Base Protocol".
[16]
TS 29.329: "Sh Interface based on the Diameter protocol".
[17]
TS 29.336: "Home Subscriber Server (HSS) diameter interfaces for interworking with packet data networks and applications".
[18]
TS 29.061: "Interworking between the Public Land Mobile Network (PLMN) supporting packet based services and Packet Data Networks (PDN)".
[19]
TS 29.212: "Policy and Charging Control (PCC); Reference points".
[20]
TS 23.682: "Architecture enhancements to facilitate communications with packet data networks and applications".
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3  Definitions and abbreviationsWord‑p. 7

3.1  Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

3.2  Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
ASP
Application Service Provider
BBERF
Bearer Binding and Event Reporting Function
BTA
Background Data Transfer Answer
BTR
Background Data Transfer Request
ECA
Event Configuration Answer
ECR
Event Configuration Request
ERA
Event Reporting Answer
ERR
Event Reporting Request
DRA
Diameter Routing Agent
DRMP
Diameter Routing Message Priority
PCEF
Policy and Charging Enforcement Function
PCRF
Policy and Charging Rules Function
SCEF
Service Capability Exposure Function
SPR
Subscription Profile Repository
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4  Nt application

4.1  Overview

The Nt application of Nt reference point is located between the PCRF and the SCEF. It is used for reporting the transfer policies from the PCRF to the SCEF.
The stage 2 requirements for Nt application are defined in TS 23.203.
Refer to Annex G of TS 29.213 for Diameter overload control procedures for the Nt application.
Refer to Annex J of TS 29.213 for Diameter message priority mechanism procedures for the Nt application.
Refer to Annex K of TS 29.213 for Diameter load control procedures for the Nt application.
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4.2  Nt Reference ModelWord‑p. 8
The Nt application of Nt reference point resides between the SCEF and PCRF. The relationship between the two functional entities is depicted in Figure 4.2-1. The overall PCC architecture is depicted in subclause 3a of TS 29.213.
Reproduction of 3GPP TS 29.154, Figure 4.2-1: Reference model for Nt application of Nt interface
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4.3  Functional elements

4.3.1  PCRF

The PCRF is a functional element that encompasses policy control decision and flow based charging control functionalities.
The PCRF uses the information received from SCEF and other available information to determine one or more transfer policies for background data to the application service provider. The PCRF provides the selected transfer policies with a reference ID to the SPR for storage.

4.3.2  SCEF

The SCEF is a functional element which provides a means to securely expose the services and capabilities provided by 3GPP network interfaces.
The SCEF is triggered by an SCS/AS which requests for the negotiation with the PCRF for providing necessary policy to transfer background data.

4.4  Procedures over the Nt reference point

4.4.1  Negotiation for future background data transfer

Based on the SCS/AS request, the SCEF shall send the Background-Data-Transfer-Request (BTR) command to the PCRF including the Transfer-Request-Type AVP with the value TRANSFER_POLICY_REQUEST(0), it shall also include the ASP identifier within the Application-Service-Provider-Identity AVP, volume of data per UE within the CC-Output-Octets AVP for downlink volume and/or the CC-Input-Octets AVP for uplink volume, or the CC-Total-Octets AVP for total volume regardless direction, expected number of UEs within the Number-Of-UEs AVP and desired time window within the Time-Window AVP.
The Time-Window AVP shall include desired start time within the Transfer-Start-Time AVP and desired end time within the Transfer-End-Time AVP.
The SCEF may also provide network area information within Network-Area-Info-List AVP.
Once the PCRF receives the BTR command, the PCRF shall retrieve all existing transfer policies stored for any ASP from the SPR.
When all existing transfer policies are retrieved, the PCRF shall determine one or more transfer policies based on the information received from the SCEF and other available information (e.g. network policy, congestion level (if available), load status estimation for the required time window and network area, existing transfer policies) and respond with a Background-Data-Transfer-Answer (BTA) command including the possible transfer policies within Transfer-Policy AVP (s) and a reference ID within Reference-Id AVP.
The Transfer-Policy AVP(s) shall include the Transfer-Policy-Id AVP, the Time-Window AVP, the Rating-Group AVP, and may also include an Max-Requested-Bandwidth-DL AVP and/or an Max-Requested-Bandwidth-UL AVP.
If more than one transfer policies are included in the BTA command, the PCRF shall also include the PCRF Id within the PCRF-Address AVP in the BTA command.
If there is more than one Transfer-Policy AVP included in the BTA command, the PCRF waits for the transfer policy selected by the SCS/AS before communicating with the SPR.
If there is more than one transfer policy provided from the PCRF to the SCEF in the BTA command, when the SCEF receives the selected transfer policy from the SCS/AS, the SCEF shall send Background-Data-Transfer-Request (BTR) command to the PCRF including the Transfer-Request-Type AVP set to the value TRANSFER_POLICY_NOTIFICATION (1). The SCEF shall also include the reference ID in the Reference-Id AVP, the identity of the selected transfer policy within the Transfer-Policy-Id AVP and the destination PCRF Id within the Destination-Host AVP.
If there is more than the one transfer policy included, the SCEF forwards these transfer policies to the SCS/AS and waits for the answer including the identity of the transfer policy selected by the SCS/AS.
The PCRF shall acknowledge the BTR command by sending Background-Data-Transfer-Answer (BTA) command.
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4.5  PCRF selectionWord‑p. 9
The SCEF or DRA (if deployed) may select a PCRF in the HPLMN based on operator policy (e.g. pre-configured PCRF identities or routing strategy, etc).


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