E.6 PCRF Addressing

29.2133GPPPolicy and charging control signalling flows and Quality of Service (QoS) parameter mappingRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

E.6.1 General

PCRF discovery at the DRA shall be done according to clause 7.1 with the additions described in this clause.

For EPC-routed scenario, the DRA keeps status of the assigned PCRF for a certain UE for the applicable reference points, i.e. Gx, Gxx, Rx, Sd (Unsolicited application reporting), S9a and S9 (for roaming cases).

For NSWO scenario, the DRA keeps status of the assigned PCRF for a certain UE for the applicable references points, i.e. Rx, Sd (Unsolicited application reporting) and S9a.The H-DRA keeps status of the assigned H-PCRF for a certain UE for Rx and S9 reference points. The V-DRA keeps the status of the assigned V-PCRF for a certain UE for the S9a and Sd (Unsolicited application reporting) reference points.

The BPCF, as a Diameter client of the DRA, shall support all procedures required to properly interoperate with the DRA in both the proxy and redirect modes.

E.6.2 DRA Definition

For the EPC-routed scenario, DRA is defined as specified in clause 7.2 with the additions described in this clause.

The DRA is a functional element that ensures that all Diameter sessions established over the Gx, S9, Gxx, Rx, S9a and for unsolicited application reporting, the Sd reference points for a certain IP-CAN session reach the same PCRF when multiple and separately addressable PCRFs have been deployed in a Diameter realm.

For the NSWO scenario, the DRA shall ensure that all Diameter sessions established over the Rx, S9a and for unsolicited application reporting, the Sd reference points for a certain UE reach the same PCRF. The H-DRA shall ensure that all Diameter sessions established over Rx and S9 reference points for a certain UE reach the same PCRF. The V-DRA shall ensure that all Diameter sessions established over S9a and for unsolicited application reporting, the Sd reference points for a certain UE reach the same V-PCRF.

E.6.3 DRA Procedure

E.6.3.1 DRA Information Storage

For EPC-routed traffic, DRA Information Storage shall be done according to clause 7.3.1 with the additions described in this subclause. The V-PCRF routing information (i.e. DRA binding) in the V-DRA is created when the S9 session establishment trigger is received.

The V-PCRF routing information stored in the V-DRA shall be removed when the S9 session termination notification is received.

The DRA has information about the user identity (UE NAI), the UE Local IP address/H(e)NB Local IP address, the PDN Id (if available) and the selected PCRF identity for a certain IP-CAN Session or a certain user.

For NSWO traffic, the DRA Information Storage shall be done as specified below:

– The DRA shall maintain PCRF routing information per UE-NAI and APN.

– The DRA has information about the user identity (UE NAI), the local UE Ipv4 address and/or the local UE Ipv6 address/prefix, the APN (i.e. NSWO_APN) and the selected PCRF identity for a certain UE.

– The PCRF routing information stored for an S9a* session in the DRA shall be removed after the S9a* session is terminated.

When both EPC-routed and NSWO traffic exist, the DRA Information Storage shall be done as specified below:

– The DRA shall maintain PCRF routing information per UE-NAI or per UE-NAI and APN.

– The DRA has information received for both EPC-Routed and NSWO scenarios and the selected PCRF identity per UE-NAI or per UE-NAI and APN.

– The PCRF routing information stored per UE in the DRA shall be removed when no more S9a sessions and S9a* sessions are active for the UE.

E.6.3.2 Capabilities Exchange

For EPC-routed traffic, capabilities exchange shall be done according to clause 7.3.2.

For NSWO traffic, the Redirect DRA and Proxy DRA shall advertise the support of S9a*, Rx and Sd (for unsolicited application reporting) applications according to clause 7.3.3.

E.6.3.3 Redirect DRA

Redirect DRA is specified in clause 7.3.4 with the additions described in this subclause.

For EPC-routed traffic, for case 1 (home routed case), the V-DRA shall behave as follows:

– If the request is an S9 session establishment trigger from the H-PCRF, it shall select a V-PCRF to handle the S9 session for that UE. It shall then send the redirect message including selected V-PCRF to the H-PCRF.

– If the request is an S9 session termination notification from H-PCRF, the V-DRA shall remove the PCRF routing information (i.e. DRA binding). If the V-DRA does not have a V-PCRF already selected, it shall reject the request.

The S9 session establishment trigger and the S9 session termination notification request shall have the same information of user identity (UE NAI), the UE Local IP address/H(e)NB Local IP address, the PDN Id(if available). The DRA shall remove the DRA binding based on the above information when the DRA receives the S9 session termination notification (i.e. a TER command including DRA- Binding AVP set to the value DRA_BINDING_DELETION).

For NSWO traffic, the DRA is maintaining PCRF routing information per UE-NAI and APN. The DRA shall be aware of the S9a* Diameter termination request as defined in 3GPP TS 29.215 [22] in order to release the DRA binding information.

E.6.3.4 Proxy DRA

Proxy DRA is specified in clause 7.3.5 with the additions described in this subclause.

For EPC-routed traffic for case 1 (home routed case), when the V-DRA receives a message from the H-PCRF, it shall behave as follows:

– If the message is an S9 session establishment trigger from the H-PCRF, it shall select a V-PCRF to handle the S9 session for that UE. It shall then proxy the request to the selected V-PCRF. The V-DRA indicates that there is a V-DRA deployed in the visited PLMN by including the DRA-Deployment AVP in TEA command.

– If the message is an S9 session termination notification from the H-PCRF, the V-DRA shall remove the PCRF routing information (i.e. DRA binding). If the V-DRA does not have a V-PCRF already selected, it shall reject the request.

The S9 session establishment trigger and the S9 session termination notification shall have the same information of user identity (UE NAI), the UE Local IP address/H(e)NB Local IP address and the PDN Id (if available). The DRA shall remove the DRA binding based on the above information when the DRA receives the S9 session termination notification (i.e. a TER command including DRA-Binding AVP set to the value DRA_BINDING_DELETION).

Proxy DRA is specified in clause 7.3.5 with the additions described in this subclause.

For NSWO traffic in both non-roaming and roaming cases, when the (V-) DRA receives an S9a* request from the BPCF, it shall behave as follows:

– If the request is an S9a* session establishment, it shall select a V-PCRF to handle the S9 session for that UE and APN. It shall then proxy the request to the selected V-PCRF.

– If the request is an S9a* session termination, the (V-) DRA shall remove the PCRF routing information and proxy the request to the (V-) PCRF. If the (V-) DRA does not have a (V-) PCRF already selected, it shall reject the request.

– If the request is an S9a* session modification, the (V-) DRA shall proxy the request.

The BPCF shall be capable of sending every message of a session to the DRA. The BPCF may be configured to bypass the (V-) DRA on S9a* session modification messages by sending these types of messages directly to the (V-) PCRF.

E.6.3.5 PCRF selection by BPCF

For EPC-routed traffic, when the S9a Session Establishment request is triggered by the (V-) PCRF, the BPCF may use the (V-) PCRF identity provided within the PCRF-Address AVP in the S9a Session Establishment Trigger.

The BPCF may also use the DRA procedures as described in clause 7.3. In order to do so, the BPCF shall provide the DRA of the PCRF realm with identity parameters during the S9a Session Establishment procedure. The identity parameters from the BPCF may comprise the UE Local Ipv4 or UE local Ipv6 address in the UE-Local-IP-Address AVP (WLAN scenario), H(e)NB Local IP address in the HeNB-Local-IP-Address AVP (H(e)NB scenario), PDN information in the Called-Station-Id AVP if available and user identity in the Subscription-Id AVP. The BPCF obtains these data from the S9a Session Establishment Trigger procedure initiated by the (V-) PCRF.

For NSWO traffic, the BPCF finds the PCRF using the DRA procedures as described in clause 7.3. In order to do so, the BPCF shall provide the DRA of the PCRF realm with identity parameters during the S9a* Session Establishment procedure. The identity parameters from the BPCF shall comprise the UE local Ipv4 adress or UE local Ipv6 prefix/address in the UE-Local-IP-Address AVP or UE-Local-IP-Prefix AVP, the APN in the Called-Station-Id AVP and user identity in the Subscription-Id AVP.

For both EPC-routed traffic and NSWO traffic, if the redirect agent is used for DRA, the DRA shall use the redirecting requests procedure as specified in IETF RFC 6733 [61], and include the PCRF identity in the Redirect-Host AVP in the Diameter reply sent to the BPCF .

If proxy agent is used for DRA, the DRA should use the proxy procedure as specified in IETF RFC 6733 [61]. For PA2 solution (described in clause 7.1) only S9a/S9a* session establishment and S9a/S9a* session termination messages shall be sent through the DRA.

For NSWO traffic in a roaming scenario the selected V-PCRF shall belong to the same VPLMN selected during the 3GPP –based authentication procedure. The BPCF uses the VPLMN-Id to find the V-DRA in the VPLMN. The V-PCRF finds the DRA in the HPLMN according to clause 7.3.8.

NOTE: The BPCF will use the VPLMN-Id to obtain the Destination-Realm AVP used to find the V-DRA and then to find the V-PCRF using Diameter based procedures as described in IETF RFC 6733 [61].

E.6.3.6 PCRF selection by AF and TDF in Unsolicited application reporting mode for NSWO traffic

PCRF selection by the AF shall be done according to clause 7.3.7.

PCRF selection by the TDF shall be done according to clause 7.3.9.

NOTE: The DRA matches the received UE IP address received in either the Framed-IP-Address AVP or the Framed-Ipv6-Prefix AVP in the Rx and Sd reference point with the UE Local IP Address received in UE-Local-IP-Address AVP or UE Local Ipv6 Prefix in the UE-Local-IP-Prefix AVP in the S9a reference point in order to select the same PCRF.

E.6.3.7 PCRF selection in a roaming scenario

For both EPC-routed traffic and NSWO traffic, the V-PCRF uses the DRA procedures as described in clause 7.3.8 to address the H-PCRF. In order to do so, the V-PCRF shall provide the DRA of the H-PCRF realm with identity parameters during the S9 Session Establishment procedure.

For EPC-routed traffic, the identity parameters from the V-PCRF may comprise the UE Local Ipv4 or UE local Ipv6 address in the UE-Local-IP-Address AVP (WLAN scenario), H(e)NB Local IP address in the HeNB-Local-IP-Address AVP (H(e)NB scenario), PDN information in the Called-Station-Id AVP if available and user identity in the Subscription-Id AVP obtained from the S9 Session Establishment Trigger procedure initiated by the H-PCRF.

For NSWO traffic, the identity parameters from the V-PCRF may comprise the UE Local Ipv4 or Ipv6 address in the UE-Local-IP-Address AVP or UE local Ipv6 prefix in the UE-Local-IP-Prefix AVP, PDN information in the Called-Station-Id AVP and user identity in the Subscription-Id AVP obtained from the S9a* Session Establishment procedure.

E.6.3.8 PCRF selection for the HNB CS Service

When the DRA receives a request for a certain S15 Session establishment from the HNB GW, the DRA selects a suitable PCRF for the S15 Session based on the HNB local IP address within the HeNB-Local-IP-Address AVP. When the S15 Session is terminated, the DRA shall remove the information about the S15 Session.

E.6.4 DRA flows

E.6.4.1 General

For the EPC-routed traffic case and for the non-roaming case, the flows for the non-roaming case in the clauses 7.4.1 and 7.4.2 are applied with the following exception:

– BPCF acts as a client and messages are S9a Diameter messages;

– The external trigger in the Establishment of Diameter Sessions is an S9a session establishment trigger message from the PCRF

For the EPC-routed traffic case and for the roaming case, the flows for the roaming case in clauses 7.4.1 and 7.4.2 are applied with the following exception:

– The external trigger in the Establishment of Diameter Sessions is an S9 session establishment trigger message from the PCRF for case 1 and home routed case.

The flows in clauses E.6.4.2 and E.6.4.3 are applicable to the EPC-routed traffic and for case 1 and UE roaming in the home routed scenario.

For the NSWO traffic case and for the non-roaming case, the flows for the non-roaming and roaming case in the clauses 7.4.1 and 7.4.2 are applied with following exception:

– BPCF acts as a client and messages are S9a* Diameter messages for the non-roaming case.

E.6.4.2 Proxy DRA

E.6.4.2.1 S9 session establishment trigger

Figure E.6.4.2.1.1: S9 session establishment trigger using DRA (proxy) – Roaming case

1. The H-PCRF receives an external trigger (e.g. IP-CAN session establishment request) and determines that an S9 session shall be established.

2. A TER command including user identity, PDN ID if available, UE Local IP address/H(e)NB Local IP address and UDP source port number(if NA(P)T is detected) is sent by the H-PCRF and received by a V-DRA (proxy) in the visited PLMN. The Auth-Session-State AVP set to NO_STATE_MAINTAINED shall be included in the TER.

3. The V-DRA (proxy) stores the user identity and creates a dynamic DRA binding for this user. (assignment of a PCRF node per UE).

4. The V-DRA (proxy) proxies the TER to the target PCRF in the visited PLMN.

5. V-PCRF-1 returns a TEA to the V-DRA (proxy).

6. V-DRA (proxy) proxies the TEA to the H-PCRF and indicates there is a DRA deployed in the visited PLMN by including the DRA-Deployment AVP in the TEA.

NOTE: The H-PCRF is aware that there is a V-DRA (proxy) deployed in the network at this stage.

E.6.4.2.2 S9 session termination notification

Figure E.6.4.2.2.1: S9 session termination notification using V-DRA (proxy) – Roaming cases

1. The H-PCRF receives an external trigger (e.g.IP-CAN session termination request from the BBERF or the PCEF) and initiates S9 session termination procedure.

2. If the V-DRA is deployed in the VPLMN as indicated in step 6 of clause E.6.4.2.1, a TER command including DRA-Binding AVP set to the value DRA_BINDING_DELETION is sent by the H-PCRF and received by the V-DRA (proxy) in the visited PLMN. The message includes the same user identity as the S9 session establishment trigger message.

3. The V-DRA (proxy) verifies that there is an active DRA binding for the user based on the user identity in the request and removes the DRA binding.

4. V-DRA (proxy) returns the TEA to the H-PCRF.

E.6.4.3 Redirect DRA

E.6.4.3.1 S9 session establishment trigger

Figure E.6.4.3.1.1: S9 session establishment trigger using DRA (Redirect) – Roaming case

1. The H-PCRF receives an external trigger (e.g. IP-CAN session establishment request) and determines that an S9 session shall be established.

2. A TER command including user identity, PDN ID if available, UE Local IP address/H(e)NB Local IP address, UDP source port number(if NA(P)T is detected) and the FQDN of Fixed Broadband network where the H(e)NB is connected to if available is sent by the H-PCRF and received by a V-DRA (proxy) in the visited PLMN. The Auth-Session-State AVP set to NO_STATE_MAINTAINED shall be included in the TER.

3. The V-DRA (redirect) stores the user identity and creates a dynamic DRA binding for this user. (assignment of a PCRF node per UE).

4. The V-DRA (redirect) sends a TEA command indicating redirection as defined in IETF RFC 6733 [61]. The target V-PCRF identity is included in the Redirect-Host AVP.

NOTE: The H-PCRF is aware that there is a V-DRA (redirect) deployed in the network at this stage.

5. The H-PCRF re-sends the TER command of step 2 to the target V-PCRF-1.

6. The V-PCRF-1 returns a TEA vailab.

E.6.4.3.2 S9 session termination notification

The detailed procedure is the same as the S9 session termination notification using DRA (Proxy), which is described in clause E.6.4.2.2.

If the H-PCRF was aware that there is a V-DRA deployed in the V-PLMN (step 4 of S9 session establishment procedure according to clause E.6.4.3.1), this procedure shall apply.