7.4.2 Redirect DRA

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

7.4.2.1 Establishment of Diameter Sessions

7.4.2.1.1 Non-roaming cases

Establishment of Diameter sessions may occur at the following cases:

– Gateway control session establishment

– IP-CAN session establishment

– AF session establishment

– For unsolicited application reporting, TDF session establishment

The DRA client (AF/BBERF/PCEF/TDF) shall follow the procedure below if an appropriate cached route table entry created from previous DRA (redirect) interactions does not exist. Cached route table entries are created from the Redirect-Host, Redirect-Host-Usage and Redirect-Max-Cache-Time AVPs as described in sections 6.12, 6.13 and 6.14 of IETF RFC 6733 [61].

Figure 7.4.2.1.1.1: Establishment of Diameter session through DRA (redirect)

1. A Client receives an external trigger (e.g., IP-CAN session establishment request) that requires the establishment of a Diameter session with a PCRF.

2. A Diameter Establishment request (e.g., a Diameter CCR sent by PGW to indicate establishment of an IP-CAN session as defined in clauses 4.5.1, 4a.5.1 of 3GPP TS 29.212 [9]) with user information (e.g., UE-NAI) is sent by the Client and received by the DRA (redirect).

3. The DRA (redirect) stores the user information (e.g., UE-NAI) and checks whether an active DRA binding exists. If not the DRA creates a dynamic DRA binding (assignment of a PCRF node per UE or per IP-CAN session); if the DRA (redirect) find there has been a DRA binding for the user, the DRA shall select the PCRF from the binding for the client.

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

5. The Client re-sends the Diameter Establishment Request of step 2 to the target PCRF.

6. PCRF-1 returns a Diameter Answer, as defined in clauses 4.5, 4a.5 of 3GPP TS 29.212 [9], to the Client.

NOTE: Figure 7.4.2.1.1.1 is also applicable when the AF/BBERF/PCEF/TDF in the VPLMN contacts the V-DRA to locate the V-PCRF.

7.4.2.1.2 Roaming cases

Establishment of Diameter sessions may occur at the following cases:

– S9 session vailability

– AF session establishment

The DRA client (AF/BBERF/PCEF) shall follow the procedure below if an appropriate cached route table entry created from previous DRA (redirect) interactions does not exist. Cached route table entries are created from the Redirect-Host, Redirect-Host-Usage and Redirect-Max-Cache-Time AVPs as described in clause 6.12, 6.13 and 6.14 of IETF RFC 6733 [61].

Figure 7.4.2.1.2.1: Establishment of Diameter session through DRA (redirect) – Roaming scenario

1. The V-PCRF receives an external trigger (e.g., IP-CAN session establishment request) that requires the establishment of a Diameter session with an H-PCRF over the S9 reference point.

2. A Rx/S9 Diameter Establishment Request with user information (e.g., UE-NAI) is sent by the V-PCRF and received by the H-DRA (redirect) in the home PLMN.

3. The H-DRA (redirect) stores the user information (e.g., UE-NAI) and checks whether an active DRA binding exists. If not the H-DRA creates a dynamic DRA binding (assignment of a PCRF node per UE); if the DRA (redirect) find there has been a DRA binding for the user, the DRA shall select the PCRF from the binding for the client.

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

5. The V-PCRF re-sends the Rx/S9 Diameter Establishment Request of step 2 to the target H-PCRF.

6. H-PCRF-1 returns a corresponding Diameter Answer to the V-PCRF.

NOTE: The V-PCRF may proxy the Rx Diameter Establishment Request to the H-PCRF directly (e.g. based on the stored information provided by H-DRA during the S9 Diameter session establishment).

7.4.2.2 Modification of Diameter sessions

The PCEF shall send the Diameter session modification message to the DRA to update the DRA binding information only if the UE’s address(es) is updated and the DRA (redirect) is maintaining PCRF routing information per IP-CAN session. For visited access case, the V-PCRF shall send the Diameter session modification message to the H-DRA to update the DRA binding information only if the UE’s address(es) is updated. The detailed procedure is similar to the Establishment of Diameter sessions, which is described in the clause 7.4.2.1.

7.4.2.3 Termination of Diameter Sessions

7.4.2.3.1 Non-roaming cases

Termination of Diameter sessions that impact the DRA binding occur at the following cases:

– Gateway control session termination

– IP-CAN session termination

The DRA client (BBERF/PCEF) shall follow the procedure below if the DRA (redirect) is maintaining PCRF routing information per IP-CAN session or an appropriate cached route table entry created from previous DRA (redirect) interactions does not exist. Cached route table entries are created from the Redirect-Host, Redirect-Host-Usage and Redirect-Max-Cache-Time AVPs as described in clause 6.12, 6.13 and 6.14 of IETF RFC 6733 [61].

Figure 7.4.2.3.1.1: Termination of Diameter sessions through DRA (redirect)

1. Client receives an external trigger (e.g. an IP-CAN session termination is initiated by the UE or PCRF) that triggers the client to terminate Diameter session with server (i.e. PCRF)

2 A Diameter Termination Request (e.g., as defined in clauses 4.5.7 (Gx) and 4a.5.3 (Gxx) of 3GPP TS 29.212 [9]) is sent by the Client to the DRA (redirect).

3. A Diameter Termination Request (e.g., as defined in clauses 4.5.7 (Gx) and 4a.5.3 (Gxx) of 3GPP TS 29.212 [9]) is sent by the Client to PRCF-1. The message uses the same Session-Id AVP value of the active Diameter session established between the Client and PCRF-1.

NOTE: Steps 2, 3 may be carried out in parallel. Otherwise, the client after step2 may need to wait for the redirect answer before sending the Diameter termination request to the PCRF.

4. DRA (redirect) verifies that there is an active DRA binding for the IP-CAN session based on the Session-Id AVP and marks the Diameter session terminated. If the DRA binding is per IP-CAN session and all the Diameter sessions (i.e. Gx session or Gxx session) of that IP-CAN session are terminated or if the DRA binding is per UE and all the Diameter sessions (i.e. Gx session or Gxx session) of that UE are terminated the DRA removes the DRA binding.

5 DRA (redirect) acknowledges termination of the session by sending a Diameter redirect answer to the client.

6 PCRF-1 acknowledges termination of session. PCRF-1 sends a Diameter Answer (e.g., as defined in clauses 4.5.7 (Gx) and 4a.5.3 (Gxx) of 3GPP TS 29.212 [9]) to the Client.

NOTE: Figure 7.4.2.3.1.1 is also applicable when the BBERF/PCEF in the VPLMN terminates the Diameter sessions through the V-DRA.

7.4.2.3.2 Roaming cases

Termination of Diameter sessions occur at the following cases:

– S9 session termination

The DRA client (AF/BBERF/PCEF) shall follow the procedure below) if the DRA (redirect) is maintaining PCRF routing information per IP-CAN session or an appropriate cached route table entry created from previous DRA (redirect) interactions does not exist. Cached route table entries are created from the Redirect-Host, Redirect-Host-Usage and Redirect-Max-Cache-Time AVPs as described in clause 6.12, 6.13 and 6.14 of IETF RFC 6733 [61].

Figure 7.4.2.3.2.1: Termination of Diameter sessions through DRA (redirect) – Roaming case

1. V-PCRF receives an external trigger (e.g. session termination request from the BBERF, PCEF) that requires the sending of a Diameter Termination Reqeust.

2 A Diameter Termination Request is sent by the V-PCRF and received by the H-DRA (redirect) in the home PLMN.

3. A Diameter Termination Request is sent by the V-PCRF to H-PRCF-1. The message uses the same Session-Id AVP value of the active Diameter session established between theV-PCRF and H-PCRF-1.

NOTE: Steps 2, 3 may be carried out in parallel. Otherwise, the V-PCRF after step2 may need to wait for the redirect answer before sending the Diameter termination request to the H-PCRF

4. H-DRA (redirect) verifies that there is an active DRA binding for the IP-CAN session based on the Session-Id AVP and marks the Diameter session terminated. If all the Diameter sessions (i.e. S9 session, Gxx session, Gx session) of that UE are terminated the H-DRA removes the DRA binding.

5 H-DRA (redirect) acknowledges termination of the session by sending a Diameter redirect answer to the V-PCRF.

6 H-PCRF-1 acknowledges termination of the session by sending a Diameter answer to the V-PCRF.

NOTE: Rx Diameter termination messages are not required to be sent to H-DRA (redirect) since such messages do not affect the DRA binding