7.4.1 Proxy DRA

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

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7.4.1.1 Establishment of Diameter Sessions

7.4.1.1.1 Non-roaming cases

Establishment of Diameter sessions may occur at any of the following cases:

– Gateway control establishment

– IP-CAN session establishment

– AF session establishment

– For unsolicited application reporting, TDF session establishment

Figure 7.4.1.1.1.1: Establishment of Diameter sessions using DRA (proxy)

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 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]) is sent by the Client and received by a DRA (proxy).

3. The DRA (proxy) 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).

NOTE 1: When the AF establishes an Rx session or TDF establishes a TDF session with the DRA, there is already a DRA binding active.

4. The DRA (proxy) proxies the Diameter Request to the target PCRF. The proxied Diameter Request maintains the same Session-Id AVP value.

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

6. DRA (proxy) proxies the Diameter Answer to the Client. The proxied Diameter Answer maintains the same Session-Id AVP value.

7. If PA2 option is implemented, the Client uses the Origin-Host AVP value providedin the Diameter Answer of step 6. This value is the identity of the target PCRF. The client populates the Destination-Host AVP with this address and sends any subsequent Diameter messages directly to this PCRF bypassing the DRA (proxy).

NOTE 2: Figure 7.4.1.1.1.1 is also applicable when the AF/BBERF/PCEF/TDF in the VPLMN contacts the V-DRA to locate the V-PCRF.

7.4.1.1.2 Roaming cases

Establishment of Diameter sessions may occur at any of the following cases:

– V-PCRF initiates S9 Diameter session to H-PCRF

– V-PCRF proxies Rx Diameter session to H-PCRF

Figure 7.4.1.1.2.1: Establishment of Diameter sessions using DRA (proxy) – Roaming case

1. V-PCRF receives a trigger to establish a Diameter session to H-PCRF (e.g. S9 session establishment request).

2. A Diameter Request involving either the Rx or S9 protocol is sent by the V-PCRF and received by a H-DRA (proxy) in the home PLMN.

3. The H-DRA (proxy) 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 or per IP-CAN session).

4. The H-DRA (proxy) proxies the Diameter Request to the target PCRF in the home PLMN. The proxied Diameter Request maintains the same Session-Id AVP value.

5. H-PCRF-1 returns a Diameter Answer to the H-DRA (proxy).

6. H-DRA (proxy) proxies the Diameter Answer to the V-PCRF. The proxied Diameter Answer maintains the same Session-Id AVP value.

7. If PA2 option is implemented, the V-PCRF uses the Origin-Host AVP value provided in the Diameter Answer of step 6. This value is the identity of the target H-PCRF. The V-PCRF populates the Destination-Host AVP with this address and sends any subsequent Diameter messages directly to this H-PCRF bypassing the H-DRA.

7.4.1.2 Modification of Diameter Sessions

7.4.1.2.1 Non-roaming cases

7.4.1.2.1.1 Client-initiated

Modification of Diameter sessions may occur in any of the following cases:

– Gateway control session modification

– IP-CAN session modification

– AF session modification

– For unsolicited application reporting, TDF session modification

If PA1 option is implemented, only steps 2, 3, 4, 5, 6 are carried out. If PA2 option is implemented, only steps 2a, 5a are carried out.

Figure 7.4.1.2.1.1.1: Modification of Diameter sessions through DRA (proxy)- AF/BBERF/PCEF/TDF interaction

1. A Client receives an external trigger (e.g. IP-CAN session modification) that requires a subsequent Diameter message to be sent to the PCRF.

2. A subsequent Diameter Request (e.g. a Diameter CCR sent by PGW to indicate modification of an IP-CAN session) as defined in clauses 4.5.1, 4a.5.1 of 3GPP TS 29.212 [9] or clause 4.4 of 3GPP TS 29.214 [10]) is sent by the Client and received by the DRA (proxy).

2a If PA2 option is implemented, based on Client configuration and operator policy, the Client communicates directly to the PCRF, bypassing the DRA (proxy), by using the PCRF identity obtained through the Origin-Host AVP (see step 7 in clause 5.2.5.7.1.1). The Client uses the same active Session-Id AVP value on the Diameter Request sent to the PCRF. In such a case steps 2, 3, 4, 5, 6 are not carried out.

3. After receiving a Diameter Request (Step 2), the DRA (proxy) verifies that there is an active DRA binding for the session identified in the request.

4. The DRA (proxy) proxies the Diameter Request to the target PCRF.

5. PCRF-1 returns a Diameter Answer as defined in clauses 4.5, 4a.5 of 3GPP TS 29.212 [9] or clause 4.4 of 3GPP TS 29.214 [10]) to the DRA (proxy).

5a Upon receiving a Diameter Request (Step 2a), PCRF-1 returns a Diameter Answer directly to the Client, bypassing the DRA (proxy).

6. DRA (proxy) proxies the Diameter Answer to the Client.

NOTE: Figure 7.4.1.2.1.1.1 is also applicable when the AF/BBERF/PCEF/TDF in the VPLMN modifies the Diameter session through the V-DRA.

7.4.1.2.1.2 PCRF-initiated

Modification of Diameter sessions occur on PCRF initiated session modifications towards the clients (AF/BBERF/PCEF).

If PA1 option is implemented, only steps 2, 3, 4, 5, 6 are carried out. If PA2 option is implemented, only steps 2a, 5a are carried out.

Figure 7.4.1.2.1.2.1: Modification of Diameter sessions through DRA (proxy)- PCRF interaction

1. PCRF receives an internal or external trigger that requires a Diameter message to be sent to the clients (either AF, BBERF, PCEF)

2. A PCRF-initiated Diameter Request (e.g. a Diameter RAR request sent to the PGW) is sent to the Clients and received by the DRA (proxy).

2a If PA2 option is implemented, the PCRF communicates directly to the client, bypassing the DRA (proxy). In such a case steps 2, 3, 4, 5, 6 are not carried out.

3. After receiving a Diameter Request (Step 2), the DRA (proxy) verifies that there is an active DRA binding for the session identified in the request.

4. The DRA (proxy) proxies the Diameter Request to the Client. The proxied Diameter Request maintains the same Session-Id AVP value.

5. Clients returns a Diameter Answer as defined in clauses 4.5, 4a.5 of 3GPP TS 29.212 [9] or clause 4.4 of 3GPP TS 29.214 [10]) to the DRA (proxy).

5a Upon receiving a Diameter Request (Step 2a), Client returns a Diameter Answer directly to the PCRF, bypassing the DRA (proxy).

6. DRA (proxy) proxies the Diameter Answer to the PCRF.

NOTE: Figure 7.4.1.2.1.2.1 is also applicable when the V-PCRF modifies the Diameter session through the V-DRA.

7.4.1.2.2 Roaming cases

7.4.1.2.2.1 V-PCRF initiated

In roaming scenarios modification of Diameter sessions may occur at any of the following cases:

– V-PCRF S9 Diameter session modification to H-PCRF

– V-PCRF proxies Rx Diameter session modification to H-PCRF

If PA1 option is implemented, only steps 2, 3, 4, 5, 6 are carried out. If PA2 option is implemented, only steps 2a, 5a are carried out.

Figure 7.4.1.2.2.1.1: Modification of Diameter sessions through DRA (proxy) on roaming scenarios – V-PCRF initiated

1. V-PCRF receives an internal or external trigger that requires a Diameter message to be sent to H-PCRF over the S9 reference point

2. V-PCRF sends a Diameter session update (e.g. an S9 session modification request) over the S9 reference point that is received by the DRA (proxy) in the home PLMN.

2a If PA2 option is implemented, the V-PCRF communicates directly to the H-PCRF, bypassing the H-DRA (proxy). In such a case steps 2, 3, 4, 5, 6 are not carried out.

3. After receiving a Diameter Request (Step 2), the H-DRA (proxy) verifies that there is an active DRA binding for the session identified in the request.

4. The H-DRA (proxy) proxies the Diameter Request to the H-PCRF. The proxied Diameter Request maintains the same Session-Id AVP value.

5. H-PCRF returns a Diameter Answer to the H-DRA (proxy) in the home PLMN.

5a Upon receiving a Diameter Request (Step 2a), Client returns a Diameter Answer directly to the PCRF, bypassing the H-DRA (proxy).

6. H-DRA (proxy) proxies the Diameter Answer to the PCRF.

7.4.1.2.2.2 H-PCRF initiated

In roaming scenarios modification of Diameter sessions may occur at any of the following cases:

– H-PCRF S9 Diameter session modification to V-PCRF

If PA1 option is implemented, only steps 2, 3, 4, 5, 6 are carried out. If PA2 option is implemented, only steps 2a, 5a are carried out.

Figure 7.4.1.2.2.2.1: Modification of Diameter sessions through DRA (proxy) on roaming scenarios – H-PCRF initiated

1. H-PCRF receives an internal or external trigger that requires a Diameter message to be sent to V-PCRF over the S9 reference point.

2. H-PCRF sends a Diameter session update (e.g. an S9 session modification request) over the S9 reference point that is received by the H-DRA (proxy) in the home PLMN.

2a If PA2 option is implemented, the H-PCRF communicates directly to the V-PCRF, bypassing the H-DRA (proxy). In such a case steps 2, 3, 4, 5, 6 are not carried out.

3. After receiving a Diameter Request (Step 2), the H-DRA (proxy) verifies that there is an active DRA binding for the session identified in the request.

4. The H-DRA (proxy) proxies the Diameter Request to the V-PCRF. The proxied Diameter Request maintains the same Session-Id AVP value.

5. V-PCRF returns a Diameter Answer to the H-DRA (proxy) in the home PLMN.

5a Upon receiving a Diameter Request (Step 2a), V-PCRF returns a Diameter Answer directly to the H-PCRF, bypassing the H-DRA (proxy).

6. H-DRA (proxy) proxies the Diameter Answer to the H-PCRF.

7.4.1.3 Termination of Diameter Sessions

7.4.1.3.1 Non-roaming cases

The procedures required are identical for both PA1 and PA2 options

Termination of Diameter sessions occur at the following cases:

– Gateway control session termination

– IP-CAN session termination

– AF session termination

– For unsolicited application reporting, TDF session termination

Figure 7.4.1.3.1.1: Termination of Diameter sessions through DRA (proxy)

1. A Client receives an external trigger (e.g. an IP-CAN session termination is initiated by the UE or PCRF) that requires the sending of a Diameter Termination Request.

2. A Diameter Termination Request (e.g., a Diameter CCR sent by PGW to indicate termination of an IP-CAN session) as defined in clauses 4.5, 4a.5 of 3GPP TS 29.212 [9]) is sent by the Client to the DRA (proxy). The message uses the same Session-Id AVP value of the active Diameter session established between the Client and PCRF-1.

3. The DRA (proxy) verifies that there is an active DRA binding for the IP-CAN session based on the Session-Id AVP in the request.

4. The DRA (proxy) proxies the Diameter Termination Request to the target PCRF. The proxied Diameter Request maintains the same Session-Id AVP value.

5. PCRF-1 acknowledges termination of the session. PCRF-1 sends a Diameter Answer, (e.g., as defined in clauses 4.5, 4a.5 of 3GPP TS 29.212 [9]) to DRA (proxy).

6. The DRA marks the Diameter session terminated. If the DRA binding is per IP-CAN session and all the Diameter sessions (i.e. the Gx session or the Gxx session) of the IP-CAN session are terminated or if the DRA binding is per UE and all the Diameter sessions (i.e. the Gx session or the Gxx session) of that UE are terminated the DRA (proxy) removes the DRA binding.

7. DRA (proxy) proxies the Diameter Answer to the Client. The proxied Diameter Answer maintains the same Session-Id AVP value.

NOTE 1: Figure 7.4.1.3.1.1 is also applicable when the AF/BBERF/PCEF/TDF in the VPLMN terminates the Diameter sessions through the V-DRA.

NOTE 2: AF/TDF is not required to send Diameter session termination request to DRA (PA2).

7.4.1.3.2 Roaming cases

In roaming cases (over S9 reference point) termination of Diameter sessions occur at the following cases:

– S9 session termination

– AF session termination

Figure 7.4.1.3.2.1: Termination of Diameter sessions through H-DRA (proxy) – Roaming cases

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

2. A Diameter Termination Request (e.g., an S9 termination request) is sent by the V-PCRF and received by the H-DRA (proxy) in the home PLMN. The message uses the same Session-Id AVP value of the active Diameter session established between V-PCRF and H-PCRF-1.

3. The H-DRA (proxy) verifies that there is an active DRA binding for the IP-CAN session based on the Session-Id AVP in the request.

4. The H-DRA (proxy) proxies the Diameter Termination Request to the target H-PCRF-1. The proxied Diameter Request maintains the same Session-Id AVP value.

5. H-PCRF-1 acknowledges termination of the session. H-PCRF-1 sends a Diameter Answer to H-DRA (proxy) in the home PLMN.

6. The H-DRA marks the Diameter session terminated. If all the Diameter sessions (i.e. the S9 session, the Gxx session, and the Gx session) of that UE are terminated the H-DRA (proxy) removes the DRA binding.

7. H-DRA (proxy) proxies the Diameter Answer to the V-PCRF. The proxied Diameter Answer maintains the same Session-Id AVP value.

NOTE: V-PCRF does not need to send Rx Diameter termination messages to proxy H-DRA (PA2 option) since Rx Diameter termination messages do not affect the DRA binding.