5.10 PMIP-based S5/S8 procedures for GERAN/UTRAN over S4

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

5.10.1 General

This clause presents the PMIP-based S5/S8 procedures equivalent to the GTP-based procedures presented in TS 23.060 [21] for interworking. The differences required for interpretation of the PMIP-based S5/S8 procedures in other clauses of this specification are clarified below.

If PCC is not deployed, only default bearers may be provided for UE connection to a PDN. This is described fully in the PMIP-based S5/S8 procedures referred to in clause 5.10. Secondary PDP context requests are not supported in this case.

Bearer-specific parameters sent along S4 are not forwarded to the PDN GW or PCRF in many cases. Bearers terminate in the Serving GW when PMIP-based S5/S8 has been deployed. Though EPS bearer identifier information is not relevant to the PCRF or PCEF in these cases, some bearer-oriented parameters must be forwarded to the PCRF for authorization and so that the PCRF will generate the correct corresponding PCC rules to send to the PDN GW for enforcement.

5.10.2 GPRS procedures that update the PDN GW

Several procedures employing GTP-based S5/S8 includes a "Modify Bearer" exchange, initiated by the Serving GW, responded to by the PDN GW. The equivalent interaction for a PMIP-based S5/S8 is shown in figure 5.7.2-1.

The following procedures in TS 23.060 [21] will make use of the procedure shown in this specification, clause 5.7.2 to signal RAT change as determined by the SGSN. Aside from the new RAT type, no additional parameter must be sent as an event report by the Serving GW to the PDN GW by means of the PCRF (as described in TS 23.203 [19]).

The procedure in clause 5.7.2 refers directly to procedures in TS 23.401 [4], while the procedures described here in support of S4 refer to clauses in TS 23.060 [21]. The following clarifications to the procedure in clause 5.7.2 must be considered to interpret clause 5.7.2:

6.9.2.2.1a: Serving RNS Relocation Procedure, Combined Hard Handover and SRNS Relocation
Procedure, and Combined Cell/URA Update and SRNS Relocation Procedure using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.9.2.2.1a, figure 39b. The APN AMBR, RAT Type and other parameters defined in clause 6.9.2.2.1a step B and C are transmitted according to clause 5.7.2, as additional IEs transmitted between the S-GW, PCRF and P-GW. IEs are returned to the S-GW (insofar as step A.2 implies a Gateway Control and QoS Rules Provision procedure as described in TS 23.203 [19]).

This procedure applies also to 6.9.2.2.3 Combined Cell / URA Updates and SRNS Relocation Procedure.

6.9.2.2.5A Enhanced Serving RNS Relocation Procedure Using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (step B and C) in figure 44b1 and steps B and C in figure 44b2 in TS 23.060 [21], clause 6.9.2.2.5A.

6.12.1A: UE Initiated Service Request Procedure Using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.12.1A, figure 50A.

6.13.1.1.2: Iu mode to A/Gb mode Intra-SGSN Change using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (A1) in TS 23.060 [21], clause 6.13.1.1.2, figure 52-2.

6.13.1.2.2: A/Gb mode to Iu mode Intra-SGSN Change using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (A1) in TS 23.060 [21], clause 6.13.1.2.2, figure 53-2.

6.13.2.1.2: Iu mode to A/Gb mode Inter-SGSN Change using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.13.2.1.2, figure 54-3.

6.13.2.2.2: A/Gb mode to Iu mode Inter-SGSN Change using S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.13.2.2.2, figure 55-3.

8.1.4A Paging response for GPRS Downlink Transfer with no established User plane on S4

Steps A.1 and A.2 of the procedure in clause 5.7.2 occur instead of the steps shown in the box (C) in TS 23.060 [21], clause 8.1.4, figure 56b.

5.10.3 UE allocated resources

The UE (or the SGSN on behalf of the UE) requests resources in several procedures in TS 23.060 [21]. The procedure described in clause 5.5 of this specification provides the PMIP-based S5/S8 describes UE-initiated resource request, modification and release. This procedure, with the additional clarification given below, will support the following procedures shown in TS 23.060 [21].

In each case, the SGSN provides a Bearer identifier (the LBI) over S4. The bearer binding performed by the Serving GW is in this case constrained to either reject or modify (increase or decrease the resource assigned to) the indicated bearer. The Serving GW shall not provide a different bearer as a result of the PDP Context Activation or Modification procedures.

9.2.2.1A: A PDP Context Activation using S4

Steps A.1 to A.4 of the procedure in clause 5.6.1 occur instead of the steps shown in the box (A1) in TS 23.060 [21], clause 9.2.2.1A, figure 64a. Step A.1 and A.3a include the RAT Type, Default Bearer QoS and APN-AMBR IEs, and other IEs defined in TS 23.060 [21] clause 9.2.2.1A, step B.

Step A.3b in clause 5.6.1 of this specification (insofar as it implies a Gateway Control and QoS Rules Provision procedure as described in TS 23.203 [19]) returns the IEs to the S-GW, including EPS Bearer QoS and other IEs defined in TS 23.060 [21] clause 9.2.2.1A, step C.

NOTE: As described in TS 23.060 [21], an S4-based SGSN applies the BCM ‘MS/NW’ whenever the S4 is selected for a certain MS. The Serving GW is not aware of the BCM.

If the UE requests a PDP context (effectively an additional PDN connection) for an APN for which the UE already has an active PDN connection, the SGSN shall reject the PDN connectivity request unless it is configured that the Serving GW supports multiple PDN connections to the same APN.

9.2.2.1.1A, Figure 66a: Secondary PDP Context Activation Procedure, PDP Creation Part using S4

Step A.1 of the procedure in clause 5.5 corresponds to the steps described in the box (A1) and (A2) in TS 23.060 [21], clause 9.2.2.1.1A, figure 66a.

In step A.1, additional IEs are required by the PCRF and PDN GW in order properly assign QoS rules and prepare the dedicated bearer. The TFT and EPS Bearer QoS (excluding ARP) IEs are received from the SGSN by the S‑GW over S4. These parameters are then forward to the PCRF as described in clause 5.5.

9.2.3.3A: MS-Initiated EPS Bearer Modification Procedure using S4, Request Part

The procedure step in TS 23.060 [21], clause 9.2.3.3A, figure 72c, step B corresponds with step A.1 of figure 5.5-1 (of this specification).

The Serving GW provides the same information to the PCRF as the PDN GW provides according to step B in TS 23.060 [21], clause 9.2.3.3A; this clause defines the IEs included in step A.1 of clause 5.5.

9.2.3.3B: MS-Initiated EPS Bearer Modification Procedure using S4, Execution Part

The procedure step in TS 23.060 [21], clause 9.2.3.3B, figure 72d, step A corresponds with step A.1 of figure 5.5-1 (of this specification). The following information elements may be sent, depending on the scenario, see TS 23.060 [21], clause 9.2.3.3B:

9.2.3.3C MS-Initiated EPS Bearer Modification Procedure using S4, Response Part

The procedure step in TS 23.060 [21], clause 9.2.3.3A, figure 72c, step C corresponds with step figure 5.5-1 (of this specification), steps B.1 and B.2, with one difference – before step B.1, step A of the procedure in TS 23.060 [21], clause 9.2.3.3C occurs. The Serving GW indicates to the PCRF the result of the resource allocation. This may result in additional interaction with the PDN GW (see TS 23.203 [19]).

5.10.4 Network allocated resources

Network entities may request resources by means of off-path signalling to support PMIP-based S5/S8. This is defined in clause 5.4.1. All IEs present in messages sent in the replaced ‘boxes’ in procedures in the following list are sent instead using messages described in this specification. The following procedures in TS 23.060 [21] employ this procedure:

9.2.2.3A: Network Requested PDP Context Activation Procedure using S4

Step A.1 of the procedure in clause 5.4.1 occurs instead of the steps shown in the box (A1) in TS 23.060 [21], clause 9.2.2.3A, Figure 69c. Steps B.1 and B.2 of the procedure in clause 5.4.1 correspond to the box (B1).

9.2.3.1A: SGSN-Initiated EPS Bearer Modification Procedure, Request Part

Step A.1 of clause 5.5 occurs instead of the steps inside box (A1) in TS 23.060 [21], clause 9.2.3.1A, figure 70c. Figure 5.5-1 refers to TS 23.401 [4] yet the procedure applies to the SGSN-Initiated EPS Bearer Modification Procedure using S4 as well.

9.2.3.1B: SGSN-Initiated EPS Bearer Modification Procedure, Response Part

Steps B.1 and B.2 of clause 5.5 occurs instead of the steps inside box (B1) in TS 23.060 [21], clause 9.2.3.1B, figure 70d. Figure 5.5-1 refers to TS 23.401 [4] yet the procedure applies to the SGSN-Initiated EPS Bearer Modification Procedure using S4 as well.

9.2.3.2A: PDN GW-Initiated EPS Bearer Modification Procedure

Step A.1 of the procedure in clause 5.4.1 occurs instead of the steps shown in the box (A1) in TS 23.060 [21], clause 9.2.3.2A, Figure 71c.

Steps B.1 and B.2 of the procedure in clause 5.4.1 correspond to the box (A2). Step B.1 indicates whether the resource allocation was successful. This may result in additional interaction with the PDN GW (refer to TS 23.203 [19]).

5.10.5 UE released resources

The UE may release dedicated resources by means of off-path signalling to support PMIP-based S5/S8 deployments, as shown in clause 5.5.

9.2.4.1A.1: MS-and SGSN Initiated PDN connection Deactivation Procedure using S4

Steps A.1 to A.4 of the procedure in clause 5.6.2.1 "UE, MME or S GW initiated PDN Disconnection" occur instead of steps shown in the box (A1) in TS 23.060 [21], clause 9.2.4.1A.1, figure 74a.

9.2.4.1A.2: MS- and SGSN Initiated Bearer Deactivation using S4

Steps A.1, B.1 and B.2 of the procedure in clause 5.5 "UE-initiated Resource Request and Release" procedure occur instead of the steps shown in the box (A1) in TS 23.060 [21], clause 9.2.4.1A.2, figure 74b.

5.10.6 PDN GW released resources

The PDN GW may release resources by means of off-path signalling to support PMIP-based S5/S8 deployments as shown in clause 5.4.1. The following procedures in TS 23.060 [21] employ this procedure:

9.2.4.3A: PDN GW-Initiated PDP Context Deactivation Procedure using S4

Step A.1 in clause 5.4.1 corresponds to the steps shown in box (A1) of TS 23.060 [21], clause 9.2.4.3A, figure 77a.

9.2.4.3B: PDN GW-Initiated PDP Context Deactivation Procedure using S4

Steps B.1 and B.2 in clause 5.4.1 correspond to the steps in the box (B1) in TS 23.060 [21], clause 9.2.4.3B, figure 77b.

5.10.7 Attach

The GPRS Attach Procedure is supported by the following PMIP-based S5/S8 procedures:

Clause 5.3 is employed instead of box (A) in TS 23.060 [21], clause 6.5.3A, figure 22A. clause 5.3 is also used instead of box (B) in TS 23.060 [21], clause 6.5.3B, figure 22B.

5.10.8 Detach interaction using S4

The MS-, SGSN- and HLR-initiated GPRS detach procedures are supported by the following equivalent PMIP-based S5/S8 procedure:

Clause 5.3 is employed instead of the gray box (A1) in TS 23.060 [21], clause 6.6.3, Figure 25A.

5.10.9 Interaction with CGI/SAI reporting using S4

In the Interaction with CGI / SAI reporting using S4 Procedure as depicted in Figure 15.1.3-3 of TS 23.060 [21], if CGI or SAI changes are considered relevant to charging, a change notification is sent to the PDN GW. There is no response to this report. This corresponds to a Location change (CGI/SAI) event report provided to the PCRF by means of a Gateway Control and QoS Rules Request, as defined in TS 23.203 [19]. This procedure ensures that the event is reported to the PDN GW as well.

5.10.10 RAU Procedure Support

RAU procedures in TS 23.060 [21] send messages from the S4 SGSN to the S‑GW and thence to P‑GW using GTPv2. For PMIP-based S5/S8, these exchanges occur via PCC.

TS 23.203 [19], figure 7.7.3-1 "Gateway Control and QoS Rules Request", depicts the procedure. The BBERF(S‑GW) sends a Gateway Control and QoS Rules Request message to the PCRF including the APN-AMBR. The PCRF sends a PCC Rules Provision message to the PDN GW including the APN-AMBR. The PDN GW responds with an Acknowledge Policy and Charging Rules Provisioning message with the APN-AMBR to the PCRF. The PCRF responds to the BBERF(S‑GW) with a Gateway Control and QoS Rules Reply message with the APN‑AMBR parameter. The response from the PCRF to the BBERF to the initial Gateway Control and QoS Rules Request message must wait (synchronously) for the completion of the PCC Rules Provision exchange between the PCRF and PCEF.

6.9.1.2.2a: Inter SGSN Routeing Area Update and Combined Inter SGSN RA / LA Update using S4

Instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.9.1.2.2a, figure 33b, the procedure described above is employed.

6.9.2.1a: Routeing Area Update Procedure using S4

Instead of the steps shown in the box (B1) in TS 23.060 [21], clause 6.9.2.1a, figure 36b, the procedure described above is employed.