Applicable Product(s) or Functional Area

ePDG

Applicable Platform(s)

• ASR 5500

• VPC-DI

• VPC-SI

Feature Default

Related Changes in This Release

Not Applicable

Related Documentation

• ePDG Administration Guide
• AAA Interface Administration and Reference
• Statistics and Counters Reference

The ePDG supports VoWiFi fresh attach request for IR subscribers. This enhancement also includes a related counter and bulk statistic.

21.25

The PGW selection mechanisms in ePDG is enhanced to provide suppressing handover request for VoWiFi International Roaming (IR) subscribers.

21.23

1

The International Roamer (IR) UE attaches to LTE for availing IMS network (IMS APN).

2

• If the UE does handover (HO) to a Wi-Fi network, ensure that the UEAP sends the request to IR supported ePDG, and not to the Non-IR supported ePDG.

• If the UE sends the request to a non-IR supported ePDG, the ePDG sends redirect request indication to the UE with the correct information. UE sends HO requests to the IR ePDG only if UE redirection is supported.

  This feature does not support redirection and it must be handled outside the ePDG.

3

UE sends IKv2_SA_INIT to IR ePDG and receives a response from ePDG to establish the tunnel.

4

• The UE sends the user identity (in the IDi payload) and the APN information (in the IDr payload, IMS APN in case) in this first message of the IKE_AUTH phase, and begins negotiation of child security associations. When the MAC ULI feature is enabled, the root NAI used has the following format: "0<IMSI>AP_MAC_ADDR:nai.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org"

  Note	The UE omits the AUTH parameter to indicate to the ePDG that it wants to use EAP over IKEv2. The user identity complies with the NAI format specified in TS 23.003 containing the IMSI, as defined for EAP-AKA in RFC 4187. The UE IP address is suppressed while sending CSReq message to P-GW.

• The UI and APN are forwarded to the AAA server. The AAA server verifies the subscriber profile fetched from HSS and the 3GPP AAA server initiates the authentication challenge.

5

UE sends the Authentication challenge-response and verifies with AAA, then responds to UE for authentication completion. During the DEA (Diameter EAP Answer) reply from AAA in this process, the AAA sets "VPLMN-Dynamic-Address-Allowed" as allowed and "PDN-GW-Allocation-Type" as dynamic.

6

Based on the P-GW identified in Step 5, the ePDG sends the CreateSessionReq with IMS APN, Handoff bit set to “off” to P-GW so that P-GW will consider this as a fresh attach. Since the new P-GW is different from the LTE P-GW, the UE context will not be present and it will allocate a new IP, which is forwarded to UE through ePDG.

The new P-GW updates the UE and APN information to AAA and then to HSS. Optionally based on the number of dedicated bearers, the Create Bearer procedure will happen.

7

Since the RAT has changed from LTE to Wi-Fi, the SIP re-register will happen.

8

P-GW will not trigger the DeleteSessionReq for LTE bearers, as UE gets attached to a different P-GW after Wi-Fi handover. On the timer expiry (probably periodic TAU timer) expiry, the MME releases the LTE bearers.