Subscription Management

OpenEPC includes a single subscription repository named HSS which includes the functionality of the Home Subscriber Server (HSS) and of the Subscription Profile Repository (SPR) from the 3GPP EPC. The OpenEPC HSS includes the interfaces towards the 3GPP access network control entities - S6a to MME and S6d to SGSN - enabling the authentication and the authorization of access over these radio technologies. Additionally, it includes interface towards the AAA Server, enabling authentication and authorization to non-3GPP accesses. As SPR, the HSS provides through the Sp interface subscription information enabling PCRF and ANDSF policy decisions. Furthermore, it provides subscription information towards IMS core and Application Servers, supporting unified subscription data for core and service platform.

1. OpenEPC Home Subscriber Server / Subscription Profile Repository

The Home Subscriber Server component in the OpenEPC project, referred to as CHeSS, builds on the established experience gained during the development of  The Open IMS Core Project. Sharing the same database back-end with the open source  FHoSS component, it stays compatible with existing subscriber data. Being entirely implemented in C and now part of the Wharf platform, it offers a very high performance, limited only by the database back-end, allowing for  IMS/NGN Performance Benchmarking.

2. HSS Cx Reference Point

The Cx interface has been implemented according the  3GPP TS29.228 and  3GPP TS29.229 Release 7/8 specifications and validated against  The Open IMS Core Project. Support for all the Diameter messages is provided and the following authentication algorithms are supported:

•  RFC3310 Digest Authentication Using Authentication and Key Agreement (AKA) (Digest-AKAv1-MD5)

•  RFC4169 Digest Authentication Using Authentication and Key Agreement (AKA) Version-2 (Digest-AKAv2-MD5)

•  RFC2617 Digest Access Authentication (Digest-MD5), with specific variations as standardized by 3GPP Rel. 8/9, ETSI NGN Rel. 1/2 or CableLabs PacketCable 2.0

3. HSS Sh Reference Point

The Sh interface has been implemented according the  3GPP TS29.328 and  3GPP TS29.329 Release 7/8 specifications. Support for all the Diameter messages is provided, yet advanced Application Server features like Dynamic Service Activation (DSAI) are considered for the next release.

4. S6a and S6d Reference Points

For the authentication and the authorization of the user endpoints for the LTE access, the S6a reference point was developed between the MME and the HSS enabling the retrieval of the subscription information required in the LTE access. The S6d reference point provides the same functionality for the other 3GPP accesses, supporting the communication between the SGSN and the HSS.

5. SPR Sp Reference Point

The Sp interface of the SPR function, although currently not standardized, has been derived from the Sh implementation according to the 3GPP EPC recommendations. Being part of the IMS HSS, together with the Cx and Sh interfaces, the common data is shared seamlessly. Currently there is no support for subscription/notification of information changes in the SPR. The following Data-Reference types have been defined and can be used to interrogate various SPR data:

• Subscription-Id - providing either an IMSI, MSISDN or IMPU, the SPR will respond with the associated MSISDNs, IMSIs or IMPUs

• Subscription-Data - providing an IMSI, MSISDN or IMPU, the SPR will responds the stored subscription profile, containing information like default QoS profiles, allowed/restricted services or access network restrictions

• APN-Configuration - providing an IMSI, the SPR will respond with the associated PDN context informations.

6. SWx Reference Point is implemented according to 3GPP TS29.273 Release 11 specifications. It supports the Diameter messages for the following authentication algorithms which are supported in the EPC by the non-3GPP authentication and authorization mechanism:

• RFC4187 Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA)
• RFC5448 Improved Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA')