Content for TS 23.402 Word version: 18.3.0

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4.4 Reference Points 4.4.1 List of Reference Points 4.4.2 Reference Point Requirements
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4.4 Reference Points p. 32

4.4.1 List of Reference Points p. 32

The description of the reference points:

S1-MME, S1-U, S3, S4, S10, S11:

these are defined in TS 23.401.

S2a

It provides the user plane with related control and mobility support between trusted non 3GPP IP access and the Gateway.

S2b

It provides the user plane with related control and mobility support between ePDG and the Gateway.

S2c

It provides the user plane with related control and mobility support between UE and the Gateway. This reference point is implemented over trusted and/or untrusted non-3GPP Access and/or 3GPP access.

It provides user plane tunnelling and tunnel management between Serving-GW and PDN-GW. It is used for Serving-GW relocation due to UE mobility and in case the Serving-GW needs to connect to a non collocated PDN-GW for the required PDN connectivity.

S6a

This interface is defined between MME and HSS for authentication and authorization. It is defined in TS 23.401.

S6b

It is the reference point between PDN Gateway and 3GPP AAA server/proxy for mobility related authentication if needed. This reference point may also be used to retrieve and request storage of mobility parameters. This reference point may also be used to retrieve static QoS profile for a UE for non-3GPP access in case dynamic PCC is not supported.

It provides transfer of (QoS) policy and charging rules from PCRF to Policy and Charging Enforcement Function (PCEF) in the PDN-GW.

Gxa

It provides transfer of (QoS) policy information from PCRF to the Trusted Non-3GPP accesses.

Gxb

This interface is not specified within this Release of the specification.

Gxc

It provides transfer of (QoS) policy information from PCRF to the Serving Gateway

PMIP-based S8

It is the roaming interface in case of roaming with home routed traffic. It provides the user plane with related control between Gateways in the VPLMN and HPLMN.

It provides transfer of (QoS) policy and charging control information between the Home PCRF and the Visited PCRF in order to support local breakout function. In all other roaming scenarios, S9 has functionality to provide dynamic QoS control policies from the HPLMN.

SGi

It is the reference point between the PDN Gateway and the packet data network. Packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. for provision of IMS services. This reference point corresponds to Gi for 3GPP accesses.

SWa

It connects the Untrusted non-3GPP IP Access with the 3GPP AAA Server/Proxy and transports access authentication, authorization and charging-related information in a secure manner.

STa

It connects the Trusted non-3GPP IP Access with the 3GPP AAA Server/Proxy and transports access authentication, authorization, mobility parameters and charging-related information in a secure manner.

SWd

It connects the 3GPP AAA Proxy, possibly via intermediate networks, to the 3GPP AAA Server.

SWm

This reference point is located between 3GPP AAA Server/Proxy and ePDG and is used for AAA signalling (transport of mobility parameters, tunnel authentication and authorization data). This reference point also includes the MAG-AAA interface functionality, RFC 5779 and Mobile IPv6 NAS-AAA interface functionality, RFC 5447.

SWn

This is the reference point between the Untrusted Non-3GPP IP Access and the ePDG. Traffic on this interface for a UE-initiated tunnel has to be forced towards ePDG.

SWu

This is the reference point between the UE and the ePDG and supports handling of IPSec tunnels. The functionality of SWu includes UE-initiated tunnel establishment, user data packet transmission within the IPSec tunnel and tear down of the tunnel and support for fast update of IPSec tunnels during handover between two untrusted non-3GPP IP accesses.

SWx

This reference point is located between 3GPP AAA Server and HSS and is used for transport of authentication, subscription and PDN connection related data.

S1 interface for E-UTRAN is the same for both the architectures.

Protocol assumption:

S2a interface is based on current or future IETF RFCs. S2a is based on Proxy Mobile IP version 6. For Trusted WLAN, S2a may also be based on GTP. To enable access via Trusted Non 3GPP IP accesses that do not support GTP and PMIPv6, S2a also supports Client Mobile IPv4 FA mode.
S2b interface is based on GTP or Proxy Mobile IP version 6.
S2c is based on DSMIPv6, RFC 5555.
The PMIP-based S5, PMIP-based S8, PMIP-based S2a and PMIP-based S2b interfaces are based on the same protocols and differences shall be minimized. The S5 interface is based on the PMIPv6 specification, RFC 5213.
The GTP-based S5/S8, GTP-based S2a and GTP based S2b interfaces are based on the GTP protocol (TS 29.274). The GTP variant of S5 interface is described in TS 23.401.
PMIPv6-based S8 interface is based on the PMIPv6 specification, RFC 5213. The GTP variant interface is described in TS 23.401.
The PMIPv6-based interfaces (S5, S8, S2a, and S2b) shall support Generic Routing Encapsulation (GRE) RFC 2784 including the Key field extension RFC 2890. The Key field value of each GRE packet header should enable the unique identification of the UE PDN connection that the GRE packet payload is associated with. These keys are exchanged using GRE Options extension to PMIPv6 Proxy Binding Update and Proxy Binding Ack messages on PMIPv6-based interfaces.
In case of CN node relocation, the GRE key for uplink traffic is forwarded to the target S-GW over S10/S11 reference point.
SWu interface is based on IKEv2, RFC 5996 and MOBIKE, RFC 4555.

The EPS shall allow the operator to configure a type of access (3GPP or non-3GPP) as the "home link" for Client Mobile IP purposes.

4.4.2 Reference Point Requirements p. 34

4.4.2.1 S5 Reference Point Requirements p. 34

Both the GTP and PMIP variants of the S5 reference point shall satisfy the following architectural principles:

There shall be only one radio interface protocol stack defined, common for both S5 variants, including both radio layer and Non-Access Stratum protocols.
There shall be only one S6a interface defined common to both S5 variants. There may be a need for different information elements specific to PMIP-based or GTP-based variants of S5 but differences due to the S5 variants should be minimized.
In the non-roaming case, there shall be only one Gx interface defined for transfer of policy and charging rules, common to both S5 variants. There may be a need for different information elements specific to PMIP-based or GTP-based variants of S5 but differences due to the S5 variants should be minimized.
Differences between S5 variants in terms of functional split between the endpoints should be minimized.

The S5 reference point shall fulfil the following requirements:

S5 shall allow access to multiple PDNs. It shall be possible to allow an UE to connect to different packet data networks. It shall also be possible to support a UE with concurrent connections to several packet data networks.
S5 shall allow multiple PDN connections for a given APN and UE.
S5 shall be able to transport both IPv4 and IPv6 user plane traffic independent of IP version of the underlying IP transport network.
S5 shall support fault handling. There should be mechanisms to identify and signal faults for groups of mobiles - e.g., if a large node handling millions of terminals goes down.